Set-Over Centre

[Fergus OMore]

It's getting worse! You are using silver steel which requires a different treatment to mild steel.

Your book of words suggests that you use Garia H and a razor sharp tool. Again Thomas emphasises rigidity and problems of overhangs.

[DaveH]

Wong,

This is a hobby mate, something we do to enjoy just doing it.

Don't get overly concerned, when things don't go the way you think (and know) they should. 

If it is not a critical size, "hit it" with some emery cloth, until it looks good. It is fine we all tend to do it. Then carry on with the next part. 


It's coming along just fine 

 
DaveH

[wongster]

Thanks Dave. You are right. I should just enjoy myself and pick things up along the way as I do more. It is a hobby.   I did use sandpaper to smooth of the surface. Wonder how you know I cheated... Hehehe...

Norman, I don't understand the use of the term "it's getting worst". What's getting worst?  It cant be as bad as the part i just scrapped. I'm trying slowly to digest the info on that book. The style of writing is not that easy for a non-tech person like me.  Anyway, the silver steel was originally part of the kit I bought from Hemingway. I merely replaced it with another section meant for the 2 adjustments screws. You mentioned about "the right size" for the ER32 collet chuck. May I know what's the max I should put in there. I've collets all the way up to 19mm.

Regards,
Wong

[DaveH]

Wong,

For a given collet size 25% increase in diameter in metal size(dia) outside the of the diameter being held in the collet  is normally fine.

Eg. if your collet size is 16mm - then + 25% = 4mm.  So 16 + 4 = 20mm diameter. So you can hold the 16mm diameter in the collet with a 20mm diameter outside, the bit you are cutting.

These ER collets were designed to hold end mills in milling machines, the forces there are far in excess that a single point tool on a lathe produces.

 
DaveH

[wongster]

Hi Dave,

I read somewhere (can recall now) that each collet in the ER series can hold down to about 1mm smaller in diameter. That is, if I'm putting in a rod or an endmill, of diameter 3/8" (which I've a few endmills or slot drill from sherline with such shank size), I should be using 10mm collet but not 9mm.  Do correct me if I'm wrong.  So for the 1/2" diameter silver steel rod from the Hemingway kit, I was using the 13mm collet.

Would your last sentence about the forces mean that it is not suitable for workholding in the lathe?  If it is, I'll start practising on using the 4 jaw chuck...  The small sherline 4 jaw seems simple to use but not the 100mm 4 jaw chuck from proxxon.

Regards,
Wong

[DaveH]

Wong,

Hi Dave,

Would your last sentence about the forces mean that it is not suitable for workholding in the lathe? 
Regards,
Wong

Not at all, just the oposite, collets are more than suitable for work holding in the lathe. The work (bar) needs to be round and clean, which silver steel is.
 
DaveH

[DaveH]

Hi Dave,

I read somewhere (can recall now) that each collet in the ER series can hold down to about 1mm smaller in diameter. That is, if I'm putting in a rod or an endmill, of diameter 3/8" (which I've a few endmills or slot drill from sherline with such shank size), I should be using 10mm collet but not 9mm.  Do correct me if I'm wrong.  So for the 1/2" diameter silver steel rod from the Hemingway kit, I was using the 13mm collet.

Regards,
Wong

Wong,

You are dead right 
 
DaveH

[wongster]

Your book of words suggests that you use Garia H and a razor sharp tool. Again Thomas emphasises rigidity and problems of overhangs.

Norman, I thought about your comment on problems of overhangs while I was driving home (I was typing the post on my little iPhone while driving... good that I didn't get caught by the traffic police...).  The ER32 chuck do extend out quite a bit.  If I would like to continue using collet chuck while I get the hang of centering stuff on the 4 jaw, should I be getting, say, ER25 or ER16 collet chuck?  I bought the ER32 because I have the full set of its collets from impulsive buying...    and also its bigger range...

