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The ER40 collets do not have a gap in their range. There are 29 collets in a complete imperial set. Most “sets” sold are not complete. I had to purchase individual collets to make a complete set. What I like about the imperial set is the collets overlaping ranges so I can select a collet in it’s middle of the clamp range.
From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> On Behalf Of Steven Schlegel
Sent: Tuesday, June 22, 2021 12:32 AM
Subject: Re: [SouthBendLathe] collets:
About the ER collets, each collet covers a range of 1mm. I use ER 32 collets because I found them on sale. I wish I had ER 40 collets because they go bigger. The ER collets go from the printed size down 1mm. Never put a bit or stock bigger than the printed size into an ER collets because it could distort the collet.
The ER collets hold bits/stock over a longer length than a 3c or 5c collet, giving them a better grip. The modestly priced sets will give you 0.0003" TIR which is pretty good. Do to the range they will hold, you do not need an exact size. Nothing wiggles I'm the ER collet like it does in the 3c or 5c collet if the size is not perfect.
I purchased both both a square and hex holder, and a lathe chuck that mounts on a backplate. All pretty reasonably priced.
I use one set of collets for both my lathe and vertical mill. While I have both imperial and metric, I have only used the metric set because it gives me complete coverage from 2mm to the top of the range. The imperial set has gaps that exceed the 1mm range. I simple measure the bit/stock diameter in mm and chose the next integer size collet larger if it is between sizes.
Just my experience...
From: SouthBendLathe@groups.io <SouthBendLathe@groups.io> on behalf of comstock_friend <jfriend314@...>
"Complete set"; are you sure you want or need 1/64", 1/32" or 3/64" collets? They're in the set. My first size either 3C or 5C is 1/16" (well, I do have a 5C 3/64" but I do not anticipate using it any time soon!) Sets of 3C's also include hex and squares (something that the ER series can't handle). Obviously more collets in 5C, as they go up to 1-1/4" or larger with closers and such. The typical max 3C (also 1A you will find interchanges easily) taps out at 9/16".