Another Rupnow 1 by 1

[Steamchick]

Nerds described it well. The caliper is a comparitor, not a measure. Set the micrometer to the size you think that you have machined the hole. Compare the feel of the caliper in the hole and the micrometer. It too tight or too slack in the micrometer, reset by a couple of thou. Try the comparitive feel again... repeat until you have a setting of the micrometer that matches the feel of the bore, when comparing them with the caliper. Just touching both means you have the size of the bore. You'll soon get a setting on the micrometer that exactly matches the feel of the bore.
K2

 

[CFLBob]

I've always had that problem with my telescopic gauges. As a result I don't use the ratchet, instead I had to develop a 'feel' for the pressure on the gauge so as to measure repeatably. If you collapse the caliper even slightly you should perceive a sort of 'mushiness' in the feeling of twisting the micrometer.

While doing my previous experiments, on one of the sets of measurements I ran into the problem of the micrometer making the gauge smaller. Tightening the screw that keeps the gauge from moving fixed it.

I think.

What if my whole problem with excessive variation in the numbers I got is actually from the micrometer squeezing the movable piston in the gauge?

 

[CFLBob]

Nerds described it well. The caliper is a comparitor, not a measure. Set the micrometer to the size you think that you have machined the hole. Compare the feel of the caliper in the hole and the micrometer. It too tight or too slack in the micrometer, reset by a couple of thou. Try the comparitive feel again... repeat until you have a setting of the micrometer that matches the feel of the bore, when comparing them with the caliper. Just touching both means you have the size of the bore. You'll soon get a setting on the micrometer that exactly matches the feel of the bore.
K2

This is completely different from the way I've been doing things and I'm not quite sure I have enough hands to do this. Do you set the mic and then set the lock to keep it from moving? Do you hold the mic in a stand?

 

[Steamchick]

Hi Bob,
Maybe you haven't been shown the simple way to hold a mic and use it.... - Fundamanetal training for MECHANICAL apprentices... but Electrical/electronic apprentices have a differnt agenda.

1. Hold the mic in your LEFT hand, using the last 2 fingers (your ring finger and pinkie) wrapped over the saddle of the mic.
2. Make sure the barrel is pointing AWAY from you, and the barrel will readily fit between your thumb and forefinger for adjustment. (You can feel better than the clicks oif the ratchet button! - and anyway you are SETTING the mic to a specific dimension with NOTHING between the jaws.).
3. You should be able to easily see the scale with a slight twist of the wrist/forearm and with a little practice this becomes second nature. - But when I was 14, with small hands, I found this quite difficult with anything bigger than a 3" mic.. the 10" mic definitely needed 2 hands!

Now set the mic to size. Then stop twiddling the mic. It will keep that size without using the lock as you won't be twiddling the barrel when comparing the caliper to the mic. Take the comparitor/caliper/Bore gauge/test piece, or whatever, in your right hand, and carefully insert between the jaws of the mic. You will now appeciate that while we mechanical oiks have a reputation with girls for having 8 hands when in the back row of the cinema, you are only using 2 of those hands. - One to manipulate the mic to size, the other to manipulate the gauge between the mic jaws.

1. It fits perfectly? Same feel as in the bore? - Great ! - That is sized.
2. It was a sloppy fit... Oh well, just more boring work to be done. Remove the caliper(etc.) and close the mic by a couple of thou. Check the caliper again. Eventually you will have enough practice so you get consistent readings.
3. It was a tight fit? OOPS! the gauge is telling you the bore is bigger than the size you set on the Mic. Just be sure and re-check the gauge in the bore...

Of course, when you are measuring a part directly, the same hold on the mic will permit you to adjust the mic carefully onto the part - often held in the other hand - when you may choose to use the ratchet knob to twiddle the mic.
Any sinistral mechanics will note I am talking about the conventional mic held in the left hand, and will be aware that you can do the same with the right hand, but ensuring the barrel is pointing to the front and a bit to the right... I have never had a "left-handed Micrometer"...
Hope you enjoy this bit of learning, and are able to follow my crazy instructions!
Cheers!
K2

 

[bluejets]

Used many brands and the only one that passes is the Moore & Wright.
Just did a one way bearing recess for the starter driver on the four cylinder.......perfect fit.
Seems it may have a rather fine thread in the shank which "pinches" the barrel under the slightest tension.
Usually give them a slight nip extra after withdrawing.
Naturally use vertical if measuring a bore in the lathe.

 

[CFLBob]

Used many brands and the only one that passes is the Moore & Wright.

Sorry, bluejets, but one brand of which: the caliper or micrometer? I've never heard of them before, but I see they make both things.

