Table Saw Kickback

[Justin Rapp]

So I did something stupid. I was cutting out a slot from a piece of plywood, making two cuts to a hole 3/4 inch hold I made in the board. Well instead of shutting the saw before backing out the board, I pulled it back and the blade caught the wood, turned it a bit and shot it at me. It was luck being punched in the gut. It broke the skin a bit and I will have a heck of a black and blue. The good news, only damage to the saw was a bit of damage to my zero clearance insert.

With the power of the saw tossing that board makes me thing of what could happen if it was a hand. I think my router table upgrade will wait and a sawstop is now in the front-runner of my next tool.

[Mark Hennebury]

Glad that you were not injured worse.

I have a hard time with partial information, and prefer photos of the set-up, so that i am sure that I understand exactly what the situation was. The size of the plywood, the fence setting, cut that caused the problem, at what point it happened etc..It all helps give us a clear picture of what happened and how.

[Lee Schierer]

I'm glad you are okay.

It is always better to shut down than it is to back out of a cut.

[Justin Rapp]

Glad that you were not injured worse.

I have a hard time with partial information, and prefer photos of the set-up, so that i am sure that I understand exactly what the situation was. The size of the plywood, the fence setting, cut that caused the problem, at what point it happened etc..It all helps give us a clear picture of what happened and how.

Mark,

The plywood was small, 10 inches wide, 16 inches deep i was cutting a 3/4 inch wide slot a a few inches deep into the 16 end of the piece of wood. This required 2 cuts from the edge of the board to the hole i bored into the wood. When making the first cut, i was backing the board out after the cut was complete, and the black caught the board and kicked it back at me. I normally would shut the saw off and let the black stop before backing the board from the saw.

[Kevin Jenness]

I'm glad you weren't seriously injured. Offcuts at 60 mph leave a mark. I still bear a light scar on my forearm from a kickback 25 years ago.

Sawstop is good technology but its not a failsafe for bad procedure. A riving knife (which Sawstop has) might have prevented this kickback, but a better approach might have been to use a bandsaw or stop the tablesaw cut before completing the cut. As Mark said, photos or a drawing would better show what happened and might help someone else avoid the same problem.

[Mel Fulks]

Some are overly careful, cutting too…sloooleee.. that makes the wood heat up and move and pinch ….and “here’s the pinch-pitch”…”it’s a high fly hit to the gut ! “. Another tip : buy and USE a RIP blade ….and avoid R.I.P.

[Ronald Blue]

Glad it wasn't more serious. Hope you heal quickly. Don't be misled that a Sawstop will prevent kickback. A riving knife is helpful but not a guarantee. A sliding table saw would probably be the safest at preventing kick back. There are several videos on kickback if you google it. I always shut the saw off before reaching in by the blade to retrieve cut offs.

[Andrew Hughes]

I have several faint scars above my belt right side. I don’t call them scars apprentice marks is more accurate. I had a unisaw that lived to throw cuts offs. My current saw has never once thrown anything. Weird

[Frederick Skelly]

It's happened to me and I agree, it's scary as crap. Glad you are ok.

[Jim Becker]

Thanks for the poignant reminder... 'glad you are ok. It's amazing at how fast, hard and far that a table saw blade can throw a piece of wood, even a larger one. And with a typical North American cabinet saw or similar, the operator is often right in the line of fire, too. (I'm currently re-training myself because I'm using a cabinet saw in my temporary shop for space reasons and have been a slider user for a decade and a half with a completely different standing position)

[Warren Lake]

I stand where ever i need to stand to feed the material properly. You will guys feeding longer solid standing at a saw right hand side on the material. No. How anyone can get a kick back with a riving knife ? First saw ive ever had has one now and I feel like im using a crutch albeit a good one.

[Kevin Jenness]

Mark,

The plywood was small, 10 inches wide, 16 inches deep i was cutting a 3/4 inch wide slot a a few inches deep into the 16 end of the piece of wood. This required 2 cuts from the edge of the board to the hole i bored into the wood. When making the first cut, i was backing the board out after the cut was complete, and the black caught the board and kicked it back at me. I normally would shut the saw off and let the black stop before backing the board from the saw.

It sounds like a riving knife would have made no difference given the short length of the offcut. Stopping the cut before reaching the hole and finishing with a handsaw would have been safer.

[Warren Lake]

what does backing out mean, you pulled it back towards you?

[Justin Rapp]

I'm glad you weren't seriously injured. Offcuts at 60 mph leave a mark. I still bear a light scar on my forearm from a kickback 25 years ago.

Sawstop is good technology but its not a failsafe for bad procedure. A riving knife (which Sawstop has) might have prevented this kickback, but a better approach might have been to use a bandsaw or stop the tablesaw cut before completing the cut. As Mark said, photos or a drawing would better show what happened and might help someone else avoid the same problem.

Yes sawstop would not have helped me from this situation, but it made me think of 'what if'. And yes, after I had the kickback I realized the bandsaw would have worked way better for this.

[Justin Rapp]

what does backing out mean, you pulled it back towards you?

Yes. I've made this cut before, I always turn the saw off and let the blade stop before pulling it back. From now on, I do this one on the bandsaw.

[Kevin Jenness]

Offcuts at 60 mph leave a mark.

Correction- the rim speed of a 10" blade at 4,000rpm is closer to 120 mph. A good reason to stand out of the line of fire (although there's no guarantee that kickbacks will travel straight back).

[Jim Becker]

what does backing out mean, you pulled it back towards you?

Yes, stopped cut. Not an uncommon operation, but as the OP mentioned, best practice is to kill power before backing the workpiece out on a table saw.

[Mark Hennebury]

How long was the cut? how far from the fence to the blade? what size blade? how far above the table was the blade? Riving knife? Were you holding the board or using some sort of "safety" device ? if so what? push-sticks, gripper etc... ? The details are important to understand what and how it happened.


