Slip gauge question.

[Tifa 8572Participant @tifa857287838]

I've been given a subsatntial slip guage set. A very greatfully received freebie.

Dozens of guages, made in the UK, certified, imperial and in a nicely made quality wooden box.

But…..the previous owner hasn't stored them very well, and on a few there's some surface rust.

My questions are…..are they now junk? And if not, what's the best way to clean and preserve them please?

Any advice would be good.

Thanks!

[Tifa 8572Participant @tifa857287838]

[EmgeeParticipant @emgee]

If the rust is not on the measuring faces there should be no harm done by using some removing agent, if the rust is on measuring faces then removing any amount of material will put the gauge out of spec.

Emgee

[Paul LousickParticipant @paullousick59116]

What level of precision do you work to ? Do you measure with a vernier caliper or micrometer ?

They are probably OK for most hobby applications where you do not need toolroom accuracy.

[Tifa 8572Participant @tifa857287838]

Posted by Paul Lousick on 17/01/2022 00:16:30:

What level of precision do you work to ? Do you measure with a vernier caliper or micrometer ?

I use both.

But I'm not good enough to be one of those super precise guys!

Aware that the damage has already been done, now at a bit of a loss as how best to tidy them up.

Brasso/soft cloth? Probably shoot the accuracy out of the window, but providing I mic up every time before use, and don't rely on the stamped sizes?

 

Edited By Tifa 8572 on 17/01/2022 00:26:51

[John Ockleshaw 1Participant @johnockleshaw1]

Hello Tifa,

Try to get some inhibited phosphoric acid, may be rust remover from automotive paint suppliers.

It converts the rust to iron phosphate, which can be scrubbed off with a nail brush.

It does not attack the parent steel. It offers no rust protection so keep your gauges oiled or vaseline coated.

John

[Pete RimmerParticipant @peterimmer30576]

However you clean them unless youuse emery they will be more usable than they are now. They may not wring but you won't be able to measure the difference even with a micrometer.

I'd be tempted to give them a couple of minutes dip in citric acid and rub with a coarse cloth. Wash and dry them thoroughly.

[John HaineParticipant @johnhaine32865]

Scotchbrite

[Michael GilliganParticipant @michaelgilligan61133]

Posted by John Haine on 17/01/2022 07:03:46:

Scotchbrite

Please, please; please look at my post timestamped 20/10/2021 22:44:03 on this recent thread:

**LINK**

https://www.model-engineer.co.uk/forums/postings.asp?th=175141&p=1

… and, most particularly, follow the link to the SEM image.

MichaelG.

[John HaineParticipant @johnhaine32865]

Well I wasn't aware that some grades of Scotchbrite have abrasive powder included, but I am pretty certain that the grade they put on the back of "non-stick safe foam pad washups" does not. It will give you a way to gently remove the rust whilst hardly touching the steel surface. Another possibility is to use a glass fibre brush though it may be a little more aggressive.

[Neil LickfoldParticipant @neillickfold44316]

A photo of the worst rusted slip will help as to what the best way is to recover the gauge. White vinegar and salt can help to get rid of light rust. It can be micro lapped on a lapped flat piece of artificial granite square sample piece, and use 0.5 micron diamond. It will require a holder to push down onto the block, so you are distorting or lapping it on a strange shape. Seldom do damaged slips wring correctly again. They will still be useful for lots of things however. I would stay away from things like wet dry paper or even Scotchbrite.

[Clive FosterParticipant @clivefoster55965]

For all practical purposes slip gauges with smooth but non wringing surfaces can be stuck together with a heavy oil or light grease. Sparingly applied and worked to extrude excess.

It will produce a positive tolerance build up but for two, three or four blocks joined together we certainly aren't going to notice.

I have a truly disgusting set of slips, found loose in the box of bits that came with a used lathe, which I use to set up the turret style bed stop on my lathes. More than good enough and I don't worry if one does take up temporary residence in the chip tray.

I also have brand new metric and imperial sets of Weber slips obtained on a whim at a price too attractive to pass up along with the two E-Bay "some wring together" bargain sets I'd previously gotten which work well enough if oil assisted.

As I also have some nanometre precision Heidenhain probes it might be interesting to set-up some tests to see exactly what the relative accuracy of the sets is in practice. I suspect the poorer sets would give rather better account of themselves than might be expected from casual thought.