 

[Sprocket]

I learned to hold the micrometer in the RIGHT hand, (I'm one of your sinistral mechanics) so the reading is toward you without the "slight twist of the wrist/forearm". Or is this only with the T gauge? Mics were made for right handers, why try to use it lefty?
Doug

 

[Brian Rupnow]

I am right handed and I always hold the micrometer in my right hand. I close it on whatever I am measuring (Which I am generally holding in my left hand). My micrometer has a lock lever on the side which I engage, then turn the micrometer so I can see what the reading is. I have learned from experience that Vernier calipers are used to get a general idea of what a dimension is, but if it's anything critical, use the micrometer.

 

[ShopShoe]

RE: Using telescope gauges...

I like Abom79's video on how he uses the guages and micrometers. I've increased my accuracy by following his lead:



--ShopShoe

 

[xpylonracer]

Nerds described it well. The caliper is a comparitor, not a measure. Set the micrometer to the size you think that you have machined the hole. Compare the feel of the caliper in the hole and the micrometer. It too tight or too slack in the micrometer, reset by a couple of thou. Try the comparitive feel again... repeat until you have a setting of the micrometer that matches the feel of the bore, when comparing them with the caliper. Just touching both means you have the size of the bore. You'll soon get a setting on the micrometer that exactly matches the feel of the bore.
K2

.
It's find it's never so easy to get the same feel as the surfaces being gauged are so different, turned bore and polished flat anvils of the mic.
Like most I always do a 2nd check.
I have a mix of Moore & Wright and Mitutoyo gauges and as you would expect both have a silky smooth movement.

xpylonracer

 

[Steamchick]

Doug,
I use the micrometer (or gauge) in the left hand and introduce the calliper (comparator) with my right, as I am not sinistral, and use my right hand for the delicate setting and feel of the calliper in the bore I am checking. To hole the mic in my right hand, would mean I was changing hands for the feel of the calliper in the "gauge". - Not good for repeatability.
As you are sinistral, I assume you use the bore gauge with your left hand, in both the bore and the micrometer. Not changing hands between bore and gauge is key to repeatability.
Irish quality control is "to be sure, to be sure" - but I Check-3-times, then put the tools down, and pick-up and check again. You quickly become accustomed to the operation and your measuring repeatability and accuracy stabilises quickly.
The major point here is that you do NOT adjust the micrometer onto the comparator (calliper or bore gauge, etc.) but set the micrometer and gauge the comparator with the fixed gap. That way you do not adjust the comparator during the check in the gauge. Screwing a mic onto a comparator will most certainly be risky for repeatability of your measurement, as that is a different contact loading to the feel you have when using the comparator in the bore, and likely to move the comparator.
I was taught by guys who machined parts for Rolls Royce Merlin engines during WW2... They were sticklers for precision and repeatability, as every engine was flown - and used to its extreme limits. Also, they had equipment that was about as accurate as most home workshops, not modern high precision CNC mass production with lazer and air gauging, temperature controlled clean measuring rooms, etc. I can only advise what I know to work for me... But many contributors have a lifetime of expertise to beat mine, so any other advice?
In the "home workshop" there are many gauges, some very high precision, like ball bearings, who's races have very precise bores and ODs - e.g. a 1" bore ball race makes a pretty good gauge for final finish checking of the comparator when making a 1" bore steam cylinder... I also use the shanks of milling cutters as "gauge standards" for ODs, and as gauges in small bores that need to be precise. (e.g. shaft bushes). I wonder, how often do many home workshop machinists check the accuracy of their micrometers and verniers? - Important when making thousands of parts, but maybe annually would be a good idea in the home workshop? - I usually do a "start of shift" check when I get a mic out of the box, and verniers get frequent zero checks. (I have mechanical verniers, not digital with "set zero" buttons. Too easy to measure something that has been inadvertently reset to a non-zero point!).
Enjoy!
K2

 

[ajoeiam]

.
It's find it's never so easy to get the same feel as the surfaces being gauged are so different, turned bore and polished flat anvils of the mic.
Like most I always do a 2nd check.
I have a mix of Moore & Wright and Mitutoyo gauges and as you would expect both have a silky smooth movement.

xpylonracer

If you can find some - - - - you might want to try some TESA mics. They're even nicer than the Mitutoyo (haven't worked with any M & Ws).

 

[xpylonracer]

If you can find some - - - - you might want to try some TESA mics. They're even nicer than the Mitutoyo (haven't worked with any M & Ws).

