Are your cuts square on your TS?

[Bill Huber]

Art Mann in another thread talked about the blade does not have to be square to the sled or miter guide, which is true. The blade should be as close as you can to parallel to the miter slot so it will not bind as you cut.
But I got to thinking about it and I have seen many times a person using a square on the miter guide to blade but really never thought that much about it. They will want to cut a 45 and put the 90/45 triangle down and check it and then wonder why it was not right on when they make they cut.
If you square the miter or sled up with the blade you may still not be making a square cut. I have always squared my miter guide with the bar that is on it and not the blade, I guess I was lucky that I was doing it right.

Here is a drawing to show what I am talking about just in case someone was missing it, I did exaggerate the .002 on the blade so it was easier to see.

80460

[Greg Funk]

Bill,

I think you need to have the blade parallel to the miter slot as well. In your bottom diagram you show the kerf as growing wider but that won't really happen. The wood will either bind and burn or if it is not held firmly on the miter gauge it will move towards the blade resulting in a non-square cut.

One way to look at it is to exagerate your drawing even further and put the blade at a 45 degree angle. You won't be able to push the wood through the blade.

Greg

[Bill Huber]

Bill,

I think you need to have the blade parallel to the miter slot as well. In your bottom diagram you show the kerf as growing wider but that won't really happen. The wood will either bind and burn or if it is not held firmly on the miter gauge it will move towards the blade resulting in a non-square cut.

One way to look at it is to exagerate your drawing even further and put the blade at a 45 degree angle. You won't be able to push the wood through the blade.

Greg

I agree..... second line of my post.


The blade should be as close as you can to parallel to the miter slot so it will not bind as you cut.

It is exaggerated a lot and it will widen the kerf of the cut as the board gets to the back teeth of the blade. I know this to be true because with my saw before I learned out to tune it right the blade was off by a mile and I could still get a square cut.

[Bruce Benjamin]

Bill,

I think you need to have the blade parallel to the miter slot as well. In your bottom diagram you show the kerf as growing wider but that won't really happen. The wood will either bind and burn or if it is not held firmly on the miter gauge it will move towards the blade resulting in a non-square cut.

One way to look at it is to exagerate your drawing even further and put the blade at a 45 degree angle. You won't be able to push the wood through the blade.

Greg

I believe that the bottom diagram is just exaggerated to show it more clearly. If a TS blade is out of parallel from the miter slot by as much as shown in the diagram then of course it wouldn't work. However, I doubt that there are too many saws with their blades that far out of alignment. Because the saw teeth are generally wider than the body of the saw the blade can be slightly out of alignment and still allow for a straight cut. The kerf created by the teeth as the blade moves through the blade will usually leave enough room for the body of the saw to pass through the wood where the teeth at the rear of the blade will widen the kerf. Think about how a wobble style dado blade works.

I'm not saying that it's ok or safe or proper or whatever to operate a tablesaw with the blade way out of alignment. But I'll bet if one were to measure a hundred tablesaws for blade to miter slot alignment there would be a very high percentage that are at least a few thousandths out. Especially if most of the saws are contractor saws because it's more difficult to align them than cabinet saws. It's when the misalignment gets worse and worse where blade marks and burns show up on one side of the cut or the other and it also can increase the risk of kickback.

When I was going through my nightmare of dealing with Jointech's owner regarding the very poor quality of the Smart Miter sled that I had unfortunately purchased he was one of the people who didn't seem to really understand how a tablesaw works. Long story short, he was insisting that the reason why the cuts weren't up to what they were promised, (Multiple problems) was that my saw blade wasn't properly aligned to the miter slot. My blade is within a .001" or .002" of being in alignment but even if it was worse than that it wouldn't effect whether or not the sled was operating correctly. It would just effect the thickness of the kerf. I did do a long and detailed write up on the Smart Miter fiasco so if anyone is interested, PM me and I'll send a link.

Bruce

[Art Mann]

Bill,

That is a very nice little diagram that makes the point well. That particular concept is just very hard to visualize unless you have something to look at.

