More questions on gauge blocks. This time a Pitter set

I just bought a Pitter Gauge & Tool Co. set of imperial slip gauges. Fair condition, I think, but there are a few questions - even after checking out a few videos.

There is no indication of grade, so would I expect that these are ‘workshop’ items?

There are seemingly spaces in the box which were not occupied (the 0.1007 slot was occupied by another slip) there being one piece (a 0.10075 slip) in amongst the four figure row (in the 0.1007 slot).

What should be in the two top row far right slots? Wear pieces? There is no indication in the box as to those slots contents.

I am wondering if there should be a 0.10075 slip included in a set such as this? Should it go in one of the unmarked slots? Or should there be another five figure slip included?

Are individual slips available for these older imperial sets? I did see one recent US video which centred around an imperial set. Nothing on epay.

Does anyone have a 0.1007 or 0.101 spare they would like to find a new home for, simply to complete the set? I, so far, have not really needed the precision/accuracy afforded by a set like this!

There were two extras in the box - an unbranded 2” (which likely belonged to a micrometer) and a Matrix 0.550 slip. Is there some abstruse benefit to having these particular ‘spares’ in the box or are they simply taking up space and potentially just rattling around.

It didn't start life with that 0.10075" slip, but I wouldn't worry about 1/2 of a tenth of a thou, half a thou is a much more realistic measurement for the real world. Anyone who says that they work to 0.00005" is either a liar, or delusional.

Sets of slips usually have a pair of 0.1000" wear slips in them, or the metric equivalent metric size.

Yes, I have since found the set is a ‘bitsa’. There are Matrix slips in amongst the set. I will not be worrying about it unduly and a thou is generally more than close enough for anything I do.

This set was too good to leave on the table. The five figure slip needed my wife’s smart-phone microscope attachment to be able to read ‘Matrix’ on it.

One thing, so far, is that every slip I have compared with my old mitutoyo digi-caliper has indicated with spot on agreement. Good to know the caliper is accurate.

Edited By not done it yet on 06/11/2019 22:15:41

Looks like a very useful set, it would be nice to complete it, and It probably is a 'workshop' set, I would expect an inspection set to be complete, because they are usually used in a controlled environment.

And I agree with Old Mart working to four decimal places (in imperial) is more than good enough for anyone in the home workshop, handling freezing cold gauge blocks with warm hands will drive anyone round the bend chasing a fraction of a tenth of a thou!

Ian

Intermediate sized blocks may be in the set to help cope with the imperial fractions that don't express well in thou or tenths. For example 7/64" = 0.109375"

Not sure imperial sets were ever completely rational. Some come with blocks that only deal with tenths, others have extra blocks covering a few or several common fractional sizes as well. I guess what was in the box depended on the purpose for which they were bought, probably in hope of saving time or money. On top of that old sets likely have chequered histories, with blocks being lost, replaced, or mixed up over the years.

Dave

Thanks, Dave.

I can see that may have been a good enough reason for it being there. Doubt if that precision will make much difference to my machining, but the set did become available after the death of a very well respected engineer who would quite possibly have attained those sort of accuracies. This, of course would require an extra level of precision for all the rest of the slips as the original set were only a ’four significant figure’ set in the first place.

So now down to just a couple of questions as I could (if I was minded to) make up all the half splits using that fifth figure if the 0.1007 were present, by using an extra four figure slip (for larger measurements than 0.2007?)

Outstanding, is about these ‘wear slips’ - are they usually 0.1000 (ceramic slips would clearly be best for that?) and availability of spares (again the US seems to be the only place that still uses imperial slips!).

Still not sure if there was a sound practical reason for the two extras, but that is not really of much importance in the greater scheme of things.

If I was the proud owner of a gauge block set, I wouldn't be using it to chase tenths! But it would be useful to own one, even one in slightly suspect condition.

At the moment my most trustworthy dimensional standard is a £25 micrometer. It's cheap certificate claims ±0.01mm accuracy and - although it performs - I've no way of checking it. My ground parallel set says its parts are ±0.02mm, not good enough for calibration purposes, or even to prove definitively that my micrometer 'feel' is correct or not. So I can only realistically say dimensions are about right to about a thou, more or less, at best. And for all I know there are dimensions my measuring instruments get moderately wrong. The Duffer Workshop could certainly do better!

As Old Mart remarked a thou is 'good enough' for most home workshop purposes. Where gauge blocks would be most useful to me is for periodically checking my digital calipers and micrometer. In particular confirming they are accurate across their full range. Bet they aren't, and it would be good to know if any gross scale errors are worth correcting.

Gauge blocks would also be useful if someone asked me to make a large number of toleranced objects. Say I was asked to turn 500 off 0.498" diameter pins where the maximum tolerance was zero and the minimum was 0.497" Rather than checking each and every pin on the lathe with a micrometer, instead I would use gauge blocks to make accurate 'go-no go' gauges. These would let me turn quickly down to 'go' and to equally quickly reject any pins where I took slightly too much off. The need is to make a trustworthy measurement tool requiring considerably better accuracy than my normal dubious workshop standard. The Go and No Go gauges wouldn't be knocked off in ten minutes. Likely they would take me considerable time and effort to get right, and a set of gauge blocks are the easiest way of getting there with certainty. The price of mismeasuring is the customer rejecting 500 out of spec pins.

Of course my workshop almost always does metalwork to suit my less demanding purpsoes. In it I slowly make small numbers of parts and fettle them to fit together. High levels of accuracy aren't needed. In that space gauge blocks are far less useful. Most of the time digital calipers are good enough or even dividers. The 'gauge' is the feel of the fit between two parts, one of which is trimmed to fit the other and possibly not measured at all.

Horses for courses again.

Dave

deleted slow computer.

Edited By mark costello 1 on 07/11/2019 18:49:09

It's nice to have something to settle the "argument." Other than the Wife.

My old firm had dozens of sets on the shop floor as well as inspection grades and a couple of reference sets which were kept under lock and key most of the time. All of the sets had calibration dates on them and if any slip failed inspection, a replacement was found, and it didn't matter if it was a different make, it was the size that mattered. As we had an account with Mitutoyo, most of the replacements came from them.

Ceramics and carbide slips are nice, but very expensive.

My box is a mixed lot, not one of which would be allowed by an inspection department.

The two vacant spaces top R H S look as if they are intended for the two 0.1" Protective slips.

If you have no luck finding replacements, PM me. I may be able to find some for you.

Howard

PS If they are inn reasonable condition, it should be possible to wring them together.  Even if you can't quite, they will probably suffice for the sort of jobs that we do.  My "condemned" ones do!

Edited By Howard Lewis on 08/11/2019 18:26:18

Hi I was lucky enough to find a complete set of imperial Pitter Jo blocks labelled inspection grade and in visually good condition, in the same box as the OP's. Howard is correct, those two spaces would have contained two 0.100 protective slips.Amazing what people sell at car boots, although it was in rural coastal Dorset!

regards Paul