Replies

1. 
   Napie | Nov 26, 2008 08:37pm | #1

   Simple is better.  I build each for a specific purpose, 90 deg, miter, bevel, panel, etc. they are cheap and easy.  Cherry or maple for the runners, good birch ply is best, I use the Baltic stuff but I would like to try the phenoic (sp?) coated stuff.  Wax the bottoms and away you go.

    

1. 
   Patrick_J_Harris | Nov 26, 2008 11:19pm | #2

   Thanks!

2. 
   Eef | Nov 26, 2008 11:51pm | #3

   napie,

   instead of wood runners under the sled, been making them out of 1/4" plexie-glass. works real good and never shrinks or swells.

   eef

1. 
   KiddervilleAcres | Nov 27, 2008 06:57am | #5

   eef,

   Have you tried the UHMW strips from Lee Valley?  I use them and they work very well - fit the mitre slots perfectly and slide like they aren't even there.

   I countersunk the screw holes so the head sits just below the surface.  The screws did dimple them slightly but a kiss or three with a sanding block and Bobs your uncle.

   Regards,

   Bob @ Kidderville Acres

   A Woodworkers mind should be the sharpest tool in the shop!

   Edited 11/26/2008 10:58 pm ET by KiddervilleAcres

1. 
   Eef | Nov 27, 2008 09:31pm | #6

   morning bob,
   i am, without a doubt, the most acronym-challenged fool one would ever want to meet. umwh. huh?
   eefsee what i mean? UHMW.

   Edited 11/27/2008 1:32 pm ET by Eef

1. 
   KiddervilleAcres | Nov 28, 2008 02:47pm | #11

   Eef,

   Oooops, it stands for Ultra High Molecular Weight.  You can get it in various sizes and works great for runners in sleds and other fixtures: http://www.leevalley.com/wood/page.aspx?c=2&p=32045&cat=1,43455,43831&ap=1

   Regards,Bob @ Kidderville Acres

   A Woodworkers mind should be the sharpest tool in the shop!

2. 
   PeteToo | Nov 29, 2008 06:17am | #13

   That's Ultra High Molecular Weight POLYETHYLENE.

   White, tough stuff, easily cut and slippery as an eel - and no tensile strength or stiffness to speak of but as we use it you don't need tensile strength or stiffness.

   Those side bulges from flat head screws can be used to tighten the runner(s) to the slot(s).

   It happens though that I need someone to tell me a foolproof way to make the sled's back rail *absolutely* perpendicular to the cut, which I understand is the real purpose of a sled to begin with.

   Respectfully,

   Pete

3. 
   PeterDurand | Nov 29, 2008 06:29am | #14

   <<*absolutely* perpendicular to the cut>>In theory no such thing. However if you are wanting the next best thing I suggest a Swiss machinist :-)The reason for that comment is that my best friend is such a creature and I am constantly amazed at what he considers tolerable allowances. He used to be the head of the lab at the university that made parts that were used in physics experiments in satellites. A whole other world, and a fascinating one at that. Cheers,Peter 

   Better life through Zoodles and poutine...

4. 
   PeteToo | Nov 29, 2008 06:43am | #15

   Thanks Peter,

   I suspected this was the case.  Some sources seem to indicate that their methods are foolproof but I always seem to turn up a flaw somewhere in their procedures - or maybe mine.

   I use a dial indicator to set up my equipment, including the tablesaw, so those things are within a (very) few thousandths of being correct.  I'll start a sled soon and find my own way of zeroing it in I guess.

   Pete

5. 
   AlanWS | Nov 29, 2008 07:28pm | #16

   "It happens though that I need someone to tell me a foolproof way to make the sled's back rail *absolutely* perpendicular to the cut, which I understand is the real purpose of a sled to begin with."My approach is to attach it down solidly close to square, and then attach and shim a replaceable face. This allows you to keep a clean kerf to measure to, and there's no need to chamfer the bottom of the fence if you mount the face up a bit to allow sawdust below.The easiest way to get the fixed fence close to correct is to attach a block to the sled, slice it, and then hold a framing square against the block as a guide while you set the fence. I'd glue and screw the fence so it won't shift.Now check how close it is to square by the "5-cut method" (google it if you're not familiar.) You will wind up with a cutoff of length L, where the difference between the thickness at each end, measured with calipers, is D. Take some tape, or whatever you will use to shim, and fold it into 4 layers with the sticky part inside. Make sure there are no wrinkles or bubbles, and measure with calipers the thickness of the 4 shim layers as T. Now calculate the correction C = L x D / T. Cut pieces of tape that differ in length by C, and stick them to the permanent fence as shims. You should be able to easily figure out which direction you want to tilt the fence, then the idea is to put a bit of tape on one end of the fence, cover it with another piece that extends C longer toward the other end of the fence, then another piece C longer than that, etc. This takes a lot less time to do than to describe. Once you have all the shim tape installed, screw a flat and accurately thicknessed face to the fence.Now check with the 5-cut method again, though you now need only 4 cuts this time since you know the first edge is straight. Check several times without reshimming because if you follow this procedure you are likely to have the fence as accurate as your cutting procedure after the first try. You should get values that cluster around perfectly square. If you are not satisfied, you can repeat the procedure using your average numbers. If the scatter is too large, you will need to fix that by removing slop from runner fit, or more consistent technique.

