Thread: Table Sled Warping during construction - plywood - you break my heart!

I've always used 18mm MDF, possibly even some HMR offcuts I had lying around. Hard wearing and stays flat.

Hardwood offcuts for the front and back rails, and I try to find some nice quartersawn hardwood strips for the runners (for stability).

Thanks Mr Brush I did have to google HMR ... Melamine! Thanks Did you glue the runners or just screw?

I have some 25mm Ply offcuts reversed and glued to form a 50mm fence. Hoping that stays stable. I do have some spare hardwood, but not sure it is quarter-sawn. I have some plywood cut down too. I'm planning on just crewing the runners in in case they need replacing too. Is that wise?

Runners are just screwed on. With the runners in the mitre slots, I put the right hand edge of the baseboard up against the fence for alignment (close enough to be a good start), plonk the baseboard down on the runners and screw down into them.

I prefer to get the runners to be a really tight fit in the mitre slots (I used the board today, and they are as tight as when I made this one 2 years ago), but I did see a trick somewhere of making them slightly undersize and wedging them against the outside edge of the two mitre slots with thin wedges before attaching the board to the runners. By this I mean left hand runner hard up against LHS of its' mitre slot, right hand runner up against RHS of its' slot. This gives tight alignment without taking the time to precisely size the runners.

Fences are fitted last. I use the 5 cuts method on a piece of ply to do fine alignment of the rear fence until cuts are precisely at 90 degrees.

Thank you - that is some really helpful advice. Particularly about the runners It might save me a tonne of stuffing around Fingers crossed I will get to the 5 cut method after dealing with all the warping timber

Good luck with ply! My last sled was 18mm marine ply and left it flat in my workshop for 2 weeks and a week after i had made it I got a bow front to back of around 6mm. I have gone back to MDF and coated with 2 coats of wop.

Originally Posted by brit

I have gone back to MDF and coated with 2 coats of wop.

Ha ha What is WOP?

Got it ...
Wipe on Poly

What is WOP?

Ply ain't what it used to be.....lol. I can still get decent, stable, high quality 18mm birch ply, but it's a bit pricey to use for jigs, etc. in the workshop. MDF is the go.

A 1 metre x700 sled? Is this normal size? Seems massive ����♂️

Originally Posted by riverbuilder

A 1 metre x700 sled? Is this normal size? Seems massive ����♂️

whoops I have just finished my first sled it’s 1200 x 800 . It should do everything I need and probably some I don’t

cheers

P.S. I thought when it came to timber/tools/shelves etc bigger is better
P.P.S. I used 18mm yellow tongue, because I had some, no warp after a month.

Originally Posted by riverbuilder

A 1 metre x700 sled? Is this normal size? Seems massive ����♂️

Yeah it is a bit bigger than many ... However i wanted to be able to cross cut pieces that are 600mm deep. It does mean I now have this big ting to lug around the workshop!

Here are some images of the finished sled. So far so good! You can see the remnants of the old dog kennel on the underside!

This first shows the general construction - its pretty much like every other sled! ITs based off the instructions made by "Fix this build that"


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Below is the detail of the T track set into the rear fence. The rear fence is 2x25mm pieces of plywood laminated together. You can see the chamfer under the bottom of the fence ta capture saw dust without interfering with the face of the fence.

IMG_8447.jpg

Below is the underside ... with the remnants of the dog kennel showing! This piece didn't warp in 5 years ... it did a little after cutting but the weight of the fence straightened it up! Let's see how it lasts ...

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Details of the runners. Just 12mm plywood, let's see how they last!

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