Vendor for diamond inserts for plastic

[Wade C]

Been contemplating trying a diamond insert for turning/boring transparent plastics - cast acrylic primarily. (finishing op - profiling - light DOC). With a primary goal of surface finish.

From what I have read, seems that a MCD (mono crystalline diamond) would be what one would want? And that an insert like this, the machine's condition will play a large role in the outcome.

I think curiosity has finally got me bad enough that I want to start researching suppliers/vendors and get a better understanding of the proper use and what realistic expectations might be. Years ago, I looked into it, and found a company (that I cant remember the name of, for the life of me) that did these inserts, and had sent me a sample piece cut with their insert. At the time, I didnt have the money to buy one, in hopes I could make it work - and subsequently lost my notes and info on them, and the inserts. So Im sort of starting at square one again...

Im presently using VCGT330.5 (profiling) and CCMT21.50.5 (boring) inserts- polished for aluminum, and they work fine, but I then have to go to a fairly time consuming polishing process to get what Im after. Im hoping that adding the finishing pass with the diamond insert might ease the polishing requirements.

Ill likely start with the boring insert, and if things go well, try the profiling insert.

Does anyone have any suggestions for vendors that they have experience with, or info they can share about using inserts like this? Im sure Ill have some stupid questions starting out, but trying to learn as much as I can about them and seeing if I can benefit from what the diamond cutting edge can do.

Hope everyone had a great Christmas and New Years!
Wade

 

[FredC]

We have been using VCGT110301FN-ALU for profiling and CCGT09T301FN-ALU for turning and boring. We get these from Arno, but they are not diamond inserts. One of the keys to getting a good finish in plastic is chip control, experimenting and getting the right size radius if you are not turning to a shoulder. You might try these while you are looking for the perfect diamond insert.

 

[Bruce Griffing]

Can you vapor polish these parts?

 

[Dan from Oakland]

Hard to believe you get a good finish in acrylic with an upsharp insert and a small nose radius like that without having to go incredibly slow to prevent chipping. But if it works for you then proceed. A nicely honed (as in sharp corner- not a honed over edge in the normal vernacular for a insert edge) negative insert with a .030 radius should give a great finish. For acrylic and a better finish, a flame polish might be the way to go and save your liver if vapor polishing now.

 

[Murf]

Hello Wade,

Have a look at these guys below, it might be who you are thinking of, they are in Canada if that rings a bell?

Electro-Optics - K&Y Diamond

Always love watching this video...

https://www.youtube.com/watch?v=jxWbz0Wf2rM


Murf

 

[adama]

Whilst not as potentially smooth finish, if i were you i would just buy a PCD diamond insert and give it a go, there available for sub £30 so its hardly a big expensive attempt to try one if you chose a shape you already have a holder for.

Swarft control and accuracy of your machine will probably then become the limiting factors. Optical finishes, need really low run out and ultra accurate spindles, i kinda doubt your going to get opticaly clear off the tool on a typical manual lathe, you may well ease your polishing efforts a fair bit.

Going in you need to google and understand cusp height, how that relates to tool nose radius and feed rate.

I find i can get a easily polished surface in acrylic of a simple round 6mm tool with a polished alu style insert with no issues with chipping, but it still needs polishing to get clear, as its very much left cloudy from the cut, but with care its minimal effort to then polish that to typical acrylic transparancy.

 

[Wade C]

We have been using VCGT110301FN-ALU for profiling and CCGT09T301FN-ALU for turning and boring. We get these from Arno, but they are not diamond inserts. One of the keys to getting a good finish in plastic is chip control, experimenting and getting the right size radius if you are not turning to a shoulder. You might try these while you are looking for the perfect diamond insert.

Thanks Fred, I may look at those. Been using polished inserts from Exkenna that work great.. just getting the urge to tinker and look for better. Im using the near sharp radius because of chatter. Lots of what I do is sort of marginal on the over hang ratio and dont have a tail stock on one machine and cant use it on the other for the drilling and boring. I started using .032 rad, and kept fighting chatter and deflection until I got down to the .0078 radius, and could get rid of the chatter. One part is a .625" "dowel" that hangs out there from the chuck 2.5"

Can you vapor polish these parts?

Bruce
Ive not messed with it, but would rather shy away from the chemical approach. I tinkered with it for a breif time years ago, but did not have much luck, and decided in the process I didnt like having the vapors around.

Hard to believe you get a good finish in acrylic with an upsharp insert and a small nose radius like that without having to go incredibly slow to prevent chipping. But if it works for you then proceed. A nicely honed (as in sharp corner- not a honed over edge in the normal vernacular for a insert edge) negative insert with a .030 radius should give a great finish. For acrylic and a better finish, a flame polish might be the way to go and save your liver if vapor polishing now.

