New chuck question

[RichardG]

I have a Simat 101 lathe which is "just" about good enough to do the small amount of metal turning I do with a 4 jaw independent chuck which has a fair bit of play. If I ever take something out of the chuck its impossible to get it back on the same centre line and I end up having to faff around to get it recentred. So I thought I'd buy a new 3 jaw self centering chuck. The lathe nose is M14x1.5 so I'm going to buy a tap and then make my own backplate which isn't a problem.

I'm not a great fan of buying unknown items off eBay so narrowed it down to one from RDG Tools and one from Warco. The RDG uses through bolts to mount on the backplate and the Warco has a threaded body. Is the through bolted design of the RDG worth having as I can't really see any advantage or am I missing something?

 

[Gordon Tarling]

The threaded body type will give less overhang than one using a backplate and thus be that little bit more rigid.

G.

 

[Phill05]

I would go for the one with a back plate then if you change your lathe in the future you can change the back plate and keep the chuck.

 

[RichardG]

I would go for the one with a back plate then if you change your lathe in the future you can change the back plate and keep the chuck.

Neither chuck comes with a backplate so I need to make one. The back plate on the RDG uses bolts through the chuck to mount onto backplate, you could use nuts or cut threaded holes in the backplate, whereas the Warco has a threaded body so the bolts go through the backplate and the fix into the chuck body.

 

[RichardG]

The threaded body type will give less overhang than one using a backplate and thus be that little bit more rigid.

G.

Sorry, my post was obviously not very clear....the Warco has 3 threaded holes for me to mount the home made backplate the RDG has through holes to mount the backplate. I guess you could use bolts and nuts on the RDG.

 

[Phil Pascoe]

Maybe ask a mod. to put your thread in metalworking? You might get some more replies.

 

[RichardG]

Maybe ask a mod. to put your thread in metalworking? You might get some more replies.

Doh, failed at the first step, will do....

 

[sploo]

If you use a lot of standard size rods then a collet chuck might be better, as they're much more suited to removing and remounting stock (without introducing runout).

Even a decent 3 jaw will give (some) problems when you remove and remount stock.

 

[Gordon Tarling]

Sorry, my post was obviously not very clear....the Warco has 3 threaded holes for me to mount the home made backplate the RDG has through holes to mount the backplate. I guess you could use bolts and nuts on the RDG.

Ah, OK. Most chucks with threaded holes are fitted to the backplate using studs in the threaded holes and suitable nuts/washers where they protrude through the backplate.

G.

 

[kenledger]

Going back to you betting a piece of work to run true after taking it out of the Jaws. You do not say how you are remounting it.
We used DTI's or clocks, you could get the work piece true that way. When it gets to 2, 3 though you would just tighten the side where it was running low, never release the jaw on the high side at all.
You may do this, if so apologies.

 

[RichardG]

Going back to you betting a piece of work to run true after taking it out of the Jaws. You do not say how you are remounting it.
We used DTI's or clocks, you could get the work piece true that way. When it gets to 2, 3 though you would just tighten the side where it was running low, never release the jaw on the high side at all.
You may do this, if so apologies.

The process I try to follow is, draw a line from a jaw onto the piece so I can put it back in the same place, undo 2 adjacent jaws, remove item, put the item back aligning to the mark and then re-tighten the 2 jaws I loosened. However this can still result in a movement of 0.1mm or more.

 

[Sandyn]

I have a 100mm 4 jaw, self centre HBM. I got it from RDG. It has a backplate. I have a Myford ML7 and it is huge compared to my 80mm 3 jaw Pratt. Twice as heavy.
The HBM is pretty good quality and accurate enough for what I do. I'm really happy with it. I just quickly checked. Run-out is about 1 thou, measured on the perimeter of the chuck. It had the backplate fitted by RDG. I would have preferred a direct mount threaded chuck, to reduce hangover, but that wasn't an option.

 

[Fergie 307]

The process I try to follow is, draw a line from a jaw onto the piece so I can put it back in the same place, undo 2 adjacent jaws, remove item, put the item back aligning to the mark and then re-tighten the 2 jaws I loosened. However this can still result in a movement of 0.1mm or more.

I use the same procedure but undo each screw by a set amount, usually half a turn. Then remount the work and do each up again by half a turn. However if you want sub 0.1mm accuracy then you will probably have to do some fine tuning. In reality you are never going to see anything like that accuracy from a self centreing chuck. You would be better off with a collet chuck. Does the machine have a MT spindle, im guessing not given its size. If you can get one to fit then an ER type collet chuck would be ok. They are designed for holding tools rather than work so dont have a pass through facility, but are good for relatively short pieces. Most are accurate to around 0.0001in, so probably more accurate than your machine. And a good deal cheaper than a chuck as well.

 

[Fergie 307]

I have a 100mm 4 jaw, self centre HBM. I got it from RDG. It has a backplate. I have a Myford ML7 and it is huge compared to my 80mm 3 jaw Pratt. Twice as heavy.
The HBM is pretty good quality and accurate enough for what I do. I'm really happy with it. I just quickly checked. Run-out is about 1 thou, measured on the perimeter of the chuck. It had the backplate fitted by RDG. I would have preferred a direct mount threaded chuck, to reduce hangover, but that wasn't an option.

Not sure that the run out of the chuck body is necessarily a reflection of the accuracy with which it holds work in the jaws, and thats what matters. Normally you would machine the backplate with it in situ on the machine it is to be used on.

 

[clogs]

I had similar prob.....always had rush jobs turning up....
so in the end bought another lathe....
Most chucks are made in Asia....u just gotta get lucky to get a good one.....
I dont buy from RDG mostley what turned up was not very well made and almost always the packaging was destroyed.....
bought a big set of adjustable reamers from them...the special wooden case was just splinters...

 

[Fergie 307]

I had similar prob.....always had rush jobs turning up....
so in the end bought another lathe....
Most chucks are made in Asia....u just gotta get lucky to get a good one.....
I dont buy from RDG mostley what turned up was not very well made and almost always the packaging was destroyed.....
bought a big set of adjustable reamers from them...the special wooden case was just splinters...

When you can pick up something as good as an old Taylor chuck for between 50 and 80 quid why would you want to spend the same on a not very good Chinese one is beyond me. For the tiny machine the OP has maybe a little old burnerd would be ideal.

 

[Fergie 307]

Looking on lathes.co.UK it appears it has a Morse 0 taper spindle and tailstock. Whether anyone does a collet chuck with that fitting I have no idea.

 

[RichardG]

Looking on lathes.co.UK it appears it has a Morse 0 taper spindle and tailstock. Whether anyone does a collet chuck with that fitting I have no idea.

It's worse than that as its a half morse 0 taper, i.e. its the thin half of a standard length morse 0!! No one makes this now.

 

[RichardG]

When you can pick up something as good as an old Taylor chuck for between 50 and 80 quid why would you want to spend the same on a not very good Chinese one is beyond me. For the tiny machine the OP has maybe a little old burnerd would be ideal.

I have been looking used but I'm unsure about buying something like this from pictures especially as I will need to turn a backplate before I can even try it and often there's no returns or spares if it turns out to be well worn.

 

[sploo]

Agreed about needing to turn a backplate, but unless a Pratt Burnerd chuck looks like trash they'll generally be pretty good (in my admittedly limited experience). This document (http://www.rotagriponline.com/datasheets/Pratt/PrattChuckSpares.pdf) is hugely useful for decoding "what" a PB chuck is based on the model number (and it also tells you the part numbers for spares).