Tiny quick change toolpost

[mars-red]

I thought I'd share one of my current works-in-progress. It's a small piston type qctp for my watchmakers lathe. I've seen tiny tool holders made by Levin, but I'm not crazy about the design and they cost an arm and a leg. If I was going to make my own, I decided I'd rather have the traditional Aloris type (but on a much smaller scale).

Here are the parts, so far, with some finishing left to do and some parts still to make. The body was milled from cast iron, and all the other pieces are tool steel (O1 and A2):


This was my first attempt at milling dovetails and it worked really well. I made up for that success by breaking off a drill bit in one of the tool holders and breaking off my M1.4 tap in the other.

I still have to make a retainer for the locking pin, the height setting mechanism for the tool holders, and finally will need to make a few more tool holders. I'll mill the dovetail in a single bar of stock and then just slice it up to make a small batch of holders.

Everything is functional (though without repeatable height setting) and it sure is a lot more solid than the lantern I was using:


The top "nut" locks the post onto the top slide, and the collar underneath that locks the tool holders in place. I'm not going to have fixed handles on either of those, as handles just get in the way on machines this small. Instead I'll continue using that 1/8" round HSS blank as a tommy bar.

I'll post up more pics when it's completed!

[SteveM]

Nice!

Only thing I would suggest is using socket head cap screws because I see that the slotted heads are going to get buggered up after repeated uses. Not sure if you can do that in the size you are using.

Steve

[mars-red]

Nice!

Only thing I would suggest is using socket head cap screws because I see that the slotted heads are going to get buggered up after repeated uses. Not sure if you can do that in the size you are using.

Steve

Thanks Steve!

I definitely agree. These screws are temporary - they're actually from an assortment of eyeglass replacement screws and are really poor quality. Not only that, but as you can see the longest ones I have still require a shim on top of the 1/8" turning tool to make contact. I was going to keep this up my sleeve for now, but one of the holders I'm going to make is a rotary broaching attachment, that will let me easily make my own socket head screws, among other things. When that's done, I can set about making a few dozen really nice, hardened and tempered, M1.4 socket head screws for these. I could buy 50 of them for about $30 but I'd much rather make them for this project.

[mars-red]

Last night I decided what to do about a height adjustment mechanism. I turned some relatively long M1.6 studs and pressed them into each tool holder. To cut down on the length of the stud that would be needed, given that the tools are mounted fairly low on this machine, I made nuts with long threaded shoulders to take up the difference. If I ever use this toolpost on a machine with slightly larger swing (like that Schaublin 70 I've been dreaming of having for years!), the nuts can be flipped upside down if necessary. The nuts were made from some scrap 1040 steel, and the studs were made from small steel nails. I used small springs to keep tension on the nuts, and it seems to be the perfect amount to avoid accidental adjustment.

I still need to make a retaining mechanism for the locking pin (so that it doesn't fall out when there's no tool holder in place), and then I guess I'll just need to make up a batch of holders.

Quick pic:

[hammermill]

ok you got me with the eyeglas screws, this is smaller than i thought. hows about throwing in a quarter for prospective. all good ken

[mars-red]

ok you got me with the eyeglas screws, this is smaller than i thought. hows about throwing in a quarter for prospective. all good ken

There's a penny in the first pic.

[hammermill]

i see that now

[ctwo]

Makes me want to get a small lathe. Nice work!

[arthur.marks]

I always enjoy your stuff, mars-red. My vote is for square head screws on the toolholders. A socket head will make the hex engagement miniscule. I could see the issue of fragility for tiny, miniscule hex sockets being no better than a slotted head. Then use that rotary broach tool to make yourself a t-wrench for the square head screws

[mars-red]

Thanks guys! Arthur, that's a good point about the square drive. You've got me thinking now - what about triangular drive? Or torx? In any case, it would be a lot quicker for me, with my tools, to broach all the screws so the only milling I'll have to do is on the broaching cutter and then the wrench or driver, rather than milling each screw. Given that, torx wouldn't take much more effort than square or triangular or hex, and seems like it would be the best amount of engagement. I've always been a fan of triple-square too, but torx certainly seems more positive to me. One thing that does occur to me, though, is that torx seems like a lot more material to remove, outside of the base circle, and rotary broaching that on my watchmakers lathe might require progressive broach sizes. I think I'll have to experiment with different shapes to find the best one that I can broach in a single pass on this little machine.

Speaking of such things, I started on the broaching tool holder for the qctp last night. No pics because there's not a lot to show yet, just a tiny block of A2 that was milled true, then slotted and dovetailed to fit the post. I'm using most of the design from Mike's Workshop - it's basically his broaching arrangement adapted to fit my qctp: http://mikesworkshop.weebly.com/rotary-broaching.html I'm thinking I'll use 24 divisions on the graduated collar - I do like that he thought to use the same tool holder for actually making the broaches, that's pretty slick.

[arthur.marks]

I was thinking of starting with square stock. Then the screws are entirely a turning operation. No milling necessary. Not sure if the needed size would work with WW collets though? Also, just as an FYI, remember that rotary broaching can be used for male forms as well as female. I don't have any experience with that, though, so I couldn't tell you if there is a difference in set-up or principle. For example, >here<

[mars-red]

I was thinking of starting with square stock. Then the screws are entirely a turning operation. No milling necessary. Not sure if the needed size would work with WW collets though? Also, just as an FYI, remember that rotary broaching can be used for male forms as well as female. I don't have any experience with that, though, so I couldn't tell you if there is a difference in set-up or principle. For example, >here<

Excellent point about broaching male forms, that didn't even occur to me. I'm afraid square stock would be a bit of a hassle for me at the moment - I don't have any 4 jaw chucks for any of my machines. The watchmakers lathe is the only one I have up and running that takes collets and you're right, I've never seen WW collets that will hold square stock (I certainly don't have any, at any rate). An independent 4 jaw chuck for the watchmakers lathe is on my Christmas list so i may actually be able to make the screws from square stock by the time I get around to it.