RAS Push Cutting Myth

[John McClanahan]

Here's what happens when you use a radial arm saw all wrong. I won't argue advantages of a negative hook blade. When the subject of pull cutting vs push cutting, all kinds of warnings pop up to only cut on the pull, never push the blade into the board. Well, I have owned my RAS for 30+ years and push cut with it. A lot of folks here think I have some sort of death wish for even thinking of push cutting. :eek:

So, I set up this recently tuned-up 1961 DeWalt Power shop radial arm saw with an old 10" combination table saw blade with positive hook teeth. I am right handed, and normally control the saw with my right hand, but to keep the view clear I am using my left hand.

Hold my beer and watch this: :D


http://www.youtube.com/watch?v=12XQR9DxhHc


I can't figure out haw to embed the video, sorry.

John

[david brum]

Dang, I can't get youtube to play it. Is the video working for others?

[Cary Falk]

Worked for me. It's easier for me to line up the cut on the pull. That's just the way I was raised.

[Ryan Baker]

Works for me.

I don't have any problem with the push cut. It's having an aggressive positive hook blade on it that can make things get scary (whether pushing or pulling). Backing off the hook angle makes a huge difference.

I'm not sure who was complaining about push cuts. Seems like the last thread I read about the subject had people pretty much split in half about push vs pull, and many who do both at times. Seems like a good way to get more tearout on the top of the board, and it probably wouldn't be a good choice in really thick material (don't want the blade pulling up more than it is pushing against the fence). Push cutting is more controllable with a positive hook blade beacause it won't climb cut and bite in too hard. People have been doing it for a long time. If it works for you, more power to you.

[Matt Day]

I'm glad to see this post. I've always been told and read on forums that you always pull cut with a RAS. The handful of times I push cut with it I felt like I was doing something bad and someone might be watching.

And I've always felt that, even with a negative hook blade, that the saw wants to come straight back at me during the pull cut. So when I'm cutting thick stock or something like maple, I'm pulling back but I have to tense up and be ready to push back on the saw to control it. If that makes any sense...

Should a negative hook blade or positive hook blade be used when push cutting?

[Ryan Baker]

Matt, that makes perfect sense (to anyone who has used a RAS). The negative hook blade will reduce the tendency of the blade to "climb" and race out toward you. I think you would be better off with a negative hook any time you can on a RAS, but it matters more when pulling than when pushing.

[Bill ThompsonNM]

When I was in my teens I tried cross cutting a thin piece plywood with my Dad's RAS with a push cut. It flipped up as the front end lifted broke the plywood with a loud bang sending chards all over. Not as exciting as my Dad ripping and sending a 3 foot piece through the garage door but too exciting for me. I've pulled through my cuts without incident since.

[Joe Angrisani]

.....It flipped up as the front end lifted broke the plywood with a loud bang sending charades all over.....

I love playing RAS charades. But I always have trouble when I get "negative hook". How would you guys act out that one? "Hook" is pretty easy, but I have trouble getting people to understand that I mean "negative" and not "opposite" or "reverse".

:D

[Rich Riddle]

Personally I liked the way he kept slamming the blade into the saw so hard that it made the entire saw jump up and backwards. We don't need no stinking safe or best practices. I need folks like that. My wife needs customers in the operating room. She needs to pay off that new Volvo.

[johnny means]

What's the RAS push cut myth?

[Rich Riddle]

What's the RAS push cut myth?

It's unsafe to cut wood with the push stroke with a radial arm saw instead of cutting the wood on the pull stroke. You have to insert the wood after you have pulled the blade toward you (even if the saw isn't running).

[Jeff Duncan]

I have to admit I'm puzzled by the myth....what would be the difference push cutting with a RAS vs push cutting (normal operation) with a sliding chop saw?

Now practicality wise is a different story. Push cutting with a RAS is not really all that practical or ergonomic. Not to mention you lose a good deal of capacity trying to push cut. Other than that I don't see the problem?

JeffD

[Rich Riddle]

I have to admit I'm puzzled by the myth....what would be the difference push cutting with a RAS vs push cutting (normal operation) with a sliding chop saw?

