Depth mike

[Snag]

I scored a Mitutoyo unit a while back at a yard sale . It only had
one rod , 0-1" and I wanted more ... so I bought some on eBay . Thing is
they must be for a different model micrometer , they're all 5/8" too
long . And not 1-2 , 2-3 , etc . So I was thinking that I can cut them
off to measure correctly in my unit . This will give me 0- 5" if I cut
them to the appropriate lengths . It looks like I won't have to be
absolutely on the mark since there is a calibration adjustment on each
rod . I'm thinking that my Dremel in the toolpost clamp and a cutoff
wheel , then a light polish with a fine grinding wheel also using the
dremel . I have 123 blocks that I can set up to calibrate - maybe not as
precise as a metrology lab , but I think close enough for what I do .
Does this sound doable , and any suggestions ?

[Bob La Londe]

  I scored a Mitutoyo unit a while back at a yard sale . It only had
one rod , 0-1" and I wanted more ... so I bought some on eBay . Thing is
they must be for a different model micrometer , they're all 5/8" too
long . And not 1-2 , 2-3 , etc . So I was thinking that I can cut them
off to measure correctly in my unit . This will give me 0- 5" if I cut
them to the appropriate lengths . It looks like I won't have to be
absolutely on the mark since there is a calibration adjustment on each
rod . I'm thinking that my Dremel in the toolpost clamp and a cutoff
wheel , then a light polish with a fine grinding wheel also using the
dremel . I have 123 blocks that I can set up to calibrate - maybe not as
precise as a metrology lab , but I think close enough for what I do .
  Does this sound doable , and any suggestions ?

There are two depth mics in my shop. One is a Shars set I bought new,
and the other is old Craftsman maybe? Anyway, they have a domed or
convex end on them so that the contact point is very small. Look at
your other anvils/rods for the shape.

If you get the dome very close, then you could polish a couple tenths
quite easily using your 123 blocks and a small inexpensive surface plate
to check as you go. You might not make the metrology snob happy, but
you should be able to get significantly closer to .000 than .001. With
some, but not excessive, care you could get really darn close. If you
have a tool and cutter grinder or surface grinder, and any kind of
fixture for turning the rods you could turn a shallow cone pretty darn
close and polish to finish with just tiniest of flats on the end. A
cone is maybe not quite as durable as a dome, but you will probably wind
up with a tiny flat or dome anyway.

I don't bother to "precision" calibrate the mic myself. I just take a
quick reading on something close like a gage block, 123 bloc, etc, and
then add/subtract the error to my final reading.

[Snag]

   I scored a Mitutoyo unit a while back at a yard sale . It only had
one rod , 0-1" and I wanted more ... so I bought some on eBay . Thing
is they must be for a different model micrometer , they're all 5/8"
too long . And not 1-2 , 2-3 , etc . So I was thinking that I can cut
them off to measure correctly in my unit . This will give me 0- 5" if
I cut them to the appropriate lengths . It looks like I won't have to
be absolutely on the mark since there is a calibration adjustment on
each rod . I'm thinking that my Dremel in the toolpost clamp and a
cutoff wheel , then a light polish with a fine grinding wheel also
using the dremel . I have 123 blocks that I can set up to calibrate -
maybe not as precise as a metrology lab , but I think close enough for
what I do .
   Does this sound doable , and any suggestions ?

There are two depth mics in my shop.  One is a Shars set I bought new,
and the other is old Craftsman maybe?  Anyway, they have a domed or
convex end on them so that the contact point is very small.  Look at
your other anvils/rods for the shape.
If you get the dome very close, then you could polish a couple tenths
quite easily using your 123 blocks and a small inexpensive surface plate
to check as you go.  You might not make the metrology snob happy, but
you should be able to get significantly closer to .000 than .001.  With
some, but not excessive, care you could get really darn close.  If you
have a tool and cutter grinder or surface grinder, and any kind of
fixture for turning the rods you could turn a shallow cone pretty darn
close and polish to finish with just tiniest of flats on the end.  A
cone is maybe not quite as durable as a dome, but you will probably wind
up with a tiny flat or dome anyway.
I don't bother to "precision" calibrate the mic myself.  I just take a
quick reading on something close like a gage block, 123 bloc, etc, and
then add/subtract the error to my final reading.

These are all flat on the tip . I can see the point of making the tip
rounded or conical . These all have an adjustable collar with a lock
ring on the top end , so I figured on polishing them a thou or three
short then adjusting - start with the collars bottomed out (lightly) on
the threads .

[Bob La Londe]

   I scored a Mitutoyo unit a while back at a yard sale . It only had
one rod , 0-1" and I wanted more ... so I bought some on eBay . Thing
is they must be for a different model micrometer , they're all 5/8"
too long . And not 1-2 , 2-3 , etc . So I was thinking that I can cut
them off to measure correctly in my unit . This will give me 0- 5" if
I cut them to the appropriate lengths . It looks like I won't have to
be absolutely on the mark since there is a calibration adjustment on
each rod . I'm thinking that my Dremel in the toolpost clamp and a
cutoff wheel , then a light polish with a fine grinding wheel also
using the dremel . I have 123 blocks that I can set up to calibrate -
maybe not as precise as a metrology lab , but I think close enough
for what I do .
   Does this sound doable , and any suggestions ?

