Lorch 8mm collet compatibility with WW?

[mbwatch]

Forgive me - I am sure this answer already exists somewhere. I have an opportunity to pickup an assortment of 8mm collets made by Lorch and I'm hoping to confirm compatibility with an American WW lathe having standard 0.275in 40tpi threads.

Looking over the lists at lathes.co.uk, Lorch 8mm are 34mm in length from the cone out to the threads, this is 2mm longer than WW. https://www.lathes.co.uk/collets/

WW thread diameter: 0.268in / 6.80mm

Lorch thread diameter: 0.275in / 6.985mm

WW tpi 40 = 0.635mm pitch

Lorch = 0.625mm pitch

So obviously the thread pitch is very close, probably close enough not to make a difference at 0.01mm. But the thread diameter as 0.275in OD on the Lorch is at least 0.15mm larger than the measured OD of most of the other WW style collet threads. I believe my drawbar has 0.275 threads ID. Do you think a Lorch collet will thread in there or is it going to be too tight? 

Edited February 25 by mbwatch

[Dell]

According to this there is not much difference .

[nickelsilver]

From memory the thread diameter of Lorch collets is an issue in drawbars meant for WW and what I would call "Swiss" (Schaublin) standards. Dell's chart above is correct for Schaublin, at OD 6.82mm (.268") and P of 0.625 . I have a G. Boley here that measures OD 6.82mm P 0.625, and a Leinen that's OD 6.85mm (.269") P 0.635 or 40tpi. A Levin that's OD 6.89mm (.271"), P 0.635 or 40tpi. Finally a Wolf Jahn that's OD 6.85mm , P 0.625.

 

All fit my Leinen drawbars fine, and the 40tpi stuff also fits my Swiss drawbars (various machines). Nothing I have comes close to 0.275", which I suspect if probably accurate for Lorch.

 

The chart is definitely off on Levin, and "Boley for later WW lathes" as well.

 

So yes, the 0.01mm difference in pitch doesn't seem to be an issue over the 8-ish threads that engage with the drawbar. But the Lorch thead seems to be somewhere between 0.10mm to 0.20mm oversize compared to average- probably why I don't have any in my sets of collets.

 

It's been a long time since I had a Webster Whitcomb, but I have a pretty clear memory that Schaublin collets fit fine.

Edited February 26 by nickelsilver

[caseback]

I have 8mm collets made by several manufacturers and did a check which collets fits which lathe (I have a Lorch, Wolf Jahn, Boley-Leinen and Wiskum lathes).

I found that the Crawford (marked cc), Wolf Jahn, Bergeon, SA, and the collets with no makers mark fit almost all my lathes. However, the Lorch collets don't fit the spindle of my WW-style Wolf Jahn lathe (which is very simular to yours I believe). For some reason they won't go all the way in and they also bind up in the drawbar. 

Is it possible for you to try if they fit? If not, and If the price is ok, you could obviously just buy them and part with them if needed. 

Edited February 26 by caseback

[Dell]

That was an old chart it’s possible it could be wrong  my Pultra P type is 10mm headstock but 8mm tailstock & the collets are Pultra conflex and they are .275 X 40 tpi and that seems odd when the 10mm collets are M10 X1, anyway I know that the 8mm fit a WW because I had one to restore & sell and the  8mm conflex collets fitted perfectly.

[nickelsilver]

There are several charts and lists of the various threads used on "8mm" collets, and all seem to be sort of accurate and sort of not.

 

Adding more info to the confusion soup:

 

Schaublin uses a 55 degree thread, which is rather Whitworth-ian. I don't know what the angle of the original WW was, very well could be 55. My Levin collet measure bang-on 60 degrees.

And, my 1913 Hardinge catalog lists the Webster Whitcomb 8mm thread pitch as 0.63mm (they very specifically state the collet body as 0.3147", or 7.993mm- which is correct, the machine bore is 8mm, so the collet body has to be a little smaller to fit). So right in the middle of the commonly stated 0.625mm and 40tpi (0.635mm).

Edited February 26 by nickelsilver

[MikeEll]

I have a combination of both types.  They physically fit my Lorch lathe regardless of the type, but the drawbar really needs to match the correct thread.  My solution was to find another drawbar to fit my lathe.  I just switch drawbars depending on which tool I'm using.

[mbwatch]

3 hours ago, caseback said:

Lorch collets don't fit the spindle of my WW-style Wolf Jahn lathe (which is very simular to yours I believe). For some reason they won't go all the way in and they also bind up in the drawbar. 

I notice on the charts the Lorch head diameter is 12.5 and WW is 12.2. That could be enough to make a difference. And I was thinking mostly about threading into the drawbar, had not even considered whether they would fit into the spindle. I don't have an opportunity to test the fit so I will probably skip this opportunity. I have already made a thread compatibility mistake once.

3 hours ago, nickelsilver said:

From memory the thread diameter of Lorch collets is an issue in drawbars meant for WW and what I would call "Swiss" (Schaublin) standards.

All right, thank you.

 

5 hours ago, Dell said:

According to this there is not much difference .

My novice problem is I still have no clue how much difference is too much!

3 minutes ago, MikeEll said:

My solution was to find another drawbar to fit my lathe. 

I think before I buy any of these I will spend some time searching to find if a Lorch drawbar is available somewhere (and its diameter & length are usable)