But life is too short. If I put the exercise onto the to-do list now it will get to the top around 2050.

Clive

[Michael GilliganParticipant @michaelgilligan61133]

Posted by John Haine on 17/01/2022 09:34:34:

Well I wasn't aware that some grades of Scotchbrite have abrasive powder included, but I am pretty certain that the grade they put on the back of "non-stick safe foam pad washups" …

.

That was the whole point of my post John

Similar to the situation with “loctite” … merely referencing a trade name is not enough !

MichaelG.

.

P.S. __ This patent from the 60’s demonstrates a previous interpretation of ‘Scotcbrite’ 

https://worldwide.espacenet.com/patent/search?q=pn%3DGB986601A

Edited By Michael Gilligan on 17/01/2022 10:47:59

[Bob Unitt 1Participant @bobunitt1]

I'm a believer in Evapo-Rust, which turns the rust into a black deposit without attacking the underlying metal, green Scotch-brite then removes the deposit leaving a clean metal surface.

Incidentally, for those that don't know (I didn't till I started turning wood), there are different grades of ScotchBrite with different grits, see – https://www.thetonerooms.com/threads/scotchbrite-grit-chart.3674/

For lightly-rusted small intricate parts I used Evapo-Rust followed by a fibreglass brush, although I'm not sure how abrasive that would be on a slip-gauge.

[Michael GilliganParticipant @michaelgilligan61133]

Too late to include this with my last edit:

.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Tifa 8572 on 16/01/2022 23:27:58:

Dozens of guages, made in the UK, certified, imperial …

But…..the previous owner hasn't stored them very well…

… are they now junk?…

Depends what you use them for. In tip-top condition slip gauges provide the very high level of accuracy needed to calibrate micrometers, go/no-go gauges and to make precision jigs and fixtures etc. They support the American System of Manufacture in which parts are manufactured within given tolerances and guaranteed interchangeable.

In professional use, it's vital that slip gauges be accurate. They come with a certificate, and are periodically re-certificated to confirm that ordinary wear hasn't taken them out of specification, which it always eventually does.

Slip gauges must wring together. Wringing detects faults like dings, scrapes, bending, rust etc. If slips don't wring, they ain't accurate! And even if they do wring, it's possible than one or more slips in the set is worn, and this can't be checked at home. Likely that old sets bought on ebay are out of specification even if they look perfect. All bets are off if they've been stored badly. Rust and any form of abrasive cleaning are death to an American System slip gauge.

But slip-gauges is reasonable condition might still be useful. As far as I know, no-one on this forum works to tolerances. Therefore owning certificated slip gauges is unnecessary! However, a set of uncertificated gauges could be useful for checking the calibration of our rougher instruments: even a degraded set of slip gauges is probably 'good enough' to assure ordinary digital calipers and thou micrometers are close.

Not good enough to confirm tenths micrometers. If uncertificated slip gauges are used don't pretend they prove your instruments are formally accurate though – the slip error is unknown! Luckily, being deluded about the true accuracy of our kit doesn't matter much because Model Engineers mostly make by fitting.

In the worst case, old slip gauges make useful shims and spacers. Or an interesting conversation piece.

On the subject of fitting, "quite interesting" to experiment making stuff on a lathe with simple tools, such as a steel-rule and spring-calipers.

Say you want to fit a 1" diameter spindle into a 1" diameter hole. With good eyes, a spring caliper can be set to within ¹⁄₆₄" and used as a comparator to turn the spindle. Then the hole can be bored slightly small, and opened up stage by stage until the spindle fits into it. Slide fits are easy. Judging push and force fits needs practice, but it can all be done without fancy measuring equipment.

Most things are done this way in my workshop except I get closer to 1" with a digital caliper, DRO or micrometer than with a steel-rule and spring caliper. Better measuring saves time rather than improves accuracy. I get to with about ±0.02mm / 1 thou by measuring, then I fit. What I don't do is turn the spindle to 0.998" ±0.0005, and bore a hole to 1.000 ±0.0005, and then guarantee by accurate measurement that they'll fit together!

Although I occasionally make jigs and fixtures, they're to save time on repetition work. I make them with ordinary care using ordinary methods and they're far short of tool-room standards.