Now practicality wise is a different story. Push cutting with a RAS is not really all that practical or ergonomic. Not to mention you lose a good deal of capacity trying to push cut. Other than that I don't see the problem?

JeffD
An old debate here at SMC. Here are some of the other viewpoints:

http://www.sawmillcreek.org/showthread.php?133866-Pull-or-push-a-radial-arm-saw

Regardless of what stroke one chooses, slamming the saw to the point of moving it isn't a safe idea.

[Lee Schierer]

I don't think I would try that with thicker stock........the thicker the stock, the more the blade will tend to lift.

[eugene thomas]

In my shop i use tools however i want, but making video showing cut. Really......

[Jim O'Dell]

I'm glad to see this post. I've always been told and read on forums that you always pull cut with a RAS. The handful of times I push cut with it I felt like I was doing something bad and someone might be watching.

And I've always felt that, even with a negative hook blade, that the saw wants to come straight back at me during the pull cut. So when I'm cutting thick stock or something like maple, I'm pulling back but I have to tense up and be ready to push back on the saw to control it. If that makes any sense...

Should a negative hook blade or positive hook blade be used when push cutting?

Matt, I feel exactly the same. In fact, I had a couple instances with my original RAS of the climbing phenomenon actually stalling the motor. I'm sure the wood moved and put the blade in a bind that stalled the motor, but I didn't like it. It was always a work out cutting big boards because of having to stay so tensed up when pulling the the blade slowly through the cut.

Yeah Joe, it's the same issue when trying to explain positive and negative camber. The you get in to the discussion of off camber for a corner and you watch the eyes glaze over.:D Jim.

[Jerome Stanek]

I cut a lot of extruded aluminum and use the push to get a good cut.

[John McClanahan]

Personally I liked the way he kept slamming the blade into the saw so hard that it made the entire saw jump up and backwards. We don't need no stinking safe or best practices. I need folks like that. My wife needs customers in the operating room. She needs to pay off that new Volvo.

I did that to demonstrate that even with a positive hook blade and gross over feeding, the board doesn't rise up. The saw wasn't jumping backwards. I moved it under the overhead light for the video and didn't fully adjust the leveling feet.

John

[John McClanahan]

I don't think I would try that with thicker stock........the thicker the stock, the more the blade will tend to lift.

Lee, you are probably right.


John

[Pat Barry]

The way you have the blade setup, what you call positive hook, means the blade is cutting from the bottom up and that is unhealthy, unwise, and potentially very unsafe. With that setup you'd be better off pull cutting. Or am I missing something?

[Rick Potter]

No myth, manufacturers recommendation.

As I understand it, the saw is designed to have the blade parked behind the fence for safety. The makers recommend you use a pull cut and return the saw to the parked position. This avoids having your hands near the blade when it is running.

Watching the video shows your hands reaching around the moving blade to adjust your cuts, when it would be safer to have the blade in the parked position. I am sure, John, that you are very carefull while doing this, but are you sure you are comfortable recommending that a novice woodworker do it this way? It is akin to saying it is ok to reach around the back of a table saw blade while running. If the novice accidently bumps the handle while his hands are back there the blade is going to move.

I am sticking with the manufacturers recommendations. Make like a chicken and pullet.

Rick Potter

PS: Quotes from the DeWalt 790 owners manual.

1: Return carriage to full rear postition after each crosscut.
2: Never reach around moving blade.
3: Place material on work table, against guide fence, draw saw blade across for the cut just far enough to sever wood.

Note that #3 is saying that you don't need to have the blade out in the full extended position where you could get your hands around it.

[Steve Peterson]

My miter saw specifically mentions in the manual that it is best to bring the blade in front of the work, then lower it into the cut and push to the back. This is not possible on a RAS (unless you want to crank the handle 100 times for every cut).

Steve

[Chip Lindley]

=johnny means;2046905]What's the RAS push cut myth?

Reply by Rich Riddle: It's unsafe to cut wood with the push stroke with a radial arm saw instead of cutting the wood on the pull stroke. You have to insert the wood after you have pulled the blade toward you (even if the saw isn't running).