Mark,

The plywood was small, 10 inches wide, 16 inches deep i was cutting a 3/4 inch wide slot a a few inches deep into the 16 end of the piece of wood. This required 2 cuts from the edge of the board to the hole i bored into the wood. When making the first cut, i was backing the board out after the cut was complete, and the black caught the board and kicked it back at me. I normally would shut the saw off and let the black stop before backing the board from the saw.

[Justin Rapp]

How long was the cut? how far from the fence to the blade? what size blade? how far above the table was the blade? Riving knife? Were you holding the board or using some sort of "safety" device ? if so what? push-sticks, gripper etc... ? The details are important to understand what and how it happened.

The cut was about 4 inches deep, not even deep enough to get to a riving knife, if my saw even had one. The saw, 10" contractor type saw, with a 10" thin kerf forrest blade. I was holding the board with my hands. The board was 16 inches deep, the cut only 4 inches, so my hands were not close to the blade.

The point of all this is, if you make a slot with the blade and need to back out the wood, shut the saw. Better yet, use a bandsaw for this type of cut.

[Charles Lent]

A lot of attention here about how to make the cut, but nothing is being said about the pushing device, which can prevent this if the proper choice is made. A pushing device than not only pushes the work piece forward into the blade, but also holds the work piece down all the way through the cut, and in this situation, all the way backwards out of the cut, would have prevented this. Something as simple as a scrap of 2 X 8" with an "L" shaped cut on one edge will work fine for this. Using the 2 X 8" standing up with the "L" cut holding the work piece down and the foot of the "L" pushing the work forward will prevent the blade teeth from lifting and throwing the work piece at you. The point where the blade teeth are rising up out of the saw table is where the problem begins. If they catch on the side of the cut, the rising teeth can lift the work piece up off the saw table if there is nothing to hold the work piece down while it's being cut. A Grripper by Micro Jig is a good, but expensive table saw work pushing device, and I have two of these for hand over hand feeding of long work pieces on my Unisaw, but there are others, both DIY and purchased. You want to use something that not only pushes the work piece forward (and sometimes backward) past the saw blade, that also holds the work piece so the rising teeth on the back of the blade can't lift it, because if it does, it will throw it at you.

I would like to hear what the OP was using to feed the work piece into and back out of the blade? Without knowing this, the whole post is useless.

Charley

[Kevin Jenness]

A lot of attention here about how to make the cut, but nothing is being said about the pushing device, which can prevent this if the proper choice is made. A pushing device than not only pushes the work piece forward into the blade, but also holds the work piece down all the way through the cut, and in this situation, all the way backwards out of the cut, would have prevented this. Something as simple as a scrap of 2 X 8" with an "L" shaped cut on one edge will work fine for this. Using the 2 X 8" standing up with the "L" cut holding the work piece down and the foot of the "L" pushing the work forward will prevent the blade teeth from lifting and throwing the work piece at you. The point where the blade teeth are rising up out of the saw table is where the problem begins. If they catch on the side of the cut, the rising teeth can lift the work piece up off the saw table if there is nothing to hold the work piece down while it's being cut. A Grripper by Micro Jig is a good, but expensive table saw work pushing device, and I have two of these for hand over hand feeding of long work pieces on my Unisaw, but there are others, both DIY and purchased. You want to use something that not only pushes the work piece forward (and sometimes backward) past the saw blade, that also holds the work piece so the rising teeth on the back of the blade can't lift it, because if it does, it will throw it at you.

I would like to hear what the OP was using to feed the work piece into and back out of the blade? Without knowing this, the whole post is useless.

Charley

That is a good point, although I wonder if using a pusher that engages with the blade doesn't have its own potential hazards. Also, it is not completely clear but Justin's description suggests that the cut was so short that the offcut may not have contacted the teeth at the back of the blade but rather may have twisted while backing up and re-contacted the front of the blade, then ricocheted off the table or the back of the drilled hole. Without a slow motion video I don't suppose we will ever know for sure. I still think it would be safer to not complete the cut or to do it on a bandsaw than to rely on a pushing device to control the trapped offcut.

[Mark Hennebury]

It seems to me that this is a relatively safe operation with no need to shut the saw down or use pushsticks etc.. If the wood is kept tight to the fence during the operation this wouldn't happen. We all make mistakes, but you need to pay attention when working on machinery or you will get hurt. Doing this operation on the bandsaw or any other machine wont save you if you are not paying attention, all of the machines can hurt you in their own special way. Be thankfull that you didn't get hurt worse, and stay alert.

[Kevin Jenness]

message deleted

[Kevin Jenness]

It seems to me that this is a relatively safe operation with no need to shut the saw down or use pushsticks etc.. If the wood is kept tight to the fence during the operation this wouldn't happen. We all make mistakes, but you need to pay attention when working on machinery or you will get hurt. Doing this operation on the bandsaw or any other machine wont save you if you are not paying attention, all of the machines can hurt you in their own special way. Be thankfull that you didn't get hurt worse, and stay alert.

You may be right, but I think that cutting the off cut free and leaving it trapped between the blade and one side of the slot was hazardous. I think I misunderstood Justin's description, in that I got the impression that he was hit by that loose piece, whereas it seems to be the larger piece that hit him. Keeping that tight to the fence would probably have prevented the accident; on the other hand, the small offcut may have become trapped and caused the larger piece to twist away from the fence. In any case, the force from a bandsaw is directed down at the table rather than back toward the operator and less likely to generate a kickback, in my opinion.

You are absolutely right about paying attention every time you step up to a machine.

