Micrometer help

[Kane]

Hello
I've not had much use out of my micrometer so far, so i thought now that im needing to use it, i better learn how ;D

well anyway ....
i know how to read it, but its converting the numbers thats the problem (brought up with silly metric's not imperial)

right say i have a reading of .587 .. how would i convert this to the closest imperial reading?

and likewise ... say i had a measurement of 5/32" to convert this to a "micrometer reading" all i have to do is divide 5 by 32? = 0.156

does this mean i need to keep a calculator in the workshop?

[Geoff]

Hi Kane,

Although other members will no doubt have their pet ways to do this, I have a drill size chart on my cupboard door. The chart has Number and Letter drill sizes, Imperial sizes and Metric sizes. Therefore it's easy to look up either your mic reading (0.587 or whatever( 0.500 is 1/2 inch, plus 0.087, the nearest fraction of which is 3/32 inches (0.0937), so therefore a total size of 19/32nds) or the fraction size you need to machine to. Or the Metric size of 0.504 =12.8mm, plus 0.0827 = 2.1 mm, total 14.9 mm. OK, I know this is 'rule of thumb', but for me it's a fair indication of the actual size!

Don't think I've ever used a calculator.

Regards

[alanstepney]

there are many charts that show the imperial measurements, with fractional, and metric equivelents.

Look out for one, and pin it on the wall.

Much easier than a calculator.

[Kane]

thanks guys

will keep a lookout for a chart

[Ianb]

Kane,
I inherited several micometers from my dad including 1",2" and I think I've still got a 3". Now that I'm getting older and seeing fine divisions needs a level of lighting that is probably visible from Mars, I abandoned them all and plunged for a digital caliper from Machine Mart (usual disclaimer).

For less than £30 it is brilliant. It converts from inches to metric at a touch of a button and in inch mode reads to four decimal places. It does internal as well as external and has a depth gauge. Alright it's not going to be quite as accurate as a micrometer but with my standard of machining it is more than adequate (I work to the old standard of + or - the thickness of an old penny). After about a year of use it went dead on me. I took it back wishing as usual I had kept the sales slip. With all credit to the company, the guy simply handed me a completely new one with the comment 'We've had a bit of trouble with a batch of these'. This new one has been going strong for almost a year now so it's not doing bad for the money.

Ian

[alanstepney]

There are charts of drill sizes that might meet your needs, at:

www.alanstepney.info/page8.html

[Deleted]

Dear I say this ….. Go real metric.
Regards
Wilfried Vermeiren
users.skynet.be/modelbouw.wilfried

[JohnP]

I'm sure I've mentioned this before, but here goes...
There's a quick way to convert fractional inch sizes to metric as follows.

Take the fraction (eg 19/64) and keep doubling top and bottom until you get to 256 on the bottom.
19/64 = 38/128 = 76/256
Now take the top number and divide by 10

76 / 10 = 7.6

That's your answer in mm (Actual value 7.540625)

The nice thing about this method is that "nasty" fractions (in 64ths) are easier to do.

Hope this helps.

Oh, don't for get the other rule of thumb that 1mm=0.040" (nearly)

JohnP

[Deleted]

Hi John,
Must have seen it before but it is a nice conversion method.
Another one is using 25.6 for an inch instead of 25.4…. gets rid of all the odd numbers in 1/100 of mm. ¼ gives 6.4 ( 6.35 ) 1/8 gives 3.2 ( 3.175 ) .
But for converting between fractional and thou of inch I try to remember the way Kane does it.
By the way most modern technical calculators are happy to work with fractions, ask your children they know but wont tell you until you ask. ;D
Regards
Wilfried Vermeiren
users.skynet.be/modelbouw.wilfried

[NZoldun]

Hey,

We all need a little lateral thinking here -you've obviously got a computer and Internet access, so....

Make your own conversion chart using something like 'Excel'

If you don't have Excel, download 'Open Office' from Open office .org (free). It has a very good 'Excel' like spreadsheet which also can be programmed, just like Excel

(Can e-mail it if you require)

[3405jimmy]

Buy yourself a zeuss book. You’re never alone in the workshop if you have one. Its got everything the average model engineer needs apart from the ability to make coffee.

Find one at

www.chronos.ltd.uk/

[Tim Bayliss]

Hi Kane,
I've stayed out of this one for some time and have enjoyed reading the comments. I started my working life in feet & inches & changed over to metric in the 70's.
One day I spotted an old and a young fabricator discussing one of my first metric drawings, the conversation went like this (true story!);
Old Fabby - What's these great big numbers on this drawing?
Young Fabby - aahh! They must be millimetres.
Old Fabby - Really, I've heard of them. How many of them millimetres are there in a metre then?
Young Fabby - I'm not sure, but there must be thousands!
As the previous contributor suggested 'get a Zeuss book'. You can't LIVE without at least one, I've got 3 from various decades located at strategic places.
Secondly I've found that cheap currency conversion calculators can be programmed with any conversion rate including the standard 25.4 mm to the inch metric to imperial. They only take a second to use and you get an exact conversion.
Incidentally you were correct for changing fractions to decimal inches, just divide the top into the bottom.
Best of luck & happy machining.
Tim Bayliss

[3405jimmy]

Although not much good in the workshop, I have been using this little free conversion programme on my desktop for years. It will just about convert lead into gold.


www.joshmadison.com/software/