collets

[john cassidyParticipant @johncassidy42216]

hi all

can anyone tell me the correct type  of steel to make collets out of and how to harden them thanks j.c

[john cassidyParticipant @johncassidy42216]

steel

[macmarchParticipant @macmarch]

Welcome to the club John,

 

Why do you need to harden the collets?  I made myself a collet chuck some 15 years ago and made the collets out of EN3A as it was then. I have never had the need to harden them.  I made 50 blanks on the one setting so that they all have the same taper. I then made a set in imperial and a set in metric with the other 30 stored for future use.  I did, when I made the first two sets, warm them up to around 200C, (in the oven) then plunged them into old engine oil overnight. I can reccommend this for any tooling you want to keep for that odd use.

If you have a particular reason for hardening then I would suggest EN19 or EN8.

 

cheers

ray

[john cassidyParticipant @johncassidy42216]

hi ray

the reason for hardening was that i thought that the hardening process was what gave the metal its springiness and will the en3 return to its original shape also will en3 harden ? .the part iam making is not a collet but pipe expander (in brass tube) i thought collet in reverse was the only thing that seemed near to a description of what i will make.like a pop rivet gun but with a expander on the end it will be used for resizing the brass push fit on old fly fishing rods. hope i have shed some light on my needs thanks for your time and the welcome john

[Keith LongParticipant @keithlong89920]

Hi John

There was a tool design published in ME sometime in the 1970’s for expanding copper piping into tube plates on boilers, It very basically consisted of a piece of rubber tube, a close fit to the inside dia. of the pipe to be expanded. Through the centre of the rubber tube was a fairly close fitting bolt  with washers at either end of the rubber tube and a nut to put it all under compression. The idea was slip the tool into the end of the pipe to be expanded, run the nut along the bolt to compress the rubber tube, which having no where else to go got fatter as it was forced to shorten. That loaded up the tube to be expanded and so job done. To get the tool out just release the nut and allow the rubber to go back to it’s original length. I’ve tried this with odd bits of tube stuck through washers and it works. The origianl tool design was more complicated having handles like a pipe wrench that you could squeeze rather than fiddling with nuts and bolts, but the principle is the same. I think for your purposes this would work quite well as you would have a lot of “feel” for what was happening. The rubber tube would be kinder to the brass than a steel expander, sizes wouldn’t be critical and you can always squeeze a bit harder if you haven’t got quite enough increase in diameter.

I’m sorry I can’t help with issue numbers, we used to get Model Engineer in our works library which is where I saw the idea and it’s stuck with me ever since.

Hope this helps.

Keith

[macmarchParticipant @macmarch]

Hi John,

Sounds like an interesting tooling problem.  EN3A is alead free mild steel that can be welded. It can only be ‘hardened’ by case hardening. EN19/EN8 will harden by heat treatment consisting of heat and quench followed by tempering at controoled temp and time. A hardened part will, in theory, NOT be springy. but as in all things they are’springy’. You don’t get hard and springy without the possibility of metal fatigue and cracking.  EN3A will suffice for your needs. I presume that the tubing you want to expand is small bore, can you not use drift expanders such as plumbers use. These work by inserting the taper drift into the bore and driving it down inside with the help of a hammer to produce a stright but expande inner diameter.

To make one.

take a piece of steel and turn the first part down to the existing dia. add a tapered bit bringing the dia up to the finished/required size and then a straight bit as long as is required.

 

cheers

 

ray

[Ian S CParticipant @iansc]

As Ray says pushing a bit of steel down the tube would work, but also a steel ball fron an old ball race with a drop of oil works quite well. The compressed rubber sounds a good system, it is of course used by Dremel to hold the sandpaper cylinders. Ian S C

[KWILParticipant @kwil]

ME 2194 [Vol 88] had a pipe expander explained and ME 3810 [Vol 159] had an expander for forming a ridge on boiler tubes.

[Ian S CParticipant @iansc]

I remember that one Kwil, it works well,havn’t seen it round the workshop in a while, the workshop gremlins have borrowed it I think. Ian S C

[john cassidyParticipant @johncassidy42216]

hi

like the sound of the rubber idea do think the use of O rings would do as there are quite a number of different sizes and its for a mate who  owns a garage and know that he has a huge box of O rings from 4 to 50 mm .I thought of the drift idea but it has 2 down falls 1 tubes will be still fixed to the fishing rods so cannot knock through a drift. And 2 the mate will be on the phone every 2 mins for a different size drift and as he he is a bit heavy handed i was looking for some thing with a possitive control which does not involve a hammer (HAMMER +DRIFT= SCRAP FISHING ROD ) . I do like this idea as it seems to be a lot easier to construct and would fit the bill

cheers J.C     P.S The tube will only need to be expanded about 2 thou

[Martin WParticipant @martinw]

John

 

This may be a stupid question but why not take 2 thou off the male ferrule rather than opening the female part of the ferrule. It would be easier and could be done using very fine emery paper followed by metal polish for a fine finish .

 

Cheers

 

Martin W

[Keith LongParticipant @keithlong89920]

Hi John

I think if you use o rings you’ll get a series of raised ridges rather than a smooth overall expansion. If all your looking for is a couple of thou, you might get that with a suitably sized dremel type sanding drum and fine abrasive paper, effectively an internal grinding/honing job, even if you have to make an extended shank to reach the bottom of the ferrule.

Martins suggestion of sanding down the male ferrule sounds a lot easier.

Keith

[Sub MandrelParticipant @submandrel]

For what it’s worth I came by some EN24T and it made nice springy collets OK with no treatment but getting a nice surface finish on the external taper was hard. I would like to try EN8 as I understand it machines more easily.

 

Neil

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