Art

[Greg Funk]

Bill,

My apologies. I'll read your post more carefully next time. I've never accurately measured how parallel my blade is. I just know the results are square when I use a crosscut sled.

Greg

[Lee Koepke]

Thanks for that Bill.

It makes sense, and now I cant wait to get home and see how I set up for my last miters that didnt fit perfect ...

[Rob Blaustein]

If you square the miter or sled up with the blade you may still not be making a square cut. I have always squared my miter guide with the bar that is on it and not the blade, I guess I was lucky that I was doing it right.

Here is a drawing to show what I am talking about just in case someone was missing it, I did exaggerate the .002 on the blade so it was easier to see.

80460

That's a nice illustration of the point that the miter guide needs to be 90 deg to the motion of the sled/gauge, not necessarily to the blade. I think the usual procedure people follow in tuning up the saw is to first square the blade to the miter slot. That then serves as a reference for squaring the miter gauge. I think people often find it easier to square it up to the blade because the blade rises up above the table so when you put a triangle on the table, you can butt it up against the blade. But you can probably just as easily square it to the miter slot as you do. Interesting point you raise.

[Steven Wilson]

Bill, a problem with typical table saws is that you don't really have enough throw to get good consistant measurements with. This makes it hard to get decent precision on crosscuts greater than 10" or so. Lack of squarness (or parallel) is really easy to measure (sometimes see) on a sliding table. You have a lot more throw to work with (the sliding table and crosscut fence lengths) which allows you to make finer measurements of angular error and more importantly fix it. I know that going through the processes of setting up a slider (5 side cut, etc) really helped me visualize the relationship between blade, fence, and carrige (you miter slot).

[Bill Huber]

The main reason I posted this was because when I was out on the net looking at the way different people made sleds one thing I saw was they used a carpenter square on the blade to get it square.

Then Art got me thinking about it and I went back and found some of the sites that I had look at for the sled. Some would go on to do the 5 cut test but others wouldn't. So if these people are doing that are they doing the same thing with the miter guide?

Just for the heck of it I called 3 different people this afternoon. Each are at a different level in woodworking, one does a lot if it and makes a tons of cabinets, one is just a newbie like myself and the other one does a little woodworking when they need to, they all 3 have good table saws.

The question I ask was this. If I ask you to cut a 1x2 at a 45 degree angel on the TS and gave you an unmarked miter guide how would you set it up.

The answer I got back surprised me, everyone of them said put a 45 on the blade and miter guide.

After I went over the reason not to, they all 3 said about the same thing, "duh"

Now if you have your blade .000 to the miter guide then this would be no problem but how many saws out there are at .000 to the miter guide. In most cases I think you could do just fine with the blade to miter but I feel that if you make all your cuts as accurate as possible then you will have less problems down the road when you go to put it all together

[Bill Jepson]

Ok I must pipe up here there is an easy way to check your blade to the miter slot. I am an ex machinist and I have a surface guage that is designed to check parallel. The guage has 2 pins in the rear portion of the block. Those pins can be extended into the miter slot, and then you can easily check how parallel your blade is to the slot with a dial indicator. I got mine within about .002 or less. I have never used any of the tools specially made for tuning the table saw although I'm sure they work well and are certainly designed to the task, they seem expensive and are certainly single purpose. Most major cities have tool stores that you can get a surface guage in. HF has had them, just be sure you get one with the extendable pins near the back side of the block. Also get a dial indicator with a .001 dial and your in business. You may pay close to the cost of one of the "tool toys" but you will have a tool you can use for all kinds of marking and measuring. Then you can square the miter guage to either the saw or the slot and you will be fine.
Bill Jepson

[Chris Padilla]

I have a SuperBar and Master Plate (http://www.grizzly.com/catalog/2008/Main/321) to adjust such issues as miter slots to saw blade and fences.

It seems best to set everything as parallel as you can get it for things, in gereral, to operate smoothly.

Of course, this thead could turn into a debate about how some think the fence shouldn't be parallel to the blade/miter slot.... :)

[Alan Schaffter]

Bill, one problem with your pic and analysis- tell me what would happen in your second pic if the outfeed side of the blade was toe-in instead of toe-out?

