making collet adapter from brass (how easy?)

[Alistair Hosie]

I have aquired last year a complete set of collets in top condition.They are designed to be used with a drawbar.Unfortunately although the collets fit exactly in the mandrel of my lathe there is not enough room to fit a drawbar. I understand that from the books I have been reading that you can fit a threaded adapter over the mandrel to close the collets from the front end.
Is this a simple procedure?
What should I look out for?
I would like eventually to get the use of these collets as they would be handy for small stuff,and even for a new boy like me it would be shameful to send off to have it done so I will do it eventually myself .Just wondered what to look out for .I have a nice bit piece of solid brass could probably have enough to start again several times if I mess up. Has anyone made one ? perhaps they could let me know.Alistair

[Thrud]

Alistair
Collets threaded at the back for a drawbar are not designed to be closed from the face of the collet. Most work pieces in collet work are pretty short.

If it is a 5C collet, the normal way to close them is with a hollow tube to allow material to pass through the headstock. A 5C chuck such as Bison's closes the collet by drawing it back with a threaded ring gear that you operate with a chuck key.

You can make an adapter for 5C to fit your headstock spindle quite easily if it has a MT#5. A sleeve is machined MT#5 outside and to 5C dimensions inside. These can be purchased as well. Then your make the hollow tube closer and you are all set. Feeding long bars will also require roller stands to support the bar and prevent dangerous "flopping about" under power.

[Uncle Dunc]

Alistair,

When you say "the collets fit exactly," do you mean that there is just room in the spindle for them, or do you mean that the taper on the collets exactly matches the taper in the spindle? In the latter case, all you need is the threaded cap. Otherwise, as Thrud notes, you'll also need an adapter to fit in the spindle and accept the collets.

I can think of several issues:

1. For testing the threads in the cap, it will be much more convenient to first make an exact replica of your spindle nose, to use as a thread gage. The alternative is removing the chuck with the cap in it, turning it around and trying to screw the cap onto the spindle. Tedious and error prone.

2. Brass is probably the ideal material. Thrud points out that collets with drawbar threads aren't designed to be tightened this way, so brass will be less wearing on the collet faces than steel would be. It's good that you have enough for several tries, but if I thought I might need several tries, I would practice with aluminum rather than brass. Of course that will insure that your first effort in aluminum is perfect.

3. Make sure the cap is short enough that it will tighten all of your collets before bottoming out on the shoulder behind the spindle threads. You'd hate to find out one of the collets is a bit short when you're right in the middle of something else.

4. Thrud also noted that a lot of collet work is short, so there's a balance between making the lip thick enough to pull the collets down securely and thin enough that you can get your cutting tools close enough.

5. Put holes or notches for a spanner on the outside diameter.

[Jack]

I'm new at this too, and I recognize the lack of instant recognition of the collet type.
If you want to know about collets you need a caliper or micrometer to measure the inside diameter, the outside diameter, and the length of one of the collets. With these measurements and a "Machinery's Handbook" you can look up and identify your type of collet and there are a bunch of different types.
The handbook has drawings of different profiles along with sizes. My set of 5C collets has outside threads only, while other brands have threads on the inside of the collet and some have threads on both inside and outside.
The handbook is available at the library, used bookstores, yard sales and brand new.
Jack

[Oso]

Quick check:

Are the collets an even taper along the length, same as the center you use in the spindle? If so, they should have a threaded hole in the narrow end.

The most common collet of this type in the US is a "Morse taper". Taper sizes go from 0 to at least 5, ranging from about 7mm to over 30mm at the wide end. Collets for sizes 2 and 3 are commonly found.

Didn't you say it is a Boxford? Then it is like a SouthBend US lathe, and likely has a
Morse 3 taper if it is a 9" or 10" swing per US measure (you would know this as a 5" or 125mm machine most likely)

I suppose you could close them from the front, but they are as you note designed to be pulled in.
ONE TROUBLE: How will you get them out? The Morse taper usually require starting with a tap on the drawbar, otherwise they stay in obstinately.

If the collets have outside threads, and a steep taper on the last bit of other end, you need a "closer" and will have to use a drawtube for best results. Otherwise the collets will not stay straight. I assume you don't have this kind.

I would go for the drawbar. Is the problem that it won't fit through? or that you don't have room to put it through due to position near a wall?

If the latter, I would move it!

If the former, something is far wrong, you should have about 20mm clear all the way through the spindle.

