Interesting…….quite a lot of members at Epping Forest Horological Club have recently aquired cheap(er) chinese ER sets and, while results are indeed mixed, I have noticed some repeating problems which can be listed under 'user error'…. Firstly, people often claim poor manufacture but when one of the more experienced members examine their set some of these defects are reduced or simple go away.

Firstly, the large number of slots in ER design allows debris to quickly upset accuracy as just one tiny piece of swarf will prevent the slots closing evenly and start to spoil accuracy. Next, people commonly try to mount the collet imperfectly and don't realise that there is a little ceremony in fitting the collet into the tensioning nut correctly first. Finally it's worth mentioning that in industry ER is used to hold cutters and its very common to 'clock 'n tap' to get proper needle placement by using a small hammer or mallet.

Additionally, it's worth mentioning that one has three options for ER collets, namely an ER chuck fitted to spindle,….a Morse taper ER mandrel that fits into the lathe throat and finally an ER fitting in a square or 6 sided block. For my small lathe I chose ER25 in a square block which I use in my 4 jaw chuck…..the drill is to grip the block, fit collet with silver steel piece, clock, adjust for accuracy…….much better than the 4 jaw on it's own IF you are going to do a session of collet work where you will need to make several changes of size etc., also, the ER is much better with the small sizes I use in clock making.

Bought some cheap ER25 collets on eBay and whilst the larger sizes were OK everything below 4mm was rubbish, I didn't need to measure the run-out, I could see it! Ended up buying the smaller sizes from Arc who also do 1.5 and 2.5mm – much better. I bought an MT3 collet chuck from them as well, only complaint is the lack of spanner flats or holes for a tommy bar, so loosening collets relies on the grip of the Morse taper.

Brian

If you require really high accuracy you’ll need to pay for it. These look good at £60 a collet!

**LINK**

Buying precision collets saves a lot down the line. I suggest buying the highest precision collet you can afford at the time. Then buy more as you need them. Having cutters run better than .01mm every time is important and does make the cutters last longer. Also it means you have confidence is setting up a part and know it is concentric within the collets accuracy. I bought some AAA from China collets that are better than 0.005mm but not 0.002mm though.

Even though they seem expensive , precision collets really are time savers in the long run.

Neil

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Does that surprise you in any way?

MichaelG.

I have an ER32 3MT collet chuck along with numerous collets which were bought on ebay. They may not be toolroom standard but good enough for the work that I do and all at a price that will not break the bank.

My lathe, mill and rotary table all have 3MT spindles and the chuck can be used on all machines. Also very handy to take a job from lathe to rotary table without removing it from the chuck. The only problem being, if the collet chuck is being used to hold work in the RT, it is not available to hold a cutter in the mill and I have to resort to different methods. And why I am thinking about getting a second collet chuck.

Paul.

That's where starting with a cheap set comes in handy. They may not be as accurate, but they still hold turned parts in collet block without marking.

Brian

Even the cheaper collets are more accurate than an older 3 jaw chuck. Jaws could be ground to make them run on centre but if the scroll is worn, it will only work for the specific diameter that you ground the jaws.

Paul.