Micrometers
 

I've been looking at mikes and am puzzled by that market relative to Porsche's specs. Most of the Porsche specs go to .001mm, but 99% of the metric mikes our there only read to .01. How to deal with this? Better to go with inch mikes going to .0001 and convert between the units?

I convert, but when you get this fine you better have a good set of gage blocks or the mic is useless.

And have a climate controlled room.

Two words: Mahr Millimess.

Mititoyo carry sets of mikes that go to 4 or 5 decimal places in Metric.
They ain't cheap...but if you need the accuracy pay the money.
On the good side...they will last a lifetime.
BUT...be advised...there are people out there that will try to borrow them...and not treat them as well as they should.
I had a friend (past tense) that borrowed one of mine...a 3 -4" one....and a month later I went to get it back and found it laying on the dirt floor of his garage...rusted!!
Made him buy me a new one...he damn near had a heart attack at the price.
Bob

Specs
 

I struggled with the same issue until I realized that I could reasonably estimate a measurement to 0.00x mm using my 0.01mm Mitutoyo mic's.

Although a 0.01mm mic has accurate measurement marks to 0.01mm - most provide a means to estimate if the measurement is closer to 0.001, 0.005 or closing on 0.01.

Also, as mentioned above, accuracy greater than 0.01mm would be a challenge for most "garage" quality measure tools and non-lab environments.

Another point - although specs go to 0.00x mm - none that I am aware of call for a non-zero x value, i.e 0.003mm vs 0.005 mm... They all spec to the 0.01mm point. For example - crankshaft main journal wear limit is 59.960mm, which is measurable with a 0.01mm mic...

Gordo

Thanks for the advice everyone. I had thought about the climate controlled room at that level of accuracy, but then again we don't know what temp the specs were taken at:), being Germany, probably cold.

Standard measuring temp for a German tool room is 20C.

http://forums.pelicanparts.com/uploa...1249571079.jpg

http://forums.pelicanparts.com/uploa...1249571379.jpg

Hahaha

Also happy with my Mitutoyo digital set.

Hahaha, lol@ John!...where did you dig those diagrams out from?

S

If you want pictures or diagrams for the ultimate in measurement...try the areospace industry.
I remember seeing some of ultra-clean rooms...men in white suits with breathing gear...and surgically clean everything.
The accuracy was to the millionth of and inch I think.
Talk about going to the extreme....LOL
Bob

I kid you not, that is actually a diagram from the Mahr-Federal calibration lab in Providence, RI. They have a climate controlled lab that is anchored to the bedrock just as you see in the diagram- so it is isolated from the vibration of the wind, passing cars, temperature changes, etc. This is where, if you send them an instrument for calibration back to reference standards, they do the work. I can only imagine what it costs . . .but if it matters. . .

What Porsche specs require accuracy to .001mm? That's 0.00003937". Latest PAG space shuttle?

.01mm is equivalent to 0.00039". That's pretty good.

BTW, .1mm is the spec for normal valve clearance (0.0039")

FWIW:
A Facom 1300 digital vernier caliper reads to 0.01mm accuracy and costs about $500.00
A Mitutoyo 0-1" Bench Mic Comparator is accurate to 0.0001". $2,899.00 on eBay.

Please check the decimal place. Your post might discourage folks from rebuilding their engine.

Sherwood

^ those are crazy accurate numbers, you cough on it and it changes, my surface table 24"x36" is only accurate to .0001 across the span close enuff

Yes, except that Mahr Millimess is a comparator, not a micrometer.

http://forums.pelicanparts.com/uploa...1407537444.jpg

? That Facom caliper is far cheaper than that from one of the UK's leading electronic component suppliers --->
Buy Calipers Facom 1300E 150 mm Digital Caliper ,Imperial or Metric Facom 1300E online from RS for next day delivery.

...and a digital Mitutoyo 0-25mm mic with 0.001mm resolution, from another authorised UK dealer, is also very temptable money --->

Mitutoyo Digimatic Micrometer 0-25mm / 0-1" with Ratchet Stop

I visited the above company last year when looking at DRO's for my lathe...it's like Aladdin's cave (except not a cave)....so much stuff in there I could've blown a few months disposable income on!

What Porsche specs call for .001mm accuracy? How about crankshaft main journals 1-7? 59.971-59.990mm (2.3610-2.3618"). Or rod journals 52.971-52.990mm (2.0854-2.0862")? Source? Porsche's spec book, Wayne's book.

I did a lot of looking/studying/absorbing before I bought my Fowler micrometer set. This guy gives a nice explanation of the options and different brands. For what I will ever use them for, my fowlers are fine. Good down to .001", you can infer the closest mm after a bit of conversion. I'd love a set of gage blocks and will probably borrow some when follow through with measuring the stuff Bruce Anderson says I should in his engine rebuilding workbook. I simply could not justify paying for a set of Mitutoyo for as must as I will ever use them. Heck, after my engine rebuild, I'm pretty sure I won't touch them until I tackle my next Porsche.