D collet or Derbyshire 10mm collet angle

[purplepicker]

I'm machining a couple of special solid collet bodies with jacobs taper to hold a jacobs chuck on my Derbyshire 10mm lathe. I assumed that the taper would be 20 degrees like the 8 mm webster whitcomb collet and most of the hardinge collet styles.
When I measured the half angle to the best of my ability it seems to come up at 15 or 16 degrees or 30 to 32 degrees included angle.
Am I getting it wrong? I have searched the web and all my watchmakers lathe books and cannot find a difinitive source for the angle on the derbyshire 10 mm which seems to be the same as the Levin D
collet.


Does anyone know the correct front angle on the collet?


Thanks,
Cecil

 

[Don B]

First off I'm not familiar at all with these collets, I did look in the "model engineers handbook" and that collet is listed with a bunch of others and a chart of body dimensions, but no angles..!:thinking:

 

[Marco Bernardini]

First off I'm not familiar at all with these collets, I did look in the "model engineers handbook" and that collet is listed with a bunch of others and a chart of body dimensions, but no angles..!:thinking:

Not even a top diameter, a bottom diameter and a distance between the two?
From that it would be easy to get the taper angle.

 

[Don B]

Not even a top diameter, a bottom diameter and a distance between the two?
From that it would be easy to get the taper angle.

No, that's the kind of info I was was hoping for, I wonder if the taper angle is standard on these type of collet or if that would be a dangerous assumption..?:thinking:

 

[purplepicker]

I posted the question to the practical machinist as well and got an answer. Thought it might be useful here as well.

The included angle is 30 degrees according to Levin, who make their version of the Derbyshire 10 mm collet appropriately called the "D type"

Here is a link to the dimensioned drawings.

http://levinlathe.com/page23.htm

The best I could measure a Derbyshire magnus collet with a starrett vernier protractor I could get from 30 to 32 with multiple measurements. Measuring the large and small diameters and length of taper is tough because of the small radius at the transitions. I didn't think to look at Levin's web site.

I have made several ww solid collets for with jacobs taper and grinding arbors for the ww lathes but never made any for the 10 mm. Makes a great project for the 10EE that I converted to CNC about a year ago.

Cecil