Hi aj
Nothing wrong with Mitutoyo mics, silky smooth operating adjustment, as I said you are comparing the feel of a turned part and polished carbide mic anvils, all you can do is check at least once to be sure of the reading.
I also use dial calipers in bores, especially useful to check parallelism of the bore.

xpylonracer

 

[Steamchick]

Xpyl...
Excellent! The bore gauges I am familiar with are a DTI at the end of a long stem, with the mechanism of a "button" that reads via levers to the DTI opposite an anvil - that can be replaced with a longer one for larger bores: AKA:
https://www.ebay.co.uk/itm/20320519...7779&msclkid=63fb2d6c877318ffe0234cbe2f18b6a8And here's one for sub 1" sizes...
https://www.ebay.co.uk/itm/25525532...7779&msclkid=b072c652ee461b3b03e8a780462d0851K2

 

[Steamchick]

Thanks for the prompt lads, I have just decided to buy this...
https://www.ebay.co.uk/itm/254450581717?hash=item3b3e6fc0d5:g:yNcAAOSwSQ9hw0qLI selected this as the description seemed to contain a better range of anvils, etc. for setting the gauge to various bore sizes. May be it's just the description, but it seemed the better kit of parts to me. And I reckon if the DTI is "not the best", I have a good one that will probably fit anyway. For conversion Metric to IMperial, I just change mics. The Zero will always be at the size I want, irrespective of the size of the "divisions" to get there. I'm happy with all dimensions anyway.
Has anyone had to work in Korean Inches? - They are 1/10th of a Foot! Their version on Metric! - Confusing when a Korean book tells you a size in feet and Inches... - A Lesson for NASA there!
I'm making a couple of steam powered water pumps, so this will help do the "boring stuff" with tools I haven't handled in a while. - I'll cross-check with my callipers and mic anyway, but it's really nice to see a dial gauge instead of just relying on "feel"! The DTI may be just a factor more precise..? (But "Feeling the bore" can be fun as well)...
K2

 

[xpylonracer]

Xpyl...
Excellent! The bore gauges I am familiar with are a DTI at the end of a long stem, with the mechanism of a "button" that reads via levers to the DTI opposite an anvil - that can be replaced with a longer one for larger bores: AKA:
.
Here's a few more gauges that I use most of the time.

Moore and Wright telescopic gauges, 1 leg slides into the fixed leg.

Small hole gauges, the top most part when screwed down expands the end to move the balls into contact with the bore, measure over balls for sizing.

Small hole gauges split end opens when top part screwed in, measure over end with mic for size.

Bore mic direct reading 0-25mm.

Bore comparator unless set ting ring used to set the zero, different sized anvils for size being measured, 0.002mm reading DTI

xpylonracer

[/QUOTE]

 

[CFLBob]

For unknown reasons the forum "Watching" this thread stopped emailing me that posts were coming in and the last update I saw was my own post last Friday night. I didn't even notice the thread in my daily "Yesterday's Forum Activity" activity emails and it should have been there.

I can't say I'm "done", just getting a feel for the new instrument (calipers). I enlarged the bore to 0.995 (by calculation) and I'm getting a feel for things.

A few things that need to be done outside the shop have bubbled to the top of my list, so I'm probably going to be here for a while.

 

[Steamchick]

Xpylon.. I have most of the gauges and comparitor you have, and have now ordered the DTI gauge, as I didn't realise before that I can afford one! They used to cost an arm and part of a leg.... as the DTI was built-in, not detachable like these modern ones. I last used one at work 30 years ago, but used one regularly when I was a lad. It will be nice to have one to use when boring my cylinders now.
But whatever comparitor is used, it needs to be carefully compared to a set gauge, whether an outside mic, ring gauge, or other .... The technique of making the comparison is the skill that doesn't come in a box. That's the bit where we should help Bob, and anyone else.
Thanks for the pictures of all your kit. Far more than I need. I guess you have the test bars and gauges for calibrating them as well.
Cheers,
K2

 

[CFLBob]

There was one scene in that Abom79 video that ShopShoe posted that made watching the video 100% worthwhile. He was showing how he checks the fit of the telescoping gauge in his micrometer. The trick was it sticks on its own, but the tiniest touch makes it fall out. That's at the 11:53 time mark. A minute or two on either side to that time mark is the meat of it.

 

[Brian Rupnow]

Bob--I use telescoping gauges all the time to measure the inside of things I am turning, and measure the results with my micrometer. I generally take three readings and then average them. Readings will be directly affected by how much you paid for the telescoping gauges. I always have some cold rolled round stock kicking around my shop. If I do get a taper inside a cylinder I chuck up the round stock (1" in this case) in my lathe chuck, dab some 600 grit aluminum oxide paste on it, then turn the lathe on relatively low speed and hold the cylinder in my hand, working it back and forth about 2" overall on the round stock. That will quickly take out any taper. You can feel the tight spots working themselves away while you're doing it. Just make sure that if it sticks, don't fight it---let it go. You don't want to get wound up in your lathe. If it does stick tight, take it over to your press and press the round stock out.