Thickness of rails on box joint jig

[Dick Brown]

I have built a few box joint jigs and always had the bottom of the jig slide on the table top. Need to build a new one and wondered how it would work to make the rails a bit thicker so they carried the weight of the sled rather than the sled bottom (Cast iron top) Less drag? What's your thoughts?
Dick

[Bill Dufour]

Then the plywood will have to be perfectly flat with no bow. The plywood will have to be twice as thick or more so it does not bow down in the middle as you push it along. a few thousandths of bow would make the joint fit poorly.
You can always wax the bottom of the plywood, even groove it to reduce friction.

[Grant Wilkinson]

If I understand your question, the bottom the jig would not touch the top of your table saw. Only the runners that slide in the table saw tracks would be in contact with the table saw. Is this correct?

The theoretical downside that I can see is you are depending on the bottom of the table saw slots to be smooth and completely parallel to the top of the table saw. Generally, in building jigs that use runners in the table saw slots, we make sure that the runner does not touch the bottom of the slot. (I'm sure that's been your practice to date.) This ensures that the weight of the jig is spread out over the entire base of the jig and that it is sliding on the smooth table saw top.

On my saw, for example, the bottom of the slots is pretty rough. It causes me no grief as I don't have any jigs that register against it. If I were to try your idea, I believe that I would encounter more resistance, not less, since the slots are not polished.

Not having tried this, Dick, I'm only speculating. If you try it, I would be interested to read your results.

[Al Launier]

If I understand your question, the bottom the jig would not touch the top of your table saw. Only the runners that slide in the table saw tracks would be in contact with the table saw. Is this correct?

The theoretical downside that I can see is you are depending on the bottom of the table saw slots to be smooth and completely parallel to the top of the table saw. Generally, in building jigs that use runners in the table saw slots, we make sure that the runner does not touch the bottom of the slot. (I'm sure that's been your practice to date.) This ensures that the weight of the jig is spread out over the entire base of the jig and that it is sliding on the smooth table saw top.

On my saw, for example, the bottom of the slots is pretty rough. It causes me no grief as I don't have any jigs that register against it. If I were to try your idea, I believe that I would encounter more resistance, not less, since the slots are not polished.

Not having tried this, Dick, I'm only speculating. If you try it, I would be interested to read your results.



My thoughts as well.

[glenn bradley]

I like the base supported by the saw. If your saw top isn't slippery, I would fix that rather than design a heavier jig.

[Al Launier]

I like the base supported by the saw. If your saw top isn't slippery, I would fix that rather than design a heavier jig.


Purgamentum init, exit purgamentum = Garbage in, garbage out. Obviously not applicable to Glenn. VIVO would be more appropriate!

[Charles Lent]

A good coat of Johnsons Paste Wax on the table saw top will make a huge difference. I re-wax my tool tables before each project, and sometimes again during projects. It not only keeps my cast iron from rusting, but makes things slide easier over them.

Charley

[Dan Cameron]

Dick, when I built my BJ jig I took a garage sale miter guage, set the angle to an accurate 90 degrees, and locked it there by drilling and inserting a steel pin (permanently) The BJ jig is bolted to the face of the miter guage. That way, the material being cut rides directly on the TS surface.