There are two depth mics in my shop.  One is a Shars set I bought new,
and the other is old Craftsman maybe?  Anyway, they have a domed or
convex end on them so that the contact point is very small.  Look at
your other anvils/rods for the shape.
If you get the dome very close, then you could polish a couple tenths
quite easily using your 123 blocks and a small inexpensive surface
plate to check as you go.  You might not make the metrology snob
happy, but you should be able to get significantly closer to .000 than
.001.  With some, but not excessive, care you could get really darn
close.  If you have a tool and cutter grinder or surface grinder, and
any kind of fixture for turning the rods you could turn a shallow cone
pretty darn close and polish to finish with just tiniest of flats on
the end.  A cone is maybe not quite as durable as a dome, but you will
probably wind up with a tiny flat or dome anyway.
I don't bother to "precision" calibrate the mic myself.  I just take a
quick reading on something close like a gage block, 123 bloc, etc, and
then add/subtract the error to my final reading.

  These are all flat on the tip . I can see the point of making the tip
rounded or conical . These all have an adjustable collar with a lock
ring on the top end , so I figured on polishing them a thou or three
short then adjusting - start with the collars bottomed out (lightly) on
the threads .

Makes perfect sense to me. Not sure about them being flat though. I'll
go double check both of my sets when I have another minute.

[Jim Wilkins]

"Bob La Londe" wrote in message news:v5i4pg$2bc2r$***@dont-email.me...

Makes perfect sense to me. Not sure about them being flat though. I'll
go double check both of my sets when I have another minute.
Bob La Londe
-----------------------------------
The rods for my Starrett are flat across the end.

[Bob La Londe]

Makes perfect sense to me.  Not sure about them being flat though.  I'll
go double check both of my sets when I have another minute.
Bob La Londe
-----------------------------------
The rods for my Starrett are flat across the end.

I went and looked. I was in the back shop slitting some stock to width,
and I was right there. The Craftsman set is flat. The Shars set is
definitely radiused on every rod. I recall using the Shar's to get some
dimensions for the rails on a handgun frame and I had to sweep it back
and forth to make sure I was getting the dimension. With a square end I
would not have had to do that.

I thought I had a benefit to the radiused end in my mind, but when I
think through it doesn't seem to add up. Maybe just ease of grinding to
length being just a theoretical single point instead of a perpendicular
flat.

[Snag]

Makes perfect sense to me.  Not sure about them being flat though.
I'll go double check both of my sets when I have another minute.
Bob La Londe
-----------------------------------
The rods for my Starrett are flat across the end.

I went and looked.  I was in the back shop slitting some stock to width,
and I was right there.  The Craftsman set is flat.  The Shars set is
definitely radiused on every rod. I recall using the Shar's to get some
dimensions for the rails on a handgun frame and I had to sweep it back
and forth to make sure I was getting the dimension.  With a square end I
would not have had to do that.
I thought I had a benefit to the radiused end in my mind, but when I
think through it doesn't seem to add up.  Maybe just ease of grinding to
length being just a theoretical single point instead of a perpendicular
flat.

And this might not be as straightforward as I thought . Those collars
at the top only want to rotate about 90° . Might be because the
setscrews have flattened the threads but I haven't pulled a screw to see
. Tomorrow will be soon enough .

[Snag]

Makes perfect sense to me.  Not sure about them being flat though.
I'll go double check both of my sets when I have another minute.
Bob La Londe
-----------------------------------
The rods for my Starrett are flat across the end.

I went and looked.  I was in the back shop slitting some stock to
width, and I was right there.  The Craftsman set is flat.  The Shars
set is definitely radiused on every rod. I recall using the Shar's to
get some dimensions for the rails on a handgun frame and I had to
sweep it back and forth to make sure I was getting the dimension.
With a square end I would not have had to do that.
I thought I had a benefit to the radiused end in my mind, but when I
think through it doesn't seem to add up.  Maybe just ease of grinding
to length being just a theoretical single point instead of a
perpendicular flat.

  And this might not be as straightforward as I thought . Those collars
at the top only want to rotate about 90° . Might be because the
setscrews have flattened the threads but I haven't pulled a screw to see
. Tomorrow will be soon enough .

I decided to look up calibrating the rods ... the collar doesn't
rotate and the nut on top adjusts the length . The setscrews lock the
collar in place . I'll be checking that in the morning .

[Jim Wilkins]

"Snag" wrote in message news:v5hnnl$29e1b$***@dont-email.me...

