|Project by Mainiac Matt||posted 04-05-2012 01:41 AM||1856 views||0 times favorited||3 comments|
I finally had to have a sled to make the final length cuts on the glued up top of a hope chest for my oldest daughter.
Nothin’ fancy… just a plane Jane utility sled.
38” x 27” between the fences, 1/2” Melamine, 4/4 salvaged Mahogony fences joined and planed dead flat.
We have significant seasonal humidity changes so I shied away from using solid wood runners, and I had extra T-slot track that was dead straight so I used that for one track and a stick of 3/4” x 1/4” UHMW for the other.
We had a little debate at work about whether to use MDF or Melamine and a guy from the millwork dept. who used to work for a hardwood lumber dist. and really seems to know his stuff said the Melamine stays flat better. I thought it would also slide with less friction… More on that.
I can stay late and use the CNC table router at work for personal projects, so I thought I’d try something a little different and routed 1/8” deep dados for the runners and then routed the perimeter in the same set up. My theory was that this would gaurantee the runners were square to the back edge so that I could simply flush mount the fences and be good to go…..... NOT!
I got the dado width spot on for a friction fit with the T-track…. but botched my measurement of the spacing between them. So I transfered the correct location to the bottom, clamped on a straight edge and used a hand router to widen the right dado. Her is where I discoverd the down side of a slippery surface…. it’s very hard to clamp anything to it and not have the clamps slip :^(
Next challenge was that the UHMW was a shade too wide for the miter slot. So I played around with trying to scrape it and file it and then pulled out my #4 Bailey and discovered that you can plane a super thin see through shaving off UHMW like cutting butter :^)
Despite my best efforts to clamp and screw the fence flush to the rear edge, the rascal slipped on me and my first 5-cut test showed I was off by .039” over 17” :^(
Never fear… using William NG’s formula I’ll dial this sucker in with one adjustment…... NOT!
I overshot the first adjustment, but managed to get within .008” over 17” after the second adjustment, so I called it good ….. and no, the fence is NOT flush with the rear edge of the board …. so much for my CNC shortcut.
-- Pine is fine, but Oak's no joke!