Needing Help Identifying Threaded Chuck Fitting

[Will RobertsonParticipant @willrobertson16447]

Sorry for taking up folks time with what’s maybe a basic question. A friend and I are looking for a replacement for this worn chuck – it’s threaded fitting that neither of us have seen before and neither of us know what this fitting is called.

Sorry I didn’t get a clear photo of the thread that attaches the chuck to the lathe – I can take precise measurements of the thread if that would help.

The company who made it does still seem to exist and is still making chucks https://www.roehm.biz/en/products/power-chucks/

[Robert Atkinson 2Participant @robertatkinson2]

What make and model is the lathe?

Robert.

[BazyleParticipant @bazyle]

Looks like an L00.

the backplate has a large diameter female cone and a threaded outside. The spindle has a male cone and captive ‘nut’.

But if you just want a new chuck you can reuse the existing backplate. If it has an L00 nose it is a reasonable quality lathe therefore you might want to go for a quality chuck but you don’t have to use one as big as the current diameter. Perfectly reasonable to fit a small chuck on the bigger backplate if you are not planning to make parts for the Titanic. Looks odd but don’t cut down a good backplate.

[Will RobertsonParticipant @willrobertson16447]

Hi Robert,

Here’s a video of it in action – I think it’s a German maker and fairly old – I’ll have a look and see if I can find the maker:

https://drive.google.com/file/d/1P-wnoWWBXqwgeacm4jns2xaTI-Y-R_aG/view

Will

[Will RobertsonParticipant @willrobertson16447]

Thank you very much!

I didn’t know about L00 – I think it could be a European / metric version of L00 – the lathe is in the Swiss German speaking part of Switzerland and as far as I know both the lathe and the chuck were made in Germany or Switzerland so guessing everything will be metric. As far as we can work out we think it’s about 50 years old but I can still get 10 micron precision out of it no problem so it is a very good lathe.

Re-using the existing backplate with a new chuck went through my mind – my friend who owns it is a Swiss trained machinist btu I think we’re both cautious about dismantling the chuck when we’re not sure if we can find a replacement. At the moment we’re getting by by using a larger chuck – which isn’t ideal for finer stuff.

Will

[Will Robertson]

On Will Robertson Said:

I think it could be a European / metric version of L00…

 

…so guessing everything will be metric.

There is no such thing as a metric version of L00 taper. Do not ‘guess’. Measure and confirm.

L-taper dimensions here: http://www.lathes.co.uk/latheparts/page9.html

There is only one Standard for L-tapers, ASME B5.9

https://www.asme.org/codes-standards/find-codes-standards/b5-9-spindle-noses-tool-room-lathes-engine-lathes-turret-lathes-automatic-lathes

The D1- taper is also in ASME B5.9. That has made it into an ISO standard (ISO 702) but the L-taper did not.

Measure the diameter (and pitch) of the thread on the backplate and that will tell you which taper it is.

[Bazyle]

On Bazyle Said:

Looks like an L00.

Would you agree that one of his pictures is showing the OD of the male thread?

Would you agree that the measurement shown is roughly 110mm?

Please remind me what thread is on an L00 chuck.

[old martParticipant @oldmart]

These backplates are available, but are expensive, that one could hold several different chucks if the fixings were sufficiantly separated. Mark the chuck and backplate before separating them, they may already have marks. Put a wooden protector between the lathe bed and the chuck body and undo the three SHCS. There should be plenty of room to fit a smaller chuck, directly, or mounted to a suitable adaptor plate if something in the 100mm size range is to be used. The through bore of that L00 backplate would be a factor in deciding.

I find it surprising to hear that a trained machinist is not prepared to dismantle a chuck, they require regular maintenance by proper washing and relubricating.

[Chris CrewParticipant @chriscrew66644]

As I have said before, if you are buying a new chuck the Chinese San-Ou brand is well worth considering, despite all the doubts some people still express about far-eastern products. I don’t work in industry so I don’t know what the requirements would be in a professional environment, but for the home workshop I have found these chucks to be accurate, of a very acceptable quality and exceptionally reasonably priced, although I have noticed the price rising recently. The Taiwanese Vertex and Rexon brands were decried in their early days on the UK market but are now accepted and sought after, I think it will be the same with San-Ou chucks.

[OldironParticipant @oldiron]

You could at a pinch hold a 100mm or smaller 4 jaw independent chuck in the larger one for small work.

This is quite acceptable. Just clock in the 4 jaw as normal.

[noel shelleyParticipant @noelshelley55608]

It is a serious error to assume that if something is made abroad it is METRIC ! The imperial system of measurement continues to be used all over the world, for numerous reasons, It is the best for the job or that to change to metric is going to be costly for little or no benefit are 2. Structural steel, cameras and hydraulics come to mind. Noel.

[Martin ConnellyParticipant @martinconnelly55370]

Looking at the table on the lathes.co site and the pictures above it may be a L0 spindle nose.

Martin C

[noel shelley]

On noel shelley Said:

It is a serious error to assume that if something is made abroad it is METRIC ! The imperial system of measurement continues to be used all over the world, for numerous reasons, It is the best for the job or that to change to metric is going to be costly for little or no benefit are 2. Structural steel, cameras and hydraulics come to mind. Noel.