[Warren Lake]

I worked for an old Navy guy once. He would start a rumour in the factory at the back and wait for it to go through the whole company to come back and see what it turned into. that is what this post is like.

if you drilled a hole 3/4" four inches in from the end of the sized board then ripped in to stop at the hole times 2 likely ply or some other but not soild then there is no reason that that kicked at you. On top its the front of the blade and not the heal of the blade where 90 percent of flinging comes from,

[Mark Hennebury]

My point is, if you are careless while using machinery, you will get hurt.
You don't want to be careless on a bandsaw, While it wont do to you what a tablesaw will do, it will do to you what a bandsaws does, and you may need a tourniquet for that.

The accident appears to have been operator error to me. That could be from lack of knowledge, or experience or not paying attention, a momentary lapse is all it takes, it happens to us all. The best defense is to be focused on what you are doing whatever machine you choose to work on. All machines are dangerous in their own way.

The kick-back was not caused by the cut-Off because this was the first cut.

[Mark Hennebury]

Hi Warren,

That's funny, I worked with a guy that had been in the Marines, he did the same thing in the shop we worked in.


I worked for an old Navy guy once. He would start a rumour in the factory at the back and wait for it to go through the whole company to come back and see what it turned into. that is what this post is like.

[Warren Lake]

there was his one huge main tool box with three of us to use it. I used my own tools. One day the other employee took that tool box apart as it stunk. He didnt know and I didnt that the boss had rubbed the underside of the drawers with Limburger cheese. The employee washed the whole tool box but not under the drawers. It was weeks before he let him know. I didnt know what was going on found out later.

One day he asked the employee to change out some flourescents way high on a ladder in an industrial building. He said he had turned the power off but he didnt or screwed up., He knew the building inside and out so more likely on purpose but he was drinking as well. The employee got zapped came down furious got in his car and went home for a few days. He did come back to work and was still there when I left.

The owner was a big time old well to do family. They had a long friendship and so navy guy was there till he retired in his 80's. Guess we all have a different sense of humour but my view he was wasting time when an owner was paying for employees. He also cut fingers off more than once. Remembering now he had an accident once broke a bottle and said part was in his hand. He went to hospital and they said no and sowed him up. For a year something was hurting him. One day he came in and had cut his hand open and there was the piece of glass. Home surgery alchohal to help, so much for the doctor. Working there ended up being positive, right time and some good things came from it. I left had my shop, and ended up doing their work for many years.

[Justin Rapp]

My point is, if you are careless while using machinery, you will get hurt.
You don't want to be careless on a bandsaw, While it wont do to you what a tablesaw will do, it will do to you what a bandsaws does, and you may need a tourniquet for that.

The accident appears to have been operator error to me. That could be from lack of knowledge, or experience or not paying attention, a momentary lapse is all it takes, it happens to us all. The best defense is to be focused on what you are doing whatever machine you choose to work on. All machines are dangerous in their own way.

The kick-back was not caused by the cut-Off because this was the first cut.

This is exactly it - operator error. When I pulled be board back I must have let the board come slightly off the fence, causing it to go out of square, catching the blade and sending back at me. I've made similar cuts, maybe a few hundred by now over the years. I ALWAYS shut my saw down before pulling it back, just in case. Band saw will be safer next time.

[andrew whicker]

I've never backed it out, but I've done the tip up method if the board is long enough to overhang the table. Learned that trick from an old timer. Now, I just hold the piece steady at the stopping point and wait for the blade to turn down.

I'm not sure I understand why a pushstick would have worked any better. I use pushsticks, etc because I don't want to chop my hand off, not because it has more control. It doesn't.

[Mark Hennebury]

We all make mistakes.
We all have those times when we are not focused or paying attention, and we need to know not to work at those times.
That said, most everything in the workshop is dangerous, and is going to get you if you blink, if you are not knowledgeable, committed and focused on what you are doing.

Changing machines will prevent the kickback that you had with the tablesaw, but it wont fix the problem that caused it, which is, you did not maintain control of the workpiece! That was the problem, If you transfer that to another machine the results will be different for sure, they may be less or more severe.

You don't need to change machines, the operation is not a problem.
You need to understand why you let the workpiece go, and work on fixing that.

There is no reason not to do this operation.
The wood is plenty large enough to comfortably and safely hold with your hands, push sticks etc would not offer any improvement in control.
You just need to control the feed until completion of the operation (as you do in any operation) and you wont have any problems.

I am not trying to give you a hard time, there are lots of people that read these threads and they need to understand what causes accidents and how to prevent them. We all need to develop a safe way of working, and that doesn't mean pushsticks etc. it means being mentally prepared for what you are doing.
I have had my share of screwups over the past 50 years.



This is exactly it - operator error. When I pulled be board back I must have let the board come slightly off the fence, causing it to go out of square, catching the blade and sending back at me. I've made similar cuts, maybe a few hundred by now over the years. I ALWAYS shut my saw down before pulling it back, just in case. Band saw will be safer next time.

[andy bessette]

So I did something stupid...

Indeed. You skipped basic training. You do not back material out of the table saw! Also you could have simply lowered the table saw blade out of the cut, for a stopped cut. Or used a bandsaw, etc.

[Warren Lake]

blanket statement does not apply to that cut. 4" into the piece of material is nothing. Didnt have the material under control. IF its ply then you will dull your bandsaw, is a table saw cut and fine.

[jack duren]

Indeed. You skipped basic training. You do not back material out of the table saw! Also you could have simply lowered the table saw blade out of the cut, for a stopped cut. Or used a bandsaw, etc.

I've done it a thousand times, but I know what happens if I do it incorrectly. Now this time it was a learning experience...

[Warren Lake]

had enough stuff even being taught some of dont do that. Accidents are not bad when you end up okay because you understand. Best is learn it from pros and follow it. Likely more accidents than ever from the designer table saw market and big box stuff and the whole huge hobby market. How difficult could it be? Here is your car, it can do 0 -60 in under 2 seconds now go have fun.

