Thursday, September 6, 2018

Jaws

Not the movie--drill press vise jaws.  I need a drill press vise with taller jaws.  The ones on mine are about 1 1/2" high.  I would like to use a drill/tap combo to do the entire operation in one pass.  The problem is that the length of the drill/tap combo is enough that it will go through the workpiece and into the vise below.  So put the workpiece higher up above the bed of the vise.  But then the workpiece isn't clamped solidly by the jaws (if clamped at all).

I built a jig that holds the workpiece above the bed of the vise.  It is slightly narrow than the workpiece so the jaws actually compress on the workpiece, but the workpiece pulls out of the jaws when the threads of drill/combo engage.  I believe this is because the jaws are not holding tightly enough.  Of course, because the jaws are no longer quite as squarely on the workpiece, the holding force is reduced, and just a little upward force pulls it out of the jaws.

1. Are there tall jaw drill press vises that still exert strong force on workpieces high in those jaws?

2. Is there some jig you can imagine that allows a very solid grip on the workpiece and yet it is a couple inches above the bed and jaws?

Found a workaround.  Between the bed of the vise and the threaded rod that clamps the jaw are gaps of .504" and .723".  Careful positioning of the workpiece allows the drill/tap combo to pass through these gaps, hitting nothing.  The downside is that I have not found the right torque setting for the Tapmatic to thread all the way through.  (This is an experimental aspect to the Tapmatic that frustrates me.)  I am tapping a somewhat gooey plastic that produces long curly strings instead of chips; in metal, where the chips are discrete, this would not be a problem.

The good news is that once I have threads started, I can put the workpiece in a vise, and use a tap in a power screwdriver to finish the 1" deep tapping.

5 comments:

Will said...

Generally, jigs/fixtures are designed for a specific application. It's somewhat rare to have a useful generic fixture. However, a vice can be considered to be a generic or universal fixture.

augustrrr said...

you could just make a taller set of jaws, possibly with a step on each side that would help holding the piece, even send the jaws out for hardening if it will be used frequently.

Probably, someone one will send a practical solution, or simply call a machining supply house or check their website.

Will said...

Some vises have a gap in the bottom that would allow a drill bit to go lower. Probably have to offset the part to avoid the drive screw in the center. I have a vague recollection of a vise that had dual drive screws to leave the center free for this sort of situation, but don't remember any details.

Might be worth the effort to design a fixture to hold this part. No idea what to suggest in this regard without knowing what it looks like. Maybe twin vises that are bolted to a common base plate?

Clayton Cramer said...

augustrr: I see replacement jaws for sale. If I buy some taller ones, will they exert similar pressure at the top to the standard jaws?

Will said...

Re the taller jaws:
The drawback is the higher the jaw, the less leverage is exerted at the tip, as they want to tilt. It all depends on the design, though. There is a reason why they aren't 6" tall, normally. Big, beefy bench vises may get to that size, but they have to be massive to work properly. You could look for a small/medium bench vise that could be fitted to your drill press table. A good one won't be cheap. Horror Fright probably won't carry a good enough quality one. It could easily cost more than your drill press.