First time cutting delrin. Tooling concerns

Ideal3675 · Mar 23, 2015

We recieved a HUGE order for a conveyer made out of Delrin. My shop has only cut various metals so this is something a bit new to me (the tool guy) and my concerns are revolving around tool life. It calls out for two 9/16 thru holes with a depth of 14.5" and i happened to have a couple HSS drills that will just barely work. Thanks to my awesome~ quoting department the time table i have is extremely tight so i couldn't approach this the proper way due crazy lead times and i'm a bit concerned about these drills making it through the whole job. New drills are 6 weeks out so theres little to no room for tooling issues. How fast can i expect this material to dull my drills?
(the ~ is sarcasm :rolleyes5:

)

TimH · Mar 23, 2015

Delrrin is very nice to cut and is gives great tool life. I'm sure others with more experience will reply but I really have never had issues with tools wearing out. Delrin also has lubricating properties which helps with tool life also

706jim · Mar 23, 2015

Well, I don't know what part of your question is sarcasm, but Delrin cuts like butter. The biggest concern I anticipate is clearing the chips from such a deep hole. Otherwise, the cutting edges should last a looooong time IMO.

And what do you mean by a "huge" job?

100, 1000, 10000?

Rstewart · Mar 23, 2015

Wow, that's like 25 x D depth!! I haven't done much with delrin, but that don't sound too fun :bawling:

Atomkinder · Mar 23, 2015

I've always just run it like aluminum. Cuts like a dream, none of the finish and cut problems that many plastics (hellooooo UHMW) have. Your holes might wind up a little small towards the bottom, but if your tolerance is ±1/64" it'll be a non-issue.

Scruffy887 · Mar 23, 2015

I run Acetal and Delrin. Tool life in years. The biggest problem with a hole that deep will be heat. Other issue is you need a peck/dwell because the chips really don't like to break apart. They can make a nasty nest that messes up the surrounding surface.
Drills that "just barely work" may not work at all. You need flute above the top at depth. Also guessing those drills have coolant holes? another thing to think about is feed rate. Aggressive enough to keep the heat in the chips but not so aggressive as to collapse the hole. You can drill at very slow speeds trying to chase this. Hole comes out on size. Go back to production and hole is oversize.

upnorth5axis · Mar 23, 2015

If the drills were used for anything else make sure to resharpen them before using. keep an eye on melting. 2 drills should be enough to do 1000's of holes

Guest · Mar 23, 2015

The only issue is going to be clearing chips, tool wear will be ZERO even if you make a trillion parts. If you drill aggressively and end up with chips blocking coolant flow you will have a melted mess. Keeping chips from wrapping around tooling and parts is the only issue with Acetal.

Ideal3675 · Mar 23, 2015

The tolerance is -.0005 +.0000 It's an interupted cut. Every 3-1/2" we have a 3-1/2 opening before it hits the hole. They programmed it to peck and then rapid down to the next hole. If i had the time i wanted to go with 14mm HSS coolant thru and then chase it with a reamer since we have to machine bushings and keeping the holes uniform is essential for this to flow through in a timely manner.

So it's safe to say that unless something drastic happens my drills should be able to get the job done. 210 of these things with 2 holes a pc is a lot for this shop as we are use to smaller runs of 50-150 pcs.
Thanks for the input so far guys :cheers:

Mtndew · Mar 23, 2015

mmmm Delrin. The stuff that dreams are made of.

Atomkinder · Mar 23, 2015

Ideal3675 said:
The tolerance is -.0005 +.0000

Uh, at what temperature? Coefficient of linear thermal expansion of Delrin is 45 millionths per degree per inch.

Acetal, Delrin, properties Data Sheet

Your tooling isn't the problem, the material is.

microgeek · Mar 23, 2015

Even if you run out of flute you can feed it past the flutes as long as your pecks are small past that point, 1.5x max for a jobber. As far as tool life, as long as you have a sharp tool it will last forever. There can't be built up metals on the drill though, delrin won't like that.

Modelman · Mar 23, 2015

Given that you are actually drilling a series of 3.5" deep holes in succession, if you need different size drills you could machine a reduced diameter boss on the end and silver solder into a hole in the end of a length of drill rod, using slightly undersize drill rod to reduce friction with the shank.

But really, you can't get long drills in a couple days? McMaster has a 9/16 x 18" showing in stock that should work:

McMaster-Carr

Dennis

Dennis

Ideal3675 · Mar 23, 2015

Modelman said:
Given that you are actually drilling a series of 3.5" deep holes in succession, if you need different size drills you could machine a reduced diameter boss on the end and silver solder into a hole in the end of a length of drill rod, using slightly undersize drill rod to reduce friction with the shank.

But really, you can't get long drills in a couple days? McMaster has a 9/16 x 18" showing in stock that should work:

McMaster-Carr

Dennis

Dennis

I need coolant thru though...

I've had multiple vendors searching for this drill and nobody can get anything here anytime soon. Like i said, we weren't given any time to really research and develop this part on the machining end. I'm lucky to have what i got here already. I think we are on the right track tho so far.

Guest · Mar 23, 2015

I must need better bifocals. I swear I read a .0005 included tolerance on plastic 14" deep. Gotta love those engineers fresh out of school that lack common sense.

thomasutley · Mar 23, 2015

I was one of those engineers once...still IN school I was hired to do the CAD design on a fancy electronics housing for the Physics Department. It was 6061-T651 aluminum, 21" OD tub by 6" deep machined from a solid billet because they couldn't tolerate any outgassing from a welded joint. Around the perimeter of the tub's face was an o-ring groove for a Viton seal between the lid and the tub.

I waltzed into our on-campus machine shop with a prints showing a tolerance of +/- half a thou on the o-ring diameter thinking how nice everything looked on my CAD drawing prints.

The sage old machine shop supervisor looked at my drawings and says, "Son, I'm going to charge you extra for requiring such a tight tolerance, on an o-ring groove no less. If you can prove I didn't hit it, I'll give you your money back."

Lesson learned, and never forgotten.

EM112358 · Mar 23, 2015

I'm going to go ahead and just say that 0.0005 total tolerance on that long of a hole in Delrin is near impossible without secondary ops. I'm not sure what the drill tolerance is, but it seems like you'd use up most of your tolerance just with that (not to mention melting material due to rubbing chips, interrupted cut, long length to diameter ratio, drill walking, etc). And even with secondary ops it will still be difficult. The part will grow/shrink due to temperature or stress relief, etc. Not saying it can't be done, but this seems like its going to be a spendy part if you want to be at all capable. I'm just really hoping 0.0005 was a decimal point mistake, because after all, its going into a conveyor?! Maybe its going on the Space Station though...

Stihl290 · Mar 23, 2015

Delrin cuts like butter. Drilling that deep, you're gunna have thermal issues. I would recommend peck drilling and thru coolant if possible.

adama · Mar 24, 2015

Thru coolant is nice, but its not essential if you drop the speeds and feeds accordingly. One hell of a lot of holes are drilled every day through out the world with out it. Trade of is time, but i could easily drill all those holes with out coolant before your 6 weeks lead time is up, ruff guess i would have at least 5+ weeks spare time :-)

azmachining · Mar 24, 2015

Somebody must not know how to weld, full pen tig weld is not going to leak.

A drill that long is going to have at least a half thou run out, those are reamer tolerances, even for acetal.

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