[Bill Huber]

Bill, one problem with your pic and analysis- tell me what would happen in your second pic if the outfeed side of the blade was toe-in instead of toe-out?


You would get an unsquare cut.
The blade would try and push the wood to the left which would cause the cut to be unsquare.

I am not putting forth a theory, just putting down the facts. If you could get a blade set perfectly square with the miter slot it would make no difference if you used the miter slot or the blade. But how many saws have their blades set perfect to the miter slot.

You should always use the miter slot to set you guide with, not the blade.

Remember the image is real exaggerated.

[Alan Schaffter]

Exactly, but in either case you still have a problem not only with cross cutting but with ripping also. The real answer is align the table (miter slots) to the blade, then you can set your miter gauge to the slots or the blade, any other way is just wrong. I don't know of any saw where you can't adjust the table, maybe a cheapy. But the tables on most (all?) cabinet saws can be easily adjusted- my Uni has Allen head bolts at each corner. Loosen the bolts a little, then use a dial indicator and a dead blow hammer- tap, tap, tap, the table into alignment- takes all of one minute. On saws where the trunion is mounted to the table it may be a little more difficult, but not much.

[Bill Huber]

Exactly, but in either case you still have a problem not only with cross cutting but with ripping also. The real answer is align the table (miter slots) to the blade, then you can set your miter gauge to the slots or the blade, any other way is just wrong. I don't know of any saw where you can't adjust the table, maybe a cheapy. But the tables on most (all?) cabinet saws can be easily adjusted- my Uni has Allen head bolts at each corner. Loosen the bolts a little, then use a dial indicator and a dead blow hammer- tap, tap, tap, the table into alignment- takes all of one minute. On saws where the trunion is mounted to the table it may be a little more difficult, but not much.


No you will not have a problem with ripping, the blade may burn or drag but you will still get a straight rip.

So you are telling me that your saw is set to .0000 front to back to the miter slot.

I have a very old contractor saw and have worked for many hours trying to get it set but I have never been about to get it less then .002 I am sure it is getting worn out, but my saw is not the only one that is not set perfect.

I would say that there are a lot of saws out there that are not perfect and I still say you should always use the miter slot to set the miter guide.

I guess will will just have to agree to disagree on this.

[Bruce Benjamin]

Loosen the bolts a little, then use a dial indicator and a dead blow hammer- tap, tap, tap, the table into alignment- takes all of one minute. On saws where the trunion is mounted to the table it may be a little more difficult, but not much.

"A little more difficult"??? I'm guessing you've never actually tried to align a contractor style saw before. It's not rocket science and it is possible to align the blade to the miter slot with a high degree of accuracy on a contractor saw. But I would never call it easy. I don't know how long it really takes to align a cabinet saw but I can tell you that I'm pretty handy mechanically speaking and it took me a lot longer than a minute. Trial and error, back and forth, I think it took me close to an hour and it's still not perfect. Close enough but not perfect. I don't think I'm in the minority either.

Another issue with aligning the fence with the blade is that sometimes blades aren't perfectly flat. In addition to that, the blade offers a much shorter surface to measure off of compared to the miter slot. Referencing the blade is the way to go to remove possible sources of error.

Bruce

[jim gossage]

bill,
what is the best way to align the miter gauge to the miter slot? it seems like you would want to register your square up against an edge rather than just eyeballing it. once the miter gauge is in the slot, you have lost the edge of the slot.

[Art Mann]

It does not present a problem with either ripping or cross cutting if the blade is slightly off from parallel to the miter slot. In fact, some texts on tablesaw setup say to tow out the back side of the blade by .003 or .005 with respect to the miter slot in order to reduce the possibility of binding between the blade and fence. I don't do it that way, at least on purpose, but lots of people do. Regardless, you should always reference the miter fence to the miter slot in which it slides rather than to the blade - if you want the best accuracy.

