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

[EdK]

(04-15-2012, 06:31 PM)Wongster Wrote: 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.

Regards,
Wong

Wong,

If that's the case then use the 10mm end mill to full depth first followed by the 12mm. The 12mm end mill will not have much material to remove after using the 10mm end mill.

Ed

[DaveH]

Hi Wong,

The 12mm c/bore, I am assuming the 7mm holes are for 6mm size screw.

Drill the holes 6.5mm diameter and c/bore using a 10mm end mill. Then turn the diameter of the cap head of the 6mm screws down to 9.5mm dia.

What do you think, I do it some times.

If you prefer to stay with the drawing and c/bore with a 12mm end mill, first do it with an 8mm, then a 10mm and finish with your 12mm end mill.


DaveH

PS that link to the pdf does not work for me. Also Ed beat me to it.

[DaveH]

Wong,

In terms of the arbour my choice would be for a 25mm dia bar turned to 20mm to go through the "chuck" with a 16mm threaded bit at the end to take a nut and washer. Centre drilled so that it can be supported by a rotating centre.

Now will you be able to drill a 20mm hole through that piece of steel, and a 16mm die to cut the thread? Do you have a 20mm drill?


DaveH

[Mayhem]

Why not turn the nose first to say 70mm. This will enable you to hold this in your chuck and face the back and turn the outer diameter to size. Then drill the holes and counter-bore them. Then you could bolt the piece into place and then turn the nose to diameter and thread and then turn the taper. That is how I would go about doing it - but I could be wrong.

[RobWilson]

(04-16-2012, 07:34 AM)Mayhem Wrote: Why not turn the nose first to say 70mm. This will enable you to hold this in your chuck and face the back and turn the outer diameter to size. Then drill the holes and counter-bore them. Then you could bolt the piece into place and then turn the nose to diameter and thread and then turn the taper. That is how I would go about doing it - but I could be wrong.

Sound advice there Wong ,,,,,,,,,, thats the way i would tackle the job , I would also mark the spindle nose and chuck so you fit it in exactly the same position every time


Rob

[DaveH]

I think the problem Wong has is holding the billet in his 3 jaw chuck, his chuck may not be large enough to hold it, even with the jaws turned around.

DaveH

[Wongster]

Thanks guys. Just got home from my last appointment and the first and only meal of the day. Feeling tired but happy that I had a productive day in the office.

Dave, Ed: I'll take note of your suggestions on the C/Bores. Will leave that to later. The bigger clearance holes and C/Bores were suggested by another nice gentleman over at Madmodder via pm. He shared that having them bigger allow the recess to sit if I can't get the holes line up. This makes lots of sense for me as I have the tendency to mis-drill a little so much so that one of the holes doesn't line up.

Dave, I don't have such big drill. Biggest I have is a 14mm which I had problem using previously. Back to drawing board?

Mayhem, Rob: that was the original plan when I first discussed with several people off and on list. My consideration is, the steel piece is too big for my 3 jaw chuck, with the jaws reversed (about 84mm max). The 4 jaw is just about max'd out but I've no confident in getting the job centered with the rough "skin" still on.

I saw in some videos or articles that use a long piece of steel with a point to centre a big piece of stock in the 4 jaw. The DTI or DI is to be applied on the rod while adjusting the jaws. Maybe I can get a piece of silver steel, as it seems to be straighter than most that I encountered so far, and turned one end to a point while the other end in a drill chuck on the tailstock. Will this work?

No harm trying the various ways though. Some wastage of materials during learning is inevitable. Maybe I can get it close enough in the first couple of tries? :-)

Regards,
Wong

[RobWilson]

Hi Wong

So you do have a 4 jaw that the job will hold the job ?. mark the centre of the job .





Sorry for poor video i was reaching over the camera

Rob

[Wongster]

Hi Rob, I like the thumbs up at the end. Can this be performed without the spring loaded rod?

Regards,
Wong