Tiny quick change toolpost

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mars-red
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Re: Tiny quick change toolpost

Post by mars-red »

Another quick update, the rotary broaching attachment for the qctp is usable now except I have not made a broaching cutter for it yet. Hoping to get that part done soon so I can try it out and see how well it works. I'll also try to take some pics and post them up tonight. I made a little 60 degree center for it, to make centering the attachment easier... if I make the broaching cutters protrude from the broaching spindle by the same amount as the center, minus the amount that the center extends into the hole I'm broaching (which would always be the same for any particular broaching cutter), then the 1 degree angle of the broaching spindle should not cause any centering accuracy issues.
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ctwo
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Re: Tiny quick change toolpost

Post by ctwo »

Just one comment on the tool holder height adjustment. I know the Aloris style holder is quite popular. I, instead, have the KDK style that came on my machine and I do not plan to switch. One thing I like about KDK is that the height adjustment is via a set screw that rests on a pin at the bottom of the tool post. The set screw is offset from center, as is the pin, so that two set screws can be placed side-by-side, one from top and one from the other top. Meaning, the tool holder can be inserted both ways and a separate tool on each side of the holder, each with independent height adjustment. That is about all I like about my tool post. Well, it has a smaller handle on the far side that only gets in the way occasionally. I like your modular handle.
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mars-red
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Re: Tiny quick change toolpost

Post by mars-red »

ctwo wrote:Just one comment on the tool holder height adjustment. I know the Aloris style holder is quite popular. I, instead, have the KDK style that came on my machine and I do not plan to switch. One thing I like about KDK is that the height adjustment is via a set screw that rests on a pin at the bottom of the tool post. The set screw is offset from center, as is the pin, so that two set screws can be placed side-by-side, one from top and one from the other top. Meaning, the tool holder can be inserted both ways and a separate tool on each side of the holder, each with independent height adjustment. That is about all I like about my tool post. Well, it has a smaller handle on the far side that only gets in the way occasionally. I like your modular handle.
Thanks! I did briefly consider a protruding pin for a height adjustment stop but then thought it would be in the way of the locking piston. I didn't want to make a wedge type holder, but it never occurred to me just to offset the protruding pin. I probably could have made room for that.
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mars-red
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Re: Tiny quick change toolpost

Post by mars-red »

I have a couple of pictures of the rotary broaching tool holder, so far:

Image

Image

The spindle is at a 1 degree angle to the toolpost mounting, and the outside face of the block is at 2 degrees. The 2 degree face can be used to set up a broaching blank for milling the cutting edges with a 2 degree relief, directly on the lathe. In the pics above, there are two tools to fit the spindle - one is a 60 degree center, and the other is a broaching blank I have prepared with a 1.5mm diameter turned on the business end. I'm going to try out either a square or triangular shape, haven't decided yet. There are 24 graduations around the collar of the spindle, which will cover both triple square and torx, should I decide I want to make anything like that.
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mars-red
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Re: Tiny quick change toolpost

Post by mars-red »

Well, I made up a square broach from that blank in the last pic - it turned out great and hardened nicely. Unfortunately, rotary broaching with broaches this small just doesn't seem to work. The tiny broach isn't able to turn that relatively large spindle (the broach just bores out the hole, much like it would if it was off-center). I did anticipate that the broaches would be sort of a pain to get centered, so that was no surprise. This spindle has way too much bearing surface though. Maybe some good miniature ball bearings would work, but I'm not sure I'll bother with anything like that. I'll have to try a much larger broach in it at some point, but for now I'm going to try some other methods of using tiny broaches like this... so far, I'm thinking I'll make an adapter for my staking tool to tap the broaches through - the brute force method probably wouldn't take much actual force, given the size. I also have a really neat miniature screw press that I might try these with, too. It did cross my mind to hold the broach in the tailstock and push it through with that... but the tailstock on this machine is lever feed. Besides, it seems like that would be bordering on machine tool abuse. :)
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