That is my take exactly! After 30 years of RAS usage, first with a Sears 10" for too many years, and now a monster Rockwell 7.5hp (max. 18" blade) but using a 14" blade and 14" guard. I do not want that huge amount of gnarly blade staring at me as I insert the workpiece! Without appropriate "hold downs" the push stroke can and will lift a board off the table and into the guard. This is not much of a problem with a powerful saw which refuses to bog down, even croscutting 3" stock. Much more of a problem on an under-powered saw such as the Craftsman, if the blade should bind in the least. But that exposed blade before each cut is still an alarming problem for me.
.
On the other hand (if you still have 5 fingers) the pull stroke can also have it problems. The blade can overfeed to jam into the stock, even with a negative hook blade. Neg. hook is not the "end-all panecea" by any means. It can also be abused to jamming. I have found that controlling the rate of feed with a stiff forearm makes for successful but tiring use of an RAS.

It works for me....but its YOUR shop and your health!

~~Chip~~

[Rich Riddle]

It works for me....but its YOUR shop and your health!

~~Chip~~


Chip, you said it best. I hear horror stories about tools from my wife on a very regular basis, stories involving serious injuries, trying to reattach body parts in surgery, or at times unexpected amputations. None of the stories involving power saws is every minor. As often as she discusses those injuries, it keeps power tool safety at the top of my mind.

I like many old tools, but some of the newer safety features far surpass what former machines could offer. When dealing with old tools, at a minimum I follow their recommendations regarding use and safety. I wish all woodworkers well no matter what safety choices they make.

[Mark Bolton]

I always thought the issue was actually the Pull-cut issue with the cheaper RAS? when the user had their hand/arm near the cut, pulled the saw into the work, the saw then "rode up" onto the work piece (like a tire on a car driving down the road) at which point the flexure in the cheaper saws allowed the blade/head/arm to bend and the blade would lay over at an angle and cause the arm to rotate/swing while the saw (car) was driving over your work piece (and your arm) and when the process was complete you would be left with a RAS motor free-wheeling at the end of the arm, clear of the work piece, an arcing slice on the work piece (which was suppose to be a straight cut/dado) and a freshly severed human arm laying atop the work piece.

There is always the issue on the push cut (just like a slider) of the piece lifting up into the blade but I always interpreted the "radical harm saw" as the fact that the pull cut is a climb cut and with cheaper saws (craftsman) there was a lot of bloodshed/potential bloodshed.

[John McClanahan]

I guess I should point out that this is not a "How To Use Your Saw" video. It is only to demonstrate that the blade isn't lifting the stock. The alignment of this saw was recently checked, and the blade is running true. If the saw was out of alignment the results would probably be quite different.

I should also ad that this is not how I use my saw.

I didn't hold the board during the cutting, and only moved it an inch or so for the next cut. I also never let go of the saw. When finished, the board was 13" long. If you hold stock in the miter gauge of your table saw, your fingers may get closer to the blade than this.

When I pull the carriage out all the way and start the motor I have nothing to fear, as it is as close to me as it can get. The only way it can go is farther away.

For everyone that prefers to pull cut, continue to do so. I'm not out to change your ways.


John

[johnny means]

I don't see how cutting that way is any more dangerous. But, I wouldn't want to position my work piece behind the blade like that. This would be especially hairy with a larger RAA. Imagine reaching across a 30" tablew trying to position a door behind a 20" blade. IMO, the video shows poor shop habits.

[Mark Bolton]

John,
I dont see anything wrong in your video whatsoever. Its likely the EXACT procedure for cutting with any slider on the market today. Our slider has warning stickers on it clearly visible to the operator that say to place your work, draw the slider back, lower the saw head, and push through the work. These are much flimsier saws than your slider.

I have several times had issues with pieces lifting into our slider. No different for a RAS. Its just something that can happen. Dull blade, short piece, rushing, nasty grain, on and on.

Procedure, and procedural over thinking can often be a bad thing....

My thoughts are always just stay on your toes and the rules are a little pliable..

10 and 10 here..