[Bruce Benjamin]

It does not present a problem with either ripping or cross cutting if the blade is slightly off from parallel to the miter slot. In fact, some texts on tablesaw setup say to tow out the back side of the blade by .003 or .005 with respect to the miter slot in order to reduce the possibility of binding between the blade and fence. I don't do it that way, at least on purpose, but lots of people do. Regardless, you should always reference the miter fence to the miter slot in which it slides rather than to the blade - if you want the best accuracy.

:confused::confused::confused: I don't think I've ever seen anything that said to purposely set the blade out of alignment to the miter slot. Are you sure you're not confusing that with setting the rip fence out by .003" to .005"? I've seen that a quite a few times. What you're suggesting would cause more binding between the blade and the fence, not less. At least as far as I can see.

Bruce

[Gary Keedwell]

A great way of squaring up your miter gage is by using a wixey digital gage by hanging your miter fence off the edge of table saw . Zero off the gage on the saw top and bring it over to the mite fence and tighten up when it registers 90º.
Gary

[glenn bradley]

I setup the blade to the miter slot, fence to the miter slot and square the miter gauge to the bar as you suggest. Works fine. Also, yet another handy use for your tilt gauge:

The pics are actually opposite of what I do but you get the idea.
Zero it on the bar 80596

and adjust to 90* on the gauge head80595

As long as your gauge is at 90* to it's own bar, the bar fits the slot without slop and your saw is setup to the slot . . . all is well.

[Bruce Benjamin]

Something to consider when squaring the miter gauge head to the miter bar is if the miter bar is actually sitting square in the miter slot. What I mean by that is, how tight does the bar fit in the slot and how did you get it that way? If you have a miter bar that has some adjustability in the form of ball plungers or eccentric disks you may have one section adjusted slightly differently than another section. While the miter bar may be snug in the slot as it slides along, it's not necessarily perfectly square in the slot. I'm not saying this is always a problem but it's worth checking.

I have two miter gauges, the stock General miter gauge and an Incra 1000SE. I have checked both by cutting a 90 deg. crosscut and checking it for square. That's the real proof. I then checked the head against the miter bar. Right now both gauge heads are square to the miter bar but I remember when I first got my General International saw I checked the cuts and the gauge head was square to the miter bar but the cut wasn't quite square. I did some thinking and it finally dawned on me that the bar wasn't adjusted quite evenly so the bar wasn't square in the miter slot. This won't happen to everyone but it's worth checking before making a critical cut on expensive stock.

I have used both the Wixey and the Beall angle gauges, (I kept the Beall) and they both claim an accuracy of + or - .1 degree. That doesn't automatically mean that every measurement is off by .1 degree but it does mean that you might want to do a test cut to find out if your gauge is really set where you want it to be. Two 44 degree or 46 degree miter corner cuts instead of 45 degree cuts will definitely be noticeable. That being said, I have used this method on my Incra gauge and the Beall matched the gauge's reading exactly and the cuts were dead-on.

Bruce

[Lonnie Cook]

Bill:

I'm sure that this thread has given a lot of woodworkers a better understanding of the geometry of a saw cut.

Even if your blade is slightly out of alignment with the miter slot, here is a fast, accurate, and cheap way to set your miter fence to make exact cuts.

Insert a nail into a tight-fit hole in the throat plate. Place your set-up reference (drafting triangle, Sliding T-Bevel, template, etc.) against the miter fence and the nail. Slide the miter gauge back and forth. Adjust the fence until the reference touches the nail along the entire path.

I prefer the 5-cut method to set the zero-deg stop, but a 90deg drafting triangle can be used against the nail, also.

http://i149.photobucket.com/albums/s50/lonnieinorlando/WoodWorking/Tools/BT3000/6T-BevOutfeed-500.jpg

Yep, it's a Ryobi with a sliding table, but this works on "old fashioned" saws with miter slots, too! ;)

- Lonnie

[Art Mann]

:confused::confused::confused: I don't think I've ever seen anything that said to purposely set the blade out of alignment to the miter slot. Are you sure you're not confusing that with setting the rip fence out by .003" to .005"? I've seen that a quite a few times. What you're suggesting would cause more binding between the blade and the fence, not less. At least as far as I can see.

