Roller Burnishing Aluminium

[ETC57]

Very interesting Rick,

and keeping Dave off the streets I'm sure is comforting to the neighborhood.

Jerry.

[Rickabilly]

Hello All,

It's been about a day now since the experiment and with the time I have considered the results a little more than I had when I wrote the first post here,

Regarding the dullish finish, The track roller used isn't polished but is a ground finish , if it were polished then maybe a brighter finish would be possible, then there is the issue of roller crown, the smaller the crown radius the higher the pressure at the working "edge" probably producing a finish in one pass with less wear and tear on the lathe, once I have mastered the the bump "knurlishing process" I think I am going to make a scissor type, for general use, where the pressure and so size can be better controlled.

Best Regards
Rick

[PixMan]

I have used professional Cogsdill roller burnishing tools for both I.D. and O.D. work. The applications were always steels. mostly 4140.

On the O.D. tools, the roller was a highly-polished narrow contact design. On the I.D. tool, is was a mutli-roll design that would remind you of a needle bearing.

In both cases the prep of the work was critical. You had to deliberately leave a very coarse finish in turning or boring, so as to leave higher "peaks and valleys" for the burnishing rolls to mash into one smooth surface. Lubrication with oils helped, as long as they had EP (extreme pressure) additives. Way lubes can work well. Feed rate is important too. If you feed too slow, you risk getting flaking and redepositing on the work. Feed too fast and you get thread-like feed marks.

It does take some experimentation to get it working consistent, but can be worth the effort.

[DaveH]

Ken,
Thanks
That's useful, now what about surface speed, any idea on say 2" diameter, - fastish, slowish ??? rough guess at the RPM ??


DaveH

[Bill Gruby]

Speeds and Feeds for internal Dave.

http://www.monaghaninc.com/wp-content/up...-stock.pdf

"Billy G"

[DaveH]

Bill,

Thanks, it is quite an interesting web site. Seems for outside burnishing one needs a small contact area, exactly the opposite to the way I was doing it

DaveH

[Tony Wells]

In a shop far away and a long time ago, we made hydraulic cylinders that were relatively thin walled (about 0.040 as I recall). The OAL tolerance was =/- 0.0015, and since they were around 16-18" long, we had to run them in a steady rest. As you all know, parts tend to "walk" out of the rest. Of course, this resulted in oh..one or two of them coming out a wee bit short. It just happened that we used a "bearing on a stick" to roll the first thread of a part we uh...cut too much off. It kept the "no-go" off.....Anyway, this "bearing on a stick" turned out to be a decent burnishing roll too, and we discovered quite by accident that if you burnished the OD of one of our hydraulic sleeves, it grew longer. Longer enough that more than once, we had to face it off a little to get it back to print. These were honed ID sleeves, down to a 2-4 finish, and if you looked inside after burnishing, you could clearly see the distortion from the stresses introduced by the burnishing. A quick pass through the hone, and all was well. The OD tolerance was sufficient to allow a light polish to blend in the burnished area. Sold many sleeves like that.

We did run a couple of parts that we used the Cogsdill tools like Ken referred to. We ended up thinking they were more trouble than they were worth. The size before burnishing had to be held almost as close as the final dimension, and the finish couldn't be too smooth, or we'd get the flaking he talked about. One example of surface burnishing that some may be familiar with is the seal surface of a torque converter for an automatic transmission. Live seal, high RPM seals require fine finish and close size control. Burnishing is an excellent means to that end if you can work out the details. Not applicable to all materials, but most can be successfully burnished.

[f350ca]

Tony
Thats interesting for the seal surface, will have to give that a try.