I am thinking of building a cross cut sled as a torsion box
#11
  
I am disabled and don;t have a lot of upper body strength. But I want a larger sled.
I am wondering if it would be feasible to make a crosscut sled about 24 x 27 using 1/8 mdf or hardboard for the skins and then 1/2 mdf for the webs.
Would it be best, if this is feasible, to build the webs, or would it be better to carve it out of the MDF by cutting out 6 x 6 square holes or similar.
Any better materials?

I would be using a solid strip in the path of the blade with a changeable insert. and probably use use a solid area where the miters tracks are and possible recess these for better glue up.

Thanks!
Bruce
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#12
  Re: I am thinking of building a cross cut sled as a torsion box by Brucej (I am disabled and do...)
(05-09-2018, 12:47 AM)Brucej Wrote: I am disabled and don;t have a lot of upper body strength. But I want a larger sled.
I am wondering if it would be feasible to make a crosscut sled about 24 x 27 using 1/8 mdf or hardboard for the skins and then 1/2 mdf for the webs.
Would it be best, if this is feasible, to build the webs, or would it be better to carve it out of the MDF by cutting out 6 x 6 square holes or similar.
Any better materials?

I would be using a solid strip in the path of the blade with a changeable insert. and probably use use a solid area where the miters tracks are and possible recess these for better glue up.

Thanks!
Bruce

Why not just use a piece 3/4" plywood and be done with it? Why the hassle to make a box, which adds thickness, making your depth of cut less?

What am I missing?

Once Favre hangs it up though, it years of cellar dwelling for the Pack. (Geoff 12-18-07)  



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#13
  Re: I am thinking of building a cross cut sled as a torsion box by Brucej (I am disabled and do...)
This is more work but could certainly be done. Look at plywood instead of hardboard and mdf. It is considerably lighter and more durable. Around here I can get 1/4" (closer to 3/16") luan ply for cheap at Menards. and 5/8" (closer to 9/16") ply handi-panels. This should give you a base a little less than an inch thick and not cut into depth terribly as compared to a 3/4 base. Do not go to all the work of carving the webbing. It is just a spacer to hold the skins apart. Not letting the skins change their relationship to each other (shear) is where the real strength is in a torsion box.
Also mark where your webbing is. My sleds are full of screw holes from fixtures used for special cuts.
Proud maker of large quantities of sawdust......oh, and the occasional project!
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#14
  Re: RE: I am thinking of building a cross cut sled as a torsion box by KyleD (This is more work bu...)
Bruce,  yes it can be done, not sure why.  I have made a few cross cut sleds.  The accuracy, afaik, has nothing to do with the base, but instead with the members that hold the base.  Many make crosscut sleds with a front and rear fence  http://www.finewoodworking.com/2011/07/0...sscut-sled     and  some have just a fence at the rear  https://woodgears.ca/delta_saw/sled.html   Either way, the main design issue is keeping the base of the sled fixed in relation to each other, with front and rear fences, that is much easier than with just one fence, though it can be done if the one fence is very rigid, and the base is attached very securely. If you make it with one fence, it will be lighter, and it allows you to cut work as wide as the miter strip, even if the miter strip is longer than the crosscut sled.

You can use cheap half inch ply  ( sandeply is one name ) from a borg, and that will give you plenty of rigidity ,  so long as the fences are rigid enough to hold them together.  While a torsion box is great at resisting bending, I don't see much bending force in use, since the sled sits on the table saw top during use. Again, so long as the two pieces of ply ( to the left and the right ) are held in a rigid relationship to each other, and the guide strip is rigid to the ply, it should work fine.
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#15
  Re: I am thinking of building a cross cut sled as a torsion box by Brucej (I am disabled and do...)
Since you use a crosscut sled while it is flat on the saw, there is no need for the stiffness of a torsion box, or even of 3/4" thickness. A sled of 1/2" or even 1/4" thick stock will work fine. It's lighter, and gives you more cut depth anyway. Yes, you need to be a bit more careful not to damage it, and need to put a little more thought into the replaceable insert (hint: repair by gluing a piece in or filling the kerf with sawdust and glue). I have a larger sled than you mention, made of 1/4" thick ply, that is still square after a decade.

By the way, I would not make the fence adjustable: glue it on. If your angle is slightly off, it's easy to shim with tape and screw on a face. If you leave a space below, that serves as the rabbet for dust.
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#16
  Re: I am thinking of building a cross cut sled as a torsion box by Brucej (I am disabled and do...)
bruce, im sure it would work but seems it would end up heavier than using 1/2" 9 ply BB.
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#17
  Re: I am thinking of building a cross cut sled as a torsion box by Brucej (I am disabled and do...)
If you build this, be sure to post about it.  I am tempted to make one like it, but I have not done so yet.



1/1/2018 Zero Degrees F, I am sick and tired of this global warming.
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#18
  Re: I am thinking of building a cross cut sled as a torsion box by Brucej (I am disabled and do...)
Hi Bruce

In your situation, I would experiment with using 1 sheet of 1/4 mdf/hardboard (no torsion table).  With a decent size rear fence, I think it would work.  The sled really doesn't have to support any weight because it rides on the table.  You'd want to store it carefully so that it doesn't warp when not in use.  It'd be easy enough to make a prototype to see if it works.

Good luck with your project.

Frank
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#19
  Re: I am thinking of building a cross cut sled as a torsion box by Brucej (I am disabled and do...)
I saw a sled that was made of 1/2" material, where the builder had removed a lot of the base to reduce weight.  It looked like a sort of web left, and it looked like it could pinch fingers, but it was low-weight and strong.
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#20
  Re: RE: I am thinking of building a cross cut sled as a torsion box by packerguy® ([quote='Brucej' pid=...)
(05-09-2018, 12:50 AM)packerguy® Wrote: Why not just use a piece 3/4" plywood and be done with it? Why the hassle to make a box, which adds thickness, making your depth of cut less?

What am I missing?

Bruce

I was really bad in a wheel chair for years and find doing things easy, simple, but works is the best.  I would do what Packerguy suggests since the plywood is really stable and lighter to use then what you plan to do.  Even 1/2 plywood would work well if cross braces on the end to keep the ends supported.
It is always the right time, to do the right thing.

Hi, I'm Arlin's proud wife! His brain trma & meds-give memory probs and has pain from injuries, but all is well materially & financially.  
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