Mystery to me, Moore and Wright

Hello all, Back again to acess the knowledge

These rods are marked with sizes, yet the tduplicate wo inch and one inch are consistently two thou over ie 1.002 and 2.002.The two micrometer heads have domed ends and are graduated for tenths.The rods have flat ends on truncated cones.Can anyone identify the name and use of these please?

Thanks paul

Just to add to my post the two adjustable heads measure 3.625 when set to zero on the barrels were these for some very particular measuring process like go no go gauges?

Thanks again for any suggestions Paul

Most probably an internal micrometer set, possibly with the heads in need of resetting to remove the 0.002 error.

Which raises the question, before making ANY adjustments, of how accurate are the devices used to measure the overall length?

Have they been checked against length standards or slip gauges, to confirm their accuracy?

Do any, or all of the other extension rods show the same +0.002" ?

If adjustment is required, the spanners with which to do it are there

Howard

They are End Measuring Rods, used on a Jig Boring Machine.

Thanks to you both or the swift response, the rods are not adjustable and were measured with Mitutoyo micrometers set to to slip gauges so I am surprised at the consistency of the apparent error. also the rods marked 8 and 4 inch are also duplicated. A Jig boring machine is beyond my skill set, but how would these be used please Nick? is 3.5/8 of particular significance and why two?

Thanks again to you both Paul

Have a look from page 10 and on of this Pratt and Whitney brochure :- Pratt & Whitney Jig Borers Circular 513

If the link fails, PM me and I'll send you the PDF

Nick

Edited By Nick Hughes on 26/04/2021 16:01:40

Thank you very much Nick, the link worked perfectly and I shall enjoy reading all of it. The penny has dropped! I doubt that I will ever use these as intended but they were too interesting to be left at the car boot! In any event I now have a set of standards up to 12Inches

Thanks Paul

As Nick says these are used in jig borers to accurately set distances. Often toolroom class milling machines had a trough on the front of the table to carry them when doing accurate work. Even Bridgeports had an accessory to enable their use.

The adjustable heads are nominal 3.625" long. They should be set to read 3.625" on zero by the usual method of turning the micrometer sleeve. However some firms preferred to leave the sleeve in a fixed poistion and note the error. My set, obtained for a specific maybe job but never used, has calibration labels for the two heads. One says 3.6258 an one 3.6250. If I ever use them I shall sort that so both are calibrated to 3.6250

The length bars should be accurate to ± 0.00005" at standard temperature. That equates to less than 0.0001 error band. No idea why you are measuring one or 2 thou over. That said out in the real world you'd expect regular calibration with last time details to be in the box

These would normally be used with a tenths thou indicator. See the picture half way down this page :-

**LINK** , http://www.lathes.co.uk/bridgeport/page3.html for the Bridgeport accessory set up.

Clive

PS Nick sent a very interesting link whilst I was typing making the above post pretty much redundant! I've grabbed the P&W information from Nicks link too.

Edited By Clive Foster on 26/04/2021 16:18:49

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Clever use of the dial indicator :

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MichaelG.