When I use dial calipers, I maintain the same thumb pressure, clean the
jaws, and zero often. I try to rock them into perpendicularity, and
measure with the same spot on the jaws each time. I check my accuracy
with pin gauges. I interpolate between the .001" hatch marks with my
eyes. My eyes can easily resolve .0002", but .0001" is harder.

0) My 8 year old Midway $20 Chinese 6" calipers can be trusted to .0002"
1) My new Enco $14 Chinese 6" calipers can be trusted to .001"
2) My new SPI $25 Chinese 6" calipers can be trusted to .0025"
3) My new Mitutoyo $72 Brazilian 6" calipers can be trusted to .0002"

The thing of interest was the $25 SPI looks like it is the same as the
$14, with nearly the same serial number sequence on the back. But the
SPI costs more and are not as good. The "SPI" name has been whore'd out
to Chinese junk.

--Maybe SPI should change their name to CPI, eh? :-)

--
"Steamboat Ed" Haas : Whatever happened
Hacking the Trailing Edge! : to Andy Philbrick?
www.nmpproducts.com
---Decks a-wash in a sea of words---

On Nov 17, 12:03 pm, Clark Magnuson wrote:
When I use dial calipers, I maintain the same thumb pressure, clean the
jaws, and zero often. I try to rock them into perpendicularity, and
measure with the same spot on the jaws each time. I check my accuracy
with pin gauges. I interpolate between the .001" hatch marks with my
eyes. My eyes can easily resolve .0002", but .0001" is harder.

0) My 8 year old Midway $20 Chinese 6" calipers can be trusted to .0002"
1) My new Enco $14 Chinese 6" calipers can be trusted to .001"
2) My new SPI $25 Chinese 6" calipers can be trusted to .0025"
3) My new Mitutoyo $72 Brazilian 6" calipers can be trusted to .0002"

The thing of interest was the $25 SPI looks like it is the same as the
$14, with nearly the same serial number sequence on the back. But the
SPI costs more and are not as good. The "SPI" name has been whore'd out
to Chinese junk.

It is VERY COMMON for companies to outsource to a much cheaper source
and not tell the consumer.

Maybe they forget or just maybe they don't want to pass the cost
savings on to the customer since that would cut into the CEO's bonus.

TMT

Your dreaming if you think a dial caliper can resolve .0002"


"Clark Magnuson" wrote in message
. ..
When I use dial calipers, I maintain the same thumb pressure, clean the
jaws, and zero often. I try to rock them into perpendicularity, and
measure with the same spot on the jaws each time. I check my accuracy with
pin gauges. I interpolate between the .001" hatch marks with my eyes. My
eyes can easily resolve .0002", but .0001" is harder.

0) My 8 year old Midway $20 Chinese 6" calipers can be trusted to .0002"
1) My new Enco $14 Chinese 6" calipers can be trusted to .001"
2) My new SPI $25 Chinese 6" calipers can be trusted to .0025"
3) My new Mitutoyo $72 Brazilian 6" calipers can be trusted to .0002"

The thing of interest was the $25 SPI looks like it is the same as the
$14, with nearly the same serial number sequence on the back. But the SPI
costs more and are not as good. The "SPI" name has been whore'd out to
Chinese junk.

On Sun, 18 Nov 2007 12:27:00 -0500, Tony wrote:
Your dreaming if you think a dial caliper can resolve .0002"

He may be confusing resolution with accuracy.

Dave Hinz wrote:

On Sun, 18 Nov 2007 12:27:00 -0500, Tony wrote:
Your dreaming if you think a dial caliper can resolve .0002"

He may be confusing resolution with accuracy.

Drop a zero and get real.

Wes

Dave Hinz wrote:
On Sun, 18 Nov 2007 12:27:00 -0500, Tony wrote:
Your dreaming if you think a dial caliper can resolve .0002"

He may be confusing resolution with accuracy.



When my cousin designed the electronics and software for some digital
calipers, he got a patent and did a great job. I got a pair. The .0001"
column is only a half a digit. It either reads .0005 or .0000". I called
him up and told him I wanted the extra resolution, because I know how to
control calipers and use it. He says that management did not want the
resolution displayed if the accuracy was not there.

On Mon, 19 Nov 2007 07:40:55 -0800, Clark Magnuson
wrote:

Dave Hinz wrote:
On Sun, 18 Nov 2007 12:27:00 -0500, Tony wrote:
Your dreaming if you think a dial caliper can resolve .0002"

He may be confusing resolution with accuracy.



When my cousin designed the electronics and software for some digital
calipers, he got a patent and did a great job. I got a pair. The .0001"
column is only a half a digit. It either reads .0005 or .0000". I called
him up and told him I wanted the extra resolution, because I know how to
control calipers and use it. He says that management did not want the
resolution displayed if the accuracy was not there.

A very skilled hand can repeatably measure to .0002" with a good dial
caliper. I once knew a machinist who used ordinary inside calipers
(not measuring tools, just adjustable feelers) to "feel" inside
dimensions and transfer to a mike. He said he could reliably do
..0002. I didn't believe him until he proved it. He really could!

He was at least 60.

The issue is in getting a consistent "feel". Dial and digital
calipers have a lot more "spring" to them than a mike does.

I don't trust calipers in my hands to better than .0005 on a really
good day, or much better than .002 most days.

I've seen older Starrett dial calipers read several random gauge block
stacks to better than 1/4 thousandth up to 6". The Phase II one I
brought in for cal was barely within 0.001" .


Jim Wilkins

On Sat, 17 Nov 2007 10:03:19 -0800, Clark Magnuson
wrote:

When I use dial calipers, I maintain the same thumb pressure, clean the
jaws, and zero often. I try to rock them into perpendicularity, and
measure with the same spot on the jaws each time. I check my accuracy
with pin gauges.

Have you adjusted the gibs on all of the calipers?


Mark Rand
RTFM