Mark

[Joseph Tarantino]

pull cut, postive hook angle blade, workpiece unsecured on RAS table top (this is not how i normally work!!!)


http://www.youtube.com/watch?v=8In_nKqW1DA

what's all the fuss about? i have, when dadoing 4x4s for deck posts, stalled the motor if i wasn't careful about the feed rate. with almost 3/4" of dado cutters and chippers spinning around, they are bound to grab the material if the saw carriage isn't carefully controlled and attempt to "move" towards the operator. easily controlled if operator's paying attention. but, that aside, since the blade is spinning down into the table, the workpiece shouldn't lift off the table.

[Joseph Tarantino]

The way you have the blade setup, what you call positive hook, means the blade is cutting from the bottom up and that is unhealthy, unwise, and potentially very unsafe. With that setup you'd be better off pull cutting. Or am I missing something?

hook angle refers to "the angle formed between the tooth face and a line drawn from the center of the blade across the tip of the tooth."

http://www.rockler.com/articles/saw-blades-101.cfm

it has nothing to do with the position of the blade relative to the workpiece.

[Steve Rozmiarek]

I haven't seen mention of the tear out and the fact that a push through cut does not use the table as a zero clearance device. Pulling the saw through has the blade pushing fibers down against the table where they are supported, pushing has the blade lifting fibers up where they are not.

Just because you can push a RAS through, there is really no benefit to doing so.

[Joe Angrisani]

I haven't seen mention of the tear out and the fact that a push through cut does not use the table as a zero clearance device. Pulling the saw through has the blade pushing fibers down against the table where they are supported, pushing has the blade lifting fibers up where they are not.

Just because you can push a RAS through, there is really no benefit to doing so.

Bingo....!

[Peter Quinn]

I can remember as a young teen working on cutting blocking in a basement with an uncle that was a machinist. The whole family was helping another uncle build his house form the ground up literally, so everybody got conscripted. We were chopping up some old doug fir into maybe 14" pieces. My uncle had a few cuts climb forward on him pretty hard (beer in one hand, cigar in the other, rammy feed rate....), he got irritated when he spilled his beer. Cusing about stupid carpenters tools making you climb cut. So he switched to a push cut. Man, that was some scary stuff. Ever use a SCMS and have a board bind up on the blade? The saw comes flying back at you trying to climb its way out of the stock. Well the radial arm has the potential to do the same thing. He hit a tense piece of 2X12, it grabbed the back of the blade, lifted up into the guard, saw slammed to the end of the arm, piece of wood breaking loose, sort of everything went wrong at once. He shut the saw off and quit, I finished the blocking alone (at about 13 years old) by pull cutting.

So I'm sure you could get away with this pushing, and its cute to put some thin soft stock on their in the video and slam that saw back into it, but that technique has the potential at least to get real wrong real fast. I've seen a piece of wood bind up a RAS in a pull cut, at least it has the decency to act as a stop and trip the over load. Too bad there isn't some way to control the saws feed rate mechanically, like a powerfeeder for the saw carriage. That would solve the problem regardless of the saws direction.

[Myk Rian]

I wonder what the next topic of argument will be.
This one is going nowhere.

[johnny means]

John,
I dont see anything wrong in your video whatsoever. Its likely the EXACT procedure for cutting with any slider on the market today. Our slider has warning stickers on it clearly visible to the operator that say to place your work, draw the slider back, lower the saw head, and push through the work. These are much flimsier saws than your slider.

I have several times had issues with pieces lifting into our slider. No different for a RAS. Its just something that can happen. Dull blade, short piece, rushing, nasty grain, on and on.

Procedure, and procedural over thinking can often be a bad thing....

My thoughts are always just stay on your toes and the rules are a little pliable..

10 and 10 here..

Mark
I guess you missed the part where the saw actually jumps due to the fast and furious way the operator is pumping the carriage back and forth.

[Brian Brightwell]

On my little Crapsman RAS every time I use it I look for the bolt stop on the end of the slide. I know it is there but I look anyway.

