Measurement equipment

[Ryan]

After discovering I was getting pretty inconsistent readings with a cheap $30 ebay Digital caliper. decided I should invest in some decent measurement equipment.

I have read advice that old school vernier calipers and micrometres, no dials or electronics to go out of calibration are every bit as accurate as their electronic counterparts. would I be correct that if you have some accurate standards like gauge blocks or setting standards then you can simply verify and adjust your mechanical micrometres at home. with electronic,well aapart from sending them to a professional calibration service there is not much a hobbyist could do?

I nearly died at the price of some top brand of electronic calipers and micrometres but thought, the price of the mechanical ones are not too bad.

I'm thinking Mityutoyo because that seems to be the most readily available brand in Australia. Perhaps 200mm vernier calipers, 25mm and 50mm outside mics and to measure internal diameter simply use inside spring calipers and take the measurements off them with the micrometres? anything else I am overlooking?

 

[aarggh]

An analog DTI/TI is handier than a digital one in my opinion as you are generally looking for deviation, and an analog DTI/TI will immediately show deviation, whereas a digital one will have lag displaying the readings. For calipers though, I believe a digital one is better than an analog for ease and simplicity. I have tried quite a few calipers and DTI's of various types and prices, and generally I've found issues with repeatability with most of the cheap ones. Enough that you don't get the same measurement twice, and the dial doesn't always return correctly. I ended up with some second hand Mitutoyo's and love them. One thing I would very highly recommend is to buy some standards in a range of sizes as thy come up on ebay. Standards are a precision rod that allows you to calibrate calipers and dial indicators so that you know if what you have isn't measuring correctly, or how much you need to add/subtract when measuring. They are usually Japanese, most available are Mitutoyo that I've seen. But I will say they are just invaluable. Nothing worse than not knowing if your precision measuring equipment is accurate!

If you can only get one of each, get as good a quality DTI/DI, and caliper that you can, and treat them as though they are priceless so you can always be assured of their accuracy and longevity.

cheers, Ian

 

[Tin Falcon]

After discovering I was getting pretty inconsistent readings with a cheap $30 ebay Digital caliper

In my experience +- .002 in is typical fine for many measurements on a model but not for pistons and cylinders.

decided I should invest in some decent measurement equipment.

I prefer Used starrette buy nothing wrong with mitutoyo.


Sounds like you are mostly on the right track. gauge blocks will keep you on track no need for outside labs in a home shop.
you only need to make sure your various instruments agree.

a 25mm mic and a set of dial or verier calipers should serve you well.

You only need a 50mm mic if doing larger than 25 mm bore on an engine.
You may want to add a height Gage ,surface plate and angle block for layouts.
Tin

 

[Ryan]

something I didn't think about. is no big deal to use metric micrometres when working from Imperial plans?

 

[Swifty]

Strange as it may seem, lots of machinists / toolmakers made do for years using micrometers and vernier calipers and produced very accurate work. I recall the first time that I used a dial caliper and later a digital caliper, it was all downhill after that, I got lazy and preferred the new verniers. Accuracy was not improved at all, probably just saved a few seconds on measuring.

I wonder how many machinists these days can read a proper vernier caliper.

Paul.

 

[chrsbrbnk]

I'm a tool and die maker and hardly anyone (except the excessively cheap) uses dial calipers except in the 12" the biggest problem with them is dirt in the rack and being dropped . the digital even the cheap ones are just tougher. all measuring tools wear out!! so don't go buying some ancient starret or brown and sharp mic. except for a paperweight . there's sort of a rule where your measuring tool ought to be several times more accurate than the part your measuring . so like a caliper is starting to get pretty marginal if you looking for +or- .001. thats kinda why they sell mic.s . most important is sit down with your measuring tool and like a set of gauge blocks and gauge pins and learn how they feel to measurement .

 

[gus]

Here is my 2 cents worth.

I have given up measuring cylinder bores with Mitutoyo or Starrett Digital or Vernier.It is a struggle to get a good reading with two contact points. A slight shift would give varied readout.
Was boring the cylinder for Webster IC Engine,I used a three point Holtest Inside Micrometer and got a good reliable reading. Was able to bore to print------spot on. The Holtest Inside Micrometer came in a set of 4 piece. China made.Finishing was comparable to Mitutoyo.
Mitutoyo quoted me US$2080. Bought Chinese Holtest from Arceurotrade.UK for US$510 landed in Singapore.
I found Outside Micrometer best to measure OD. When turning critical ODs,I have stopped use Vernier or Digital Calipers as I get varied readings.

 

[Anko]

I use a cheap dial caliper, I checked it agains some gage blocks in five points of the scale and I got a margin of about +/-0.02 mm, not bad for the price.

For presision instruments you can get very lucky with chinese stuff, but you have to inspect what you are getting frist, of course you will never get the smoothness and quality feeling of a brand name instrument.

As for brand names, I heard that Starrett is now making some of his products in China, also Moore & & wright seems to be now onle cheap chinese stuff with logo (please correct me if I´m wrong).

Mitutoyo would be my choice.

Saludos

 

[tornitore45]

I have
1 Mitutoyo Digital
1 Mitutoyo Dial
2 Chinese Digital
3 Chinese Dial
1 German Wernier with a 50mm nonius

3 Vintage American Made Micrometer
1 Chinese Micrometer
1 Chinese Micrometer with the mechanical counter

ALL of the Calipers repeat to 1/1000 on a gauge block regardless of origin
ALL Micrometers repeat to "the right line" if they are off 1 tenth I can not tell for sure. I could see 3 tenths even with my poor eyesight.

