Lever operated collet chuck for Schaublin B32 collets on the Chipmaster Lathe

Usually when starting with a project I realise what I need in order to complete the project, and often get stuck on some prerequisite to get to the actual project. a tool to make a tool, to make a tool..

This project is no different, I will need an ID and OD grinder, should I want to preserve some of the Schublin collets accuracy. Here I can convert my Eagle Surface Grinder to hold ID and OD spindles perpendicular to the existing spindle axis. Well I need to rebuild it first. Or build a tool post grinder for the Chinese lathe.

Scouring the internet in search of ideas of how to construct such a beast, I came across some similar but different ways to implement the lever closer.

Originally I wanted to base my design on this drawing out of  the book "Taschenbuch für den Maschinenbau" by Dubbel. A plate clutch mechanism similar to the one used in the Matrix clutch on the Chipmaster lathe. 

Below two designs from South Bend Lathe co. The first drawing uses balls for the wedging action. The later heavy 10 model uses a more "common" lever arm action.

 

 

http://cdn0.grizzly.com/manuals/g4026_m.pdf

http://sherline.com/Wordpress/wp-content/uploads/2015/09/1150inst.pdf 

Design elements to consider

• physical dimension (constrained by lathe spindle bore and collets) 
• materials
• clamping force
• balance
• safety
• easy to maintain, quick to install, usability, ease of use, attention to detail

The spindle bore on the Chipmaster is 35mm, the minimum OD for the pull bar is specified at 33.5mm, this gives the the draw bar its dimension of OD 34,5 x ID 27.7 

sources on popular forums suggest the pulling distance to be no more than 1/8 inch

The collect requires a clamping force of 11500N. My interpretation of this is 112,8 Kg. How to derive the distance the draw bar needs to be pulled back? The lever pull on the ramp, which engages the lever action to pull the draw bar in. Lever action on lever action with force on incline.

https://www.engineeringtoolbox.com/inclined-planes-forces-d_1305.html

Collet pull force	11500	Newton	1173,469
lever ratio prawl	2,75
cam force	4181,818	Newton	426,7161
Cam Angle	37	deg
C3*SIN(RADIANS(C6))+0,2*C3*COS(RADIANS(C6))	3184,631	Newton
	324,9623	Kg
Lever closer ratio	10
Force required	32,49623	Kg

Schaublin Collets B32 72 65

With the Deckel FP2, I got a box of what looked like big Deckel collets, as used on my Cutter Grinder, but the threads where finer.

A bit of googling revealed the Deckel cutter grinder collets are part of the standard  DIN 6341 - 300 Series, more precise 355. So I assumed it might be the same series just bigger, but could not find any match on size and threads. 29.7x1.693mm ; 15TPI ; 45°/5° buttress

(http://www.schaublin.ch/app/webroot/pdf/cat/5.pdf, threads page 57)

So I cleaned one up to measure and found the VS engraving on the face, never seen it before and postponed my investigation. Then an australian youtube contributer posted a video on restoring an old schaublin lathe, which he had found under a tree. Wow and I recognized the logo :) Back to my google search now I knew they where most likely schaublin collets, so I started searching for old catalogues, and eventually found the spec in the modern catalogue. So I decided to make use of these on my Chipmaster, but could not find any collet chuck for these online. So I have to build my own. And so the journey of learning about collet closers and collet chucks started.