Knurling Delrin

Has anybody had experience of knurling Delrin ?

I need to make a quantity of thumbscrews, out of 20mm acetal rod, and just wondered if the material could be knurled, or whether I would be wasting my time trying.

TIA for any info ...

Probably need something like a quick-cut knurl which removes material rather than pusheing it about.

You could mill a straight knurl pattern I do that quite often as I don't have a set of straight wheels but depends how many your quantity is.

J

Never tried Knurling Delrin. As said, cut Knurling will work ok. Typical "crush" Knurling may work ok though with a coarse wheel?

I think I'd try cutting a series of V grooves first with a threading type tool then mount the tool to cut along the axis and "push cut" some V grooves at 90° to the first ones. You'll need to index the part somehow though.

Cut knurling works fine but never had any success with normal crush knurling.

I even tried doing some Corian the other day for some brush caps and it cut knurled far better than I expected, then tries a straight crush knurl and it just powdered it all up.

When I tried the results were terrible but then I only have ordinary knurls design for metal.

I'd like to get a couple knurls that cut rather than crush. Any ideas where from?

Roger,

It's more the design of the holder than the wheels. For a straight knurl you need a helical wheel but it's held so the teeth are parallel to the work.

The face of the knurl has to be surface ground to give a sharp edge to the knurl. Normal knurls usually have a chamfer but it can be ground off.

Dave Fenner did an article in MEW not too long ago.

Thanks to all who have replied so far. I haven't actually got any knurling kit, but would have invested if the vibes had been good.

I think I will change my modus operandi.

To minimize material wastage, what I can do is cut 6 equally spaced grooves lengthways on the perimeter of the 20mm rod, using a table mounted router and a sled, and then, in the lathe, drill and tap a blind M10 hole in the end, 10mm deep, and part off at 15mm lengths.

That will give me the head of the thumb screw and I can then insert M10 delrin rod of the right length to complete the screw.

If anybody has any suggestion about a good glue for delrin, I am all ears ... I could of course cross drill the head and insert a dowel ...

If anybody has any suggestions for commercially available black delrin M10 rod, I would also appreciate that. I could of course thread plain rod using a dieholder in the tailstock, but would prefer to buy ready made, if possible.

Can you get the press-on knurled caps for SHCS in the UK .... this type of thing?

Would it do the job?

Hi murrmac,
Heating the knurls to near the melting point (175 Deg. C) might work.

Les.

Hi, yes, these would actually be ideal ! Thank you.

I can get hex headed delrin or nylon bolts no problem, but I have in fact searched for press-on knurled hex caps with no previous success. I will contact the company when the holiday period is over and see if they export to the UK.

I suppose heating might work, Les , but I would prefer an easier option, given that I have quite a few of these to make.

Ah, spoke too soon ... these press on caps are for socket cap screws ... my bad.

I don't know if it is possible to get socket head nylon screws ...I suspect not ...

Hex head delrin bolt, turn head down to fit press on knurled cap, attach with suitable adhesive?

John

Edited for fat fingers!

Edited By John Corden on 01/01/2015 16:55:51

I haven't found a glue or locktite to date that will bond acetal to steel with any degree of success. Better off counterboring for head and using the acetal as a washer if you like. Can swage cap head in to anything, leave the splines on.

Regarding knurling acetal I do it from time to time, its easy by crush methods. Finer the easier not other way round.

Acetal knurl will come out just as good as aluminiums, copper, brass, steels, titaniums, pvc, nylon 66 etc Just leave running and or work the knurler until becomes sharp edged. I say that as not seen to date any knurling I would be happy with, all having flats whether cut or crush.

Happy New Year to all!

I’d be very careful applying (especially flame) heat to polyacetal (Delrin).

Fumes are extremely deleterious and if you breathe in even the slightest whiff you’ll wonder what hit you.

It’s lovely stuff to machine, but I can only guess that pressing a knurl into polyacetal will be largely unsuccessful.

Good luck,

Sam

.

I think you might do better using standard thread inserts, press fitted into warm Delrin.

See here for some typical styles.

MichaelG.

I have used superglue to bond delrin to itself and this works well so I assume it would also work when used to bond delrin to metal.

Doug

Lots of interesting suggestions here ... thanks all.

I think that the way i will go is to use these **LINK** black nylon hex bolt caps in conjunction with hex head nylon bolts, pressed on and glued, and run six (or more) shallow grooves in each cap with a table mounted router. This should give adequate grip.

Thanks again for all suggestions, much appreciated. If anybody has any ideas where I can obtain black nylon M10 bolts, I would be interested ... I can get natural (white ) nylon bolts easily enough, and it isn't really a huge deal, but black nylon thread would just give that finishing touch.

.

Like these ?

MichaelG.

yes, these would be ideal, Michael ... but at $2.20 each ??? ...maybe not ...

I can get the M10 natural nylon bolts for 15p each from shop4fasteners (my fav hardware supplier )

Hi,

I've used this product :- **LINK** to dye natural colour nylon "p" cable clips black in the past.

Nick.