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beanbag
03-26-2013, 02:23 PM
I got myself a few used gage blocks off ebay to play around with micrometer testing and measurements. Most are in good condition, but some have little dents near the corners that prevent a good wring. Since I am just playing around, I would like to be able to repair them for cheap.

The official Starrett gage block stone is $100. I don't feel like paying that much.

Over on PM, there have been various admonitions about taking any kind of abrasives to these blocks. To be honest, I am not worried about taking off a few millionths, as long as I can still get a good wring.

I also don't have an optical flat for finding tiny defects, although I may be able to ghetto rig something up for cheap by getting an un-aluminized mirror, which has one really flat side, and one frosty side. There is a trick where you can clear up the frosty side by putting a piece of scotch tape over it.

Failing that, is there some scraping-related way of finding the high spots, like bluing up the face and rubbing it on something flat?

Some of the things I have at my disposal are:
Diamond file
very fine sandpaper
an aluminized mirror which probably is very flat.

Jaakko Fagerlund
03-26-2013, 06:26 PM
Probably easier and cheaper to buy new ones (though they do get expensive if bought one by one, a set is always a good option). If you can't stone two pieces of steel to wring together, then you won't be able to fix those blocks either.

Toolguy
03-26-2013, 07:02 PM
These ones were dropped and hit on the corner. Just use the diamond file on the raised area only and don't mess with the main surface. Then you can wring them together and they will maintain their accuracy. The corners and edges don't matter.

J. R. Williams
03-26-2013, 07:02 PM
Any worn or damaged blocks are now simple spacers.

tdmidget
03-26-2013, 08:34 PM
beanbag;840271 " I got myself a few used gage blocks off ebay to play around with micrometer testing and measurements. Most are in good condition, but some have little dents near the corners that prevent a good wring. Since I am just playing around, I would like to be able to repair them for cheap.

The official Starrett gage block stone is $100. I don't feel like paying that much."

Good thinking, used blocks are not worth that much.

"Over on PM, there have been various admonitions about taking any kind of abrasives to these blocks. To be honest, I am not worried about taking off a few millionths, as long as I can still get a good wring."

Not likely

"I also don't have an optical flat for finding tiny defects, although I may be able to ghetto rig something up for cheap by getting an un-aluminized mirror, which has one really flat side, and one frosty side. There is a trick where you can clear up the frosty side by putting a piece of scotch tape over it."
If you are talking mirror as in looking glass, both sides are equally wavy. If that would work , there would be no market for optical flats.

"Failing that, is there some scraping-related way of finding the high spots, like bluing up the face and rubbing it on something flat?"
No.

"Some of the things I have at my disposal are:
Diamond file
very fine sandpaper
an aluminized mirror which probably is very flat."

It could keep you out of trouble for a while.

J Tiers
03-26-2013, 09:52 PM
The important parts of gage blocks are the two faces. Every thing else is just there to support them.

If you remove the dinged parts of the faces, without damaging the good parts, the accuracy has not been damaged enough to bother *you*. The NIST would care, but the NIST would "laugh at" the gage blocks anyway. They have better things, and you don't.

Will the work throw them off a bit? Yep.

Can you tell the difference in size before and after? Nope..... and neither can most of the folks who are telling you it's silly.

What have you got to lose?

Mcgyver
03-26-2013, 10:03 PM
you could lap each of the 81 pieces down to the next smaller size, but its a lot of work

lazlo
03-26-2013, 10:32 PM
The official Starrett gage block stone is $100.

Anyone know what grit the Starrett gauge block stone is?

I ended up with a miniature Collins MicroFlat "surface plate" (the surface is about the size of a business card) that I assumed was intended as a paperweight, but I wonder if its actually a gauge block stone?

beanbag
03-26-2013, 10:42 PM
The un-aluminized mirrors are 1/10th wavelength on the smooth side and frosty on the rough side. The store checked that indeed the scotch tape trick works to clear up the frosty side. For $6, that's not a bad deal. (surplusshed.com) However, it's not an optical parallel, like in those mic check kits.

BTW, the larger blocks are the super bling Webber croblox. They are reputed to have good dimensional stability, so even though they aren't recently certified, they are probably still good.

beanbag
03-26-2013, 10:46 PM
Anyone know what grit the Starrett gauge block stone is?

