COMPAQ Bore Gauge

[Howard LewisParticipant @howardlewis46836]

I have a very used COMPAQ bore gauge. It is intended for measuring bores from about 0.750 to about 1.500 inches diameter.

No Model No. is evident.

One of the Anvils, and two of the extension pieces are missing

The longest Anvil, No.6 and extension pieces A and B are missing.

(Needless to say, these are the ones needed to measure my latest project! ).

By examining the existing parts, it is possible to find that the tread is Metric,

5 x 0.5mm pitch.

My attempts to estimate the length of the missing parts correctly has been unsuccessful.

Can anyone, please, provide dimensions, so replacements can be made?

Thanks, in advance.

Howard

[Howard LewisParticipant @howardlewis46836]

Missing Parts

[Michael GilliganParticipant @michaelgilligan61133]

You might find something by browsing around Long Island

… This looks a reasonable place to start: **LINK**

http://www.longislandindicator.com/p84.html

MichaelG.

[Howard LewisParticipant @howardlewis46836]

Thank You Michael.

Long Island do not sell parts, since they need them for repairs.

By the looks of it, they can be made to order, but with a lead time of anything up to 8 months.

And judged by the eyewatering price of a complete bore gauge, at USD 5K+ , (Plus shipping, VAT and duty no doubt ) I can afford neither the cost, nor the time, for an instrument that has spent most of the last 15 years on the shelf., and will have to be restricted to work where it can be used with the contacts and extension that I have.

Pity, it would have been the one instrument capable of measuring what I am making.

Looks like a long and probably frustrating journey into making plug gauges and suck it and see land!

I don't think that the width of the knife edges on digital callipers will provide enough accuracy for me to make a bore giving a 0.001" interference fit for an existing shaft.

Life never was for the faint hearted!

Howard

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Howard Lewis on 22/06/2020 22:03:38:

Thank You Michael.

Long Island do not sell parts, since they need them for repairs.

[…]

.

Yes, I was aware they don’t sell parts … but I thought you might find some useful detail amongst their pages.

Sorry if raised your hopes unreasonably.

MichaelG.

.

P.S. ___ I just found this gem amongst their pages:

”The contacts for this size bore gage have M5x0.5 threads. Overtightening the contacts will easily strip the threads in the measuring head. If the threads become stripped, you'll have no choice but to replace the entire head (part 044100).“

… Focuses the mind, doesn’t it !!

Edited By Michael Gilligan on 22/06/2020 22:16:40

[Howard LewisParticipant @howardlewis46836]

Thanks for that. Michael.

I tried guessing the dimensions, and got them wrong !

Have ordered 5 x 0.5 tap and die from Tracy Tools, in the hope of being able make my own., Had worked out from what I had that that was the thread, but did not fancy screwcutting my own!

Can easily imagine the ease of damaging such a fine thread by heavy handed overtightening.

Will probably make the external threads by producing a length, screwing it into the internal thread and shortening to length. By my standards, this is close to watchmaking territory!

Being an optimist, I can only ask Long Island if they would be prepared to give the dimensions for the No.6 Contact, and the A and B extensions.

If not it will be suck it and see again, in the hope of guessing more accurately.

All this in the expectation of just measuring one bore!

Howard

[Kiwi BlokeParticipant @kiwibloke62605]

Howard, can you put up a pic of your Compaq device? I have a beautiful, complete, Compaq (dial) bore comparator set, but it will take some finding (I'm 'between workshops' and much equipment is stored away in boxes). Mine is for larger bores, but there may be parts of interest in common. If yours looks similar, I'll organize a search party to find mine and measure whatever you're interested in.

Edited By Kiwi Bloke on 23/06/2020 10:29:13

[JohnFParticipant @johnf59703]

Howard a few photo's may help everyone to understand better and a model number could be useful.

John

[Former MemberParticipant @formermember32069]

[This posting has been removed]

[Kiwi BlokeParticipant @kiwibloke62605]

Bother! Too late to edit my post. It's 'Compac', isn't it? Compaq made computers, PDAs, etc.

[Howard LewisParticipant @howardlewis46836]

Thanks for all the advice and offer of help. As ALWAYS, help and advice from Forum members.

