Punch holder
© 2007, Brian Meek
V1.01, All Rights Reserved


Overview: Adapting an antique drill chuck to serve as a quick change tool holder for a Bonny Doon hyraulic press.

This isn't a project, it's just documentation of one particular Frankenstein.
Any attempt to replicate this modification is undertaken at your own risk.

Once upon a time, I went to the estate sale of a retired gunsmith. It was the mother lode. Picture a shop that I would consider excessive. Ponder how discombobulated I'd have to be for there to be 2 anvils for sale....and I completely missed them. Yeah. That kind of a sale. From which both I and the Wake Center scored greatly. Wandering around in slack-jawed awe, I noted the 'going to the dump' scrap pile. Knowing that they also serve, who only lurk and pry, I dug into it a bit. I discovered a couple of interesting gems. Among them was this antique drill chuck. It's of the two jaw type that was used on drill-presses in the late 19th and early 20th centuries. They're not as accurate as modern style 3-jawed Jacobs style chucks, but they do have several interesting properties.
(A) They have two jaws, with 'V's ground into them, which means that they'll grab square rod accurately.
(Chasing punches anyone?)
(B) They are new enough to use a modern tapered socket as a mount. The tapered socket, (JT-33) is still a standard taper. However, the important thing about the JT-33 taper is that the hole goes all the way through, into the inside of the chuck. Which means that anything grabbed in the chuck that presses up against the back of the chuck is actually pressing against the adapter, not the chuck body itself.
(C) they're built like solid steel tanks. The area of the chuck body that surrounds the socket is 1" deep, and 1.75" in diameter, solid steel.

Part of my plunder from this sale was a large kickpress. This new one is my fourth. Unfortunately, the first three are in mothballs back in Ohio, while I'm in California. (California was originally supposed to be an 18 month adventure....ten years ago. (Hey, there's winter everywhere else!)) The big advantage to kick presses is their speed. They don't hit nearly as hard as a screwpress or a BD style hydraulic, but they hit fast. They can strike as quickly as you can kick your leg, which is just perfect for repusee or other forming/stamping operations.

Both styles of press require some way to hang on to tooling. Looking at this old chuck sitting on the junk pile, Dr. Frankentool's whiskers began to twitch.


The antique chuck. Note the size of the gripping jaws, and the internal shot showing the "V" of the jaws.
It'll securely grab either round or square stock.


The short version of the FrankenForming™ of this particular drill chuck follows.


The important thing to remember is that the pressure needs to bear against the taper adapter, rather than being carried by the chuck body or jaws. The chuck is just along to hang on to things. If the forces get misaligned or tilted, the chuck could easily break or be damaged. Thus the 1/2 inch diameter taper adapter needs a little more width, to help it resist the strains from angular misalignment.

I'm showing the chuck/holder set up to fit my Bonny-Doon press, as those are vastly more common than kickpresses. I'm generally going to use it in the kickpress, as that's the one where I'm more likely to need to change tools quickly, and to be using chasing/dapping punches. The setup for the kickpress just adds a 1" diameter shank that screws on to the top of the adapter plate.

I'm not going to give step-by-step instructions for this one, as there is some risk that a poorly executed version of this tool could break catastrophically, causing injury. Not much chance, but enough that the Lawyers are antsy.
So what I did in this particular instance was this:
I cut off the end of the Morse adapter, leaving about an inch above the back of the chuck. I turned it down to a cylinder, and left the bottom bit at the max diameter I could get out of the remnant of the Morse adapter. I left a bit of a step at the bottom of it, and then turned the rest of the body to a slightly smaller diameter. I used a piece of 1.25" stainless scrap to make a large, thick washer that was a press-fit onto the smaller diameter I turned onto the remnant of the Morse adapter. This washer will spread the contact area of the tool, and help it resist misalignments. It will also help reinforce the remnant of the Morse adapter once I drill out the center of it to tap it for an attachment screw.
The critical thing about the washer is that it not press against the back of the chuck itself. It should be stopped by the little step left at the bottom of the adapter remnant. Once that was pressed into place, I drilled and tapped the center of the adapter, making sure not to drill all the way through the bottom of the adapter. I left metal down there for the tools to press up against. After that, it was done, except for screwing it into place on the press using a grade 5 bolt. If you don't know what a grade 5 bolt is, or understand why you want one here, think seriously about whether you should attempt to make this tool.

Remember that there are two critical things about this toolholder:
(A) whatever tooling you use must fit all the way up into the chuck, and press against the bottom of the adapter.
(B) you must make absolutely sure that all forces stay aligned vertically up the center of the chuck.
Depending on how well it's made, it may not take much misalignment to either break it, or send it blasting across the room. Both of these results are bad.


The toolholder installed on my Bonny-Doon 20Tall press. Note the amount of clearance available.
This tool is not practical for the shorter presses.


The installed tool holder, with illustrated cross section to show the various parts.
The remnant of the Morse adapter is in red, while the washer is in green.
Note the step at the bottom of the adapter stub that prevents the washer from pressing down against the chuck body. I left a gap of exactly .050" inches between the back of the chuck and the washer, so that I could use feeler gages to inspect the tool to make sure the adapter does not bend or distort.
(Inspections prevent surprises. Surprises are almost always bad.)
All forces are directed down through the adapter, not the chuck body.