If you simply clamp a short length part in an ER type collet it will tend to close bell mouthed and does not secure the part well.
In order to prevent this it is necessary to support the rear of the the collet vis :-
In this example I needed to turn a bearing bush with a shoulder in the middle - so turn, drill, bore and part off - turn around to bore the rear end.
However I turned the finished diameter over a longer length of stock than required for the part vis:-
And used this at the rear of the collet :-
Now you can tighten without difficulty as the part front and back are exactly the same diameter.
If you need to secure a really short part - like a washer - then you can cut the "backup" to come almost to the front of the collet - in this case you will need to polish off a couple of microns off the backup to ensure you are gripping the part. The backup also ensures the part runs true / doesn't "wobble"
Regards, Ken
In order to prevent this it is necessary to support the rear of the the collet vis :-
In this example I needed to turn a bearing bush with a shoulder in the middle - so turn, drill, bore and part off - turn around to bore the rear end.
However I turned the finished diameter over a longer length of stock than required for the part vis:-
And used this at the rear of the collet :-
Now you can tighten without difficulty as the part front and back are exactly the same diameter.
If you need to secure a really short part - like a washer - then you can cut the "backup" to come almost to the front of the collet - in this case you will need to polish off a couple of microns off the backup to ensure you are gripping the part. The backup also ensures the part runs true / doesn't "wobble"
Regards, Ken
Last edited:
