ER32 Collet Chuck for Proxxon PD 400

[Wongster]

With the Set-Over Centre now out of the way, I'm planning the making of the ER32 Collet Chuck. I draw references from resources available on various forum and from inputs given to me by various good folks of the forums.

The material on hand is a piece of mild steel measuring slightly more than 100mm in diameter and about 45mm in length (maybe a little shorter).



This is what I drew up:



and the dimensional drawing:



By the time I square things up and remove the "skin" of the stock, I will left with a smaller piece. I don't know how small with it be but I believe I've to adjust the dimensions accordingly to suit.

I've a couple of questions to ask before starting work:
1) I'll be turning up a piece of arbor to hold the steel piece for turning the exterior. What diameter should I go for to have it withstand the weight of this piece of steel and cutting forces?
2) The drawing shows 44 mm length, leaving a short section of the parallel bore after the taper. If I'm left with only 40mm after cleaning up the surfaces, will this still work?

The plan I'm following from the 7x12minilathe group (http://f1.grp.yahoofs.com/v1/8FKLT5h3Q-T...0CHUCK.pdf) has the length at 2.25" (or about 57mm). I'm not sure if this is critical for the chuck to work properly.

Also, I'm not sure if I'm able to make use of a 12mm endmill to cut the counterbore on my Sherline mill. I was told that the mill can take at most 3/8" or 10mm endmill at very slow speed and feed.

Appreciate any comment(s).

Regards,
Wong