Roller burnishing tool

Roller burnishing is mostly found in production, but can be a useful process in any shop. Production tools like this are expensive, and the cheap one are...cheap. Accurate and constant pressure force is essential in getting good results, and force indicator desirable.
Having little more time now that I am semi retired I've decided to design and built one. The design is a simple, a one piece tool that can provide adjustable pressure without sliding parts that are prone to binding. It has, as well, a force indicator in the form of a re-calibrated dial gauge. The tool is made out of heat treated D2 steel and was designed (using simulation) to provide a force of 0-600 Newtons (0-135 pounds-force) with a deflection of 1mm indicated on the dial indicator (one revolution) at the back of the tool. The burnisher wheel is a ball bearing with the outside race edge rounded and polished. Pictures show the design, the simulation and the tool in use. I hope this design can be useful for those contemplating to build one.

The bearing companies make ball bearings with thick outer races with a slightly crowned much more suited to the application . a ball bearings outer race will flex between the balls .
Do not get me wrong I love it and sure it works but the mechanics of it kind scare me I have seen failure of bearings when used in stead rest on a lathe The big end of these bearings commonly seen on fork truck masts. For giggles take one of your bearing apart and squeeze the outer race while measuring I will bet it will flex in your hand or pushing on more than you would realize .
I am a huge fan of burnishing I ball broach allot .

The common capstan/turret lathe roller turning boxes use the rollers to both support the cut and burnish the surface.........and make a big difference,even if they are only flattening the peaks of the rough cut finish.............a similar false surface to that made by negative rake carbide........shiny smear of metal ,with voids under the surface,leading to rapid wear ,and problems in heat treating.

The roller burnishing tools my family used to build used a 3" diameter wheel. The bearing is a harden dowel pin, later ones used needle type bearing. Of course, we only ran them at about 100-200 RPM. The OD's ranged from about 4" up to 12" in diameter.

Ken hosford said:

The bearing companies make ball bearings with thick outer races with a slightly crowned much more suited to the application . a ball bearings outer race will flex between the balls .
Do not get me wrong I love it and sure it works but the mechanics of it kind scare me I have seen failure of bearings when used in stead rest on a lathe The big end of these bearings commonly seen on fork truck masts. For giggles take one of your bearing apart and squeeze the outer race while measuring I will bet it will flex in your hand or pushing on more than you would realize .
I am a huge fan of burnishing I ball broach allot .

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You are completely right and I am aware of the fact that a regular ball bearing is not designed to work in this way. Shown is just a first test and used with light force on non-ferrous materials. I am now putting together a needle bearing with a heavy roller - basically a cam follower. The roller is hardened D2, but would prefer a carbide bushing if I can find it.

Cam followers also called track rollers are the ticket.
I made a tool like that although not adjustable for pressure.

We have all kinds of small rollers and conveyor rollers that retain the bearings by rolling the outer edge of the roll to retain the bearing instead of using a snap ring.

Making that tool makes it quick and simple to roll the edge and does not take very much pressure.

We roller burnish ID's of thousands of copper parts before and after plating, air gaged to close tolerances. I don't know how the finish compares to diamond turned but tolerances are very repeatable.

A manual lathe I bought came with a setup like yours, I mean with a ball bearing on the end of a rectangle, I used it to spin some sheet metal over a form I made up. It never occured to me to use it as a burnisher. Maybe when one is creeping up on a bearing fit and it's just barely oversized a light burnish might do it.

partsproduction said:

We roller burnish ID's of thousands of copper parts before and after plating, air gaged to close tolerances. I don't know how the finish compares to diamond turned but tolerances are very repeatable.

A manual lathe I bought came with a setup like yours, I mean with a ball bearing on the end of a rectangle, I used it to spin some sheet metal over a form I made up. It never occured to me to use it as a burnisher. Maybe when one is creeping up on a bearing fit and it's just barely oversized a light burnish might do it.

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The burnisher is producing a fine finish, though I do not think it is the same as diamond turned parts on a tool-room lathe with a precision spindle that gives almost optical quality. One think I have noticed working with commercial burning tools (and my own) is that the even pressure is essential for quality finish. So using a burnishing wheel without accurate pressure control will not work well.