Mini lathe chuck size

[Stuart Smith 5Participant @stuartsmith5]

[Stuart Smith 5Participant @stuartsmith5]

I am trying to decide which 'mini lathe' to buy.

I am looking at the small Chinese lathes from Chester, Amadeal, Warco etc.

Some have 80mm chucks and some 100mm chucks.

Any advice on if there any problems with the 100mm chuck on a small lathe? I have seen a comment that this size chuck is too big for the power of the lathe.

Thanks

[HOWARDTParticipant @howardt]

It's not the size of the chuck it's the size of what you put in or and the speed you can run it at. I have a 7 x 400 and run a 125mm 4 jaw with no problems.

[Brian GParticipant @briang]

One big advantage of a 100mm chuck is that you can use the full size of the spindle bore (our 80mm independent 4-jaw allows this but not the 3-jaw). Generally the lathes with 100mm chucks also come with a quick release tailstock, and are probably worth getting for that feature alone – getting a 17mm spanner under the compound handles is no fun.

Brian

[Neil WyattModerator @neilwyatt]

You can fit a 100mm chuck to a 80mm spindle with a backplate and get full size access to the bore (I have) but the other way around is problematic.

I think most mini lathes have a QR tailstock these days.

Personally I would always go for the standard spindle as unless you have it you can't fit the standard ER25 chucks or faceplate and a 4" 4-jaw might be over the top so being able to fit an 80mm one will be a benefit.

I nearly swapped a 100mm spindle into my mini lathe and decided against it.

Neil

[jimmy bParticipant @jimmyb]

I have put bigger chucks on my smaller lathes, I think it’s worthwhile. Really improved the work holding. Ran a 100mm chuck on a C3 and 125mm on my C4 with no problems.

Jim

[Martin Shaw 1Participant @martinshaw1]

I have an SC3 and decided I wanted 4" chucks for all the reasons outlined above however whilst the 3" chuck is fine when I put the 4" backplate on there is a distinctly unpleasant vibration around 1000rpm, and thats before the chuck is fitted. There is a slight but noticeable movement between the spindle register and the backplate recess which is undoubtedly a major contributory factor as well as the unbalanced drilling in the universal backplate. I am discussing this with Arc and we will get to a satisfactory state in due course, but worth being aware of.

Regards

Martin

[john carruthersParticipant @johncarruthers46255]

some say the balance is improved if you plug the unused holes in the backplate ?

[Russell EberhardtParticipant @russelleberhardt48058]

Or drill two small holes, one either side of the common hole. Each being 0.7 times the diameter of the existing holes.

Russell

[Martin Shaw 1Participant @martinshaw1]

Russell

No doubt drilling extra holes is easier than plugging unused ones but may I ask whether the spacing from the common hole is critical or not and presumably they should be on the same PCD?

Regards

Martin

[Alan VosParticipant @alanvos39612]

Posted by Martin Shaw 1 on 25/10/2017 17:37:28:

No doubt drilling extra holes is easier than plugging unused ones

I wish to introduce some doubt.

When faced with the unbalanced hole in the same backplate, I turned up a mild steel plug with a 'good enough' fit. In use, the plug cannot escape. So quick to do that I didn't spend any time researching whether it was worthwhile. Reversible if needed. It never occured to drill more holes.

[Martin Shaw 1Participant @martinshaw1]

Alan

Yes quite probably, but the holes in the backplate are counterbored as well so whilst I could make three plugs, drilling two holes is obviously easier, and having got the backplate balanced it will remain with it's respective chuck for ever more. It's currently not very usable so worth having a go, and not too horrendously expensive if I make an a*** of it.

Martin

[Martin Shaw 1Participant @martinshaw1]

An update

I followed Russell's advice and drilled two holes. Because the existing holes are counterbored I calculated the volume which then gave me the size for drilling, following the advice of 0.7 resulted in an 8MM hole. This was easily enough done on the mill and I just spaced then equidistant by 18.5mm from the common hole. Back on the lathe there is a significant improvement, still a slight wobble at 1300-1400rpm but less than before and at the 900-1000rpm nice and steady. Without being able to dynamically balance or start from scratch I have a compromise that will at least allow use of the machine.

Regards

Martin

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