Guy I learned the most from did a thing he was told not to do and changed one finger. Him telling me dont do that, then saying he was told and showing me struck home.

[Doug Garson]

Indeed. You skipped basic training. You do not back material out of the table saw! Also you could have simply lowered the table saw blade out of the cut, for a stopped cut. Or used a bandsaw, etc.
Not sure lowering the blade is a good alternate, difficult to maintain control of the workpiece while you look down and crank the blade down. Bandsaw is a better option as you and several others including the OP have suggested.

[Warren Lake]

lowering the blade is simple done it forever, or lift off the table which has other dynamics depending and I would not recommend that and its more suitable to other cuts.

Hold you work left hand, reach down and wind the blade down or press stop or on my saw just press stop with your knee either way. Knee is better.

[jack duren]

You wind that blade down, I may not look like Patrick Swayze, but I can live with the teeth I got..

[Warren Lake]

I wind the blade down, or turn the saw off with my knee or depending on the piece lift off the blade.

Made tons of jigs turning up blade or drop on and turn up more to full blade height to change the blade angle where I stop before making the next cut.

[andrew whicker]

Am I reading it correctly that slot means blade not all the way thru the thickness of the board?

[jack duren]

I wind the blade down, or turn the saw off with my knee or depending on the piece lift off the blade.

Made tons of jigs turning up blade or drop on and turn up more to full blade height to change the blade angle where I stop before making the next cut.


So.... Your a seasoned pro?

[Mel Fulks]

Warren is a many seasons pro

[Michael Schuch]

I can't say I have ever tried to backout a cut on a table saw. I use my radial arm saw for cuts like this.

[jack duren]

Residential cabinet, commercial or funiture company?

[Warren Lake]

call it whatever you want its just label, licensed cabinetmaker since 84. Own shop since 81. Mentor highly respected in the trade. What ive said there is no big deal its a minimal cut and didnt have potential to be bad unless something was done to cause it to kick back.

[jack duren]

I guess we're both seasoned pros. But I won't do it. I lost the tips to two fingers on a tablesaw in 1983 at a commercial shop. I won't dip down to lower blades. I will lower work on a running blade.. Forced into retirement after 37 years...I started in 1981. I got lucky and became a furniture maker for a company the last 7..

[Warren Lake]

if I drop on plywood to do four cuts to make a jig I wont pull back of course I have I get it and dont do it, ill lower the blade and move the part and come up again, Ive dropped on lots on jigs or dropped on raised higher after so the blade is more of an angle when I stop and less or no clean out as the cut points meet then you are left with the blank then knee turn off. Im not so focused on some stuff how i do it as I just do it. IF i understood what he did here which was go in four inches and stop and pull it back honestly I cant see where the kick back came from. I dont think that is a dangerous cut.

If you want to talk about pull back look at endless people on you tubes on a shaper with a carriage almost all of them pull back once they machine the part. Its already machined it does not need to see the cutter head again. Yes its way safer than the saw thing as its clamped in a carriage. All I can think is they drag it back as its more convenient to remove it. 90 percent of people do. Old guy gone id ask him why. He had most of the answers and didnt need to think after a lifetime in it.

Im no role model on machines and ive said that a few times but if I think a thing is safe which I do here, that is if I understand then ill say so. I saw a guy once tighten a blade on a hand plane, he slipped and sliced his chin badly. Better than the vein in the side of his neck. Headline would read man killed by angry Record Hand plane. Personally I think the slice some hair off his arm test would have been okay. Stuff can happen and does.

Knee turn off is still great, hands stay on the part blade comes to a stop unless you have a wadkin saw but it still stops usually by the next day.

[jack duren]

Running door parts forward and back is pretty common on rails . Often them flipped to do the other side. It's just safer. Shops don't usually put there must expensive guy on doors.

[Mark Hennebury]

Two mistakes were made as far as I can see;

1. Low blade;
It would seem to me that you would have to have the blade really low to have this happen.
If the blade had been full height the plywood would never have ridden up on it.
The only teeth in contact with the plywood would have been two or three at the front and they would be cutting down and pressing the plywood down.

2. Not controlling the work-piece through the operation.
I did ask the blade height, but I don't think he answered.

[Kevin Jenness]

My point is, if you are careless while using machinery, you will get hurt.
You don't want to be careless on a bandsaw, While it wont do to you what a tablesaw will do, it will do to you what a bandsaws does, and you may need a tourniquet for that.

The accident appears to have been operator error to me. That could be from lack of knowledge, or experience or not paying attention, a momentary lapse is all it takes, it happens to us all. The best defense is to be focused on what you are doing whatever machine you choose to work on. All machines are dangerous in their own way.

The kick-back was not caused by the cut-Off because this was the first cut.

Mark, I was mistaken about the offcut- poor reading comprehension on my part. My apologies. I agree completely that keeping the workpiece against the fence would have prevented the kickback. I do still think that cutting both sides of that slot free is problematic on a tablesaw and best avoided. Thinking through what can go wrong with a cut and being aware every time that the spinning blade is unforgiving is essential.

[Justin Rapp]

Two mistakes were made as far as I can see;

1. Low blade;
It would seem to me that you would have to have the blade really low to have this happen.
If the blade had been full height the plywood would never have ridden up on it.
The only teeth in contact with the plywood would have been two or three at the front and they would be cutting down and pressing the plywood down.

2. Not controlling the work-piece through the operation.
I did ask the blade height, but I don't think he answered.

Blade height was just above the surface of the plywood. This is another huge discussion we could have regarding the safety of blade height. I run my blade height at 1/8 inch over the cut depth. The lower the blade, the less damage to your hand if you make contact.