I ended up with a miniature Collins MicroFlat "surface plate" (the surface is about the size of a business card) that I assumed was intended as a paperweight, but I wonder if its actually a gauge block stone?


All I know is that there is more than one Starrett stone. There are two that are Sintered Aluminum Oxide and work on carbide blocks (part number SAO**) and another one which I forgot, but the part number is GS** and it is for steel only.

I imagine the only difference between their stones and normal ones is that they are super flat and very fine, although I don't know the grit. Is it possible for the grit to be so fine that if you use oil, the block floats on this oil layer and the stone really does only take off the high spots?

adatesman
03-26-2013, 11:26 PM
you could lap each of the 81 pieces down to the next smaller size, but its a lot of work

Probably the funniest, while still correct, thing posted on HSM in a long while.

David Powell
03-27-2013, 12:11 AM
Probably the funniest, while still correct, thing posted on HSM in a long while.

Mcgyver is a very capable and determined fellow. He probably could actually do that, to a standard for the blocks to be useful in a home shop environment. But I would not expect him to waste his time doing so, machine tools are much more fun.( His eyes light up when he looks at those in need of TLC, bet he is not much of a card player. Regards David Powell.

SGW
03-27-2013, 12:14 AM
Brownell's www.brownells.com used to sell, and maybe still does, a fine ruby stone that is so fine it has no noticeable "grit" at all -- it's smooth. Expensive though, and possibly not very useful. It would take "forever" to stone off even a small burr with it.

I'd opt for maybe a fine hard Arkansas stone or even a fine India stone as fine enough for what you need to do. As others have said, knock off just the burrs and try not to touch the rest of the surface.

Davo J
03-27-2013, 12:27 AM
What about taking the edge back enough to remove the damage (say 45 degree), this way your not touching either face.

Dave

Black_Moons
03-27-2013, 06:21 AM
Just touch the corners up with a diamond file to remove any raised nicks.

If any are damaged on the face, you could try painting them with sharpie felt pen and then using a high grit diamond file on them till sharpie all over the face is knocked off (Not all of it, just spots all over the face)
Likey take off a few ten thou, but then, you likey only care about thou accuracy anyway or you wouldn't be trying to repair these.

Peter.
03-27-2013, 06:31 AM
Any worn or damaged blocks are now simple spacers.

If they are carbide they are now scraper tips round here :)

J Tiers
03-27-2013, 09:14 AM
Just touch the corners up with a diamond file to remove any raised nicks.

If any are damaged on the face, you could try painting them with sharpie felt pen and then using a high grit diamond file on them till sharpie all over the face is knocked off (Not all of it, just spots all over the face)
Likey take off a few ten thou, but then, you likey only care about thou accuracy anyway or you wouldn't be trying to repair these.

If there is that sort of damage to the entire face, the blocks are no good at all.

The only reason we are taking seriously the idea of "repair" is the idea that the blocks have damage to an edge, which does not involve the entire face. The damaged area can be removed without affecting the rest of the face more than a few millionths or so. It isn't credible that removing an edge ding will cause even a "tenth" of growth in the block.

The principle is that the blocks were accurate to around a 100 to 1000 x smaller increment of dimension than is of interest. Therefore, minor edge damage is unlikely to reduce the accuracy of the remaining surface by 100 to 1000 times. They will still perform the function of keeping your measuring tools "honest".

If you are working over the whole surface, now you are with McGyver.........basically grinding to the next size smaller. You'd have no idea what you have done to the dimensions. This isn't cleaning them up with the $100 Starrett stone to remove a scratch, it's grinding them down...... NOT credible or productive work.

Mcgyver
03-27-2013, 09:29 AM
If you are working over the whole surface, now you are with McGyver.

if not obvious, that was in jest.

other than edge damage I would not bother. replace individual ones or scrap the set.

If you have to stone something precision (not gauge blocks) a hard Arkansas stone is the best choice. Nothing cuts more slowly or finer, you'll be there a day and just polish the high spot .....thats a bit of an exaggeration...but if you get a tiny ding on something precision, caliper leg, 123 block etc they're your best bet as they will remove almost nothing from a broad surface

RussZHC
03-27-2013, 09:49 AM
but if you get a tiny ding on something precision, caliper leg, 123 block etc they're your best bet as they will remove almost nothing from a broad surface

would this include the faces on micrometers?

