Need a very small 4-jaw chuck

hman

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Here's my dilemma - I'd like to put/renew a nice point on a prick punch or center punch. The problem is that several of my punches have square bodies. So I can't just chuck them into an electric drill (3-jaw chuck!) to rotate them while holding the tip against a grinding wheel or belt sander. If anybody has an idea or knows of a small 2- or 4-jaw chuck suitable for use in an electric drill, I'd be happy to hear about it.

... and here's a crude and imperfect "field expedient" solution I've come up with. I had this old bit brace, acquired at a garage sale years ago. I'd originally intended to chuck up a countersink and use it to deburr drilled holes. Never got around to it. I recently came to realize that a bit brace is designed to hold square shanks.
kHPIM5956.jpg

So today I removed the chuck assembly from the brace, disassembled and cleaned it, and chucked up the core in my lathe. Machined off the ratchet action splines and turned it down to a diameter my drill would be happy with - just under ½". After a light greasing and reassembly, I now have what amounts to a 3-jaw to 4-jaw (OK, 2-jaw) adapter. It happily accepts square shanked punches. Runout isn't perfect, but not really too bad. Now I can regrind the points when I need to.
kHPIM5958.jpgkHPIM5960.jpg

As I said, it's a bit crude. But it's the best I've been able to come up with so far. Suggestions welcome!
 
Square 5C collet in a whirly jig . As soon as I get this grinder hooked up this would take less than a minute . :encourage:
 
Make a simple chuck or use an old collet if you have one and use a 3 jaw chuck. A piece of tubing that fits over the square portion of the punch. Even better would be a piece of tubing that fits over the round section but it's overall thickness has a larger diameter than the square part. Then 3 slits and tighten it down in a 3 jaw chuck. Easy to visualize tougher to explain.
 
Looks to me that it could be chucked up with the square shank behind the back side of the jaws.
 
Why avoid the obvious; do like machinists have been doing for literally hundreds of years, do it by hand -- hold between thumb and forefinger near the end to be sharpened, while twisting, or rolling between the thumb and forefinger of the other hand at the appropriate angle, 60 deg. for a prick punch, 90 deg. for a center punch (or nearly so).
 
Check size of square across corners and collet that dia.
 
Thanks for the responses so far. I guess I could use a square-hole collet, but I have several square-shanked punches, all of different sizes. So a chuck, with its wide adjustment range, makes a bit more sense to me. Kind of a ditto as far as round sleeves is concerned - especially for my largest punch, about 7/16" square. A round sleeve would have to be larger in diameter than ½", the capacity of my drillmotor. And yes, I could spin the punch by hand. I'm just not that good at doing so.
 
Hmmmm ... Looks like a useable size. But, wanting my cake and eating it, too, I went looking at some of the "related sponsored items" in search of a scrolled 4-jaw. There were at least two offered. Here's what I think would be bestfor my needs:

Hard to decipher, but it appears that it used an M14 mounting thread. If so, it would be easy to machine up a ~1" "spindle" with M14 threads on one end and ~½" diameter at the other. MANY THANKS for the link!!! I'd seen 4-jaw chucks in the 4" size range, but even never thought to search for smaller ones. Your "kick in the pants" was helpful.
 
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