[Warren Lake]

i say take a photo of what you did this is all just a bunch of people guessing. Its not clear to me, maybe im just slow

[Justin Rapp]

i say take a photo of what you did this is all just a bunch of people guessing. Its not clear to me, maybe im just slow

I already tossed that piece in the trash and it's gone 2 days back. In a nutshell, just think about making a cut in a piece of plywood, 4 inches deep and than backing it out.

[Mark Hennebury]

False sense of security.
If the blade had been set high even up to full height, you would not have had the kick-back, even if you did not have proper control.
With the blade set that low, you have given yourself a false sense of security, you were actually making the operation the more dangerous and unforgiving for that operation.

I set my blade height to best suit the operation. No set formular, a judgement made for each operation.

I find the concept of the " rules" is scary and probably the root cause of most accidents. People need to apply analysis and judgement, attention and focus to each operation.
Following a set of rules allows you to not think about what you are doing.
The "rules" may be great in one instance and deadly in another.
The "rules" that are often quoted were not handed down from God, they were written by man, quite often men that don't know what they are talking about, then they are repeated and written in books and repeated some more until everyone believes them.

What we should do is analyze and understand the machines, the tool geometry, the wood and the process, then develop the habit of thinking about the whole operation and how to do it with reasonably safety.
There is no absolute safety, (unless you are already dead) So you have to have the mindset of working within what is reasonable for you, what you feel comfortably doing. And put an effort into learning to understand the relationships of cutting tool, machine, material, process and you.

There are no "rules"




Blade height was just above the surface of the plywood. This is another huge discussion we could have regarding the safety of blade height. I run my blade height at 1/8 inch over the cut depth. The lower the blade, the less damage to your hand if you make contact.

[Justin Rapp]

False sense of security.
If the blade had been set high even up to full height, you would not have had the kick-back, even if you did not have proper control.
With the blade set that low, you have given yourself a false sense of security, you were actually making the operation the more dangerous and unforgiving for that operation.

I set my blade height to best suit the operation. No set formular, a judgement made for each operation.

I find the concept of the " rules" is scary and probably the root cause of most accidents. People need to apply analysis and judgement, attention and focus to each operation.
Following a set of rules allows you to not think about what you are doing.
The "rules" may be great in one instance and deadly in another.
The "rules" that are often quoted were not handed down from God, they were written by man, quite often men that don't know what they are talking about, then they are repeated and written in books and repeated some more until everyone believes them.

What we should do is analyze and understand the machines, the tool geometry, the wood and the process, then develop the habit of thinking about the whole operation and how to do it with reasonably safety.
There is no absolute safety, (unless you are already dead) So you have to have the mindset of working within what is reasonable for you, what you feel comfortably doing. And put an effort into learning to understand the relationships of cutting tool, machine, material, process and you.

There are no "rules"

This is really a call of judgment, what is safer, a higher blade or risk of kickback. Kickback would have been avoided if I did what I always do for this type of cut and shut it off before moving the piece. I'll take the lower blade. It's personal risk assessment when you touch machinery. Do what is safe for your situation and for your level of knowledge. Do I feel comfortable with a blade 2.5 inches high instead of 5/8 high? If I get hit from the kickback, and fall face first into my saw, what will do more damage, 5/8 blade or 2.5 inches of blade? I'll take the punch to the stomach from the kickback and keep the blade low.

[Mark Hennebury]

Justin, I am glad that you were not hurt to bad,

Thanks for posting your experience, and for the discussion, hopefully discussing accidents from a variety of points of view will be of some help to others.

[Malcolm McLeod]

...

There are no "rules"

Here's a story about another man with apparently similar beliefs (https://www.nbcdfw.com/news/local/addison-plane-crash-that-killed-10-was-pilot-error-ntsb-says/2635615/).

[Edwin Santos]

False sense of security.
If the blade had been set high even up to full height, you would not have had the kick-back, even if you did not have proper control.
With the blade set that low, you have given yourself a false sense of security, you were actually making the operation the more dangerous and unforgiving for that operation.


Would you further explain your thought process behind these two statements?

I have a suspicion that it has to do with blade geometry and the changing physics of cutting force at different blade heights, but I'm asking for myself, just to be sure and because this thread has taken a educational turn the answer may be helpful to others. Thanks

[Mark Hennebury]

Bored Malcolm?

If your in the mood to go a few rounds, i am always game, as long as you back up what you say.

So, I just have to run out to the town, that should give you some time to explain what you mean.
Catch you later.



Here's a story about another man with apparently similar beliefs (https://www.nbcdfw.com/news/local/addison-plane-crash-that-killed-10-was-pilot-error-ntsb-says/2635615/).

[Malcolm McLeod]

Bored Malcolm?

If your in the mood to go a few rounds, i am always game, as long as you back up what you say.

So, I just have to run out to the town, that should give you some time to explain what you mean.
Catch you later.

So no pilots in the family..?? I'll be happy to explain (and quickly, too).

The Beech King Air crashed largely due to a missed throttle lock and a selectable auto-feather feature on the props. Checking them would have saved 10 lives. These checks are both part of the pre-flight checklist (aka the 'rules' to operate the aircraft).

Friends of the pilot indicate he had a disdain for use of those rules. Take care.

[Warren Lake]

I know people that have lost fingers on jointers that had their guards in place.

Original guy made a post, maybe screwed up in some fashion, never clear about the cut not showing what he did. Was there one cut to the hole or two. it two then there was an off cut which changes dynamics. Was it four inches in from the leading edge then backed out?

[Mark Hennebury]

You must be quite desperate to stir up some shit. .
You trying to compare what I said into what caused an air crash.
That's quite a stretch... even for you.

