Home made collet draw tube

[TomW]

I needed a simple collet draw tube to use on a hercus 260 for use with W20 collets.
I made it from tube to avail of the advantages of the hollow centre.
The brazing of parts enabled it to be made of scrap pieces and during the process there was surprisingly little distortion of the tube.
The internal thread of 1 2/3 mm pitch or 1.667 mm was simply achieved by placing a 30 tooth stud gear and setting the quick change box to cut a 1 mm thread.
The collet adaptor to go in the spindle was made to suit the collet dimensions.
A nice piece of she oak was selected to go on the end to facilitate hand tightening.
P/S The steering wheel is very useful for cutting large threads up to shoulders and eliminates brown pants moments
Cheers Tom

[Michael G]

The Sheoak knob certainly looks classy but if it were my workshop with all the dirty, graphite and grease it would soon get confused with a piece of ebony.
If you are using W20 collets, does that mean you are a Schaublin owner as well?

Michael

[TomW]

Michael
I wish I was a schaublin owner ( maybe one day)
The W20 collets came with an old Simonet lathe a lesser known Swiss machine of 90 mm centre height but still a quality item.


I wish my pictures were the right way up!!

Tom.

360239

[YBAF]

I wish my pictures were the right way up!!


For us ipad users there's an easy fix.:U

[Gavin Newman]

I wish my pictures were the right way up!!

They are the right way up where the lathe was made though.

[kwijibo99]

Great job Tom, I love the steering wheel hand crank, that's an idea I reckon I'll be stealing.
Cheers,
Greg.

[Pete F]

The internal thread of 1 2/3 mm pitch or 1.667 mm was simply achieved by placing a 30 tooth stud gear and setting the quick change box to cut a 1 mm thread.

Cheers Tom

Tom did you grind the internal buttress tool?

[TomW]

I'm afraid not Pete
I copied an original one and it didn't seem to have the internal buttress thread just a 60 deg standard metric profile (collets definitely have buttress)
Don't quite understand how it will wear being forced up against a thread of different profile?

tom

[Michael G]

Don't quite understand how it will wear being forced up against a thread of different profile?

Simply that if the thread profiles are the same, the load is theoretically spread across the whole face of the thread but if they are different the force becomes a line contact, increasing the local pressure on the contact surfaces. This in turn could lead to galling, distortion and things coming loose. Both threads should be the same type although whether it is a major concern in real terms depends on a number of factors - I suspect that there are millions of Whitworth bolts out there assembled with UNC nuts for example.
For something like a collet there are high loads on the thread so it would be better if the threads matched. My concerns would be either the threads binding up or alternately it coming loose while being used.

Michael

[Pete F]

Yes, unremarkably I agree with Michael on this one. Indeed the designers went to the effort to specify a buttress thread (a weird angle pairing at that too) instead of a V profile, because of their concerns about thread strength in torsion.

I haven't had a need to cut any Schaublin internal threads, but have done externals, and once the gearing is sorted they're no more difficult than a conventional thread and are cut the same way. The difficulty is in fact in grinding the tool, and even that isn't exactly difficult, just fiddly. IIRC I set it up on the surface grinder in a ball vice and digital angle gauge and was able to grind the tool quite accurately. However the same accuracy could probably be achieved by various other means and a creative mind.

[BaronJ]

I used an old washing machine tub pulley when I made mine. Very useful gadget, particularly when setting up to thread something especially if its an internal one.

[BaronJ]

I used an old washing machine tub pulley when I made mine. Very useful gadget.

I found some pictures of mine.

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The brass collar prevents putting it to far up the spindle.

[TomW]

Very well done
i love the way our little machines turn us into masters of improvision