chuck fitting

[Black Cat2Participant @blackcat256889]

I bought a nice little 4 jaw chuck for my little Chester lathe and now I want to use it realise I cant fit it..The mounting holes dont go right through and i will not be able to copy the threaded holes back to back..
The headstock has a no 3 morse taper and the chuck is threaded inside..Presumably I can go that way?
Is there something I can do stop the chuck irrevocably tightening itself on the thread as I can use it elsewhere with a smaller taper
Thank you very much..
meeeeoow

[Black Cat2Participant @blackcat256889]

face to face threaded holes!

[JonParticipant @jon]

Take it apart and see if any of the internals will foul a through holes or can be repositioned then decide.

Is it the ones with three awkward nuts to attach.

[Capstan SpeakingParticipant @capstanspeaking95294]

You can make a morse arbour for it using a soft morse shank.

A mini lathe will never produce so much torque that it permanently locks, or worse strips.

[Black Cat2Participant @blackcat256889]

Yes Jon its the one with 3 awkward nuts..Even if it could be drilled I m thinking there are going to be a lot of holes and there are lots of places to buy threaded arbors ..
What about an Amolco mill? Thays one other machine I ll use it on ,would be likely to lock up on that please..

[LambtonParticipant @lambton]

The Hobbymat lathe has chucks fitted with protruding M6 studs which require the nuts to be put on in the limited space behind the mandrel flange and it sounds like your little Chester lathe is similar. When I fitted a 4 jaw chuck to my Hobbymat I used a short adaptor ring of the type provided in those days by Essel Engineering (they no longer supply them). This ring once fitted to the mandrel flange needs to be have a register turned and hole drilled at the particular PCD for the chuck in the normal way.

I also use flange nuts to secure the chucks to the Hobbymat as they are much easier to align and handle in the tight space available behind the mandrel flange.

[Capstan SpeakingParticipant @capstanspeaking95294]

The Chester Conquest has the spindle mounting flange drilled in both 3 hole and 4 hole patterns.

A standard 80mm Chinese 4 jaw chuck is tapped on the back in a 4 hole pattern.

It is very difficult to get screws in behind the flange. However it is easy to cut the heads off 4 screws and turn them into studs. Putting nuts on the back is then no worse than the 3 jaw.

I found the chuck register was too small as it came and I had to open it up slightly though.

[RobboParticipant @robbo]

Before using a chuck on the Amolco you need to check which version you have. The earlier Amolcos have a Myford spindle thread, but no chuck register, as they were designed to use Myford collets not chucks.

Later versions have a chuck register behind the thread, as it was obviously realised that users wanted this.

The Amolco is unlikely to produce enough torque to lock anything up too tight.

[alan smith 6Participant @alansmith6]

Hi All,

I`ve uploaded the recommended fitting instructions for Pratt Burnerd three jaw chucks, in case anybody reading this thread needs them. If the image is too small to read the text, then go into my photo album for a larger image.

Alan

Edited By alan smith 6 on 26/06/2015 12:31:34

[AjohnwParticipant @ajohnw51620]

You could make a back plate for the chuck but I suspect you will have fun adding the thread for the chuck to it. They are usually rather coarse and I'd guess your lathe doesn't go below 100 rpm. Power might be a problem too but very very fine cuts at the thread angle usually help with that. You will have the same problem with a morse adapter. It's also best to do this sort of job with a chaser but it can be done with an ordinary pointed tool providing you calculate how much undersized the od needs to be. Even metric threads have a rad on the crests in practice.

The sort of chuck mounting the lathe has usually has some sort of register. Hopefully a plain diameter. It's best to turn up a sort of plug gauge that is exactly the same with a short section say 0.02 to 0.03mm under sized on the end. You can then machine the recess for the plate and reduce the size of the cut to very low levels when this part just goes in. Say you take 0.005mm cuts then that will be the fit when it goes in. Then as a check remove the chuck with the plate in and check it fits.

You could mark the position for the studs using engineers blue. Normally that has to be used so thin that it can hardly be seen but in this case you could smear a thin layer on the area on the lathe's plate and press the chuck plate against it. Maybe having to rotate it a little each way to get it to take and leave a mark . Then carefully mark the centre of where the studs have to go. There is usually some clearance on the studs so this wont be as bad as you might think but will need care.

There is a way that you could avoid turning the thread for the chuck. Mount the plate and turn the register. Use the same very light cuts technique to get a good fit. 4 jaws are usually mostly solid metal and there will be a rim around the register. Simply drill through the back plate into the chuck at a thread core size and use high tensile screws to hold it to the plate. Countersunk will probably be best. Smallest you could get away with is say 3 or 4 M4's. Fully fit one before drilling the others. The 1st one will make sure things stay in place when you do the others.

I have used the blue idea for spotting holes like this from a chuck but didn't have any blue so used wet paint. It can be done. Biggest problem was a drill running off a bit but in this case it didn't matter. I just had to make the hole in the plate a bit bigger.

You might be able to find something that already fits the lathe – say a budget collet holder, turn that off and then fit the chuck adding thickness if needed. Or maybe a back plate – ArcEuro stock several sizes, maybe Chester do too. I assume that the ones with thread still have holes positioned to fit studs correctly. The nice thing about studs is that the chuck doesn't suddenly spin off when threads are being cut and the lathe has to be reversed. It happens.

Been out and also have eaten lunch since starting this so some one else might have posted similar suggestions.

John

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[Black Cat2Participant @blackcat256889]

Funnily enough John ,thats virtually what I m going to do but with an mt arbor ,a backplate screwed on ,that screwed to the lathe s backplate and a turned piece down the hole to centre the chuck..Just to fit it not to leave it there whilst in use..The lathe starts at 0 rpm -I made sure of that when I bought it!

[Black Cat2Participant @blackcat256889]

Mine is a later Amolco Robbo..thanks for that

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