How to machine Acetal

[DanielParticipant @daniel]

Posted by Ian Johnson 1 on 17/06/2019 00:41:14:

Hi Martin I get those tips from JB Cutting Tools. They usually have a stall or two at classic bike shows (Stafford), steam fairs or model engineering shows. I think you can order on-line too although I haven't tried that yet. I don't know the technical specification for the tips, but if you ask Jenny she will give you the same ones, very good quality. About £3.50 each Silver or Gold I think they are the same spec, gold is prettier though!

Ian

I order regularly through their online shop.

Their website is great to navigate and the whole process very simple.

ATB,

Daniel

[AdrianRParticipant @adrianr18614]

Smart work.

Presumably it's not just rake you'd need when cutting, but a helluva lotta trailing side clearance to avoid rubbing on the helix angle.

I meant to ask: would have been easier to find a way to re-use the business end of the existing stirrer by joining to a new stem in some way?

I must admit I did not worry about clearance, The tool was quite small and had a good front clearance so it did not interfere much.

I did think about fixing the old one but;

• The plastic feels like the type that doesn't glue well.
• I thought of splinting with a stud down the middle, and in fact the motor spindle end is threaded, but the motor runs backwards and it would unscrew.
• I thought of making a socketed sleeve, but I am not sure how good the alignment between the motor and the oil tube is, so It could end up stressing the shaft.
• The mill is 19 years old, and the plastic could be brittle.
• There is no way to know if the oil pump is working.

So I decided making a new one is probably the safest. The Acetal does seem to be slightly more flexible than the old one, and I have strengthened the point that broke.

Adrian

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