surface plate goo removal?

[coppercone2]

How do you remove goo from a surface plate? I got a 4 inch thick starrett and there are some old stickers on the side.

Can you use goo-gone on this stuff? will it soak into the granite and cause it to deform? Do I just need to scrape it carefully with a razor?

They are on the side (not the measurement top) and it looks shitty.

It's A grade.

[David Hess]

I start with naphtha because it is plastic safe but mineral spirits would be another good option.

[wraper]

Remove all stickers as best as you can. Hot air such as from hair drier will help to soften adhesive. Then take adhesive tape (scotch). Wrap a piece of it around your finger so it faces with adhesive side outside. Then start to fast pushing against the dirty surface, then pull it back. Some amount of adhesive will stick to this tape. Repeat many times. Once it's contaminated or no longer sticky, take a new piece of tape. Usually it's possible to completely or nearly completely remove adhesive remains within a minute or two.

[coppercone2]

tell me this, how the fuck does the surface plate have a high spot near the threaded insert? its like bulging some how.

it looked like something was fixed to it and it took a impact, there is damage around the insert (missing material) but the back of it reads 0.001 inch high for about 0.5cm from the hole.

should i just crater it out so there is a full crater around the insert so its standing like a castle in a moat?

i tried working on the glue with nitroethane to dissolve it a bit and pick it out, but it evaporates fast and its expensive. Do you think drilling the insert out would relieve pressure and rescue it?

not economical to relap

[David Hess]

Oh yea, a heat gun usually does a marvelous job before using a solvent.

[Dubbie]

1 thou out is a mile for a surface plate. I’m sorry to say it’s not grade A. Not even Workshop grade. Taking the insert out won’t do anything. The only way to get it flat is re-lap it. Or else just don’t use the non flat area. I suspect that this is why you have it. Because it is scrap.

[coppercone2]

well how does a surface plate get RAISED?

I don't really care, I can remove the spot, but I wonder if its just deflected or if there is a subsurface crack or something. I plan on just dremeling it out with a diamond (the center punch got the loose stuff out). then just scribe a line around it to remind me that this area is unsupported.

but if its just being strained upwards (is this possible??) then I can potentially remove the insert that is right next to the elevation to save a tiny bit of space

what exactly happens, does it crack under neath then get strained (like putting a hydraulic cylinder under the edge of a protruding cliff ?)

[coppercone2]

is this what happened?

can someone draw me a diagram of wtf is going on around the insert?



or is the post slightly bent and bending the granite? maybe removing it would remove the bend and leave me with a smaller crater?

I thought granite cannot bow upwards, only have divets. I was wrong. I think there was a post attached to it, someone was moving it or slammed something heavy into the post or possibly over torqued it (it has a torque spec)

The part I drew that looks like a crater towards the left side actually had granite in it, which came right out with modest pressure from a dental pick. The bulge extends about 0.2 inches from the edge of the hole around the post hole. The material here is hard and does not seem to dislodge even when its struck with a hole punch.

It shows up at ~0.0007 when measured with a dial.  Its the pink granite, when I think about whats going on it almost reminds me of a delamination in wood or something. I did not think this could happen with solid stone. Starrett brand.

[coppercone2]

I don't want to try lapping it because I don't understand why its bulging. I would rather just destroy all the area around it. it seems very suspicious to me.

[coppercone2]

could a strong impulse cause the granite to get plasticky and reform  in a different orientation or something?

It's hard to imagine why a fucking 4 inch slab of hardened granite (pink) would develop the same problem as wet plywood. I don't even think copper would gall like that, I think the lip would be way bigger not this weird 1/4 inch long minor elevation change.

I will buy the finest span test indicator and make a topographical map of the area.

[coppercone2]

heavy percussive maintence revealed the traces of a circular crack that mates with the missing piece forming around the area around where the test indicator begins to deflect upwards.

Now it is plainly visible. Time to cut out the cancer.

can I just core this shit out with a diamond saw so I can put a big machine pin in the area to act as a post?

[eKretz]

Everything is flexible. The modulus of elasticity for granite is considerably less than for steel. It is possible that pressure from the deformed insert was causing the raised surface. It's also possible that there was a hairline crack and a slightly displaced bit of stone. No way to know for sure without investigating it yourself. Hitting it may have caused the flexure to turn into a crack.

You can core drill around the insert with a diamond drill, then chip out the core and install a post, yes. Epoxy will work well to secure the post.

For sticker adhesive residue I normally use acetone - as long as the surface is not going to be damaged by it. One or two wipes usually does the trick.

[coppercone2]

I think it sustained impact because most of the chipping was there already.

Is it possible during impact the epoxy turned elastic and reset in a position where the granite is elevated?

I don't think starrett would mess it up this bad by manufacture. It also looks like is sustained some impact damage along the edge.

I almost imagine as if the post "rung" like a bell and made a crack in the granite, which is why a significant quantity was removed with the most mild pressure with a dental pick. The granite chips were like 1/4 inch deep around the area where they were 'sitting'. The extra banging just caused the crack to show (it meets the lip of the missing material perfectly)

I hope I did not damage it more.


Can you patch the hole with epoxy granite? It is possible to just lap that surface without lapping the rest of it (it was actually calibrated a few years ago, I am scared that lapping will damage the other areas wheras now I just have a Chernobyl Exclusion Zone.

Maybe to just reduce danger, if I can get the filler to fill the cavity slightly (i.e. 0.005 under) then I can polish the lip a little bit with diamond to prevent granite blocks from crashing into gnarly rock surfaces.