What's new
What's new

Finest finish achievable flat surface

toolsteel

Titanium
Joined
Nov 9, 2012
Location
NW Wisconsin (BFE)
Since some of the discussion has involved lapping....
In a previous life (it seems) I worked for a defense contractor. One product we made was made from a special glass. The glass block got holes and various features machined into it. I operated a lap that was around 10' in diameter. We would mount the glass blocks on a special granite fixture and "let them ride" on the lap for 5 or 8 minutes. The slurry was actually made from a specific dirt / sand that was found in only a few places in the world. In assembly a mirror would get wrung to the lapped surface. I was told that the finish on the mirror and the lapped surface were so good that after wringing them together they could not be seperated without destroying the glass block.
One might ask me what the Ra on that surface was.....my answer would be....how the hell do I know. Its amazing I paid enough attention to remember this much since I was around 22 at the time and everything that was in my head revolved around drinking beer and getting laid. :cheers: :drool5:
 

michiganbuck

Diamond
Joined
Jun 28, 2012
Location
Mt Clemens, Michigan 48035
likely there is a trade-off from grinding to lapping/polishing of how much time for a finer wheel or switching from the grinder to other methods.,
60 to 120 (and finer) gt is very time-consuming.. some old clay wheels could get very near mirror on a SG with oil scraped ways and a plane bearing spindle.

Plus the grits comming up in colant can jepordise the finiah.

Belts drive spindles gave a better surface finish..some old-time grinders even had the motor off the machine and belted to the spindle..I never ran one of these.
 

TDegenhart

Diamond
Joined
Mar 26, 2011
Location
Geneva Illinois USA
I have heard a lot about wheels and such but how do you know the grinder is capable of what you want. Have you defined what you want or need and why? Mirror finishes are not good around measuring equipment unless you are dealing with optical flats and gage blocks.

Tom
 
etOH ????????

I actually spelled it EtOH. Couple saturated carbons in which one of the bonds attaches a hydroxl group. (C2H5OH)
My dad was a chemist. So of course I hated it and have no facility.
But under the bench in the home workshop, along with the carboys of Carbon tet, Trichloro ethane, Di-ehtyl formamamide, containers of toluene, Xylene, and mixed solvents, the containers of alcohol were marked with an abreviation for the carbon number or arrangement (Me-, Pr-, Bu-, Et,) followed by "OH".

Didn't remember much useful, but peering under there sorting for a likely cleaning solvent, some labels stuck

smt
 

Yan Wo

Hot Rolled
Joined
Jan 22, 2014
Location
South Jordan, Utah, USA
Emo expo, machine tools, germany, where I was in 2012, with Haas.

They had a grinder that ground flat steel ..
to a perfect mirror finish, better than a bathroom mirror, and possibly close to an optical finish.

The samples were kept under glass, so we could not touch them.

I don´t know if You can do that, but grinding will definitely produce a mirror finish.
That can even be flat and straight, if your machine and technique allows.

Typical modern T&C cutter grinders, 5 axis, will likely make mirror finishes on anything, given the right tooling.
They cost 500k, so that might be a problem.

My clients used them to grind stamping dies, in carbide, to make tuna fish cans.

Amazing! I would never have imagined I'd need a $500,000 grinder to make a carbide die to make a tuna fish can! :)
 

WesY

Plastic
Joined
Jun 16, 2021
If that was for me, my apologies. My first post here and thought it was applicable to the question. What was wrong?
Thanks
 

michiganbuck

Diamond
Joined
Jun 28, 2012
Location
Mt Clemens, Michigan 48035
The mirror-finish is somewhat hypothetical, very rarely do find that need on a part print.
Some old clay wheels could get near that with the use of fresh water because most coolant has abrasive qualities that mar the surface finish. Bearinged spindles and ball ways transmit .?? micron bounces on the finish. Perhaps an air spindle grinder with oil scraped way would be good for mirror finishes.

Basic grinding is making size rarely closer than 6 to 12 millionths with one or two tenths common, making surface finish spec, making flatness, making inside corner to spec, dressing or crushing a special form like a radius, angle or shape to the wheel and then grinding it, making good time for set-up and grinding, hitting a step-height or step-over spec, making a pert square, choosing the best wheel and set-up method, likely more I can't think of just off the bat.

The mirror finish is way down or not on the list.
 

Janderso

Aluminum
Joined
Feb 15, 2018
Location
Chico
cphockey16,
Interesting you are discussing a surface gauge. Someone gave me an import piece of crap surface gauge. Let's just say it was not stable on my surface plate.
I just finished making some lapping plates ala Tom Lipton.
I lapped this surface gauge to a flat condition. At least I can use it as it no longer moves and hinges properly.
A little elbow grease kept it out of the scrap pile.
 

michiganbuck

Diamond
Joined
Jun 28, 2012
Location
Mt Clemens, Michigan 48035
cphockey16,
Interesting you are discussing a surface gauge. Someone gave me an import piece of crap surface gauge. Let's just say it was not stable on my surface plate.
I just finished making some lapping plates ala Tom Lipton.
I lapped this surface gauge to a flat condition. At least I can use it as it no longer moves and hinges properly.
A little elbow grease kept it out of the scrap pile.

Good to learn how to use a surface gauge for checking the squareness of a part, see youtube.
Here is an Ok Youtube, but does square off a ball. Perhaps see this guy's next youtube.
transform a surface gauge into a squareness comparator - YouTube
 








 
Top