Precision tools

[blue82coupe]

I'm in the " slow" process of a 3.0 engine build. What brands and suppliers would you guys reccomend for a dial bore guage and micrometer.Thanks, Dan

[RLJ]

IMHO If you are not going to "ever, or maybe a coupe of times" do this again you are talking about some large money, don't know your budget. take your parts to a good auto machine shop and let them do the measuring and save your money for speed parts. If I were to buy a bore measuring device it would be a three point like the Sunnen rather than an inside micrometer. Remember before I get flamed here this is IMHO.

Randy Jones
1971 911

PS........Not to seem rude just honest, they also use these tools every day and do it very well, want to learn on your own expensive part?

[blue82coupe]

Hey Randy. All points are well taken. It's not a matter of need,it's a matter of want. This engine build is exactly as you stated.. I'm learning. Dan

[ChrisBennet]

I would suggest a middle road between what you want to do (buy everything) and what Randy suggests.

I would get or at least price a set of (relatively) inexpensive micrometers. Make sure they either come with a "standard" or buy one so you can practice until you get consistent results. MSC, Enco, McMaster-Carr all sell these tools. Ebay should have them as well.

It might take you 5 times as long as a pro to measure up a crank but you will know if the crank is in spec. The last crank I got from a customer's machine shop after a $125 a "crack check and micropolish" was deemed good but measured totally out of spec.

I would skip the bore gage and have that stuff measured by a pro.
I have a $200+ bore gage and I've never been truly happy with the results. Maybe it's the tool or my (poor) technique. Alas, last time I looked, a Sunnen bore gage was several thousand dollars.

-Chris

[randywebb]

Mitutoyo has been the std. ever since they entered the market decades ago and were able to undercut the top Amer. manfs. I didn't say best...

There might be India or China brands now that are good - dunno. India more or less wiped out the Am. machine tool industry at about the same time that Mit. came in with meas. instruments.

[Grady Clay]

I agree with Randy, Mitutoyo has the market. They are to the
industry what L.S. Starrett was during WWII. I like having the
ability to check an automotive machine shop’s work to levels
better than they can do. It keeps them on their toes. Chris is
right. If NASA can put the Hubbell in orbit with 0.20 mm optical
mistake, just think what a careless crank grinder can do.

Mitutoyo has some regular hand micrometers that read to 0.001
mm (yes, that is 1 um or 10,000 A). To get any sort of
repeatability (a precursor to accuracy) you must be very careful
and have everything under temperature control. This level is
usually reserved for electronic comparisons to a high level
standard.

Note the insulation on the instruments (red arrow) to prevent
your gloved hand from changing the temperature. This one has
direct digital reading to 0.010 mm and a vernier (green arrow)
for the 0.001 decimal. The 50.000 mm standard says +/- 0 um
(blue arrow).
IMAGE ToolMicrometer01



Here are the 3-point bore gauges. The spring loaded piece and
the anvil (red arrows) center the instrument in the bore and the
measurement is taken with the sensing point (green arrow).
The instrument is set to a standard, usually a very accurate micrometer or a bore ring standard.
IMAGE ToolBoreGa01a

IMAGE ToolBoreGa02




Of course you need dial indicators and the very useful vernier
calipers. I use the one on the left all the time for measurements
to 0.01 mm.
IMAGE ToolCaliperDial01


Best,
Grady

[Zeke]

Originally posted by ChrisBennet
The last crank I got from a customer's machine shop after a $125 a "crack check and micropolish" was deemed good but measured totally out of spec.

I would skip the bore gage and have that stuff measured by a pro.


-Chris

But not the same [i]pro]/i], right?

I trust a good machnist to do things right and then I check like Grady. However, unlike Grady, I'm not qualified to be checking. I just do it to see what I come up with. If it says the same as I expected, I'm happy. If it doesn't, I don't trust my measurements. That's when I have someone else look at it.

I have a complete set of Starrett mics, a decent dial indicator, a decent insdide mic and a caliper. NOt a real good one. I can check the caliper against the Starretts at various places along the scale. I need a top flight caliper to replace what I have.

So, I don't have a bore gauge, but what I have is pretty basic and can get you most places you need to go. Before I bought a bore gauge, I would get a depth gauge.

[randywebb]

Or you can solve all your problems by getting a metrologist as a girlfriend...