Dan
I do have my feed rate down to get a good finish, but I could never get the feed rate up enough to get rid of the chatter in the past with a larger nose radius. So I figured that was what I was left with. I probably spent a couple years or so, on and off working at getting better and better surface finished. Finally stopped where I am... but starting to get the learning more "bug" again.

Im not sure what youre meaning by, "A nicely honed (as in sharp corner- not a honed over edge in the normal vernacular for a insert edge)". Are you meaning an insert that was honed, but no chip breaker type affair - held in a negative holder? Can you point me at an example of an insert like you are meaning? Im happy to give something new a try for sure! Back when I was working through things, the negative inserts (VNMG various nose rad) I tried would pull chips out of the surface (when looked at with a loupe it looked pitted) and that went away when I went to the sharp inserts for aluminum, so figured that was something to avoid.

Hello Wade,

Have a look at these guys below, it might be who you are thinking of, they are in Canada if that rings a bell?

Electro-Optics - K&Y Diamond

Always love watching this video...

https://www.youtube.com/watch?v=jxWbz0Wf2rM


Murf

Murf, I think that might be them... Canada does ring a bell!

Whilst not as potentially smooth finish, if i were you i would just buy a PCD diamond insert and give it a go, there available for sub £30 so its hardly a big expensive attempt to try one if you chose a shape you already have a holder for.

Swarft control and accuracy of your machine will probably then become the limiting factors. Optical finishes, need really low run out and ultra accurate spindles, i kinda doubt your going to get opticaly clear off the tool on a typical manual lathe, you may well ease your polishing efforts a fair bit.

Going in you need to google and understand cusp height, how that relates to tool nose radius and feed rate.

I find i can get a easily polished surface in acrylic of a simple round 6mm tool with a polished alu style insert with no issues with chipping, but it still needs polishing to get clear, as its very much left cloudy from the cut, but with care its minimal effort to then polish that to typical acrylic transparancy.

Adama
Illl look at PCD inserts as well - as long as Im trying things, it cant hurt to check them out.
I feel like I have the chips controlled, and get pretty good results - but I also know when a coolant nozzle gets bumped... But yeah, if I get a MCD insert, I was thinking the machine would be a limiting factor. Im running two Okumas (a 1980 LC10 and a 1994 LNC-8), and Im sure Ill never get "optical finishes" - but the closer I get the less time I have to mess with polishing. I should have qualified that as more of the "Unobtainable goal" and just getting closer than I am now maybe well worth the cost of the tooling change. Its almost more of a personal vendetta than anything. Everything now, is plenty acceptable for me. Sure faster would be better, and better surface finish would be even better yet... but I have a decent balance presently. So I can go about my daily stuff, while experimenting over time.

In all honesty, if I never got better than I have today, Id be fine. But my brain doesnt work that way... always looking for better. Like mentioned earlier - the chatter I was getting with larger tool rads were causing problems for me and why I ended up with the 0.5 nose rad. And that the cusp height I fight there is of my own doing.

My issue with polishing is my hands/wrists. I can buff them up (opaque colors) or flame polish them (transparent colors) pretty easily and awful quick - but I just cant take the repetitive hand work. After about 1/2 hour of polishing my hands start getting numb, and if I push it, then I spend the next week or three being woke up through out the night with my hands numb. Ive been working with some other methods that seem to work fine - that have little hand work involved, but take a long time... and I feel like I could cut that time in half if I had a bit better surface finish.

I also have some customers that want the parts unpolished, and they polish themselves. And my thought is, if I could make the surface finish better, I could save them time polishing as well, and I might be able to drive more business my way because of the improved surface finish, and/or be able to justify a bit a bit higher price. Obviously I would have to work that out once I know the cost of the tooling and the life span of the inserts etc... but thats some of my logic.


Im certain there is plenty of room for improvement in how I do things. And I always have open ears and open mind to trying things. So I really appreciate everything everyone has said.

Thanks!
Wade

 

[Harri]

A good PCD insert will do wonders, and I can guarantee it will outperform the machines you mention, as far as surface quality is concerned. As long as you can keep heat out of the cutting area you can cut at amazing speeds. I wouldn't even consider MCD, unless you have machines with air spindles and hydrostatic bearings. And tons of money..

Regards, Harri

 

[brucecu]

Some sources for monocrystalline diamond tools:

Sp3 in California
Morgan Advanced Materials in Pennsylvania (was Diamonex)
Element 6 in the UK
KeenKut in California
J&M Diamond Tool in Connecticut

Unless you have a diamond turning lathe or a machine fitted with an air bearing spindle and stiff, fine resolution axes, you're probably still faced with a polishing step(s).

 

[Wade C]

Thanks!
I appreciate the names!

Wade