Asking as sometimes used mics come up but with a "ding" in the face...sometimes they also are "chipped" which I assume is different in that there is no raised area (but rather just a piece broken out). Carbide face a different case?

beanbag
03-27-2013, 01:21 PM
What about taking the edge back enough to remove the damage (say 45 degree), this way your not touching either face.

Dave


That's the plan, but first I'd need to find the raised edges, hence the optical flat.

If there's a raised spot in the middle, then maybe a dremel tool?

I still don't understand how any stone can be flat enough for the surface.

Mcgyver
03-27-2013, 01:34 PM
would this include the faces on micrometers?

Asking as sometimes used mics come up but with a "ding" in the face...sometimes they also are "chipped" which I assume is different in that there is no raised area (but rather just a piece broken out). Carbide face a different case?

maybe, not sure I'd bother when carbide tipped mics good shape ones are so inexpensive on kijiji. The anvils are a small area so it would be easier to stone a curve into it and micrometer anvils are supposed to be dead on, parallel and flat. Still, they do cut so slowly that if I had a damaged mic it would be worth a try. Experiment on something less critical and you get the feel for it, the hard arkansas stone is good for small dings as it polishes away the bruised area without appreciably changing the dimension of the larger area....must because its so fine and cuts so slowly

Davo J
03-27-2013, 10:24 PM
That's the plan, but first I'd need to find the raised edges, hence the optical flat.

If there's a raised spot in the middle, then maybe a dremel tool?

I still don't understand how any stone can be flat enough for the surface.

If you use a dremel tool on a spot on the face make sure it's visible so if you check your Mic's with it you don't go near that spot, but it will let them wring together at least.
They are no good now so it's worth a try.

Dave

Mcgyver
03-28-2013, 12:03 PM
If there's a raised spot in the middle, then maybe a dremel tool?

I still don't understand how any stone can be flat enough for the surface.

dremel will throw up a burr making things worse.

I don't think you can rely on the stone for flatness....but it will naturally interact more with high spots. If its slow enough in its cutting you're relying on it not removing much from the broader area will it does from the tiny high spot.

Kernbigo
03-28-2013, 08:38 PM
for what you want it for stone the corners with a arkansaw stone and don't touch the flat ,i used to make thread gages down to 140 tpi

huntinguy
03-29-2013, 12:40 AM
IF you touch the surface of the block it is done for.

The starrett stone is flat, not so much the super fine grit, which it is. I would guess around 1200 grit.

It is possible to clean the block, I have done it. I use a ground hard Arkansas stone flooded with kerosene. It is possible, if one is very careful, to knock off the high spot, and that is all you are doing, with a ultra fine sharpening stone. The key is one pass... maybe two. Keep in mind you are not cutting the block, only the burr.

dp
03-29-2013, 02:19 AM
I got myself a few used gage blocks off ebay to play around with micrometer testing and measurements. Most are in good condition, but some have little dents near the corners that prevent a good wring. Since I am just playing around, I would like to be able to repair them for cheap.

Repair them with the best stone you can. Those that are damaged have no present value, and if you screw them up you can replace them. Using powers of two sizes you really only need a small number of blocks to cover several decades of scale.

1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768

This is just 16 blocks, 64,535 increments from 0.000" to 65.535" in 0.001" steps. Augment with 1", 2", 4", 8", etc., to get quickly to the scale of interest in the fewest stacked blocks. I think nobody makes them in these sizes. Maybe Sol could.

beanbag
03-29-2013, 05:14 AM
Using powers of two sizes you really only need a small number of blocks to cover several decades of scale.

1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768

This is just 16 blocks, 64,535 increments from 0.000" to 65.535" in 0.001" steps. Augment with 1", 2", 4", 8", etc., to get quickly to the scale of interest in the fewest stacked blocks. I think nobody makes them in these sizes. Maybe Sol could.

This sounds like something only a computer dork would say :)

Let me know how I am going to wring a .001 block, or .0001 block if I need tenths.

beanbag
03-31-2013, 05:24 AM
I ended up with a miniature Collins MicroFlat "surface plate" (the surface is about the size of a business card) that I assumed was intended as a paperweight, but I wonder if its actually a gauge block stone?

You might be onto something:
http://www.ebay.com/itm/Vintage-Gage-Block-Black-Granite-Dressing-Plate-Do-All-SHIPS-FREE-/221207539201?pt=LH_DefaultDomain_0&hash=item3380ff2e01