In the Duffer Workshop, second-hand slip-gauge sets fail my 'fit for purpose' test. Certificated slip-gauges fail my 'Value for Money' test. And having decided I don't need slip-gauges, I spent the money on something else…

Dave

[Rik ShawParticipant @rikshaw]

The condition of my slips were suffering a little when I acquired them as well but I treated them to a little bit of brasso on one of those green washing up pads and that made them look a lot better. As for accuracy after such treatment?

Unless you are doing a lot of high precision grinding / lapping you need not worry. All you want now is a nice vernier height gauge to make your slips so much more useful as long as they are not jammed in the T slots on the milling table .

Rik

[peak4Participant @peak4]

Here's quite a useful little video on gauge blocks by Dan Bailey

One way of cleaning de-burring Jo blocks is to use a stone supplied by one of the block manufacturers, but that will likely cost as much as a set of second hand blocks off ebay.
This video is also worth a watch, on precision ground stones for the home workshop.

I've been meaning to make a set myself, having now fettles a little Herbert grinder; I've got some stones in stock to try, but currently suffering from inertia on that one, as I still need to make an arbor for my diamond wheel, and then a wheel dresser etc. etc.

Mr Gotteswinter's stones are not available for shipping to the UK post Brexit, so you'll have to make your own.

If you don't fully watch either of the latter two videos, note that these stones are not designed to cut on a flat surface, in the same was as a sharpening stone would, and they should also be used dry.

Bill

[David ColwillParticipant @davidcolwill19261]

I have made precision ground stones and find them very useful. However for gauge blocks I find a small ruby stone (very cheap off ebay) seems to work very well. It is very hard, seems to be very flat and does not scratch the surface of the gauge block. As to the blocks you have, even worn they are very useful as packing and for other setups. I always pick up odd junk ones when I see them.

Regards.

David.

[SamsarandaParticipant @samsaranda]

Is jewellers rouge any good for cleaning slips? Dave W

[Howard LewisParticipant @howardlewis46836]

For slip gauges, NOTHING abrasive should be used.

In a Calibration Room, both temperature and humidity are controlled, and the item is allowed to "soak" for at least 24 hours to ensure minimal temperature effects, before being checked.

As manufactured gauge blocks are accurate to within a millionth of an inch, which is why the conditions under which they are checked are so carefully controlled.

Their accuracy is FAR beyond what we can, as hobyists, attain.

If rust is present, it should be removed chemically, using phosphoric acid, citric acid or acetic acid, (Vinegar),

This will affect the rust far more than the clean steel.

If you use an abrasive of any sort to remove the rust, you might as well use your Micrometers as G clamps. the damage to the accuracy might well be of the same order.

It just depends on how much respect you have for precision items.

Howard

[Clive SteerParticipant @clivesteer55943]

I concur with Howard .

Iron oxide (rust) is very hard and an abrasive in itself (rouge) so more damage can be done to the slip gauge if removal is done mechanically. So use phosphoric acid or another mild acid to soften the rust and scrub with a tooth brush. When hardened steel, and I believe slip gauges are, become rusty the rust may form along weakness lines in the crystal lattice so appears as strands or small pockets. Once the rust is softened with the acid and scrubbed check, under a microscope, to see if the rust has gone and if not gently use a pointed stylus to pick it out. Better to use several short acid/scrub sessions than leaving them in the acid too long. Also make sure you dry the gauges after each acid/scrub/rinse session as a film of rust can quickly form. Be sure to clean the slip gauges in isopropyl alcohol or another degreasing fluid as the rust may have formed under the layer of protective oil the gauges should have on them. The oil can soak into the rust making the action of the acid less effective. Cleaning the gauges in a ultrasonic tank may also help liberate stubborn rust but check this on the worst affect gauge before doing it to the rest.

All said and done slip gauges are essential for the Gods of Precision but not so much for us mortals of imprecision.

Clive

[Tifa 8572Participant @tifa857287838]

Thanks all!

Up to now, I've given them a quick wipe over with a soft cloth and coated them with acf50 until I've got the time (and patience!) to sort them properly!

[not done it yetParticipant @notdoneityet]

Even if they won’t wring together they are useful for checking the width of slots for most standard keyways, etc. The error on any couple of blocks used together will be minimal in those situations. You may have noted that one of the responders has multiple sets, ranging from ‘chip tray’ quality to tool room grades. I doubt he is the only one on the forum with more than one set.

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