Er25 collets

Will metric er25 collets work with imperial sized milling cutters? I’m looking at this set.

Link Removed see C of C

Edited By JasonB on 03/01/2021 15:25:51

Hi Jeremy,

I have ER 32 collets that cover most of the sizes I use. I did buy Imperial ER collets for 1/8" from Arc since I have a couple of tools with 1/8" shank. Clamping a 4mm metric ER collet down to 1/8" may reduce the accuracy so I bought the Imperial collet. If you use many imperial tools a 1/4" and may be a 3/8" collet may be worth the money. A 16mm ER collet will easily clamp a 5/8" shank tool.

Thor

I have a similar set. Some imperial sizes will go in , others not. Hang on i will post a picture of the writing on the collets. They do have a 1mm tolerance.

Steve.

Edited By Steviegtr on 03/01/2021 15:23:41

Yes, broadly speaking. ER collets have a clamping range of up to 1 mm, so, for example, a 13mm collet will tighten up on a ½” shank ok. However, I have a suspicion that closing up a collet by a lot will increase the chance of it running out of true, or possibly permanently distorting the collet, so prefer to use something that is the right size. You can always buy a few extra imperial collets to suit particular imperial cutters you have, which is what I have done - particularly for ¾” and ¼” shank tools.

Hi Jeremy you can use meteric ER 25 collets to hold imperial cutters as long as they are less than 1 mm deflection. You can use a 10 MM collet to hold a 3/8 inch cutter.

David

It is normal for ER collets to fit a (small) range of sizes - normally they are marked eg: 12-13mm. So that size would do for a 13mm shank and a half-inch shank (=12.7mm). For 5/16" you will find 8mm to be within a couple of thousandths, and for 1/4", use 6-7mm. Theory tells us that the accuracy and grip reduces as the collet is compressed. You can get inch-sized ER 25 collets, but you may have to search (and quite likely, pay extra). When I clicked on your link, a quarter-inch version was shown below the advert, at over 60 dollars ... !

Regards, Tim

I tend to not like squashing my collest down too much so have 0.5mm steps in teh smaller sizes and imperial ones for common tool shanks such as 1/8, 1/4 & 3/8 available from some of our suppliers as already mentioned at the same price as metric

As Thor has mentioned, ARC has inperial size er25 collets and it would be best to get e few in the exact sizes to complement your metric collets.

Out of interest has anyone tried the 1" size now available for ER32 collets? - forget where I saw them advertised but seems a useful item as I have some 25mm and 1" shank cutters.

Hi Oly Rag,

I got an Imperial ER-32 collets for 1" shanks just before Xmas but haven't had time to use it yet. It is shorter than the 20mm collet. I got my 1" from Ebay - Gloster Tooling.

Thor

Edited By Thor on 03/01/2021 15:40:21

Yes I bought one. I don’t check stuff with a DTI before I use it so can’t tell you how accurate it is but it’s suited my purpose without problems so far. Bought on eBay from Gloster Tooling. Wish they were cheaper or I’d buy a couple more of the over size ones.

Thanks Vic and Thor for your responses. I was given some 1" and 25mm shanked Clarkson type cutters that are around 2" and 38mm diameter. I only intend to use them for roughing out so might invest in an oversize collet. Might need to cut the threaded portion off the shanks though!

Martin

I use them all the time , never a problem. Imperial end mills etc get a quick measure with the digital calipers just to see theres no brain failure and away you go. I can't think of a good reason to buy both metric and imperial sets.

Hello Jeremy, I bought a few imperial collets for the convenience of the cutter not falling out of the collet when I release it. For example a 1/4" shank imperial cutter falls out of a 7mm collet when it is released, in a 1/4" collet it stays put.

It’s a valid point, I actually bought a few imperial collets to avoid over tightening metric collets as well. I bought 1/8”, 1/4” and possibly a 3/8”.