No, no pilots in the family,

My best friend was the pilot of a helicopter that crashed killing him and nine others, Something to do with a catastrophic mechanical failure 2 mins after take-off on it's first flight after being re-assembled.
He was by all accounts an excellent pilot, meticulous with his safety checks,
But he didn't build the helicopter, and didn't pack it and ship out the resort islands in the Indian ocean and put it back together. I believe that's Engineers that did that.

I also had another pilot friend that died in a fixwing crash at an airshow.

But none of that has anything to do with this discussion.

If you have something to add to the discussion please do so.

Maybe with your Engineering background you could better explain the mechanics of cutting with a low blade and a high blade, so that everyone is clear as to why I am so dangerously wrong.

Give a shot Malcolm.

This is how they ship a helicopter.

467475


So no pilots in the family..?? I'll be happy to explain (and quickly, too).

The Beech King Air crashed largely due to a missed throttle lock and a selectable auto-feather feature on the props. Checking them would have saved 10 lives. These checks are both part of the pre-flight checklist (aka the 'rules' to operate the aircraft).

Friends of the pilot indicate he had a disdain for use of those rules. Take care.

[Mark Hennebury]

Hi Edwin,

I will be more than happy to explain my statements to you.
I will do up a sketch and get back to you a bit later.


Would you further explain your thought process behind these two statements?

I have a suspicion that it has to do with blade geometry and the changing physics of cutting force at different blade heights, but I'm asking for myself, just to be sure and because this thread has taken a educational turn the answer may be helpful to others. Thanks

[Malcolm McLeod]

...
But he didn't build the helicopter, and didn't pack it and ship out the resort islands in the Indian ocean and put it back together. I believe that's Engineers that did that.
...
Truth be told the listed tasks were probably (at least legally should have been) conducted by certified aviation mechanics, depending on what aviation authority had jurisdiction, but I'm wandering now. ETA - My condolences for the loss of your friend.


...
You trying to compare what I said into what caused an air crash.
...
Your post closing would seem to indicate a similar disdain for rules, as per the referenced pilot. Checklists are a good thing, even if mental only. Sincerely, please be careful this attitude does not turn into a tragedy - regardless of the perceived magnitude.


...
Maybe with your Engineering background you could better explain the mechanics of cutting with a low blade and a high blade, so that everyone is clear as to why I am so dangerously wrong.

Give a shot Malcolm.
Actually agree with you, and practice the same at times - depending on where my hands fit. A high blade's cutting action ("force vector" for those so inclined) is largely down into the (TS) top; a low blade's cut vector is biased toward the operator. Should we talk about the forces being tangent to the tooth's path?

But as with all things, there are compromises. A 'high' blade is less likely to kick back and more likely to remove a finger. Reverse these for a 'low' blade, of course.

So, I'm afraid I can't help much with the "dangerously wrong" aspects (or the Engineer-angst). Let's all be careful out there!

[andy bessette]

Blade height was just above the surface of the plywood. This is another huge discussion we could have regarding the safety of blade height. I run my blade height at 1/8 inch over the cut depth. The lower the blade, the less damage to your hand if you make contact.

You really did miss basic training. That low a blade height is simply asking for trouble. You would do well to abandon that foolish practice.

[Thomas McCurnin]

To add my two cents to this, I have an opinion which may be contrary to others.

I think backing off the cut, even while the blade is spinning is not a problem per se. However, when doing such cuts, I would have spring type hold fast aka hold down aka feather board mounted on the miter slot to press the piece into the fence. I think I could use a push stick to push the piece down to the table, but if not, a similar hold down installed at the fence pressing down would hold the piece in place.

Make the cut, back it out. Nothing will move, so there is nothing for the blade to make contact with to cause any kickback.

If I could, I would use my knee to shut off the saw, but only if that could be done safely while at the same time maintaining pressure on the piece.

[Warren Lake]

so you want to possibly put some pressure onto the blade? Ive seen people set up feather boards that just dont get it.

My view ask a question then show what you are doing. Kreskin does not read this forum.

[Mark Hennebury]

As much as I enjoy jousting with you Malcolm, lets at least try to stay on the same planet.

If you want to insult me, that's fine, knock yourself out.
If you want to talk about aircrashes, start another thread.
If you want to discuss the issue bought up on this thread, I am more than willing to discuss it, It may actually help prevent someone from getting injured.

Your convoluted attempt at tying me into this air crash is pretty sad.

I never mentioned anything about not doing your own checklist, that was just you making shit up, trying to muddy the water and distract from what i actually said.

I do have a disdain for "rules" in relation to woodworking, I have heard a lot of them, mostly by people that don't know what they are talking about.

I spoke of "rules" quoted by woodworkers, as in this discussion on a woodworking forum.

So lets discuss the rule mentioned early:

"Indeed. You skipped basic training. You do not back material out of the table saw! "

Who made that a rule?
Why should it be a rule?
What is the problem, ( in reference to the cut in this discussion) with backing out of the cut? What is the saw going to do?
If you control the wood, your hands are not close to the blade, you hold the wood down to the table and into the fence, when you feed in and when you feed out, where is the problem?
With the blade up or down nothing is going to happen unless you make it. You may make a slip and get hurt. You could use a bandsaw, you don't want to make a slip on one of those either. A butcher told me once how customer reached across his bandsaw to point to the piece of meat he wanted, didn't end well. A plastic surgeon that I did some work for told me about a guy that ran his hand over a jointer. One day when I went out to see the surgeon about doing some work on his yacht he had just spent the day reattaching some ones hand, he chuckled and said that us woodworkers paid for his yacht, these things I keep in mind. The workshop is an unforgiving place.

I don't entrust my safety to someone else. My machines are nasty, my table saw has an 18" blade that protrudes 5 1/2" inches, so if it gets you it's going to make a mess.

