Gallery, Projects and General > How do I??

Quartz Surface Plate?

<< < (9/13) > >>

PekkaNF:
Good or bad, we need to know!

I haven't found any dead sure way telling the good and bad appart. They all look good and most of the ones that looked like a real surface plates were pretty bad.

Pekka

Pete.:
A dial gauge and stand will tell you how flat they are.

DavidA:
Pete,

How would you set about doing that ?

I would have thought that you would need to know that your dial guage stand was precisely square to the slab under test and that the vertical shaft was also dead on vertical at any position of the base.

Any error at all and the dial guage will move relative to the slab.

Dave

sparky961:
Funny, I was just going to pose a similar question.

I've done a fair bit of reading and watching videos on this subject.  It seems that there are two checks, one for local flatness that uses a height gauge and DTI (or similar contrivance) and a more elusive overall version.  The former I can do, but how do I know that the whole thing isn't concave or convex?  Add to this the requirement that it be within the reasonable limits of a home shop budget and environment.

I did try some off-hand "lapping" of just two pieces; a smaller one on a larger one.  I did this mostly to test the"feel" of the operation, which was interesting to say the least.  When I was using water with toothpaste (yes, you read that correctly) it was smooth in some spots and then just sort of "stopped" as though a corner dug in, or the friction or suction became strong very quickly.  It didn't slide smoothly as I expected, rather in a bit of a "jerky" motion.  Dry was considerably better, but my selection of readily-available fine hard powders is very limited.  I tried using talc, but I know this is very soft.  I was thinking it would be more of a dry lubricant and the two granite surfaces would wear each other.  Maybe it would work just completely clean and dry to start even?

I haven't put any measuring devices on there yet, save for an angle plate with a cross-hatch pattern drawn on it with a sharpie.  The pattern didn't wipe off as consistently as I'd have liked, but this is all far from scientific. 

I did notice that the formerly shiny surface has begun to take on more of a matte finish.  I hope this indicates something beneficial, and not just some residual toothpaste haze...

Pete.:
You can spot dishing or twist in a plate by trying the stand and DTI at different angles and directions across the plate.

Navigation

[0] Message Index

[#] Next page

[*] Previous page