Polishing turned 6061 parts with as little effort as possible

Jay Fleming · May 17, 2017

I would like to be able to mirror polish turned 6061 parts without so much hand finishing. Think of handrail ballisters for an idea of the profiles. Where would you start, from most desirable insert, speed and feed, to some sort of cylindrical polishing machine? I did a short search for cylindrical polishers with little luck but I suspect I can fashion something using a bench grinder and some sort of follower. What about sanding or burnishing to remove the tool marks? I know sanding dust is a no-no in a lathe but could something be accomplished while the part is still in the lathe?

Jay

michiganbuck · May 17, 2017

Like a clothes pin (larger)made of wood to clamp over with an abrasive paper.3 such polishers with 3 grades of grit.
Going travel one way, not back and forth can do a quick job .

Tool bit nose a small flat to cover feed lines can help.

Jay Fleming · May 17, 2017

michiganbuck said:
Like a clothes pin (larger)made of wood to clamp over with an abrasive paper.3 such polishers with 3 grades of grit.
Going travel one way, not back and forth can do a quick job .

Tool bit nose a small flat to cover feed lines can help.

So you're saying a clothes pin type setup for each, sand paper and 3 different polishing compounds?

DanielG · May 17, 2017

I haven't used them myself, but my old shop liked the Dynabrade belt sanders for polishing on the lathe.

michiganbuck · May 17, 2017

I have done that with abrasive paper not compounds. The wood so a little flex to not lock-up and take off your hand...The small nose flat perhaps .015 / ,025 or larger nose radius can help if the lathe amn material can handle that.

FredC · May 17, 2017

Maybe it is so obvious it does not need to be mentioned, wet sanding is faster and makes clean up easier. We polished some parts near the collet in a lathe and the wear to the spindle and collet was surprising. Petroleum as a wetting agent cuts faster than soap and water kerosene, diesel fuel or Wal-Mart brand WD-40 depending on what you have on hand or how many you are doing.

If you have a big enough tumbler available use appropriate polishing stones followed by burnishing stones. We get our stones from UM Abrasives not far from you if you are near Dallas.

triumph406 · May 17, 2017

Jay Fleming said:
Where would you start, from most desirable insert,

Jay

I used TPGT inserts in an HLV and get finishes in good quality 6061 that I don't need to polish. Poorer quality 6061 might have a duller finish and need some polishing. I don't as good a finish on a Takasawa TSL lathe, so the machine tool will effect the finish

rons · May 17, 2017

Do you have a second operation lathe? Makes life easier for just what you are describing.

Limy Sami · May 17, 2017

Try a 3 M none woven pad, ....with a drop of oil kero mix they work wonders.

adama · May 17, 2017

PCD inserts when used right will give you a mirror if the lathes upto it, yeah it slows things down a bit, but very carefully dropping polished parts is often worth the time penalty of no post polishing.

HuFlungDung · May 17, 2017

I like Iscar cut-grip for turning out a very smooth finish (scallop free) at a brisk feed rate. You'd still have to buff it for a shine afterwards, but I wouldn't really call that 'sanding' because there are no feed marks to remove, so very little dust produced.

Sea Farmer · May 18, 2017

DanielG said:
I haven't used them myself, but my old shop liked the Dynabrade belt sanders for polishing on the lathe.

I do exactly this all the time. but it's way too aggressive for polishing/buffing 6061. The above suggestions, scotchbrite, sandpaper, etc. are more suitable.

The Dynabrade will take off enough material to alter the dimensions or the profile on something soft like 6061, and do it damn fast too.

Great tools though.

CarbideBob · May 18, 2017

Turn to a 4rms or under finish to start with, why add a polish step?

magicmaker · May 18, 2017

Do nice clean cuts with the lathe, apply spinning lube to the aluminum, sand with 220 abrasive belting, prepolish with Bounty paper towel. The final polish can be done in seconds on a buffer. I use a blue Formax bar on the buffing wheel.

Alternative method is to turn clean cuts on the lathe, prepolish on buffer with black Formax bar, finish with blue bar.

If production numbers warrant it, use beater lathe with swing down buffer wheel.

Jay Fleming · May 18, 2017

Thanks for all the replies. I've got quite a few places to start and test.

I'll take what everyone said and do some more testing later on. The first test I did was using my i****t single phase lathe, running max speed (1400 RPM), turning at .0012 IPR with a DCMT 32.51 insert (all I have) which should have netted a 4 RMS finish. I polished a small area using a woven buffing wheel and white rouge compound (all I currently have). The finish is shiny but the tool lines are obvious. I turned again running same speed but the slowest feed (.0004 IPR) which would equal a 1 RMS finish. I polished using the same wheel and compound and there is a near mirror finish but the tool lines are still apparent. I think more polishing would remove the tool lines. The process used wasn't that painful as far as time goes but can I still gain some time. I spent about 1 minute polishing each time, and while I couldn't get too aggressive because I only temporarily set up my buffer, I was still pleasantly surprised.

Ultimately the parts would be run on my Okuma Cadet, so more RPM and more feed options are available.

Jay Fleming · May 18, 2017

4 RMS after polishing

4 RMS before polishing

1 RMS after polishing

1 RMS before polishing

DanielG · May 19, 2017

Sea Farmer said:
I do exactly this all the time. but it's way too aggressive for polishing/buffing 6061. The above suggestions, scotchbrite, sandpaper, etc. are more suitable.

The Dynabrade will take off enough material to alter the dimensions or the profile on something soft like 6061, and do it damn fast too.

Great tools though.

Have you used the Scotchbrite belts for the Dynabrade? I haven't, but they look pretty nice. I wonder if they have the same issue.

CarbideBob · May 19, 2017

I am not seeing picture one as 4RMS, what are you gauging with and how long is the check span?
If you tell me you calculated it from a CAD or other and feedrate/nose radius I'm gonna give up.
The "turning at .0012 IPR with a DCMT 32.51 insert (all I have) which should have netted a 4 RMS finish." statement is a bit scary.
Bob

triumph406 · May 19, 2017

Jay Fleming said:
4 RMS after polishing

That first image may be polished, but look at the patterns in the reflected light, and you can see a wave in the finish, it might have a polish finish but i wouldn't consider it acceptable, but then I guess it depends on what your trying to achieve

Sea Farmer · May 19, 2017

DanielG said:
Have you used the Scotchbrite belts for the Dynabrade? I haven't, but they look pretty nice. I wonder if they have the same issue.

No I haven't. I have a couple I bought on a whim, but haven't tried them.

I like using the dynabrade for lathe polishing/smoothing etc. but it is pretty aggressive. Buying the different belt tips helps a bit, the one made for round stock is pretty handy.

Polishing turned 6061 parts with as little effort as possible

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