[Andrew Hughes]

My first job after high school was a in a lumber yard building trusses I was the sawyer.I was one of only a handful of people working there that could understand how to run the metra cut center line saw.I think it had a 16 inch blade.My buddy produced the cut list I cut the the webs and cords.We did a lot of crazy stuff during lunch and this thread brought back fun memories.Dont remember using the saw for a push cut.Guess I didn't want to cut my arm off.

[Mark Bolton]

I guess you missed the part where the saw actually jumps due to the fast and furious way the operator is pumping the carriage back and forth.

Obviously for effect only but for sure an angry woodworker could really do some wonders with that technique.

Ive had pieces catch on an SCMS a few times, it sucks, and I wish it never happened but it has. That said, Ive seen far spookier things happen when someones trying to pull cut though an SCMS and an RAS are two different animals. The saws power vs. rigidity play a huge role with RAS. Catches aside, it has always seemed to me the majority of the RAS horror stories come from the craftsman flim flam saws and the only benefit is they are as a rule under powered so as stated they stall or trip the overload. If I were to guess twenty, it would be too few, times guys on jobs or that pulled up to my shop offering one, "Its free" they say. Needless to say its a pass.

I cant count the times on jobs Ive seen near amputations with cheap craftsman or b&d radial arms from guys running vinyl siding. They go to cut a piece of OSB or ply (pull cut) and next thing you know the saw is on top of the work, blade dished over, trademark arcing slice followed by a set of fully dilated pupils. Thankfully Ive never witnessed a live amputation.

[Chris Fournier]

I'm unaware of any myth but in my experience a pull cut can still climb even if you have a negative rake blade. A push cut will not climb and I have never lifted a piece of wood doing this but feed rate is key to doing anything safely when sawing on any type of saw. Positioning your piece for push cutting requires caution but a RAS climb cut does not give you the luxury of planning -it's on you in an instant if the saw doesn't bog. the lesser of two evils I guess.

I have only used a RAS for material break out and that is pretty much what I consider it good for. I've always had the luxury of using a TS, CMS for joinery or finish work.

[Mark Bolton]

a RAS climb cut does not give you the luxury of planning -it's on you in an instant if the saw doesn't bog

This has always been my point exactly. Not to say that I dont pull cut with RAS but when it goes bad your out of control in a millisecond. I personally dont think its as much of an issue with heavier, more industrial saws, though its still an issue but a climb cut gone wrong is a runaway disaster an no amount of reaction time can save you. Its an out of control situation thats moving in one direction and one direction only.

[Charlie Velasquez]

? . . . but a climb cut gone wrong is a runaway disaster an no amount of reaction time can save you. Its an out of control situation thats moving in one direction........

Mark, I am not sure I understand what you are saying.

First, I am an experienced Dewalt RAS user, as it was/is my main saw, for the last 35 years. I had experienced unintended "climb cuts" while pulling through the cut a number of times before I actually researched the use of the saw. After reading about proper techniques, proper maintenance, correct alignment, and recommended blades -and implementing same- that experience is now almost non-existent (did have a wet, pressure treated, maybe a little twisty board grab the blade half-way through the cut recently). So I am familiar with the blade trying to climb.

But getting back to your comment.
Even when it started to climb, I felt perfectly safe. As you said, the saw was moving in one direction, and one direction only. The motor, and the attached blade, were restrained by a cast iron arm and steel
carriage/yoke.
The climbed cut was still on-line with my mark before it started to bog down. I turned off the saw, returned it to it parking spot behind the fence, raised the saw about an inch, and made the cut in two passes (actually three passes as per Jon Eakes suggestion for precision -cut just a tad long, then skim cut to exact length).
The board could not be thrown as the blade is pulling it towards the fence and the wood behind the blade has not been cut yet.

In the push cut, if for some reason the blade would to grab the board (resin knot, or embedded nail or piece of metal -found a rifle slug once) with the wood behind the saw cut already, it seems more likely to launch. Maybe I am way off; I have never experienced a kickback on my RAS, no flying projectiles, so I may not understand the physics of it.

It still seems like a "climb cut" is not as much a disaster as a "kick back" -should that be "kick forward"