Regards,
Wong

[Miner]

Hi Wong,
Your current ER'S should be just fine, It's the distance away from your lathes spindle bearings that is creating a rigidity problem. I'n not familer with what system Proxxon uses to attach the chucks to your lathes spindle nose. Replicate that exactly on a roughed in ER collet chuck out of a piece of good steel. After its attached to the spindle nose, You then bore the ER internal taper and cut the threads for the ER nut. That will get you as close to the lathes spindle bearings as possible and leave your spindle thru hole open while turning longer stock with the collets. The system you have right now does work fine on a mill. But the chuck is supported much closer to the mills spindle bearings.

Pete

[wongster]

Hello Pete,

Thanks for your input. I was thinking of making or finding one ER32 chuck like what you mentioned but couldn't figure out what to do it or find one that fits. The Proxxon lathe holds the 3-jaw chuck by 3 M6 screws. The PCD is 83mm and the recess is 70mm in diameter.

I bought a piece of 100mm diameter mild steel but find it hard to mount on my 4 jaw chuck (my 3 jaw chuck max'd out at 80mm+). I put this on hold for the time being to gain more knowledge doing some simpler project while I think of how I should approach this.

Regards,
Wong

[Miner]

Hi Wong,
Unless Proxxon offers an actual ER-32 collet chuck, It would be highly doubtful you'll find a off the shelf one that fits your lathe. Your 3 jaw is maxed out at 80 mm? You should have a second set of chuck jaws that are designed for holding larger diameter work by the outside diameter. That second set of jaws should have been included with your lathes 3 jaw chuck. There's a few more tips that could be mentioned about the best way to build an accurate collet chuck, But were pulling your thread off topic so I'll apologise for that.

Pete

[Fergus OMore]

This is when a faceplate is desirable- and the ability to use it.

[wongster]

Pete,

Don't be. I would like to hear how I can go about making one. The 3-jaw chuck max'd at 80mm+, with the jaw reversed. The 4 jaw allows up to slightly about 100mm, with the jaw reversed.

Both are 100mm chuck.

Regards,
Wong.

[Miner]

Wong,
Well for starters you need to build an EXACT reproduction of your lathes spindle nose. Every dimension is as close as you can get to EXACTLY the same as your lathe has and your measureing equipment will measure to.

That reproduction will be used as a proper gage while machining your embryo collet chuck. If that gage tightly fits the machined rear face of your soon to be collet chuck, Then it will fit just as tight on your lathes spindle nose. Less than .001" for tollerance would be what you'd want on all dimensions. Once that's achieved, You then accurately drill your bolt hole pattern to attach the unfinished collet chuck to your lathes spindle nose.

Now you can precision bore the diameter, depth, and collet angle into that collet chuck blank. Once those dimensions are correct. You can then single point thread the collet chuck to fit your ER nuts dimensions.

All of this just requires very careful work and not trying to rush the job. Any inaccuracys you machine into the collet chuck will repeate themselves in any further work you machine in that chuck.

There's probably a few real good examples on this forum showing how other people have done this job.

Pete

[wongster]

Pete,

Pardon me for my ignorance. When you mentioned spindle nose, are you referring to those with threads on it? If it is, I don't have any. The round plate is where the chucks, centre turning attachment, and face plate are attached to, using the M6 bolts. From the exploded diagram in the manual (all parts labelled in Germans), this round plate is part of the spindle. to mount the workpiece directly to this plate, I'll need to drill the 3 or 4 clearance holes right through.

The plate measures about 100mm:



I did something like what you discribed on my Sherline before, which has a 3/4-16 nose. Once I've the thread done in the middle of a work piece, I was able to machine the face and cylinder surface with it mounted on the spindle nose.

The steel stock I bought:



I'm trying to figure out how to start...

