Old Pratt & Whitney Supermic Help

[toddsilvey]

I was a machinist for 17 years, and have read many micrometer scales and vernier scales and dials but I'm really struggling with knowing how to read this guy here(picture below). I can't find anything on how to read this scale. My trainer isn't explaining it in a way I can comprehend, feel like I need a book called old vernier type dials for dummies sheesh. I think it's a model A and is considered obsolete by P&W but we still use it on rare occasions and I really have to be able to read it on my own. It's making me feel really old because my brain just isn't having that AHH HAA moment yet, i'm just not getting it. Hoping somebody on here can explain it better or differently than my trainer or maybe has access to a pdf manual or something. It's supposed to be 5 place (.00001) and the current reading is supposed to be slightly off my zero mark. (.99999) I think the big wheel on the left is out of alignment so that's not helping either. I see that the the 0 to 10 scale on the right is lined up on the 9 and then I'm lost as how to get the rest. I may not even be explaining why I can't make sense of it well either. Any help would be appreciated.

 

[Clive603]

Verniers laid out like that always look wrong but the reading process is the same as a normal one.

Left hand dial, 100 spaces, two digits 00 to 00. Reads 0.00 but mis aligned relative to arrow.

Second dial, 100 spaces, single digits with intermediate slashes. Reads -.- - 08 slash aligns with the vernier.

Vernier, 10 spaces, digits 0 and 1 with intermediate slashes. Reads -. - - - - 9 vernier slash aligns with dial slash

Reading 0.00089

Only way I can make sense of such is to do it backwards by sorting the right hand scale and its vernier out first then mentally add in the two digits from the left hand dial.

I imagine things are written that way so the right hand pair behave like a round version of a normal vernier caliper.

Hafta say there was reason why digital displays were invented.

Clive

 

[toddsilvey]

OK so you are saying the current reading is .00089? With what you are saying I think I got it. I have one more pic and I'll read it and if you have time or anyone else sees it maybe they can tell me if I'm correct or not. Thank You so much, the AHH HAA moment is near and you are right it is pretty much the same as other vernier scales in it's own way. Have to agree about why we have digitals now. The supermic I use daily is digital but only does up to 10", the old one does up to 25".

Reading= .95046 ????

 

[Clive603]

Looks good to me. I think you have it now.

Clive

 

[eKretz]

No, I don't think so. You guys are both off as I read it. The first image in the original post shows a reading of .00998" or .00999" - it's sort of in between, but closer to the 9.

Second image in post #3 is .95986" - you guys are missing the reading of the 3rd and 4th digits.

For example on the last image, the first two digits are directly read from the left dial - .95. The next two digits are read from the second dial. The first of those comes from the major number on that dial, IE in this case it would be 9. The next digit comes from the lines, and you get that from which one lines up with the zero on the vernier. In this case it is between 8 and 9, so you use the smaller of the two, hence 8. Last digit is read from the vernier, and that is whichever one is aligned. In this case that is 6. So you have .95986 as the reading.

If the first major dial is off, all bets are off. Either get that fixed or there should be a label attached in the dial area that mentions the necessary compensation.

 

[toddsilvey]

head goes back down, fingers rubbing forehead... F@#$%!!!

 

[eKretz]

It's really not that complicated. Just a multi-row dial until you get to the last digit. Just remember to count up on the dial, and that your 4th digit comes from wherever the "zero" on the vernier coincides with the left dial, *not* the digit that lines up with where the vernier coincides with a line from the previous dial.

 

[John Garner]

Does the leftmost "wheel" move continuously or incrementally? If continuously, I'd expect the index's would indicate more-than or less-than. If incrementally, I'd want to know what the second wheel's position is when the first one indexes.

 

[toddsilvey]

It's really not that complicated. Just a multi-row dial until you get to the last digit. Just remember to count up on the dial, and that your 4th digit comes from wherever the "zero" on the vernier coincides with the left dial, *not* the digit that lines up with where the vernier coincides with a line from the previous dial.

View attachment 409602

ahh I see it now, thanks for drawing me a picture(unfortunately it takes that sometimes). So basically the zero on the right(the bottom of the vernier scale) is pretty much doing what arrow on the left is doing.It's not quite on the zero so it falls back to 9 then you also have 9 more lines, that's the 4th digit (9) and then it's basic vernier scale which line is the closest, 9 again.

Alright I even went back to my other picture without re-reading what you wrote it was so I wouldn't be biased and wrote down what I came up with =.95986 and scrolled back up and it matches!! Thanks a lot for taking the time.

 

[eKretz]

ahh I see it now, thanks for drawing me a picture(unfortunately it takes that sometimes). So basically the zero on the right(the bottom of the vernier scale) is pretty much doing what arrow on the left is doing.It's not quite on the zero so it falls back to 9 then you also have 9 more lines, that's the 4th digit (9) and then it's basic vernier scale which line is the closest, 9 again.

Alright I even went back to my other picture without re-reading what you wrote it was so I wouldn't be biased and wrote down what I came up with =.95986 and scrolled back up and it matches!! Thanks a lot for taking the time.

Yes, now you've got it. You're welcome.

 

[toddsilvey]

Does the leftmost "wheel" move continuously or incrementally? If continuously, I'd expect the index's would indicate more-than or less-than. If incrementally, I'd want to know what the second wheel's position is when the first one indexes.

sorry but I'm afraid to even answer you after having the ahh ha moment twice now. You say something different I'm liable to jump off a bridge!

 

[toddsilvey]

Yes, now you've got it.

It made sense finally, when it makes sense it's the only way it can be. It really is how most vernier style scales work. 1 digit at a time! thanks again. Now that I can read it, I get to practice mastering with 24" of gage blocks to measure a 24" length standard.

 

[eKretz]

sorry but I'm afraid to even answer you after having the ahh ha moment twice now. You say something different I'm liable to jump off a bridge!

I think he just wants to know if that first dial moves gradually in proportion to the others or if it "jumps" position to position like an auto odometer. Looking at your photos, I'm guessing the former.

 

[toddsilvey]

sorry but I'm afraid to even answer you after having the ahh ha moment twice now. You say something different I'm liable to jump off a bridge!

Yes it is gradual, doesn't jump and thinking it's off a bit too.

 

[eKretz]

Yes it is gradual, doesn't jump and thinking it's off a bit too.

Yes, if that first photo is with the mic set on a .99999 block, it is very definitely off.

 

[toddsilvey]

Yes, if that first photo is with the mic set on a .99999 block, it is very definitely off.

Yeah this whole thing leaves a lot to be desired, they nicknamed the thing "the dinosaur". It's only being used on rare occasions to do comparative measurements of longer than 10" length standards. I'm new so I try not to rock the boat too much, but this thing did get me pretty heated thursday and they realized I needed more time to practice on it. Now I can at least go in tomorrow and read the damn thing. Sometimes I'm not exactly sure why I got out of machining, haha!

 

[gbent]

Get it properly calibrated before starting or you will make a mistake that matters. The .XX digits need to be properly aligned with the pointer. Even if it's dead on away from zero, that device is out of calibration.