Turning Delrin

[KC2IXE]

Hi Gang

I've been working on a job where I'm turning some black delrin. Nice and simple, huh? Except for a few details - like an ecentric hole where I have to turn to within a few thou of the hole (aka VERY thing walls on one side), and a LONG overhang (like 5x the diameter). Of course, the ecentric hole prevents the use of a center.

The trick I came up with was a sacrifical rod the length of the part, that JUST fits the hole (light press fit) and a center,

What I have NOT come up with is a way to deal with the birds nest of chips. I've tried 4 different chip breakers, from "flat" to high positive for aluminum, to UF to MF, different speeds and feeds, and I still get birds nests

Any ideas?

 

[kuksul08]

Funny you make this thread. I am also working on a project for a friend that involves turning some 2" black delrin that extends 8 inches from the chuck. The 'birds nests' are also an issue for me. What I found works is doing short cutting intervals so that the confetti-like string of chips can break and fall down before wrapping around everything.

 

[KC2IXE]

Been doing that, still birds nesting more than I want. Read somewhere that you need to take VERY agressive (read deep) cuts, and just get used to it, and use airblast to direct the birdsnest where you want

 

[precisionworks]

short cutting intervals so that the confetti-like string of chips can break and fall down before wrapping around everything.

+1

Take all the DOC you want & run all the sfpm you like but only advance the carriage 1" & immediately back the carriage up. YOU are the chipbreaker.

Sometimes you can let it pile up but waiting one micro second too long spells disaster.

 

[scott011422]

We turn delrin here from time to time. Damn near impossable to break. We use Kuksul08's methode of peck turning. feed .125, pause, feed .125 pause...ect

 

[KC2IXE]

Sigh - was hoping for a real answer. I was reading something about airblast being a trick

I was turning the parts at first without a mandrel, and blew up two of them, then put un the mandrel, but had all sorts of fun, as I only have a standard dead center for my tailstock (or a nice bullnose), so I was having to turn part of the end close chucked, then move it out. Ordered a "Made in USA" "CNC Point" live center today.

Geeze, helping out at my old school's shop is getting expensive. I also ordered them 6 disposable deburring tools, and got an expanding hand reamer to do one job on the robot (but that will come home with me)

BTW This is what they are involved in

http://www.usfirst.org/

 

[precisionworks]

was hoping for a real answer.

Well excuse us all :nana:

After filling two 55 gallon drums with shavings it seemed like a nuclear powered shop vac would be the ticket. Something with a hose 6" diameter & attached to the tool post so the hose stayed right with the part at the point of contact. Setups like that are used in shops that run DuraBar all day long & there's not a spec of cast iron in the shop.

But ... Delrin isn't DuraBar. And a super sucker like that would run at least $10k.

I was reading something about airblast being a trick

Air could be used to pile the ribbons somewhere else (which may help) but if your feed is fast the ribbon is really thick, almost impossible to cut with a knife. Unless of course the feed was very fine & the ribbons were so thin they could be broken by hand.

 

[darkzero]

My shop instructor taught me a trick that will break long strings & help prevent birds nests without having to stop feeding periodically. While the carriage is auto feeding, tap on the carriage wheel handle when you want to break a chip. I do this quite often & it's effective but of course it will affect the finish but I don't run into this issue much on finishing passes.

 

[wquiles]

Same here guys - I have not found a way to prevent the birds nests either with Delrin, so like posted above, I turn, stop, continue, etc., until the very last (finish) pass where I don't mind a very light weight "small" mess ;)

Although I do have one insert (can't remember which one at the moment), where if I turn the Delrin as fast as I can on the carriage, I then "do" get a shower of small chips - but you have to be going pretty scary fast, which is why I don't do it all that often. One of these days I will try to take a short film of the shower of Delrin chips ;)

Will

 

[kuksul08]

Another thing I just thought of was when I used a flat end tool (I think it's used for grooving) to do the turning. This is probably the wrong use for that tool, but it seemed to work. It ended up spraying out little chips and left a nice glossy surface finish. There must be something about that tool geometry that created chips instead.

 

[MartinDWhite]

I turn a little delrin here and there....a regular ShopVac worked well to keep the nest from forming, the ribbon just went in the vac and not between the ways. This was real cumbersome to use with the vac mounted to the tooling, so I reverted to just making sure the starting end of the ribbon doesn't get wrapped around the work piece and it generally all falls in a nice pile (nest) between the ways. After each pass stop the lathe, remove the pile (nest), start lathe. Fortunately most of the parts I make only require one pass.

 

[brickbat]

+1 on the shop vac...