PTFE machining properties
PTFE machining properties
(OP)
hi
we have got to machine lots of various sized PTFE seal rings biggest being about 220mm outside diameter , 200mm inside diameter and they all are about 10mm thick . Obviously they have to be fully machined then parted off due to there flexible nature .But what we have been told buy the customer is that the material will change diamensions after a period of time , so they recommend roughing out the seals then after about a week finish turning them . This seemed a strange request and not practical , what i would like to know is if the ptfe does change can you work on a percentage to allow for this . We would be machining the seals from a 9" billet 300mm long and would be using coolant .
Cheers
Chris
we have got to machine lots of various sized PTFE seal rings biggest being about 220mm outside diameter , 200mm inside diameter and they all are about 10mm thick . Obviously they have to be fully machined then parted off due to there flexible nature .But what we have been told buy the customer is that the material will change diamensions after a period of time , so they recommend roughing out the seals then after about a week finish turning them . This seemed a strange request and not practical , what i would like to know is if the ptfe does change can you work on a percentage to allow for this . We would be machining the seals from a 9" billet 300mm long and would be using coolant .
Cheers
Chris






RE: PTFE machining properties
Fortune favours the bold and avoids the unprepared.
RE: PTFE machining properties
The business side is that if the customer requests a specific procedure, deviating from that procedure can lead to misfortune. I'm sure they compensated you the extra set-up and machining time
Regards,
Mike
RE: PTFE machining properties
Thanks for advice
material is virgin ptfe
What i forgot to mention is we have to machine the mating surrounding piece for these as well from billet brass same sort of dimensions as above . So we will machine these first as the brass hopfully won't move to much , then at least we can put the ptfe seals in them to hold them round enough to get a decent measurement .
chris
RE: PTFE machining properties
Now with that done - machine up a mandrel to be held in the four jaw chuck, dial it in as above and machine a step 8 or 9mm in width and 1/10th larger in diameter than the internal diameter of the seals.
You will now be able hold the seals on the mandrel to machine the OD and face them off to 10mm dimension.
Your cutting tool should be HSS not TCT, you will need a positive rake cutting tool with no chip breaker. speed of spindle around 1500 rpm.
RE: PTFE machining properties
Thanks for the replies
Just an update job was done
Mat'l used virgin PTFE , customer happy with 8 out of 10 seal sizes but had problems with 2 which did change dimensionally . After a few phone calls we have now been told the seals should have been made from glass filled PTFE instead ( not specified before ) anyway job now on hold , the seals are for a plastic extruding machine i would imagine there might be a bit of heat involved ( can only guess at this stage as need to be informed ) but what advantage does glass filled have over PTFE
Cheers
Chris
RE: PTFE machining properties
Regards
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