Even if that rose tinted view of Imperial were up-to-date, we are trying to identify the thread on a German made chuck, fitted to a German lathe, that lives in Switzerland!   More likely to be Metric than Imperial, so I’d start by looking at continental standards, not British or American, even though there’s plenty of cross-over.

The normally wonderful lathes.co.uk has let me down on this one.   Their ‘Spindle Nose and Backplate Fittings’ page has a link to ‘German Standard Spindle Noses‘, but I think it’s wrong or incomplete, returning only BS4442 Part 1 / I.S.O. R702 Part 1.   Does this Sandvik page help?

As no-one recognised the beast immediately, I think Will will have to accurately measure the thread and other dimensions.  I’d need more than a few camera shots involving a tape measure to identify it, even if I had a complete list of all the possibilities.   As a starter for 10 though, should be easy enough to eliminate several possibilities using the dimensions given here.    I’m happy to be proved wrong if it turns out to be L00 because the goal is to get Will sorted.

What’s the best way of measuring a largish unknown thread with simple equipment?   I find it all too easy to get threads wrong with calipers, especially when there’s more than one similar candidate.

Dave

 

[SillyOldDuffer]

On SillyOldDuffer Said:

…we are trying to identify the thread on a German made chuck’.

As no-one recognised the beast immediately, I think Will will have to accurately measure the thread and other dimensions. 

1. We are not trying to identify a chuck thread. We are trying to identify a spindle nose (or maybe backplate) thread.

2. The second reply to the original question has identified the correct type of spindle nose. That reply only errs in incorrectly identifying which specific number from the L-taper series the photographed item represents.

3 Does the photograph showing the measuring stick on the male thread of the backplate, the one showing roughly 110mm, not give enough information for a positive identification? Look at the page you cite. There is only one L-taper that would measure near to 110mm.

[old martParticipant @oldmart]

The whole lot of information given seems to me to be strange. The op says the lathe gives 10 micron accuracy, but cannot manage better than a folding rule to measure with. The chuck clearly says 200mm, 8″ size which does not need measuring. The rule covers up the keyway in the backplate and seems to read about 110mm which would be the L0 size. And the thread pitch would be worth measuring. The smallest chuck that would fit directly on a L0 backplate would likely be 160mm as smaller chucks rear fitting screws would get very close to the spindle size. Smaller chucks could certainly be attached to a secondary backplate, say 200mm od by 20mm thick.

[duncan webster 1Participant @duncanwebster1]

OP is looking for a replacement for a worn chuck, so why not just use the existing backplate and dump the old chuck

[Howard LewisParticipant @howardlewis46836]

My lathe is basically Metric, but eventually the chuck thread was found to be 2.25″ diameter x 8 tpi Whit form.

Until I found that, my head was well and truly scratched trying to work out what I had.

MORAL

MEASURE in both Metric and Imperial Units.  You might be surprised.

If your chuck fitting is L00, the thread will conform to the appropriate standard, whether Imperial or Metric.

BUT, if Imperial check the thread form, whether Unified or Whitworth.

If the standard is Imperial, don’t waste your time trying to work in Metric units.

You could spend a lot of time trying to find a Die or to set up the lathe to cut a thread 57.15 mm diameter  x 8 tpi Whit form. 2.25 x 8 tpi is a lot easier!

Howard

[old martParticipant @oldmart]

The first picture shows the left side of the backplate and it is somewhere in the region of 110mm. L00 threads are 3 3/4 x 6 which is about 95mm, and L0 threads are 4 1/2 x 6 which is about 114mm. Therefore I think it is L0 size, not L00. The ruler is obscuring most of the keyway which is a shame, but it would be very shallow at that end of the taper.

Pretty much any 160 or 200mm rear mounting chucks would be easy to fit to the existing backplate. Bison and Pratt Burnerd are very expensive, but Vertex made in Taiwan are good and much cheaper. I have been very lucky with even cheaper Chinese chucks, but it is a lottery with them.

[Martin ConnellyParticipant @martinconnelly55370]

I wonder what the wear is? If it is just the faces of the jaws, which is what it looks like in the picture, I would clean them up with a sturdy carbide insert boring bar. Just jam some suitable steel in the gaps between the jaws to hold them steady and tickle the gripping faces until all surfaces are cleaned up.

Martin C

[old martParticipant @oldmart]

I had wondered about the wear on the jaws, the body of the chuck looks very nice. If the chuck was mine, I would drill the flat outer faces of each jaw with a solid carbide drill and then use a ring with pegs to tension the jaws and either grind them, or as M C mentions, a indexable boring bar. The chuck should be throughly cleaned before and after any reworking.

The last jaws that I trued up were a set of Chinese K11 outside for a 125mm size chuck. The jaws were close to the size of the 137mm Deckel which I have recently bought on ebay which only had the inside jaws. After reworking them to make them fit the chuck, I found that the three steps needed truing up. I put the chuck on the rotary table, trued up the body to 0.0005″ tir and used a solid carbide endmill to machine the steps and faces after tensioning them. I got 0.002″ tir or better, not as good as the inside deckel jaws which are an outstanding 0.001″tir or better at several diameters, but good for me.

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