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What measuring tools do I need?

squale

Cast Iron
Joined
Aug 10, 2004
Location
NY, USA
I am looking into learning how to measure parts for our machinest to cut. These parts are usually no bigger than about 6" long, and sometimes square with holes in them, other times round, sometimes angled, etc. They are both metal and plastic. I was wondering, what are the basic measuring tools I need to be able to take the measurements of the parts and then I can draw the parts in CAD such as Solidworks.

Could somebody please help me out with this. Also if there is a good place online to read about how to use these different measuring devices that would be very helpful. I keep seeing a lot of talk about 'Calipers' and 'Micrometers' online. Who makes the best precision measuring tools? And should I get digital or dial guages?

Thanks for the help!
 
My answer, is going to be somewhat convoluted but it is going to depend on the tolerance of what you expect to receive.

For example, if you are expecting .0002" precision and are using a dial calipers, this won't turn out well.

For "general" use I find a dial caliper to be good for most projects, I'd argue that the expected precision is .002" and it is definitely high on the speed chart.

Closer tolerance objects such as bores that have to fit pins, have press or controlled slip fits are better measured with micrometers and telescoping gages. I'd argue you can get within .0005" with decent tools.

I strongly prefer the Starrett brand, but there are other brands with a reputation of quality and accuracy.

-Matt
 
I need to get to .005 precision. Yeah I see the Starett brand has many tools, are they about the best made?

are there any sort of KITS I should look into getting?

also, how do you measure round corners like fillets and chamfers, and also how about arcs and radius's?
 
.005 is pretty easy to measure even with the cheapest brand of calipers or micrometers - just be sure to have some sort of "standard" available to check them against periodically.

Fillets and radii you can check with radius gages, sold in sets, by matching the gage with the object by trial and error until you find the one that is the best match.

You can probably find everything you need on ebay.

BTW...when you get what you need, you might want to consider checking your measuring equipment against that used by your vendor/customer, so that you both can be in agreement on the dimensions.
 
Squale
Your ignorance is about where mine was a few years ago. I don't say that as an insult, ignorance is curable and the more I know about the question your asking the more I realize how complex the subject is. I would suggest that if you have access to a machinest that you sit with him awhile and have him show you how to measure the part that you are trying to draw. Metrology is a field in itself and what your asking is for someone to teach you to do it in a few sentences what they have spent years learning. I would suggest that if your trying to duplicate parts that you will need calipers, micrometers, surface plate, height guage, rule, some clamps, angle plate, protractor, and a lot of hours learning how all these items work together. I'm not sure if Starrett is still selling books but they used to have training aids that would help you learn to use the tools.
Good luck
lg
no neat sig line
 
thanks for the replys, yeah a lot of the parts have holes in them, screw holes, some gear teeth, etc. What are the tools called that measure the size of the holes, screw holes, thread sizes, etc?

it seems that a digital slide caliper can do MANY different types of measurements, so it seems that is probally the most used tool huh? for instance, anything I can see a micrometer doing, I think you can do with a slide caliper right?
 
anything I can see a micrometer doing, I think you can do with a slide caliper right?

Except measure accurately to closer than .003" or so...

The more accuracy you need, the more tools (besides your basic dial or digital caliper) you will need.

And regarding digital vs dial (aka "manual"). You'll be better off learning how to read the dial "manual" type instruments quickly and accurately.
Digital is great for some of the things it can do with the push of a button, but getting your brain wrapped around the mental math to read, add, subtract, and divide (etc) with a manual is more useful a skill to have!

Sounds to me like you'd be well served with;
a 6" dial caliper (possibly an 8")
a 0-1" micrometer
a 1-2" micrometer
a 2-3" micrometer
a surface plate
a dial height gage
a set of radius gauges.

At least as a good healthy start.
Add bigger mics later. Maybe some digital tools, and maybe a couple dial indicators.
There are a quite a few good makers of all this stuff.
It would be hard to go wrong with Starrett or Brown & Sharp though.

All this is just my opinion...
Paul F.
 
do you have a link for a a surface plate and radius gauges? I don't know what these things are and what they are used for....

with the above tools you mentioned, could I measure screw holes, thread sizes, and just regular smooth holes? how about gear teeth?
 
Squale, your best starting point might be to go to ebay, or other suitable suppliers, and purchase a few books on basic machine shop and mechanical inspection practise.

Ask here for recommendations for specific titles and authors.

These books are cheap, readily available, and will show you the standard techniques for interpreting drawings and measuring/inspecting your workpieces.

The generality of mechanical inspection work is pretty straight-forward, but there are commonly accepted practises and standards you must learn in order to communicate clearly with suppliers and clients. The work involved in adequately inspecting gear teeth, for example, requires a basic knowledge of the terminology of gearing, and at least basic 'over-view' understanding of the existing standard practise in that field.

You really should, in my opinion, take the time to learn 'fits and tolerances' generally, to develop at at least a generalised 'over-view' understanding of the reasons for the levels of fits and tolerances needed or specified in your particular applications. (and being able to sound knowledgeable about technical this-and-that will impress people sometimes....thats the famous old tradition of 'an ounce of image is worth a pound of performance'...... : )

cheers

Carla
 
Hmm...
Add a thread gauge (for finding the number of threads per inch...)
And, a copy of Machinery's Handbook for every standard thread dimension known to man.

Gear teeth..well... I'll leave that to people who know more about measuring those than I do... (the average cocker spaniel for example...).

A surface plate is basically a very smooth, very flat peice of granite. It gives you a known FLAT and SMOOTH surface to measure from. The height gage is a lot like a caliper on a stand that measures from that surface plate to things.

Radius Gauges are pieces of steel with a radius machined onto them... they're an "eyeball measure" of a radius... you hold the gauge against the unknown radius, and see if it's the same.. if not, you grab the next radius gauge in the set.

Get a hold of an MSC catalog, or Travers Tool, or Reid Tool, or any of a dozen others, and just spend some time looking through the measuring tool section. You learn a lot looking at the nice toys! :)

Paul F.
 
the machinist I know uses Mitutoyo brand tools.. are they a big, good brand?

those hole guagues that look like a T, do you put the long end into the hole to see the diameter of the hole?
 
Yes, you do.

Inside where the "T" intersects are two angled mirrors, just like inside a periscope. You take off the screw cap, look down into the long end, and there will be a direct reading of the required distance across the T. You can set them to inch or metric, too.

It is so cool !! :cool:
 
Yes.. you CAN do a whole lot of things with a caliper..
But that does not always mean that the caliper is the most ACCURATE way to make the measurement.

Paul F.
 








 
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