For OD I use the caliper until I am about 0.020" over and then switch to Micrometer so I am in the same or at most in the next 25/1000 division and dumb ass reading error are harder to do.

I woulod trust my calipers to 0.002 if had no micrometer.

 

[Tin Falcon]

something I didn't think about. is no big deal to use metric micrometres when working from Imperial plans?

That my friend that is a decision you must make.
the whole metric conversion translation adaptation subject has been discussed here probably a dozen times.

All my machines and all but one micrometer I have will measure in imperial units and that is the common material size so that is what I work in.

if you machines and local material sizes are metric that is probably the route to go.

as far as converting plans from imperial to metric you have three choices.
1 simply do the math multiply the dimension in inches by 25.4 to get a true conversion.

2 Scale the model up make 1/32 in = 1mm

3 scale the model down and make 1/16 in = 1 mm

Tin

 

[Hopper]

If you want accuracy and reliability, get the Mitutoyo or similar quality mechanical micrometers. The larger ones usually come with a test bar for setting.

Calipers are handy for depth measurements and length measurements etc but it is very difficult to get as good a "feel" with them and hence often not as accurate as mikes.

 

[Ryan]

what do people seem to find more useful in model engineering. 0.01mm graduation or 0.001/micron graduation indicators?

 

[rodw]

what do people seem to find more useful in model engineering. 0.01mm graduation or 0.001/micron graduation indicators?

I am only a noob but I have been setting up a DRO and recently purchased a TESA 0.002mm indicator but for this project I went back to using my cheap Chinese 0.01 indicator.

 

[OrangeAlpine]

Not only are all machinists not created equal, their eyes are not either. I find that vernier calipers are almost impossible to read. I know how, my eyes just will not cooperate. Same with Starrett mics. Nothing wrong with them, my eyes just do not correctly see the line alignment. As a result, I use dial calipers most of the time. When they are not good enough, I use my Lufkin mics. Calipers are no better than your technique. I find they agree with the mics down to one thou.

No one has mentioned the telescoping gauges for measuring bores. Cheap and give readings as good as your and your primary measuring device.

Bill

 

[Tin Falcon]

A couple more thoughts.
get mic with the fine reading. You may not always need it but there when you do.

Verier are fine. and IMHO reading a verier is a skill all machinists should learn. In USAF tech school that is what was in the tool box. some of us had and brought our own dials to class.

I think the main appeal of the digital calipers ie ease of reading there is no math no counting lines etc.

when my son was young I tough him to use verniers only after he took a measurement and did the math was he allowed to use the digital as a check. same thing with math do the math and then check on the calculator.

Like others have said even the cheap import stuff can be good. but the only way to know that is try before you buy check the feel and accuracy in the store.

Tin

 

[Paulsv]

I just broke down and bought a Mitutoyu digital micrometer. I have a Starrett analog micrometer, but it was becoming a PITA to read with my old eyes, especially when miking something that was held in the lathe or milling machine, so that I had to read it at a funny angle, or in less than ideal light. Also, I like the fact that with the digital, you can read either imperial or metric with the same mike. I have a mitu dial caliper that I like, and that seems to give me very repeatable measurements, if I am careful, but I think I will ask Santa for a mitu digital caliper next Christmas, for the same reasons.

 

[Paulsv]

No one has mentioned the telescoping gauges for measuring bores. Cheap and give readings as good as your and your primary measuring device.

Bill

The problem I have with telescoping guages is in measuring the guage after I have guaged the hole. Hard to manipulate the guage and the mic, and get repeatable readings off the guage. Any secret to this, or tips anyone can give me?

 

[Swifty]

The problem I have with telescoping guages is in measuring the guage after I have guaged the hole. Hard to manipulate the guage and the mic, and get repeatable readings off the guage. Any secret to this, or tips anyone can give me?

After using the gauge on the bore, I always hold the gauge by the plunger end and aim to get the same feel on the micrometer as I did on the bore. Move the micrometer around slightly to make sure you have the highest point, this helps if using gauges that may have a slight flat worn on the end.

Paul.

 

[Goldflash]

The problem I have with telescoping guages is in measuring the guage after I have guaged the hole. Hard to manipulate the guage and the mic, and get repeatable readings off the guage. Any secret to this, or tips anyone can give me?

With using Tele gauges the trick I was taught in the air force was to take 4 0r 5 measurements and then average out the readings which will be reasonably accurate. ( you can normally get a reading that is accurate to 0.0005" or 1/2 a thousandth of an inch which is close enough for most work.
The hard part is when you are measuring a deep bore and trying to see if the bore is either parallel or tapered depending on the final result that you require.
I still have my Mitutoyo Micrometers and Verniers etc that are 30 years old and as good as the day that I bought them.
My eyes aren't as good as they used to be and sometimes I find a head magnifier really usefull for taking readings and checking surface finish and assembly of small components.

 

[Bastelmike]

I would trust my calipers to 0.002 if had no micrometer.

Agreed. Except the 3€ plastic ones I use to check the size of screws.
With my best brand quality ones measurements are repeatably correct within +- 0.001"

For OD I use the caliper until I am about 0.020" over and then switch to Micrometer so I am in the same or at most in the next 25/1000 division and dumb ass reading error are harder to do.

When working on the lathe, my practice is similar. When machining good fits, I turn them down to 0.3-0.4mm oversize using a caliper and then start using an OD mic for final cuts.

If tolerances of 0.1mm or more are acceptable, I only use my better calipers on the lathe.

Mike