Surface gauge reconditioning

[StuartParticipant @stuart18648]

[StuartParticipant @stuart18648]

Evening all,

Just checking before I potentially do something daft.

I'm reconditioning a pair of old surface gauges which had moderate corrosion on the bases. Is there any issue with sending them out to a local machine shop to have the bases surface ground clean again?

Edited By Stuart Pain on 10/08/2020 21:12:23

[Grindstone CowboyParticipant @grindstonecowboy]

I wouldn't have thought so, as long as they take reasonable care to set them up with the existing surface as flat as possible.

Rob

[BazParticipant @baz89810]

Nothing at all wrong with grinding a couple of thou off the base to rescue them.

[BazyleParticipant @bazyle]

Since the cost of fuel to get to a machine shop would be more than they are worth how about the old trick of emery paper on a surface plate followed by learning to scrape them true.

[Bill Davies 2Participant @billdavies2]

Or even a bit of firm polishing with green 'scotchbrite' scouring pads. If case hardened, the case may not be very thick.

[Mike PooleParticipant @mikepoole82104]

Unless you have mates rates I would think the cost would be beyond any value added. Lapping with grinding paste on a piece of plate glass can work well. Do you just want a functional tool or a concours winner?

Mike

[Mick B1Participant @mickb1]

Posted by Bill Davies 2 on 11/08/2020 09:19:48:

Or even a bit of firm polishing with green 'scotchbrite' scouring pads. If case hardened, the case may not be very thick.

That's what I'd start with, plus WD40 to lubricate. Least chance of disturbing any original dimensions.

Then use fine 1500 grit emery paper on a surface plate if you're still not happy.

Only go to grinding and removing measurable amounts of material if necessary and (economical or piece has sentimental value).

[HOWARDTParticipant @howardt]

Why not scrape them. Good little exercise, I still have my apprentice one from nearly sixty years ago, was well oiled before putting away for fifty years, now back in use.

[John HaineParticipant @johnhaine32865]

Good grief! That's not corroded! Stone it off with a diamond lap or similar with some thin oil – or Scotchbrite You would be surprised how hard it is to remove significant amounts of steel with a fine abrasive, and certainly for the kind of job a surface gauge does it won't have any effect.

[Henry BrownParticipant @henrybrown95529]

I recently did the base for the one I made as an apprentice, that was made from GK3 and nitrided. I gently stoned the base and blued it against my surface plate – all good. As long as it doesn't rock unduly it will be fine for scribing lines, I would use a mag base if I needed to use with a dti as a comparitor.

[Howard LewisParticipant @howardlewis46836]

The corrosion is little more than pitting, a very high percentage of the surface is still there.

As working tools rather than exhibition exhibits, I would feel inclined to follow the Scotchbrite route, to ensure that there is nothing protruding above the surface.

Not perfect, but will do the job quite well, possibly better than regrinds, if the case hardening were to be removed.

Grinding costs would probably exceed value, and could make the bases worse, in terms of accuracy or durability, than if just cleaned up.

Howard

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