Tips for MACHINING Delrin

[Crawling Calvin]

Ok i noticed it has been asked about *cutting* it... I am talking machining the stuff down

My questions are:
Lubricants: I get the idea to use either compressed air and/or regular cutting fluids
Cutters: I was going to first surface mill the edges since I got the rough delrin skin surface () instead of smooth... *OOUPS* Then I was going to machine a slot on the sides to allow the chassis to not scrape

I have machined Nylon before without issue, just took it at a moderate feed with a nice spindle speed and things turned out just fine I have heard things about it smelling... I am in a shop training class so the last thing I want to do is be "the kid making the awful smell on the Lagun"

Other than that, i guess its just "wait and see"

[CadToChrome]

I cut Delrin with carbide although Highspeed steel works too.
On the CNC I feed it at about .002 - .003" /tooth per rev. if the cutter is 3/16 or larger. and feed it around .001-.0015/tooth per rev below 3/16"

If your running a manual machine, just don't take too deep a cut per pass
keep it at .05 or less and a steady movement.

If it gets hot from the cutter it will melt. ( like the shaft of the cutter rubbing on the material).

I run regular machine coolant without issue.

P.S. it does not smell.

[Crawling Calvin]

Ok thanks, its a manual machine. Any "range" for RPM's and feeds. When I machined some Nylon (cutting board... started the joke I was making "shredded coconut ) I took it at about 1,000 RPM and a moderate feed rate with a multi toothed facing cutter, and had no issues. I didn't even use lubes since I was mostly smoothing the surface down and it turned out mad smooth I will pretty much just take it easy and not try and hog the crap out of it, and if I see any problems, stop, and let it cool

[CadToChrome]

Originally Posted by Crawling Calvin

. When I machined some Nylon (cutting board... started the joke I was making "shredded coconut ) I took it at about 1,000 RPM and a moderate feed rate with a multi toothed facing cutter, and had no issues.

That is about right. you should get shredded coconut style chips.
if your running 1/2" Dia maybe around 2500rpm and 5/16 down 4000rpm is fine.

the higher the rpm the faster you can feed (rpm up chip load per tooth goes down). The main thing is not taking too deep a cut. on a manual machine I would not take more than .1" deep and med/slow speed. as you lessen the depth you can pick up on the travel speed.

Find some scrap and experiment a little with rpm's and travel speed at different depth's if you can, and you find the sweet spot for given conditions.

Hope this helps,
Chuck

[Jkelley]

I would also be careful with the cutting fluid. I was machining some parts made of delrin at work one day and I'm assuming that the cutting fluid was cold and I machined it to a certain size with the cold cutting fluid (was the first part of the day) to the print. It was fairly warm in the plant after I finished machining. I picked it up about 30 mins later and the dimensions had changed. No shit. I thought I was loosing my mind but I went into the bathroom and ran cold water over it and remeasured using my calipers and it had shrunk and grew around .005-.010. depending on hot and cold. Not sure what kind of tolerances you are holding just something to think about.

[Crawling Calvin]

Ok, I am machining up a skid plate so I don't think dimensions have to be "totally" perfect! I plan to mostly hit the cutter with compressed air (while spinning) between passes to cool the puppy down if I think things are gettin a tad to warm

[pbarsamian]

On my equipment I use compressed air, no lubricants. I usually run moderate to low RPM and low flute count (2 or 3 at most). I've been able to do .25" punch through slotting with a 3/32 2 flute and still get a pretty decent edge finish at any where from 7-9 ipm on my cnc router bed with about 7K on the spindle (manual dial pot on the router so estimated RPM). I use bulk purchased resharpened carbide mills for that since they do break once in a while.

I've only had swelling or balling up when I run too high of an RPM

[cro-magnum]

liquid laundry detergent. An old machinist used it all the time on the part of an ATM that you slide your card into. I don't know if it helped anything but it would lube and be easier to clean. This particular machinist is the best I have known

Travis

[Crawling Calvin]

Ok, I have machined a slot in nylon (yep not the same density as Delrin but... it turned out just fine with no lubes and NO compressed air ) So I think the best thing to do will be use the amount I have to remove from the edges to make the piece to spec as my "practice" space I just hope I don't become the hatred of the class for making all the "neat stuff"... bah I will throw some envy in there if I pack the AX along Other than that I can't think of "much else" to ask for. Many thanks Just got to wait for Monday

[JeepinDoug]

You can machine it just as you would nylon. Nylon I would use coolant, delrin you could use air.
I like to use moderate RPMs and higher speed rates when hand machining.

I was told yesterday from a reputable source that Delrin will emit cyanide when laser cut, I have no idea if it's true.

[Crawling Calvin]

Ok thanks, I had good results with no lubes for Nylon... heck the cutter had some oil residue on it . Hmm, that sounds a bit odd if laser cutting Delrin released cyanide... well either way, laser cutting plastic isn't really recommended because of the fumes

[Crawling Calvin]

Well that stuff sure machined up nice and fast now if the operator was more observant.... It turned out real nicely, I think the lathe was at like 400 RPM and it was fed at whatever rate but it machined my slots perfectly and the surface was real good so enough said

And no lubes and/or smell was really generated... unlike the old guy on the huge lathe cutting a slot for a bearing

[binaryterror]

When Acetals (Delrin is just a trademark) burn they emit Formaldehyde gases which can be lethal.

[Crawling Calvin]

Good to know

Ok I am picking my self up my own cutter for machining
I am looking at McMastercarr part # 2782A72 < its a 2-flute cobalt steel end mill, 1/4" diameter, the shank needs to be (in theory) 1/4" but I can try and get by with a 3/8... you can't always win in life Does that seem pretty good for the job considering I am going to be doing a lot of plunge starting cuts, I need to be able to slice away cleanly and the 2-flutes makes sense for good chippy removal

[Cave Dave]

You're on the right track Calvin. I use always 2 flute hss steel for Delrin unless the parts are very thin walled,then a 4 or more flute will help you avoid chipping the material.

[Crawling Calvin]

Ok thanks I am going to be "slot cutting" 1/8" delrin for the most part so would that be good or Just want to make sure I get what works. Sucks that the "router" im using only takes 1/4" shafts with a collet and 3/8 without (um don't want to do that ) Hmm, carbide...

EDIT: Part# to Mc again 8923A53 I think thats what I need... correct me or put a part # up if im wrong