Getting a TS crosscut sled perfectly square

[Jack Ganssle]

Folks,

I find the TS crosscut sled I built is slightly out of sqaure - about 0.004" over a 2" cut, which is about 0.1 degree of error. So the shoulders of tenons cut using a dado aren't perfectly flat. (No one else notices this, but I sure do).

One source suggests getting it close, then gluing and screwing the fence onto the sled, and quickly making some test cuts, banging with a hammer to adjust the fence before the glue sets up. That sounds like a great way to make a big pile of not-quite-perfect sleds!

How do all y'all get that perfect alignment of the rear fence to the miter slots?

Thanks,
Jack

[Doug Barker]

I learned to always make the rear fence of a sled adjustable.

If yours is fixed, you me be able to shim it with some tape. Posibly some of those junk credbit card material would e a good shim.

Good luck

BTW: I now make ll of my jigs adjustable...

[Cliff Polubinsky]

I'm doing just that right now. One way is to bolt, not glue the fence to the bed. 4-5/16" bolt, 2 on each side of the cut will hold the fence securely. Make the first cut almost to the fence, then loosen all but one bolt on the end of the fence. Measure and adjust for squareness, then tighten everything down. Make a 5 cut test for squareness and adjust if needed. This way adjustments can also be made in case wood movement tweaks your sled out of true.

Cliff

[glenn bradley]

My latest sled has an adjustable fence. I'll never go back. It is soooo easy.

http://www.sawmillcreek.org/showthread.php?t=50581

[Brad Noble]

Well, you will probably get several different responses to this question. Those opinions change with each individual.

Mine was built in a shop about 45 miles from my saw. Point is, it is easy to do and can be accurate. You make your bottom as square as you possibly can, then build your fence(s). Attempt to attach your rear fence as square to the table (sled bottom and mitre slots) as possible. There are many ways to accomplish this. Anyway, once you get the partially built sled to your shop and sitting on your saw, make the runners so they will slide properly in your saw. Next, work as long as necessary to make your table saw fence parallel to the mitre slots and blade as possible. Now, place some small flat washers in the bottom of the mitre slots to set the runners on (and let them stand proud of the table surface slightly), then set your fence so that the measurement from the fence to the blade is exactly where you want your cut slot to be in the sled bottom (plus 1/2 the thickness of the blade) and lock it down. Now, place the runners in the mitre slots, on top of the washers, and put some glue on them (or double side tape if you prefer) and line up your sled to the fence and the rear edge of the saw table and while holding it firmly against the fence set it down on top of the runners. Put some weight on the sled to hold it down on the runners and go to bed. Tomorrow everything will be fine.

I did mine like this and the 5 cut method shows mine to be off .001. It is wide by .001 at the rear of the blade. I'm happy with it.


Brad

[Al Willits]

Got my sled anchored by 1/4" machine screws, washers and nuts, used a fostner (sp?) bit and made a hole a bit bigger than the washer I used, maybe a loose .1".
Also made the hole the 1/4" screw goes though about a .1 to big too.
Got the fence as close to a 90 as I could, then drilled the holes.
By loosening the screws, I can adjust the fence a bit to make of for any error.
Al

[Dan Forman]

A "post it" note is .004" thick. If you need to adjust your fence in the direction toward the blade, you can just use a post it for a shim right at the end of the fence near the blade. If the fence needs to adjust to the rear, you could try moving the shim further down the fence, which should make the correction on the other end.

[Jack Ganssle]

Thanks, all for the great ideas.

Jack

[Jesse Cloud]

My bias is that anything that is adjustable, has to be adjusted, and unless you adjust it each and every time, it will probably be out of adjustment. So I make mine fixed.

Technique for getting it square is to glue the fence down, close to square, drive in one screw from below - to act as a pivot point. Get it close to square and shoot in a brad. Make a test cut and tap with a mallet to get closer, the brad will bend. When you are satisfied, clamp it.