Tablesaw Crosscut sled

[Alan Schaffter]

If you want a simpler, quicker and just as accurate method as the 5 cut method read post #10 above. If your bade has flex or its not parallel to the slots etc then the 5 cut method won't be as accurate. When adjusting fences on sleds and gauges its important to reference off the slots not the blade because those fences are moving via the slots. The dial indicator method is referencing off the slots. This video explains why you should do that ... https://www.youtube.com/watch?v=NrTeFQ0iQ5k

Yup, even if the blade is not square to the slots you will still get a square cut. People always ask what happens if the blade is not square? Well you get a wider kerf, that's all. Not exactly the same but sorta similar to making coves on a tablesaw - the greater the angle from the blade, the wider the cove.

[Dan Forman]

Hmm, having the blade parallel to the slot is the most important adjustment to make, as all other adjustments are made with the assumption that table and blade are indeed parallel. That is the foundation upon which everything else depends, so it seems it would be important to make sure that that relationship is dead on.

If the blade is out of alignment to the table such that the rear is canted to the right, a crosscut will indeed be be square, (cove analogy works here), although the offcut won't be square. But if canted to the left, unless the work piece is pushed all the way past the back of the blade, which few of us actually do with crosscuts, the result will be out of square if the work piece is wider than the blade, as the back of the board will have been cut by both front and back of blade, whereas the front will have only been cut once.

The beauty of the 5 cut method is that it measures the actual cut, which is always more accurate than measuring the mechanical bits of the saw. That's why you can't just lay down a square to the blade and set the fence with that. Any misalignment, blade flexing, runout and such is already factored in when you measure how the saw actually cuts rather than how it should cut.

The GargaeWorks guy in the video linked to in post #53 did get a good setup, but we never saw how it actually cut, so we can't be sure of how it actually works out. We also didn't see how long he had to fiddle with the fence to get that final result, he edited that part out. Even if it does cut as true as the setup, technically William Ng's result is ten times as accurate (.001 over 8" vs .001 over 80" respectively). Though most of us would be satisfied with the former, if you can easily get the latter, why not go for it? The other thing is, I would have to order that square and wait for it to arrive, whereas with the five cut, all I need to do is find a scrap of mdf or plywood, no waiting. That said, if I already had a square like that, the scientist in me would want to give that method a try.

GarageWoks guy did have a great idea for the wood adjustable runner though!

Dan

[Doug Garson]

Actually you don't need a special square to use the Garage Workshop's method, all you need is a piece of plywood or MDF with one square corner and one straight edge. If you have a quality miter gage you can easily cut a piece that is just that. Or you can make a square like Marius Hornberger, can't seem to link his video but I'm sure you can find it on Youtube.

[Johnny Barr]

The GargaeWorks guy in the video linked to in post #53 did get a good setup, but we never saw how it actually cut, so we can't be sure of how it actually works out. We also didn't see how long he had to fiddle with the fence to get that final result, he edited that part out.

Dan, I didn't want to make this a "my way is better than your way" discussion but that fiddling takes 5 minutes. His other videos show the fiddling. ( https://www.youtube.com/watch?v=UC_iF5pZxmI&t=5s ) and this one ( https://www.youtube.com/watch?v=tZM1OBcC6ok ) As in the 5 cut method you use one screw to use as a pivot and then adjust the fence with light taps until the dial indicator hardly moves (roughly under .002") across the length of the square. Then lock it and make a test cut. I actually did an experiment. Using the dial indicator method I ended up with .002" error over 10" on my engineers square. Then I did the 5 cut method and ended up with the same error over a 10" cut. A test cut checked with that square and a digital protractor showed a perfect 90. I have used the 5 cut method for many years but I'm convinced this alternative is just as good. Actually William Ng's isn't 10 times more accurate. The actual error or accuracy in the 5 cut method is taken after the 5th cut eg .003" over 8". That error is then transferred to the length of the fence. After adjustment and doing the 5 cut method again you won't get .0003" over 8". Using a large framing square with the dial indicator method with an edge closer in length to a cross cut sled fence will achieve the same accuracy as the 5 cut method. I've never seen an 80" crosscut sled fence

In the real world and at the end of the day both methods will give perfect 90 degree cuts. I'd like people to try it. They then can decide which way is easier.

