Scratched surface plate care

This topic has 5 replies, 4 voices, and was last updated 1 July 2016 at 19:46 by Rainbows.

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30 June 2016 at 13:42 #244791
Rainbows
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@rainbows
So was using a smallish surface table as a straight edge while scraping. While picking it off the work I miss judged where it was pivoting off and it sort of fell out of my hands.

So two questions

1. Is it possible to drill and tap holes into the webs of a surface plate without distorting it? I'm worried about the energy of drilling distorting the precision edge somehow but I really need something easier to hold onto.

2. There are a few small scrapes in the plate now, is there a good way to remove the burrs from these? Not sure how to remove them without damaging the accuracy of the rest of the plate.
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30 June 2016 at 13:42 #24614
Rainbows
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@rainbows
30 June 2016 at 14:26 #244793
Speedy Builder5
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@speedybuilder5
How many tenths of a micron are you working to ? I bet you could not measure the difference in most of our workshops. If you are not maintaining a constant temperature at which the plate was finally made in, that would have its own effect ? As for the burrs, you could just scrape these off without removing anything outside of the scratched area.
I am often amazed at how some of us worry about accuracy when the drawings we often work to are in fractions of an inch. Turn off tolerancing on your AUTOCAD drawings and enjoy the hobby – Or have I got it wrong again ?
BobH
30 June 2016 at 22:46 #244883
Howard Lewis
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@howardlewis46836
Rather than drill into the plate, (which might release some stresses, and as you say, produce distortion), how about making a frame to carry it, and put the handles on that?

With regard to recovering the damage, how about this as a suggestion?

Take a smaller plate and by whatever means, get it as flat as possible, and then blue and scrape it using an undamaged area of the surface plate. When you are happy with the result, use this "sub master" to check the areas that you have been carefully scraping to remove the burrs. You will have to live with the damage below the general surface, but don't add to it by going wild with the scraper around the dings!

Howard
1 July 2016 at 04:20 #244907
John McNamara
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@johnmcnamara74883
Hi Rainbows

When scraping you raise burrs that are normally stoned off lightly with a small stone.

An alternative is a scrapers block. a small piece of hardened and polished steel with rounded edges that will force the burs down. the advantage being it will only flatten the high spots, the stone tends to lower the whole area particularly if it is used with too much force.

A (very blunt all over) file also works. make sure the belly (Bow) in the file is lightly pressed against the workpiece, used the other way it will only burnish on the ends and may scratch.

Make sure the work and tools are all perfectly clean, any grit can scratch.

Regards
John
1 July 2016 at 19:46 #245015
Rainbows
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@rainbows
At the moment I'm still just scraping so I just knocked the burrs off as suggested. Though I do wonder about getting a small block of steel (I have many about) and using one of the more pristine areas of the surface plate to make it dead flat. Then using it to inspect the dinged up areas. Not sure how well that would work.

Might weld a square out of steel bar and then use screws to pinch onto the bottom of the surface plate.

Is that scrapers block something that tends to get made in the toolroom? Couldn't find much on the internets about them, does sounds useful though.
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