People need to understand the machines, and make their best judgement for their own safety. That is not to say that all of the rules are wrong or right, just that you need to examine them with an open mind and if someone states a "rule" to you make sure that they can explain it.

Picture 1. is a representation of a 10" blade cutting 4" with minimum blade height.
Note. the teeth that are in contact with the wood. Front teeth are running down, teeth at the back running up, on the top running forward.
Any movement of the wood away from parallel to the feed will bring the back of the wood to press into the teeth at the back, lifting and sending it your way. Depending on what way you move the wood will determine whether it comes straight back or rotates around like a frisbee, either way will hurt.

467481

Picture 2.
raised blade, 4" into the rip. Note the teeth that are in contact, Note that they are pressing down.
No need to get close to the blade with this size piece of wood.
You should have a crown guard to cover the blade anyway.
I almost forgot to mention; if you tilt the wood away from parallel to the feed It won't kick back!

467483

Keep in mind that the fence plays a part in this.
Fences can be parallel or toed in or out.
If they are toed one way or the other they will run one side or the other of the sawcut against the rear of the blade. with a low blade this is more likely to try and kickback.
Even a parallel fence, may flex when you push the wood against it and can rebound when you release the pressure, putting the wood into the back of the saw.


467484








Truth be told the listed tasks were probably (at least legally should have been) conducted by certified aviation mechanics, depending on what aviation authority had jurisdiction, but I'm wandering now. ETA - My condolences for the loss of your friend.


Your post closing would seem to indicate a similar disdain for rules, as per the referenced pilot. Checklists are a good thing, even if mental only. Sincerely, please be careful this attitude does not turn into a tragedy - regardless of the perceived magnitude.


Actually agree with you, and practice the same at times - depending on where my hands fit. A high blade's cutting action ("force vector" for those so inclined) is largely down into the (TS) top; a low blade's cut vector is biased toward the operator. Should we talk about the forces being tangent to the tooth's path?

But as with all things, there are compromises. A 'high' blade is less likely to kick back and more likely to remove a finger. Reverse these for a 'low' blade, of course.

So, I'm afraid I can't help much with the "dangerously wrong" aspects (or the Engineer-angst). Let's all be careful out there!

[Edwin Santos]

Mark,
I didn't mean to put you to the trouble of making diagrams to answer the question I posed. But I appreciate that you did, and they demonstrate where I thought you were going with your earlier comments.

In 25 years I have had only one table saw kickback incident, and indeed it was when the teeth were only minimally above the surface of the cut. But there were other factors going on, one of which was that I was cutting a piece of plywood, fairly square, but where the cut was pretty far (maybe 16" from the fence). The physics of the workpiece size made it much easier for the plywood to catch and rotate away from the fence, and then the low blade height only further encouraged the kickback. You raise other issues such as the fence toe or flex situation, and then there is the phenomenon of tension present in hardwood that can create problems. I happen to believe that the physics of high tooth count blades and worse yet, dado stacks, will escalate the force vector even further and introduce yet another factor to consider.

I was taught early on that everything in woodworking happens for a logical reason. These threads are great for dissecting the cause and effect of why what happened happened.
I will echo your point that understanding the physics and dynamics of every machine, every cutter, and the material, is important and every situation becomes a calculated product of a handful of factors to consider.
Not trying to inflame the debate but I agree that the calculation is too situational for one-size-fits-all rules.

Edwin

[andy bessette]

..."Indeed. You skipped basic training. You do not back material out of the table saw! "

Who made that a rule?
Why should it be a rule?...

Table saw 101 basic training rule. You must have missed it also.

Pretty simple stuff--common sense, really--obvious to most who have even only rudimentary woodworking experience. Wood goes in one end of the machine, the infeed table, and comes out the other, the outfeed table. Self explanatory, you might say.

Another is "Thou shalt not touch spinning saw blades." But a few here ignore that simple rule as well. Maybe missed basic training. :)

[Mark Hennebury]

Hi Andy,

Apparently I missed it Andy, is that your rule? or did you read it somewhere? Can you explain why it is a rule ? because I don't understand. And I have a rudimentary woodworking experience.
So, Smiley faces and jokes aside

This is actually quite a serious discussion with real consequences for those that screw up, so maybe you can elaborate, explain to those like me that don't posses that "common sense"


Table saw 101 basic training rule. You must have missed it also.

Pretty simple stuff--common sense, really--obvious to most who have even only rudimentary woodworking experience. Wood goes in one end of the machine, the infeed table, and comes out the other, the outfeed table. Self explanatory, you might say.

Another is "Thou shalt not touch spinning saw blades." But a few here ignore that simple rule as well. Maybe missed basic training. :)

[Mark Hennebury]

Edwin, I was happy to do the sketches, I need to keep up on the drafting anyway,


Mark,
I didn't mean to put you to the trouble of making diagrams to answer the question I posed. But I appreciate that you did, and they demonstrate where I thought you were going with your earlier comments.

In 25 years I have had only one table saw kickback incident, and indeed it was when the teeth were only minimally above the surface of the cut. But there were other factors going on, one of which was that I was cutting a piece of plywood, fairly square, but where the cut was pretty far (maybe 16" from the fence). The physics of the workpiece size made it much easier for the plywood to catch and rotate away from the fence, and then the low blade height only further encouraged the kickback. You raise other issues such as the fence toe or flex situation, and then there is the phenomenon of tension present in hardwood that can create problems. I happen to believe that the physics of high tooth count blades and worse yet, dado stacks, will escalate the force vector even further and introduce yet another factor to consider.

I was taught early on that everything in woodworking happens for a logical reason. These threads are great for dissecting the cause and effect of why what happened happened.
I will echo your point that understanding the physics and dynamics of every machine, every cutter, and the material, is important and every situation becomes a calculated product of a handful of factors to consider.
Not trying to inflame the debate but I agree that the calculation is too situational for one-size-fits-all rules.