It is an OLD, ex Industry, Swiss made, Compaq 1A2A . From new, and complete, it was capable of measuring from 0.8" – 2". So I was hoping to use to measure a hole, as I bored it to produce a one thou interference on a column which measures 1.122" Needless to say, the Extension, or Contact needed for this is missing; probably why it was condemned and taken out of service.

Since the objective is an interference fit, without cracking the 1.25" thick x 6" diameter cast iron, probably the 0.0005" resolution of any of my Lidl, M&W or Eagle digital callipers would probably suffice.

My worry was that the width of the knife edges on the jaws might let me think that the bore was to size, when it was oversize to the extent that any interference was either too small, or non existent.

Thanks to Michael Gilligan, I have contacted Long Island, knowing that they do not sell spares (Just as well since a new instrument is priced at over USD 5K, and lead times can be as long as 8 months! ). I have asked if they are prepared to supply the dimensions of the missing Contact and Extensions, so that I can make replacements.

Otherwise my new 5 x 0.5 mm Tap, and Die, will both be redundant, unless I can guess better the next time around!

Knowing the anticipated very limited amount of use, soft, shop made ones should last beyond my expected lifetime!

Howard

[Clive FosterParticipant @clivefoster55965]

Howard

As its for a one time job can you not simply make an extension piece to a best guess close dimension by extrapolating from the extensions you have and calibrate the error using good micrometer or vernier.

I'd expect the error to be the same right through the range so, with luck it will be just add or subtract ….. from the dial reading. The dial on the similar instrument I have is arranged to rotate so as to allow such calibration. Or so I was told.

Making a short intermediate piece to extend an existing extension is possible but probably monumentally frustrating when it comes to getting the length right.

Clive

[Howard LewisParticipant @howardlewis46836]

Hi Clive!

Yes, that's what I did, but managed to guess wrong in the vital case, and very probably in the other two as well!

Hence my search for more accurate dimensions!

The old "If all else fails; read the instructions" syndrome

The dial rotates so that the Zero point can be set using a ring gauge of known size.  The needle should then show any departures from that size.

With the correct Contacts and Extensions, the gauge can be set to any dimension, within its range, using a Ring Gauge or a Micrometer held in a bench clamp.

Howard

Edited By Howard Lewis on 23/06/2020 13:32:32

[Howard LewisParticipant @howardlewis46836]

Clive,

Thank You for persuading me to put my brain back into gear.

Although I was measuring in Imperial units, I spotted that the Contact lengths increased in 1 mm increments, the penny still did not drop.

Then, realised that the instrument was Swiss made, the dimensions would be Metric.

Spent the afternoon remeasuring everything, and Bingo!

So, instead of trying to think of the Extensions in three increments, but in four, it was obvious that they increment by 5 mm, not 7.5.,

In this way, extensions could cover the range from 5 mm to 20 mm with just three.

The 5 x 0..5 mm Tap and Die arrived, from Tracy Tools, the morning after they were ordered

Have already almost finished the No.6 Contact, (Just needs the spanner flats milling ) so the next task is to make the other two extensions.

It is a straightforward job, but not easy because the die cannot cut right up to the shoulder.  But have a found a way round that; as long care is taken when the parts are used.

Eventually, I shall be able to proceed with the job for which the Compaq was needed to measure the bore.

It sounds as if SWMBO has lined up a job to repair a garden hose for a 90+ year old lady over the road, which will take precedence over boring the cast iron!

Again, Thanks to everyone for advice and offers of help.

Howard

Edited By Howard Lewis on 25/06/2020 08:18:31

[Howard LewisParticipant @howardlewis46836]

Congratulations to all who corrected the name to COMPAC.

If all else fails read the label, rather than relying on memory!

The Contacts and and two Extensions have now been made, and the Bore Gauge used once already.

Things improved once I started thinking in Metric, (It is Swiss made! ) in stead of the Imperial units in which it calibrated.

I shall not be taking up making spare parts for it as a hobby, too much like watchmaking!

Howard

[Michael GilliganParticipant @michaelgilligan61133]

You deserve every success, after all that effort, Howard

MichaelG.

[Howard LewisParticipant @howardlewis46836]

Thank You Michael!

But, "When needs must……" and all that.

It was an interesting, and satisfying exercise, but not one that calls for too much repetition.

Taking 0.010" deep cuts, is not a problem but being 0.020" long is a bit finicky! (Especially when the whole thread is supposed to be 3.5 mm long )

Howard

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