Bruce

Good catch. The rip fence should always be set exactly parallel to the miter slot from all I have read. But, you are right in that I said the wrong thing about the blade. What I meant to say was some authorities say to set the back edge of the blade out from the rip fence, not the miter slot. I thought one thing but typed out something else.:o

[Art Mann]

Lonnie, that is a neat trick. I also prefer the 5 cut method as it amplifies the error X4 so you can see it better.

Bruce, in your example, don't you mean 44.9 and 45.1 instead of 44 and 46? I'm not so sure this amount of error will be very noticeable. The gap produced varies like the sine of the angular error. The sine of 0.1 degree is about 0.0017. A miter cut that is 2 inches in length with a 0.1 degree error will produce a gap of about 3.4 thousandths. That is a little less than a dollar bill thickness. Of course, you have to multiply that by 2 for a mitered joint if both angles are out by 0.1 in the same direction. I used to check the blade after setting it with the Wixey using a machinist square, but I never found any difference. Test cuts are the only way to really know for sure if bevels are right. I use an Incra 1000se for cutting miters and after I calibrated it, the angles have always been right on the money. I don't do trial cuts every time with the Incra because I found it isn't necessary.

[Gary Keedwell]

Good catch. The rip fence should always be set exactly parallel to the miter slot from all I have read. But, you are right in that I said the wrong thing about the blade. What I meant to say was some authorities say to set the back edge of the blade out from the rip fence, not the miter slot. I thought one thing but typed out something else.:o
The Blade is always supposed to be parallel to the miter slot. What you should be saying is the fence is sometimes skewed out a few thousands on the back side of the saw.;)

Gary

[Bill Huber]

Bill:

I'm sure that this thread has given a lot of woodworkers a better understanding of the geometry of a saw cut.

Even if your blade is slightly out of alignment with the miter slot, here is a fast, accurate, and cheap way to set your miter fence to make exact cuts.

Insert a nail into a tight-fit hole in the throat plate. Place your set-up reference (drafting triangle, Sliding T-Bevel, template, etc.) against the miter fence and the nail. Slide the miter gauge back and forth. Adjust the fence until the reference touches the nail along the entire path.

I prefer the 5-cut method to set the zero-deg stop, but a 90deg drafting triangle can be used against the nail, also.
- Lonnie

Very neat idea, I like it......!!!

I tried it this afternoon and I used one of those On/Off magnets and it did just fine.

I used the 5 cut method to set the miter guide up to start and when I checked it with your method it checked out.

Thanks for the idea, this is a quick check, a little faster then the 5 cut.

[Bruce Benjamin]

Lonnie, that is a neat trick. I also prefer the 5 cut method as it amplifies the error X4 so you can see it better.

Bruce, in your example, don't you mean 44.9 and 45.1 instead of 44 and 46? I'm not so sure this amount of error will be very noticeable. The gap produced varies like the sine of the angular error. The sine of 0.1 degree is about 0.0017. A miter cut that is 2 inches in length with a 0.1 degree error will produce a gap of about 3.4 thousandths. That is a little less than a dollar bill thickness. Of course, you have to multiply that by 2 for a mitered joint if both angles are out by 0.1 in the same direction. I used to check the blade after setting it with the Wixey using a machinist square, but I never found any difference. Test cuts are the only way to really know for sure if bevels are right. I use an Incra 1000se for cutting miters and after I calibrated it, the angles have always been right on the money. I don't do trial cuts every time with the Incra because I found it isn't necessary.

As you said to me in a previous post, Good catch, Art.:D Yes, that is what I meant but not what I typed. However, a .003" gap is easily visible even to my tired eyes and a .007" gap should be visible to anyone's eyes.

As I said, my Beall gauge has been dead on when compared to any other tool or method I have, including the all important, "Does the part actually fit test". But that doesn't mean that people should just automatically discount the margin for error listed by both Beall and Wixey. I would suggest that everyone test their gauge once in a while just to see where it is.

My Incra 1000SE is attached to Incra's miter sled. It has been dead on right out of the box but I still checked it to make sure. I'm really impressed with Incra.

Bruce