Hello,
I’m building a cross cut sled from 3/4″ bb ply. I cut two lengths of 24″ and glued them up with a level to help keep things flat. Once I removed the clamps and the level, my glue up still bowed a bit. Is there anything I can do do get this strait again?
I’m thinking I was going to clamp it back to the the level while I do William Ng’s 5 Cut method and get it attached to the sled base, then I’d remove the clamps/level – hopefully this would help.
Any suggestions would be GREATLY appreciated!
Thank you,
– theArk
Replies
There are many articles and videos for unlimited members to get ideas about glue ups. Here's one video.
https://www.finewoodworking.com/2012/10/31/3-steps-to-great-glue-ups-edge-joints
Unfortunately I'm not an unlimited member. Which is why I'm on the forum. Yes, I will join but can't at the moment.
- theArk
I would suggest clamping the piece to your level again, then gluing an additional piece of plywood on, at 90 degrees to the face.
In other words, all of the grain in your plywood runs vertical or horizontal. The flat sawn face being the 'front' and 'back' of the fence, that runs at 90 degrees to the sled base. Once the fence is flat again, add a piece with the flat grain running on the top or bottom edges of the fence and parallel to the sled's base. I would definitely suggest glue and screws.
Don't try attaching the fence to the sled until it's flat and stable. Clamping it to the level to glue it in place will cause problems if the fence REALLY wants to move back at all.
so glue another piece's face to the top edge of my already glued up fence?
- theArk
For a crosscut sled the fence is critical. Don't try to save it. Scrap it and start over with something more stable than b-grade plywood. Maybe you can use it for the rear block so you dont have to waste it. If you decide to try with ply again, use epoxy instead of a water based glue and clamp it flat to your workbench under a caul, not just covered with loose clamps.
well, I didn't just have it clamped with clamps. I had the whole lot clamped to levels, which numerous number of woodworks have done, with baltic birch ply (which im using) and have had it come out straight. not sure why mine came out a wee bit bowed.
could I joint it maybe?
-theArk
Not being critical, and I read your post as B-grade ply... not Baltic Birch ply which should be plenty stable.
Jointing it is certainly an option.
oh haha, no worries.
- theArk
Use a jointer to get it perfectly straight and square.
Minor bow, right? Clamp a straight edge to it and mount it to the sled.
and yes, its very minor. 1 or MAYBE 2mm in the middle. Considering I don't have a real jointer just a table saw sled - would this is my best option?
- theArk
Glueing two pieces together even along a flat surface will not necessarily end up straight. The glue line being in the center of the cross section has very low impact unlike when multiple layers are laminated. Actually being in the center means that it does not help in maintaining the overall straightness, the further out the layers are the more they contribute. Straightening what you have on the tablesaw will be as good as with a jointer , as long as it is straight.
So, if for another sled one day, should glue 3 pieces of 1/2" together? As you can probably tell I'm all new to this.
And I hope its straight lol.
- theArk
Glueing pieces together does not make a piece straight, it only stiffens it, whatever you want to be straight needs to be jointed.
yeah, im looking into getting one of those lol. I might just get a little 6" bench top jointer. im not building anything large any time soon.
- theArk
Interesting post. I have x - cut sled made with ply that I use for my most critical cuts, used five method for alignment. It is one of three and relatively small, not symmetrical, 26" overall, 16" to the right of the blade. I designed it to cut shoulders for tenons, works very well. I never checked for bow.
If you attach the fence with the bow cupped toward the blade, your cut piece will hit the the two highest points. If all your cuts are beyond those points, your alignment will be good. Frankly you could just glue in two dowels and then align sled.
My sled #2 is larger and used to cut repeats like table legs or spindles. So if the top is off square by 0.001" it does not matter. The #3 is a one runner sled is for panels and is accurate enough for that purpose.
What you plan to cut? Do you REALLY need super accuracy for every cut? You are working with wood that will respond to humidity and temperature.
Good luck with your projects. Woodworking is a journey not a destination. I learn something with every project. (Sometimes sadly. . . )
Well, I'd like as accurate as possible but I don't need it to be so accurate. the bow isn't as bad as I thought so I'm just going to clamp it back to the level while attaching it to the base via William Ng's 5 cut method.
I've determined its only about 1mm out, so won't cause much issue down the road if I attach it this way.
- theArk
Hello, A little late. But if interested Tom McLaughlin has a free video on "How to Make a Cross Cut Sled." at about 12:30, he talks about issues with and techniques for making a fence dead flat. The link is: https://www.youtube.com/watch?v=uccUgHAQB28
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