MechanicalHg Posted January 22, 2016 Report Share Posted January 22, 2016 I built my first crosscut sled and squared it up with William Ng's five cut method. Used it for six months and was forced to take a break for about 6 weeks due to an injury. Went to cut some stock and realized the sled was totally warped. In particular the left and right side of the sled don't both sit on the tablesaw top at the same time unless I hold them down. It looks like the cut through the front fence weakened it enough to spread apart, and either the ply warped or the cut relieved stress in the fence. For reference the fence is about 4" tall, 2" thick oak beam on a 3/4" thick 2' x 2' birch ply. Identical fence on the rear. For a new sled I'm thinking MDF would be much more stable this time around, at least for the fence. But am I running the same risk of the ply potato chip effect due to the nature of the cut? Should the fence be taller or thicker? Anyone else run into warp issues after a while? How long do sleds typically last you before you make a new one? Quote Link to comment Share on other sites More sharing options...
Trip Posted January 22, 2016 Report Share Posted January 22, 2016 Assuming 3/4 'birch' ply translated to 3/4" Baltic Birch ply, then the issue is most likely the Oak fences... I use BB for all my jigs, never had an issue... If you use hardwood fences (which I tend to do), your best bet is QS stock and a climate controlled shop... If you have neither, then laminate some 3/4" BB for your fences... Good luck. Quote Link to comment Share on other sites More sharing options...
drzaius Posted January 22, 2016 Report Share Posted January 22, 2016 My bet is that the oak is at fault. Unless it's a very good piece of solid wood (straight grain), changes in humidity can cause warping. Laminating layers of solid wood or BB ply will yield a very stable fence. What kind of ply is it? Regular ply with a birch veneer isn't that great. I find that Baltic Birch stays very flat. My sled is only 12mm BB & it's stayed dead flat for years. Quote Link to comment Share on other sites More sharing options...
Cliff Posted January 22, 2016 Report Share Posted January 22, 2016 I pulled my old sled apart the other day and saw that the oak I had in place for blocking the blade from coming through the fence, and the non-ply fence had both moved enough to snap the 4 3 inch screws that i used to help hold them together. That's how I determined 100% plywood from now til forever. Quote Link to comment Share on other sites More sharing options...
MechanicalHg Posted January 25, 2016 Author Report Share Posted January 25, 2016 On 1/22/2016 at 1:14 PM, Cliff said: I pulled my old sled apart the other day and saw that the oak I had in place for blocking the blade from coming through the fence, and the non-ply fence had both moved enough to snap the 4 3 inch screws that i used to help hold them together. That's how I determined 100% plywood from now til forever. I thought about whether adding this feature would help keep the movement in check. Thanks for confirming that it doesn't help much. If the wood is allowed to move it will. On 1/22/2016 at 9:43 AM, drzaius said: My bet is that the oak is at fault. Unless it's a very good piece of solid wood (straight grain), changes in humidity can cause warping. Laminating layers of solid wood or BB ply will yield a very stable fence. What kind of ply is it? Regular ply with a birch veneer isn't that great. I find that Baltic Birch stays very flat. My sled is only 12mm BB & it's stayed dead flat for years. Admittedly it's veneer core from a big box store, who can't tell me the species. Since I don't have a jointer or planer I've had to source all my wood from there, whether boards or plywood. Is getting plywood from there generally a no-no? Am I better off buying it online or at a local hardwood dealer? Quote Link to comment Share on other sites More sharing options...
gee-dub Posted March 24, 2016 Report Share Posted March 24, 2016 On 1/21/2016 at 6:39 AM, hhh said: Assuming 3/4 'birch' ply translated to 3/4" Baltic Birch ply, then the issue is most likely the Oak fences... I use BB for all my jigs, never had an issue... If you use hardwood fences (which I tend to do), your best bet is QS stock and a climate controlled shop... If you have neither, then laminate some 3/4" BB for your fences... Good luck. BB ply for jigs here as well. I do have a couple of sleds with straight grained hardwood for the fences but, more recent sleds have laminated ply. My sleds stand on edge near the saw, sort of "nested" and have for many years without problems. Quote Link to comment Share on other sites More sharing options...
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