Need Help!- Preferred choice of insert for Aluminum turning

[buffaloguy]

I'm looking to see how others produce a 'mirrored' surface on aluminum. I currently use a Trigon insert which does a great job ripping stock down but lackes the finish I seek. Would a ceramic, Cermet Diamond or PCD accomplish this? If I make a finish pass, what depths are reccomended for best results with the new insert? I only use 2011 aluminum. Oh and speeds and feeds would be nice too!! (yes I'm new, can ya tell ha)

Thanks!

[K&Y]

The only way to get a true "mirror" or "optical" finish on aluminum is by using a single-crystal (monocrystalline) diamond tool. I have attached some photos to give you a much better idea of what I'm referring to. Please bear in mind that the quality of the surface finish will be dependent on the rigidity of your machine and spindle. If you need any more information or have more questions, please feel free to send me a message and I will do my best to help you out.

P.S. I know that the application that I posted the photos for was a milling application. With regards to turning inserts, they can still be made with single-crystal diamonds in order to achieve the finish you require.

[PixMan]

PCD (Poly Crystalline Diamond) seems to work just fine too, as that's what the automotive guys use in a lot of applications. Of course I can appreciate that what you (K&Y) make and sell is the best (certainly from the K&Y seat), it can be cost-prohibitive for a short run jobs.

The OP is asking about turning, not fly-cut milling.

For turning, consider PCD inserts from any of a wide variety of sources. Whose products do you buy now, or whose do you have a good distributor for? PCD inserts are sold by Kennametal, (Walter) Valenite, Sumitomo, NTK, Sandvik Coromant, Iscar, the list is long.

Tell me what insert holders and/or shape your lathe uses, I'll make a suggestion.

You may not even have the speed to run PCD or MCD tools, and a highly-polished uncoated carbide would probably be fine. Fair warning, 2011 aluminum is called "Microchip" for a reason. It's very granular structure helps prevent long stringy chips, and that also results in grainy-looking finish even when its very smooth from high-speed/low-feed rates.

Again, tell me what insert size you have in holders for the trigon, and I can recommend from there.

[K&Y]

Originally Posted by PixMan PCD (Poly Crystalline Diamond) seems to work just fine too, as that's what the automotive guys use in a lot of applications. Of course I can appreciate that what you (K&Y) make and sell is the best (certainly from the K&Y seat), it can be cost-prohibitive for a short run jobs. The OP is asking about turning, not fly-cut milling. For turning, consider PCD inserts from any of a wide variety of sources. Whose products do you buy now, or whose do you have a good distributor for? PCD inserts are sold by Kennametal, (Walter) Valenite, Sumitomo, NTK, Sandvik Coromant, Iscar, the list is long. Tell me what insert holders and/or shape your lathe uses, I'll make a suggestion. You may not even have the speed to run PCD or MCD tools, and a highly-polished uncoated carbide would probably be fine. Fair warning, 2011 aluminum is called "Microchip" for a reason. It's very granular structure helps prevent long stringy chips, and that also results in grainy-looking finish even when its very smooth from high-speed/low-feed rates. Again, tell me what insert size you have in holders for the trigon, and I can recommend from there.

Thanks Pixman. That is why I included the P.S. statement:

"P.S. I know that the application that I posted the photos for was a milling application. With regards to turning inserts, they can still be made with single-crystal diamonds in order to achieve the finish you require."

With regards to the speeds to run PCD tools; if you can turn with a carbide insert, you can still effectively do so with a PCD insert even though PCD tools show their true worth at higher speeds.

We have several aerospace and automotive clients that have made the switch from carbide turning tools to PCD and they haven't looked back since.

The overall cost is always a point that has to be thought out prior to making the decision to change, I concur. If the project is big enough where you can take into consideration that using PCD tools will lower your overall cost per piece, then it's a viable solution to carbide tools. If it's a very short, run, then it can be an expensive.

[PixMan]

Originally Posted by K&Y Thanks Pixman. That is why I included the P.S. statement: "P.S. I know that the application that I posted the photos for was a milling application. With regards to turning inserts, they can still be made with single-crystal diamonds in order to achieve the finish you require." With regards to the speeds to run PCD tools; if you can turn with a carbide insert, you can still effectively do so with a PCD insert even though PCD tools show their true worth at higher speeds. We have several aerospace and automotive clients that have made the switch from carbide turning tools to PCD and they haven't looked back since. The overall cost is always a point that has to be thought out prior to making the decision to change, I concur. If the project is big enough where you can take into consideration that using PCD tools will lower your overall cost per piece, then it's a viable solution to carbide tools. If it's a very short, run, then it can be an expensive.

Sorry I hadn't noticed the "P.S.".

I have a couple of PCD inserts myself, and the main difference I notice when trying to get a "mirror" finish is that the carbide tools will sometimes get built-up edge at lower speeds, whereas a PCD tool resists that. If one can find a single PCD tool for the right price, it's worth it even on short run or home shop jobs.That's why I have some! (I have CBN too, for when i need hard-turning capability.)

[K&Y]

Originally Posted by PixMan Sorry I hadn't noticed the "P.S.". I have a couple of PCD inserts myself, and the main difference I notice when trying to get a "mirror" finish is that the carbide tools will sometimes get built-up edge at lower speeds, whereas a PCD tool resists that. If one can find a single PCD tool for the right price, it's worth it even on short run or home shop jobs.That's why I have some! (I have CBN too, for when i need hard-turning capability.)

No worries, it's all good.

PCD tools can give you up to approximately 8 Ra surface finish, which is pretty good, but not a mirror surface finish. With the SCD tool (dependent on the machine rigidity and spindle) you can attain less than 1 Ra. by taking roughly .002"-.007" finishing cuts. In most cases though, PCD tools will suffice for the finish requirements being sought.

And you are absolutely correct with regards to the pricing of PCD tools. If one does their homework, they will find that PCD tools are not as expensive as they are being marketed as by the "larger" cutting tool companies.