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Care of Slip Gauges

Good (used) set acquied - thinking about how to protect them

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IanT16/04/2018 10:16:03
1109 forum posts
107 photos

I've recently acquired an Imperial slip gauge set, that on first look seems to be in generally very good condition. Only one or two faces have any evidence of 'scratching' and they seem to 'wring' well. They were acquired off eBay for what I considered a very reasonable amount - although sight unseen - it was a real gamble.

I was a little swayed by the fact that they were originally made in Mitcham (by Precision Grinding Ltd) not too far from where I was born and where my Grandad delivered milk from a handcart (sometimes assisted by my Mum - as a small girl). Seemed like a good omen for some completely illogical reason!

Fortunately, the Sellers description was an honest one (not always the case in my experience) and I am very pleased with them generally. The box is not marked with any 'grade' as such and unsurprisingly there is no calibration information - although a positive sign is that it does have two 'P' (Protector) slips, which seems to indicate good original quality (not that I doubt PGL produced anything other).

As shipped they are 'dry' (no protective coating) but I have been careful in my handling. I have looked on the web for guidance in their care and the advice does vary somewhat (especially on YT). The seemingly best (and most technical) reference I have found is here:

So at the moment, I'm planning on using petroleum jelly but have looked at other (more modern?) solutions as offered by our usual suppliers. I was a little off-put by reading the H&S notice however...

So I'd be interested in others views in this area - and any good advice concerning their care and use generally,



Chris Evans 616/04/2018 10:52:31
1200 forum posts

I have had my set over 40 years, second or third hand when I got them. In all those years I have not done anything other than use them and maybe once a year give them a rub with an oily rag. They still wring as they should and have seen a lot of use, I doubt the use of petroleum jelly due to the fact that every time you pick one out of the box they will need a good wipe but it will certainly keep rust at bay.

Andrew Johnston16/04/2018 11:11:04
3853 forum posts
456 photos

I've got two steel sets of gauge blocks, imperial and metric, both bought on Fleabay. I keep them in the dining room rather than the workshop. I keep them clean with a cloth before use but don't worry too much otherwise. Since they're in the house I don't have corrosion problems.

Personally I'd ignore 99% of the stuff on pootube. Instead read this link from a manufacturer:



Neil Wyatt16/04/2018 11:27:38
13606 forum posts
577 photos
68 articles

"The average life expectancy of a gage block is about 3 years."

Production really is a different world to our workshops

Clive Foster16/04/2018 11:30:18
1348 forum posts
29 photos

Seems like Starrett M-1 oil is the right stuff but seems to be unobtanium in the UK. Does anyone know a source at reasonable price?

Apparently white spirit is the UK equivalent to the American mineral spirit advised for cleaning purposes. But which brand of white spirit to use. Seem to be considerable variations between them. Some of the more economical offerings appear to be a bit dubious from the residue aspect and, probably, chemistry too.


SillyOldDuffer16/04/2018 11:39:58
2942 forum posts
593 photos

I'm no expert but suggest a pure thin oil like medical paraffin rather than a grease.

Much depends on what they're used for. In my workshop even slip gauges in poor condition would likely outperform my mike and calipers. My purposes are crude, others do more demanding work.

If I recall correctly the rule of thumb is that a gauge should be about 10 times more accurate than whatever it's calibrating. So there's a hierarchy of gauge qualities, with gauges used to check other gauges needing lots of care not only in manufacture, but in storage, temperature control, handling, calibration, absolute cleanliness, and technique. Far more to high precision than buying a box of gauges - it isn't easy.

If you want to be really obsessive, it might be fun to determine if your set is pre-1959. Before then the UK inch and US inch were different. In 1959 the yard was redefined to be 0.9144m and the UK and US both altered their inch definitions to match the International Inch, which is exactly 25.4mm. With very careful measurements it's possible to see what your set is made to. Don't expect to do it with a micrometer though, the difference is measured in millionths.

I ought to buy a second-hand set myself. Every so often I need to up my game and they would be useful.


