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Thread: Proxxon Chuck on a Toyo ML-1
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14th May 2021, 06:56 PM #1Most Valued Member
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Proxxon Chuck on a Toyo ML-1
Finally got the Proxxon three jaw chuck for my Toyo ML-1. Chuck register on spindle measures 21.99mm. Chuck itself is more like 21.98mm. It does not slip straight on and not game to use any force at all. If I freeze the spindle it may go on but then I may never get it off again. These chucks mount to spindle with three M4 bolts through the chuck face. After suggestions on what to do to make it fit without affecting the accuracy.
Nev.
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14th May 2021, 07:07 PM #2Most Valued Member
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For those who want more details on this chuck and the Toyo take a look here -
https://metalworkforums.com/f65/t192...hlight=proxxonNev.
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14th May 2021, 08:21 PM #3Most Valued Member
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Have you got any other workholding for the lathe like a 4 jaw chuck or collets? Id turn a piece of stock in whatever you have, clamp the new chuck on that and just skim the new chuck ID.
Sent from my SM-G973F using Tapatalk
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14th May 2021, 08:30 PM #4Most Valued Member
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Toyo is still in pieces. No other chuck for it yet. The Optimum is still in trailer. Great idea though. I think I need less than half a though to make it fit. Very expensive little chuck so don't want to stuff it.
Nev.
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14th May 2021, 08:45 PM #5Most Valued Member
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15th May 2021, 05:33 AM #6
Hi, Guys,
Silly idea and you would need to be very careful.
Will the chuck grab a piece of bar with a few thou skimmed off to ensure that it is true to the spindle, and then polish off a couple of tenths with a round stone, say 600 or finer grit held in the tool post, just using the front edge of the stone. Lots of diesel fuel to stop the stone clogging.
I've only done this once on a hardened steel shaft to make a bearing push fit rather than a very tight push on.Best Regards:
Baron J.
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15th May 2021, 02:09 PM #7I break stuff...
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The problem with this approach is that 3 jaw scroll chucks inherently have some radial runout, no matter how good they are. While you could hold the bar in a 4 jaw, and then adjust the 4 jaw to get the register running true, or try shimming a jaw of the 3 jaw to get there, probably just as easy to set it up in the 4 jaw directly (time to get the Optimum out of the trailer?).
I found a chuck for a Proxxon PD250 listed online, which specifies 0.04mm concentricity. If that is the runout spec, even if it chucks up at half that, you're still going to be taking the 0.01mm on diameter just from one side. From memory this runout 'moves' around the chuck depending on workpiece diameter etc, so it won't get canceled out by cutting the register to match it, and in some situations it will be additive.
The 'good' news is that if I understand the style of mounting correctly, overshooting the target diameter is probably not going to be the end of the world and a ruined chuck, it just means the chuck just becomes a 'poor mans set tru'.... May not be the fit you wanted, but in some ways a better solution, and certainly easier.
If you ended up at say 22.1mm, with a chuck runout spec of 0.04mm, that would mean you should be able to bump the chuck 100% true for any workpiece clamped in it, even after a little bit of wear....
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15th May 2021, 07:34 PM #8
Hi J&H, Guys,
I 100% agree with you !
In my case I held the bar in soft jaws, so runout wasn't an issue and that is why I said taking a skim off the bit of bar that you were going to use as a mandrel. But you are right half a thou runout at worst is two and a half times greater than the amount of material that is wanted removing.Best Regards:
Baron J.
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15th May 2021, 08:14 PM #9I break stuff...
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That doesn't solve the issue of the runout in the new chuck that needs modifying though, which is where the potential problem arises. The approach you mentioned can be a valid solution for the right circumstances (like facing off the flat mating face for example), but clamping the new 3 jaw onto that machined stub will only get the register on the back that needs modifying running as concentric as the new chuck happens to run for that diameter. Axially it should run perfect if it's a good quality chuck and the machined bar has no taper, but radially it's going to have some amount of runout.
Probably not that clear from my previous post, but that is what I was getting at, for best results if you're using a tool rigidly fixed to the toolpost you need some way of dialing out whatever runout the new 3 jaw has (hence my comments about holding the bar in a 4 jaw, or shimming the jaws of the new (added for clarity) 3 jaw chuck with paper to get the register running dead nuts. Of course that assumes that the central point of the chucks runout is concentric to the register to begin with. You would certainly hope so on any decent chuck, but....
Polishing it with a hand held tool in theory mostly removes this consideration. Creates some slightly different ones to do with how consistent you are with angles and pressures, but that's a bit beside the point...
Or ignore it all, and deliberately bore a touch oversize for a poor mans set true, if the mounting style allows it as I suspect it does. A decision for the OP.
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15th May 2021, 08:44 PM #10Most Valued Member
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Thanks to everyone for the replies. A bit to think about and not going to rush it. The chuck was just over $300. Was lucky to get one, as they are now very hard to find. The original Toyo impossible to get. Considering the four jaw proxxon as well, but having trouble finding them anywhere as well now.
Nev.
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