Using metric Collets with Imperial Endmills

@oskar

As an aside to all of the above..

If you are not inerested, yet, in acquiring a full set of imperial collets, you can actually acquire a 3.175mm metric collet. I have just added one to my metric set as I do have a couple of 1/8" shank end mills.
 
Thanks for the help, I just bought a set of 7 metric collets, 1mm to 7mm for CAD$14.00 shipping included from AliExpress. Don't know about their quality but I only do hobby work. I didn't know that a 3.175mm existed.

At the same time I ordered a set of 7 end mills, 3mm shank, 1 to 7mm. Don't know where I will use the 1, 2, and 3mm ones, they are so small I think they will brake in no time, but it was a set.

Ordering metric end mills and collets gives me.....headache, will never be able to grasp the darn metric system, lol
 
oskar said:
Thanks for the help, I just bought a set of 7 metric collets, 1mm to 7mm for CAD$14.00 shipping included from AliExpress. Don't know about their quality but I only do hobby work. I didn't know that a 3.175mm existed.

At the same time I ordered a set of 7 end mills, 3mm shank, 1 to 7mm. Don't know where I will use the 1, 2, and 3mm ones, they are so small I think they will brake in no time, but it was a set.

Ordering metric end mills and collets gives me.....headache, will never be able to grasp the darn metric system, lol
Click to expand...

Metric is easy once you know that 1" is 25.4mm and that you can work from that point. A metric/imperial or imperial metric (depending which way you look at it) "conversion table" is also handy to have on hand as a reference.

I do agree though, converting between imperial and metric or metric and imperial can be a real PITA. Once you do a few conversions, have a few key sizes and conversions memorised as well as have a conversion table to hand it does get easier.

Re the 3.175mm ER32 collet... Here is one on ebay... Can't speak to quality, but they are out there.....

https://www.ebay.com/itm/355485855154?var=624640667068
 
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*purist mode on*

It doesn't matter what collet system it is, it will only grip tightly when the shank is exactly the same nominal size. It all comes down to circumferences being unique, so only two of the same diameter share contact points in all angles. An ER collet in particular acts like a drill chuck with any other size, with one contact point per slit, instead of 3 (the amount you get with 3 flat jaws). Since ER collets typically have 16 slits, it works like a 16 jaw chuck, with 16 contact points.

Are 16 contact points good enough? It's up to you to decide. But remember that whole purpose of ground surfaces is to spread stresses over a large area. And since you're exactly defeating that goal, the collet will inevitably wear much faster.
 
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oskar said:
Thanks for the help, I just bought a set of 7 metric collets, 1mm to 7mm for CAD$14.00 shipping included from AliExpress. Don't know about their quality but I only do hobby work. I didn't know that a 3.175mm existed.

At the same time I ordered a set of 7 end mills, 3mm shank, 1 to 7mm. Don't know where I will use the 1, 2, and 3mm ones, they are so small I think they will brake in no time, but it was a set.

Ordering metric end mills and collets gives me.....headache, will never be able to grasp the darn metric system, lol
Click to expand...
They'll probably be fine. My cheap Chinese set I bought from Amazon were perfectly fine...

...but only after I had thoroughly cleaned out the slots in the collets. There was quite a fair bit of dust and swarf from the grinding in the slots and it caused inconsistent clamping in the collets and thus some runout.

Honestly, make sure you do the cleaning when you receive the collets before you use them; use something like acetone or isopropyl alcohol. It reallywill make a big difference.
 
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