Micrometer

[thiggy]

I know what the basic tool is, but what I would like to know is what the shape of the spindle is intended to be for.  My other mikes all have the same size spindle and anvil.  thanks for any information.

[oldgoaly]

my guess is it had multiple tips for measuring threads & other things

[lptools]

Hello, Is there a number on the back of the frame?

[leg17]

Customized for application.
You had to be there.

[thiggy]

It is a Starrett  No. 230, Oldgoaly.

[turnnut]

perhaps someone machined the end, why ?  only they know ? a finer feel ?

if it was for adding diff. types of attachments, you would have to recalibrate every
time you changed tips. and that is down time.

[Lewill2]

I have 2 old Starrett catalogs, in both catalogs a group picture of various micrometers in the beginning of the micrometer section appears to show one with a turned down spindle end but I can't find anything in the details in the micrometer section of the catalog that offer it as an option. I think both catalogs are from the 1930's era. 

[Billman49]

Micrometers usually have hardened steel, or even tungsten faces - impossible to turn down, so this is a factory made tool. Thread micrometers often have Vee shaped anvils. I guess this is a special for a one off usage....

FYI in France they are known as Palmers.... (ex Wiki:The first documented development of handheld micrometer-screw calipers was by Jean Laurent Palmer of Paris in 1848)

One of the first was by James Watt in 1772...

[Billman49]

At the beginning of the 19th century Henry Maudslay  built a bench model, referred to by his staff as the 'Lord Chancellor' - as it was the final judge on measurement in the workshop. In 1840 Joseph Whitworth in the UK built one accurate to one millionth of an inch....

[leg17]

Micrometers usually have hardened steel, or even tungsten faces - impossible to turn down, so this is a factory made tool.

Not necessarily.
Any shop with grinding equipment can modify as shown.
Every shop I have worked in had at least one modified mike.
I have several myself.

[Billman49]

Agreed, grinding would be the most likely way to alter the tip, if not the only way..

[oldtools]

Maybe the hardened anvil tip came off  & that is just retainer it was mounted on,,,

[Bill Houghton]

Is the spindle touching the anvil when the mike's zeroed out?  If not, then one of the theories in this thread - that it had a permanently installed tip that's gotten lost (which has my vote) or that it took attachments for specialized use - seems likely.

[leg17]

Is the spindle touching the anvil when the mike's zeroed out?  If not, then one of the theories in this thread - that it had a permanently installed tip that's gotten lost (which has my vote) or that it took attachments for specialized use - seems likely.

Carbide tips are cemented on flat.

If you look at the picture, you can see the mike will about zero out when closed.

You all are making this WAY too complicated.

[oldtools]

"If you look at the picture, you can see the mike will about zero out when closed."

Good point,  maybe designed to measure wall thickness of "O" ring grooves.. (ID)