KWIL16/04/2018 11:44:47
2974 forum posts
55 photos

Personally I use Japanese Camellia oil on all my fine tools, unbelievable thin and effective. I am with Andrew, a controlled storage environment is best for safe keeping.

Howard Lewis16/04/2018 14:38:34
1201 forum posts

At the risk of stating the obvious, do wipe them clean, with a chamois, ideally, before use.

If they will wring together, they are in a good condition.

DON'T buy the set i saw last Saturday, for sale for £25. Originally made by Harbots of Leicester, The box had become damp, and although they looked a little care worn at first glance. Removing blocks from the box showed the lower ends to be badly rusted.

Display only; no way could they be cleaned up enough to be properly useable.


geoff adams16/04/2018 14:49:39
77 forum posts
61 photos

hi Ian

did my first year off the job training at the EITB Purley way we had an apprentice from precision grinding

one of our projects involved grinding some 12"x!2 " plates and we went to there site to use one there surface grinders this was back in the seventies don't known if they are still in business


IanT16/04/2018 15:39:46
1109 forum posts
107 photos

The reason I purchased them is a bit of a round-about story. I needed some 'wide' micrometers to check some work I was doing a while back and purchased some rather grubby ones off eBay. I was again lucky, in that whilst the general cosmetics were not good - the anvils seemed fine and there was no noticeable wear. I cleaned them all up (there are some photos in my album) and they worked fine as 'comparators' - which was all I needed to do. Checking whether a number of surfaces were the same width apart and (if not) what was the difference between them?

However, several times recently, I've wanted to measure something 'absolutely' and of course the mic's were not calibrated. I'm sure there are ways around this but for simplicity I had a look around for setting gauges. These were not quite as expensive as I'd expected but still started to add up for something I'd use only very occasionally. For not too much more money, I've been very lucky and acquired the slip gauges which will do this work and much more.

It seems a bit 'grand' (quite cheeky in my case) to state that they will only be used for 'calibration' purposes but I think that's probably going to be the case. I run two workshops and they will be living in my 'inside' shop (where conditions are generally much nicer than the 'shed' ) but I do still sometimes get a very slight film of rust on newly machined parts if not wiped with the proverbial oily rag (which in my case is not that oily and not rag - but you get the general idea).

So thanks guys - I need a new chamois for the car - and perhaps a small bit will get requisitioned for 'other uses'. I think the slips will get a wipe with a fine oil before storage (just in case) with a light clean before use.




P.S. A word (or two) for newcomers to this hobby. A (good) set of slip gauges is quite expensive and is really not required for most of the work that you will likely need to do. I took a high risk by buying a second-hand set on eBay (sight unseen) as these are items that (if they are worn or even slightly damaged) are essentially useless for their intended purpose. I certainly saw sets offered that were clearly (just from the photos provided) in this category - but for which the seller was asking really silly money. Whilst some second-hand tooling can be "improved" if it's slightly worn or perhaps even damaged - slip gauges are not amongst them - at least not in most home workshops.

Edited By IanT on 16/04/2018 15:42:21

IanT16/04/2018 15:49:09
1109 forum posts
107 photos


I've checked - and I think PGL may still be around and are now known as "PG Technology Ceewrite" - which suggests they are part of a larger group these days.



...Ooops - seem to have a double post - Moderators to the rescue??

Rik Shaw16/04/2018 18:01:55
1134 forum posts
318 photos

I don’t have a problem with rust or condensation. However, If I did, I would keep my old but cherished Coventry Matrix slips indoors. I keep a sheet of brown paper sprayed with WD40 in the slip box. They really do not need this protection but I always reckon that the skill and effort that went into producing some of Englands finest deserves my respect. God save the Queen.


Neil Wyatt16/04/2018 19:51:32
13606 forum posts
577 photos
68 articles

I'm sorry folks, but Starrett are quite definite, if they are over three years old, your slip gauges are useless.

I suggest you send them to me for safe disposal


IanT16/04/2018 20:20:31
1109 forum posts
107 photos

Please don't do that Rik - the Daughter-in-Law gave me a very strange look just then when I stood to attention...



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