Regards,
Wong

[Miner]

Wong,
Nope, The actuall "spindle nose" would be where your chucks attach to. They can be threaded, D series, Tapered like the L series chuck mounts ect, ect. You just need to duplicate all the dimensions that affect your chuck mounting. Possibly? The system your lathe uses for chuck mounting may be designated with and as a proper european DIN number. In fact I'd be suprised if it wasn't.

Pete

[andyf]

Hi Wong,

As "7x minilathes" have a spindle flange similar to yours, though different as to register diameter and PCD of the mounting bolts, you might find it useful to join the Yahoo 7x12 Minilathe Group and have a look in its Files section at "ER Chuck Construction", and at the last file in that folder.

Actually, I don't think that's the way I'd attempt it, but you have taken your own thread a bit off topic, so  perhaps a new thread might be the right place for further discussion when you get round to the job.

Andy

[wongster]

Hi Andy,

Apologies for veering off course. I'll start a new thread when getting to making the collet chuck.

Just a last bit. The chuck is fastened to the spindle flange from the from with 3 M6 bolts. I'll check out the file section you do kindly shared to see if I can understand how to go about mounting the big chunk to make the collet chuck.

Thank you.

Regards,
Wong

[andyf]

Hi Wong,

It is I who should apologise. It wasn't meant as criticism. This is your thread, after all.

If you want to look at files on the 7x12 Group, you will need to join it first; it isn't open to the public like Madmodder.  But membership is automatically granted to everyone who applies.

Andy

[wongster]

 Hi Andy,

There will not be an end to apologizing to each other then. 

Found that I've those files on my iPhone. the chuck is for those with threaded nose, which I have mental images of the process needed. The front mounting one is something that I can't figure out how I can start. I'll think some more and start another thread if need be to gather comments and/or criticism.

Regards,
Wong

[andyf]

I think those are different files, Wong. The ones I referred to are definitely for a collet chuck which bolts on to a 75mm spindle flange.

Andy

[wongster]

Wife was away with her pastor and church friend for dinner.  The tension at work today was so great that I promised myself to spend sometime in the shop no matter how short the session is going to be.  The session was indeed very short; I only had like half an hour after dinner.

I angled the tool away from the workpiece this time and it really cut.  The entire edge of the tool was too close the previous time that it rubbed on the workpiece than cut.  Genek was quite quick to point this out when my blog post went up the last time.

The short section for threading done.  Finish not fantastic but it was much better than the previous attempt.  In this pic, the tool was set to cut the shoulder.



The same method was used to square up the 5/16 die with the stock by pressing it against the live centre on the tailstock.  Once I've a few threads going, the tailstock was removed and the thread was finished up by turning the die handle and chuck by hand.  Instead of using the cutting oil I normally use for turning and milling steel, some tapping compound recommended by the tool shop I frequent was used.  It seemed much easier this time and the threads was done in a flash.  I turned the die around and chased the thread but remembered that both side of the die are tapered.



The same gap is still there.  Why can't it go all the way in?



From another angle.



Any suggestion?

[DaveH]

Wong,

Although the die seems to cut right up to the face of the die, like you said there is a chamfer to the die. Hence the thread is not cut right up to the shoulder of the work piece.

You can "undercut" the thread, which means using something like a parting off tool and reducing the diameter of the threaded part just a 1mm wide or so right next to the shoulder. Reduce the diameter and see if it wll screw on all the way, leave the work piece in the lathe until it fits correctly.

Thats one way.

 
DaveH

[wongster]

Dave,

I tried that the last round and I've to use a plier to screw on the last bit.  Maybe I didn't get it right.  Read on one site that I should cut it down to the root diameter of the thread?

Regards,
Wong

[DaveH]

Dave,

I tried that the last round and I've to use a plier to screw on the last bit.  Maybe I didn't get it right.  Read on one site that I should cut it down to the root diameter of the thread?

Regards,
Wong

That is correct, then it will screw up to the faces.

We all have to do it - you are not special 

 
DaveH