[Alan Schaffter]

Hmm, having the blade parallel to the slot is the most important adjustment to make, as all other adjustments are made with the assumption that table and blade are indeed parallel. That is the foundation upon which everything else depends, so it seems it would be important to make sure that that relationship is dead on.

If the blade is out of alignment to the table such that the rear is canted to the right, a crosscut will indeed be be square, (cove analogy works here), although the offcut won't be square. But if canted to the left, unless the work piece is pushed all the way past the back of the blade, which few of us actually do with crosscuts, the result will be out of square if the work piece is wider than the blade, as the back of the board will have been cut by both front and back of blade, whereas the front will have only been cut once.

Dan

In no way was I endorsing accepting a blade that is not parallel to the miter slot. Skew can result in binding, burning, kick-back, sideways force on the stock, etc. And depending on the direction of skew, the kerf may cut off the line or result in a short board (board stretcher needed ), and as pointed out, the cut-off may not be square if that is the piece you need (which piece is square depends on the width of the board, height of the blade, whether a full pass is made, and of course, the direction tilt of the blade. Hopefully, any skew is minimal because for some, depending on the saw, adjusting the blade parallel can be a major undertaking.

Of course, there are so many factors that can affect the squareness of the cut- both machine and man caused. There was an earlier discussion about miter slot slop and man-caused fence skew (or flex). The first one can be fixed, but the second is only rectified by skill and attention- even pressure across the back of the fence, not just at the miter bar. In addition to checking the obvious- that the blade is parallel and the miter gauge/sled fence is square, and there is no slop in the miter bar on a regular basis, the blade should be sharp and the miter slot/bar, table top, and fence should be lubricated. How many of us have neglected those last items until it becomes too obvious. How many of us have struggled to feed stock into a tablesaw, planer or jointer, then are amazed how much easier it is after the surfaces are lubricated.

[Dan Forman]

First let me say that I'm sorry if my tone has become argumentative, I'm really just trying to sort things out and thinking out loud here. I don't wish to alienate anyone. I am in the process of building a sled, and want it to be a accurate as possible, so this topic is important to me at the moment. I've been away from woodworking for a while, and have been on a mission to get all of my machines dialed in "dead nuts", at least as far as humanly possible. I want to focus on boxes, and as Doug Stowe points out in one of his books, boxes will be scrutinized a lot more closely than many other woodworking projects, and any errors in squareness on end cuts have a way of affecting the outcome of the joinery of the box sides.

Doug - I found that video on making squares, thanks for mentioning it. In all of the plywood and MDF that I have, the factory edges are rough enough to make the dial indicator dance, but I did manage to get my miter gauge tuned well enough to not show any light against my reference combo square, so I'll give that a try.

Johnny - Thanks for posting the Garage Works video. I have been looking at some of his other stuff, and he has some really interesting things on there. As I said before, my "inner scientist" does want to try anything at least once. He actually made a video comparing the five cut method the the square + dial indicator method, timing both operations, and the latter was the fastest. My frustration with him is that in all three videos he made, he never did a fair test of the accuracy of the result. If it was my video, I would have demonstrated the result by doing a five cut on each of the fence settings so we could compare the real world accuracy. Then we would have a real basis for deciding whether the extra time is worth putting in to chase the best result, whatever that might be.