6. 
   AlanWS | Nov 29, 2008 07:35pm | #17

   Was that over analyzed? Of course. But it does work, and it's practical for those who want to bother. It's less work than repeated tweaking, and if it does not work it means there is another problem and tweaking won't help until you fix that.

7. 
   PeteToo | Nov 30, 2008 03:16am | #18

   Thank you Alan,

   I'll now cut and paste your description and save it in my woodworking notes.  I believe the method as you state it is about as fine as one can slice it (pun intended).  I'll put it to work as soon as I finish tuning my jointer *and* the various jobs the "boss" (that is, the manager of this household) has waiting for me.

   Appreciatively,

   Pete

8. 
   KiddervilleAcres | Nov 30, 2008 05:11am | #19

   Hi Pete,

   How accurate do you really need it to be is my first thought/question?  Trying for absolute perfection in terms of being square to the fence really involves a lot of different things, not just the sled.  Before making any sled make sure the mitre slots are nuts on to the blade.  If they aren't then a sled is simply frustration, nothing more or less.

   I have a very accurate framing square that I use and also like the secondary fence approach as well.  I make the primary fence from two layers of baltic birch and make a secondary fence out of any straight piece of hardwood after milling it as square as I can. 

   Lay one side of the L against 2 teeth (front & back) on the blade and lay the primary fence against the other L and clamp firmly in place.  Then screw it to the bed of the sled with several screws spaced along its length.

   I then clamp the secondary fence to the primary and make some test cuts - sometimes I get lucky and that's it.  Oh yeah, the test piece also has to be nuts on square too!

   If not lucky I figure out how much I'm off and make some shims out of flashing material then shim/test cut till I'm square.

   Once square, screw the secondary to the primary and test again.  That's good enough for me.

   Regards,Bob @ Kidderville Acres

   A Woodworkers mind should be the sharpest tool in the shop!

3. 
   PeterDurand | Nov 27, 2008 02:06am | #4

   You realize of course that you have now run afoul of real woodworkers who maintain that a table saw should ONLY be used for ripping. :-)CheersPeter(unpure) 

   Better life through Zoodles and poutine...

1. 
   Buster2000 | Nov 27, 2008 10:14pm | #7

   You realize of course that you have now run afoul of real woodworkers who maintain that a table saw should ONLY be used for ripping.

   You can do whatever cut you want on a table saw as long as it's on a European saw.  They are far superior you know...  :)

1. 
   PeterDurand | Nov 27, 2008 11:32pm | #8

   Let me rephrase that:You realize of course that you have now run afoul of real woodworkers who maintain that a table saw (and only Europeans make real table saws) should ONLY be used for ripping.That should about cover it ;-)Cheers,Peter
    

   Better life through Zoodles and poutine...

2. 
   roc | Nov 28, 2008 12:30am | #9

   This is what I use. I have different ones for different purposes as recommended.

   For the base I use 1/4" masonite. Seems to work for me and saves some blade hight for tall work.

   The stop is part of my metal working jig fixtures. I threaded the wood using machine thread tap and works great; makes a better jig than wood screws. The metal is simple aluminum flat strips from Home Depot layered to make an adjusting slot. Could use wood. Add a flip down stop not shown. Note holes on both ends of fence so can put stop on either side of fence.

   On working side of fence at the bottom cut a rabbit less than 1/8" tall so there can be a place for a bit of saw dust to go without your work being "spaced" out from fence by saw dust.

   
3. 
   Yitz | Nov 28, 2008 06:05am | #10

   I've seen two ideas for cross cut sleds which I thought were pretty neat:

   1)  Some people build a little "garage" hanging off the back of the sled to cover the blade as the sled slides all the way forward.  This protects your hands if you happen to go brain-dead (who me?) after a cut.

   2)  If you make your runners out of hardwood, chamer both (long) corners that will end up against the bottom of the sled.  This makes it much easier to touch up the runners with a block plane if you need to fine tune the fit.

    

   Happy Turkey Day y'all!

1. 
   Dave45 | Nov 29, 2008 04:04am | #12

   I also make my runners so they run ~1/16" above the bottom of the miter slots. That way, I don't have to worry about having a bit of sawdust in them.

4. 
   stillfigurinitout | Nov 30, 2008 08:52am | #20

   for the record my tolerance for accuracy is just under 0.001 inches.  howls, just kidding.  the fellow woodworker in the attached link has a unique approach to aligning the sled fence 90 degrees.  i tried it the day after reading his blog and so far, i'm happy with the results.  after getting the fence square and tightening down the two wingnuts, i gingerly fastened the fence to the sled with a few more screws.  the blogger just used screws on the left and right side of the fence.

    

   http://lumberjocks.com/jocks/GarageWoodworks/blog/6395