[JCHannum]

For information on collets, go to www.cox-internet.com/drspiff/machining/collets/Collets.htm
There are other links to collets there as well.
There are some collet fixtures that hold 5C collets from the front as you suggest.
My advice is, if you have an idea, try it. That is a part of what this hobby is about. If it works for you, then it works. Think it through, of course, and take no shortcuts where safety is involved.
All projects are difficult at first. Things get simpler as we gain experience, mostly from our mistakes. The only only way to gain that experience is at the machine.
The mistakes go back into the scrap box, and are dusted off later as a base for some other project, so it is not all a waste.
Link should work now. Also www.loganact.com has collet info. and some other things of interest. Logan are nice people.

[This message has been edited by JCHannum (edited 05-09-2002).]

[Paul Gauthier]

Wasn't there an article on making a collet adapter such as the one Thrud mentioned in HSM or the other magazine whose name I can't remember at the moment, at 53 things start to fade away even though I aquire both mags. It may have been spread out over several issues. If I remember right it should be exactly what Alistair needs.

Paul G.

[SGW]

I don't think brass would be my choice for a collet adapter. it would certainly work...for a while, but I question how well it would stand up to use.

Why can't you use a drawbar? If it's because you're up against a wall, I'm with Oso: move your lathe. You need access to the left-hand end of your lathe, anyway, to feed long stock through the spindle, etc. (If that's not the issue, please elaborate.)

[SGW]

I don't think brass would be my choice for a collet adapter. it would certainly work...for a while, but I question how well it would stand up to use.

Why can't you use a drawbar? If it's because you're up against a wall, I'm with Oso: move your lathe. You need access to the left-hand end of your lathe, anyway, to feed long stock through the spindle, etc. (If that's not the issue, please elaborate.)

[JCHannum]

It appears that the hole through spindle is not large enough to accomodate a drawbar. "The Shop Wisdom of Philip Duclos" has write up on spindle adaptor for 5C and R8 collets for 1-1/2-8 spindle. Made R8 for my Atlas, and it worked well.

[Alistair Hosie]

Dear all,Sorry if My question about the collets came across as vauge however the situation is this.
The collets I have are not tapered they are straight and long.I looked again today both up and down the mandrel with a fine surgical torch and it seems to me that although the fit isn't tight,I.E. that on retrieving them they would need to be knocked out with an instrument or anything.But as I look up from the left side of the mandril and with the aid of the light I cannot see how there would be enough room for the thickness of the drawbar on top of the threads .It seems to me that the space between the end of the collets I.E. the threaded end and the inside diameter of the mandrill would not allow for the extra thickness of the drawbar unless the drawbar could be made exeedingly thin perhaps however I am wrong on this.A drawbar would of course be the best solution.Am I doing It all wrong? Needless to say I would not set the lathe so close to the wall so as to lose the advantage of being able too feed in long stock from the left through the headstock mandril but I have heard of people doing that you are right to point out the possibility.I thank you all very much so far regards Alistair

[Herb W]

Alistair
Which type of collet do you have? According to the Boxford info at the UK lathe site, the spindle (mandrel) in those lathes is the same as the South Bend 9" machines. If this is so, the standard collet is 3c and requires an adapter sleeve to fit the 3 mt of the spindle. With the 3c collet, there is room for a drawtube.
Sounds like you have a different type of collet. Does Boxford have their own collet setup? Or, perhaps the spindle is not the same as SB? Here's the link to the Boxford page http://www.lathes.co.uk/boxford/index.html

[This message has been edited by Herb W (edited 05-09-2002).]

[Alistair Hosie]

Dear Herb: no these are not Boxford collets I was given (during a bit of bartering )actually two full sets of collets one set would not fit in the lathe mandril as they were too large but the other would but as I say I am encountering these problems.Alistair

[gvasale]

Have we forgotten about the Sjorgen speed collet chuck? probably too expensive for the mome machinist. For reference check MSC catalog pg #1653. Lathe where I once worked had one, but his was a long time ago. Might there have been one to fit the Boxford way back when or some other maker with the same spindle nose/ chuck mount?

[JCHannum]

Alistair, if you could identify the collets, it would make it easier for us to envision a solution. They can most likely be made to work, but will probably need some sort of adaptor made to fit them to the MT #3 bore of your spindle, or a holder to mount on the 1-1/2"-8 nose of the spindle. Take a look at websites, or Tony at lathes, I am sure they can help you.
You also be able to do more bartering, and get collets more suitable to your needs.
Best of luck.