One thing I admire about both Ng and Brian (GarageWorks) is their grasp of math and ability to to put it to use in creative ways to solve woodworking problems. I apparently didn't get the math gene, so I struggle with these things. I went back and reviewed the five cut video, and saw that I did indeed misinterpret it, I had thought that the difference between top and bottom represented the error relative to all four cuts combined, hence the 80" (my test piece ended up about 20" on the longest side), but now I see that it applies to only the length of the fifth cut. Thanks for setting me straight on that!

Alan - You have hit on a key frustration for me at the moment. I'm trying to sort out what may be operator error, and what might be due to the machinery. My Jessem sliding table has been particularly hard to get consistent results with. Last week I thought I finally had it dead on with the five cut method (a 22" square of 1/4" MDF) , but a couple of days later cut a smaller piece of 3/4" ply and it was significantly off. All of this talk about miter slots being parallel to the blade got me wondering if the slider was out of line with the blade, and it turned out to be the case. Given the design of the slider, it's really hard to get dead on, but I did get it better, and the cuts have improved in consistency, at least for now. I also waxed the saw table to cut down on any resistance there.

Dan

[Johnny Barr]

My frustration with him is that in all three videos he made, he never did a fair test of the accuracy of the result.

Dan, perhaps I was getting a little defensive myself but anyway I do agree, he should have shown a test cut with some way of showing the accuracy, for example, make a cut then flip one piece, rejoin the pieces and see if there any gaps. I discovered this method after searching for a way to accurately adjust my Incra miter gauge which I knew wasn't cutting square. The 5 cut method and feeler gauge usage isn't appropriate for a miter gauge and more suited to a crosscut sled. Anyway I tried this method after many years of doing the 5 cut method and loved it. I had it squared in literally minutes. I didn't believe it was square until I checked it with the 5 cut method and it was spot on. Did some test cuts over various lengths and they were all bang on 90. I was still sceptical until I checked my crosscut sled, using the new method, which was squared using the 5 cut method. it had the same error which was virtually zero. I was then absolutely convinced that this was a great alternative. I no longer use the 5 cut method despite it being considered as the definitive way of squaring a fence. While MrGarageWorks should have shown the accuracy I can vouch for it.

Also now that you have explained it, if you get .003" over a 20" length error after all the cuts then you are right the error is .003 over 80". I thought you were talking about the fence. If I got .003" over 80" then I would be ecstatic. That's an error of .0000375 per inch. Outstanding result but I would expect that error after the adjustment using a feeler gauge, not before. The new method can also get within 0.001 or better over 12". I've done that and its not difficult. That's an error in the tenths of thousandths as well. Once again an outstanding result, way beyond what's needed for "normal" woodworking, after all we are not doing precise engineering here. One final comment about the 5 cut method and then I'll shut up about this, the feeler gauge is the least accurate part. You're meant to be able to move it snugly (scientific woodwork term) between the fence and reference piece but what does snug really mean. Two different people could differ by thousandths of an inch using the same feeler gauge. One has a tight fit and one has a loose fit.

If anyone owns a dial indicator and a magnetic base then give it a go. You'll be surprised!

[Curt Harms]

I need to make a new sled. I've used oak runners and I had problems with them seizing up due to expansion. For my next one I'll try quarter-sawn instead.

I actually HATE making table saw sleds because I really struggle with the process to make it perfectly square. Yes, I've seen the YouTube videos where you rotate a piece of wood 4 times taking a cut to measure the total amount off. But trying to nudge a fence into alignment with that whole screw method is just tortuous for me.

If anyone is reading, any recommend plans for a fence that is adjustable?

No plans but I made a 'Norm style panel cutter' but made the blade to stationary fence a half smidge over 90*. I then made a second fence that would move a few degrees. Horizontal T nut in the fixed fence furthest from the blade. I put a screw and locking nut thru the T nut so it pressed on the movable fence. This provides a fine adjustment mechanism and helps to keep the adjustable fence from moving. The movable fence is held in place with two screws into T nuts. I made the outside hole in the movable fence a little oversized so there is some adjustment. Tighten everything down then check for square using the "5 cut" method.