Edwin

[andy bessette]

...Andy, ...explain to those like me that don't posses that "common sense"

Read the OP's first post and you may find subtle hints .

[Warren Lake]

you are making up rules andy. After learning stuff to do and not do ive spent over 40 years on my own saws, likely less than a number of other guys here im sure.

Mark thanks for taking the time to do that. I get it most of us do, its clean and clear. The sharpness of the blade and tooth configuration enter into this as well, if a blade is dull the low blade will have more lift on the material. Ive changed out some tooth grinds that should have worked well on ply. New world for me now with the slider having up to 16" blade. Its different in good ways.

You drew exactly what was in my mind for the circle and stop cut I questioned it further that if the second cut was made I think you did as well earlier it was in my mind as well. that is a game changer second cut and a trapped offcut. You drill a hole you cut into to that hole and stop, you do the same at the other side of the circle that is why you are doing it but there was no mention of that part of it or I guess mission was aborted after the first part.

Cut in from ends many times and pull back, there are no issues with a 4' deep cut. You are in to the heal of the blade you are front of the blade, whole other world than the back. Its still not friendly but the back is angry.

The high blade when doing cutouts for jigs is important as the amount the blade cuts high is so much less that when you are working to a top stop line you get a lot closer to your line with out under cutting at the bottom if that makes sense. i did tons of cut outs for jigs to use for router templates you can make any size nicely with a router with a template bushing in the base.

This is not a dangerous cut the first cutting 4' in. Id be thinking about not much more. Id determine that on my saw what is right look at it and run it to see what is comfortable. It will step up in seriousness quickly. Kick backs happen at a speed that almost defies logic.

The second cut there you better get your stuff together before you do that. Unless you needed a round end I would have done that cut with Dadoe blade.

[Warren Lake]

I cut in 4" deep 25 times with a small piece of baltic so maybe five by ten inches didn't look it was sitting there, then cut in 6" several times. There was zero pulling in anyway on any of those cuts. Even at six inches which is past half way on the blade there was zero tendency to kick back as it was not in contact with the blade or any teeth, the blade plate is smaller than the kerf. If that ply was larger I could have gone further. Higher the blade the safer the cut, the force is pretty much down with no tendency to lift up. As well the low blade does not work to your advantage to cut to a stop point as it has a long arc rather than a smaller area from the high blade. This is less clean up time on jigs or often the blank just falls out with no work at all.

[Justin Rapp]

Read the OP's first post and you may find subtle hints .


So are you saying I have no common sense?

[Malcolm McLeod]

...
There are no "rules"


...
I never mentioned anything about not doing your own checklist, that was just you making shit up, trying to muddy the water and distract from what i actually said.
...
467484

I hope I didn't mis-quote you ... It seemed clear there are no "rules", so what do you base your woodworking table-saw cutting anti-kickback techniques checklist on?

Are rules and checklists not the same thing, or at very least interdependent? (To me they are.)

And please let me know what you found insulting in my posts. I'll gladly remove it.

[Zachary Hoyt]

I have usually kept the blade low, especially when cutting plywood. I get a lot more tearout of the bottom ply if the blade is high.

[andy bessette]

I have usually kept the blade low, especially when cutting plywood. I get a lot more tearout of the bottom ply if the blade is high.

You can eliminate the tear-out by scoring it first with the blade set to barely penetrate the bottom of the plywood.

[Zachary Hoyt]

That makes sense, I'll do that next time I'm cutting plywood.

[Warren Lake]

high low there is in between as well, was he cutting cross grain? did any chip out matter, I cut cross grain not slow, had a combo blade on with no support from an old broken insert below, chip out was not much even with the blade highest.

Operator error plain and simple. Never said if it was first cut or second cut issue.

Sawstop will do zero in this case. I went in and out 25 times, nothing not even the blade rubbing on the material likely six inches into the blade.

Ronald you posted a riving knife is helpful, its not he was on the front of the blade.

[Kevin Jenness]

. Never said if it was first cut or second cut issue.

Warren, actually he did say in his second post that the kickback happened while pulling the piece back after the first cut- there was no loose offcut.

I was cutting out a slot from a piece of plywood, making two cuts to a hole 3/4 inch hold I made in the board. Well instead of shutting the saw before backing out the board, I pulled it back and the blade caught the wood, turned it a bit and shot it at me.

The plywood was small, 10 inches wide, 16 inches deep i was cutting a 3/4 inch wide slot a a few inches deep into the 16 end of the piece of wood. This required 2 cuts from the edge of the board to the hole i bored into the wood. When making the first cut, i was backing the board out after the cut was complete, and the black caught the board and kicked it back at me.


I too missed that detail. It would seem that the workpiece was not held tight to the fence and the low height of the blade enabled the kickback. Had both sides of the slot been cut that would have introduced another factor.

[Warren Lake]

simple photo so people can see what is going on. You really think Mark should have to go to all that trouble to explore what happened and teach some realities.

Operator error, Marks polite, Im blunt. shut off back out take your pick safe either way. Safer the higher the blade is. Ill do it 25 times with a low blade and still have no issues, understand the reality of high blade and dynamics change and explained further the advantage in cutting out jig templates from a high blade.

[Justin Rapp]

Ok we have BEAT this to a dead pulp folks. I stated right away there was operator error. I been asked the same questions a few times, but people don't read the thread, just the first post and respond, even though there is 82 replies already.

There are multiple ways to do this safely, or use another tool instead. The point of this thread was not to have people argue, but to learn from my mistake.

[Christopher Charles]

Jason,

Thanks for your original post and courage to remain engaged with the thread.

Best,
Chris