|The undercarriage of the step stool I'm making|
This is not too complicated, but there are a few things you've got to be careful about. I'm mainly concerned about the angles used to drill into the legs for the rail tenons. I'll get to that in a bit.
The first step was to find the vertical location for the connecting rails. So with the legs dry-fit into the top, I turned the stool over and measured to mark each leg a consistent distance from the underside of the top.
|Using a combo square to find the vertical location of the rails|
|About 5 1/2" got me to the fattest part of the legs|
|Marked a location midway between rubber band strings to get "dead center"|
|First bevel gauge gets the rake (or is that "splay") angle|
|Second bevel gauge records the splay (or is that "rake") angle|
|Leg in a "cradle", leg is at the angle of the first bevel gauge|
|Drilling at the angle of second gauge|
The stretcher that connects the two rails didn't need any special angles. Just straight 90° drilling into the rails. I'm sure there are other ways to work out the angles for drilling the legs, but this worked for me.
|Here's what it looks like right-side-up|
The strength that the undercarriage adds, compared to a stool with only legs, is remarkable. After gluing, this stool is so much more rigid than any others I've made.
|And here she is all gussied up|
Second, the glue up was interesting. Even though I had my legs and all parts numbered and did a couple dry-runs, I still put a leg in the wrong hole when gluing up! Fortunately I was able to knock it apart and get it right. The order of gluing was as follows: stretcher to rails (a tad loose), rails to legs (a little looser), then legs to top. You need to have the undercarriage joints a little loose so there is some flex - otherwise you can't bend the legs enough to get them all in their angled mortises.
Comments and suggestions welcome!