Useful Dial Indicator Range

[Joe Piro]

First the question: Why do almost all the YouTube videos demonstrate with 1 inch stroke dial indicators when they are measuring a few thousandths?
Even the popular Fowler brake rotor measurement kit comes with a 1 inch stroke dial indicator. There must be something I don't understand...?
And this is my situation: I am shopping for a dial indicator to set up my VW Jetta clutch. The VW Jetta TDi DSG Transmission wet clutch pack comes with a pack of 10 retaining clips of varying thickness (see photo) and you measure the end play with a dial indicator (another photo) and select the retaining clip that meets the spec. So we're measuring a few hundredths of a mm.
In the Volkswagen training video they used an indicator with 1 mm dial with .01mm divisions and it had a ten revolution stroke of ten millimeters,
In the future I'll probably do this same job again as well as measure brake rotors and possibly set up gear lash in a transmission or rear end.
I'm going to switch the discussion to inches because I can visualize it better.
Wouldn't it be better to buy an indicator with a 1/4" range (or even 1/8") with .0005" graduations and + or - .0005" accuracy (per Mitutoyo) ? (They also sell 1/2" stroke indicators with .001 divisions which is plenty for these applications i suppose.)
I like the idea of a one revolution indicator but I can see that might be hard to zero on a magnetic stand like the NOGA I bought to do this job.
Please share your opinion on useful range. Thanks guys !

 

[robert6715]

0 to 1" are a lot easier to set up. You set your indicator holder by hand with the indicator depressed about halfway & lock it down, then re-zero the dial, done. Very quick & easy. Takes about 15 seconds. Most jobs just don't need accuracy to the 4th digit.

 

[jayemm]

If it's used frequently the 0-1" are easy to set up as mentioned above. The other part is a good magnetic (or clamp on style depending) indicator base. The snake like Starrett or the Noga or Noga style were my favorites. Cheap bases ****. For my very infrequent need to measure very small displacements I have a small economy 1/4" travel/ 0.0005" indicator. Cost me all of $15 from Shars Tools a few years back. They have a website and ebay store.

 

[rsanter]

It’s a machinist thing
The typical micrometer and dial indicator has a 1 in range
Sure they have ones with longer and shorter but that’s the basic.
There are also run out indicators you can get, those have a small range

 

[Xcursion88]

I don't understand why you seem hell bent on a shorter than 1" travel

The 1" is pretty much standard of the industry because it gives the most flexibility when setting up. Sometimes angle, position, etc ...require a travel of let's say .600

Once set and zeroed now you have an additional four hundred thousandths to work with

As far as increments....
There is absolutely nothing in the automotive world that requires getting a threshold or tolerance down to the ten thousandth (.0005) like in your example.

.001 (thousandths) is certainly suffice

 

[MBfreak]

There is another measuring instrument available when the 0,01 mm resolution is not sufficient.
It is called (in Swedish) Microcator and has a resolution of 0,001 mm but the range is very limited , 0,05 mm .
Great for checking crankshaft runout and a million other high precision jobs
But on modern lathes, mills and grinding machines it is all built in.
Ola

 

[MushCreek]

I have indicators ranging from .008" range up to 2" range. As said, the longer range is less fiddly to set up. My 2" indicator is a cheap Chinese one, yet when I tested it with gauge blocks, it was out less than .001" over it's full range. They make digital indicators with an accuracy of .0001" over an inch travel, but they ain't cheap.

 

[bob15]

Do you really think 5 tenths is going to matter on your clutch set-up?

Serious question, have you ever used a 1/4" travel drop gauge? They can be a PIA to set-up.

 

[dutchgray]

Do you really think 5 tenths is going to matter on your clutch set-up?

Serious question, have you ever used a 1/4" travel drop gauge? They can be a PIA to set-up.

Yep just get a 1" travel DTI and be done, you can get them in 5 tenths or better, they just cost more. For this application a cheap import would do just fine.

I got a 125mm travel Starrett which is nice to have especially as my machines have no DRO's at present but the instrument is long and unwieldy to use.