Thursday, July 30, 2009

making sleds

Jim writes this question in reference to my DVD Basic Box Making:
In the 3rd chapter you showed us how to make a cross-cut sled (something I’ve always needed) and I was successful in getting the sled made!! The problem I’m having is that the sled doesn’t slide as easily as I thought it would. I know there are probably a number of things to try but have you ever had a sticky sled? I tried soaping the runners and I also tried steel wool. I then tried sanding the entire under-carriage of the sled. It just seems to take too much effort to push the sled. I checked the spacing between runners and they appear to be the right distance. Any suggestions would be appreciated.
My response: How many screws did you put in the runners? One problem I've seen is that woodworkers think that if two screws go in, surely 5 or 6 more would be even better. If your runners slide smoothly then two screws in each should be enough. More will actually expand the runners, making them fit too tightly in the miter gauge slots. Wax will help. If you've put in lots of extra screws, begin removing some until it slides smooth. Did you follow the sequence I showed in the DVD with the first screws being installed from beneath, using a square to align? Then, I assume you added the second runner by screwing in from above. If you only used two screws in each runner as I suggest, remove one screw and see how it slides. If it is still tight, put that screw back and remove the other. Check it. When it slides smoothly, put a 2nd screw in at another spot along the runner, this one also from above.

In a magazine, I had noticed that one well known woodworking writer made a sled with lots of screws holding the runners in place. He then spent another 15 minutes or so, sanding the runners to fit the slots. You can always sand like he did, but it is much better to get it right using the easier method.


bko said...

Hi Doug,

Aren't you worried that with only two screws per runner the whole sled assembly will shift like a parallelogram and not stay square to the blade? I would have thought that 6 screws was the minimum.

Thanks for all your great books and blogs--I really enjoy them!


Doug Stowe said...

The plywood sled base can't shift like a parallelogram. It is dimensionally stable. Any screws used over the necessary 4 put stress on the runners. The screws can be slightly offset, warping the runners in the slots, or can actually widen the runners slightly, so keeping them at a minimum is a good idea.

Also, when you make sleds, don't use glue. I had an apprentice one time who thought he was really doing a great job by adding glue between the runners and the plywood base. Then when they were too tight, they had to be thrown away rather than fixed.