I scored a Mitutoyo unit a while back at a yard sale . It only had
one rod , 0-1" and I wanted more ... so I bought some on eBay . Thing is
they must be for a different model micrometer , they're all 5/8" too
long . And not 1-2 , 2-3 , etc . So I was thinking that I can cut them
off to measure correctly in my unit . This will give me 0- 5" if I cut
them to the appropriate lengths . It looks like I won't have to be
absolutely on the mark since there is a calibration adjustment on each
rod . I'm thinking that my Dremel in the toolpost clamp and a cutoff
wheel , then a light polish with a fine grinding wheel also using the
dremel . I have 123 blocks that I can set up to calibrate - maybe not as
precise as a metrology lab , but I think close enough for what I do .
Does this sound doable , and any suggestions ?
Snag

-----------------------------------

How about making a 5/8" long adapter sleeve for the head end, with
appropriate threaded ends?

If you set the lathe compound 6 degrees off square each 0.001" division on
the dial will move the bit 0.0001" sideways.

The mike will read the zero error and corrections will be to the one DIY
sleeve, not all the rods. A screwup will cost you only the sleeve.

The biggest problem may be matching the threads. You need to match only the
mike end, you can make the cap.

My depth mike is a Starrett so measuring its thread won't help you.

When I set my South Bend up for metric threading I found that the standard
100/127 gear set wouldn't give me the fine lens threads I wanted, 120/127
gave more. I used a spreadsheet to calculate and tabulate the inch - metric
equivalence of several possible choices. Change gears were much cheaper in
the early 90's. They weren't a direct fit, I had to make a bearing adapter.

[Snag]

  I scored a Mitutoyo unit a while back at a yard sale . It only had
one rod , 0-1" and I wanted more ... so I bought some on eBay . Thing is
they must be for a different model micrometer , they're all 5/8" too
long . And not 1-2 , 2-3 , etc . So I was thinking that I can cut them
off to measure correctly in my unit . This will give me 0- 5" if I cut
them to the appropriate lengths . It looks like I won't have to be
absolutely on the mark since there is a calibration adjustment on each
rod . I'm thinking that my Dremel in the toolpost clamp and a cutoff
wheel , then a light polish with a fine grinding wheel also using the
dremel . I have 123 blocks that I can set up to calibrate - maybe not as
precise as a metrology lab , but I think close enough for what I do .
  Does this sound doable , and any suggestions ?
Snag
-----------------------------------
How about making a 5/8" long adapter sleeve for the head end, with
appropriate threaded ends?
If you set the lathe compound 6 degrees off square each 0.001" division
on the dial will move the bit 0.0001" sideways.
The mike will read the zero error and corrections will be to the one DIY
sleeve, not all the rods. A screwup will cost you only the sleeve.
The biggest problem may be matching the threads. You need to match only
the mike end, you can make the cap.
My depth mike is a Starrett so measuring its thread won't help you.
When I set my South Bend up for metric threading I found that the
standard 100/127 gear set wouldn't give me the fine lens threads I
wanted, 120/127 gave more. I used a spreadsheet to calculate and
tabulate the inch - metric equivalence of several possible choices.
Change gears were much cheaper in the early 90's. They weren't a direct
fit, I had to make a bearing adapter.

The way this is made there's nowhere to add a spacer sleeve . I've
got a whole 40 bucks in this set of used rods o it's not a big deal if I
screw one up . I think shortening the rods is really the only way to
make this work . In case you aren't familiar with Mitutoyo depth mikes ,
the thimble is 2 pieces . The top half unscrews and the rod is dropped
thru the hollow lower half . The top half is then screwed on to clamp
and retain the rod . The top of the rod is threaded , the collar that is
the clamping surface has 2 tiny setscrews plus a lock nut on top .
There's enough threads that if I screw up and have to take a little more
off I can , up to maybe .060" . About the only way I can see ruining one
is to bend it . That's a tight hole it fits in .

[Jim Wilkins]

"Snag" wrote in message news:v5i7b1$2cc9v$***@dont-email.me...

On 6/26/2024 5:21 PM, Jim Wilkins wrote:
...

The way this is made there's nowhere to add a spacer sleeve . I've
got a whole 40 bucks in this set of used rods o it's not a big deal if I
screw one up . I think shortening the rods is really the only way to
make this work . In case you aren't familiar with Mitutoyo depth mikes ,
the thimble is 2 pieces . The top half unscrews and the rod is dropped
thru the hollow lower half . The top half is then screwed on to clamp
and retain the rod . The top of the rod is threaded , the collar that is
the clamping surface has 2 tiny setscrews plus a lock nut on top .
There's enough threads that if I screw up and have to take a little more
off I can , up to maybe .060" . About the only way I can see ruining one
is to bend it . That's a tight hole it fits in .
--
Snag
It's great to be straight !
---------------------------------------
OK, a photo of one shows a small knob which on a Starrett is where the rod
is inserted, and retained by the knob. Unlike the Mitutoyo the rod rotates
with the thimble. I don't know why the rod not rotating would be an
advantage, but they claim it as one.

I've found an inexpensive inside micrometer useful, to reach deeper and
match the curve better than calipers in a small hole, and not shift as
easily when taken out. It can be checked with a more precise outside mike. I
used it this morning to check the tapped hole for my sawmill blade tensioner
screw, which had seized. The threads stripped off the 1/2-20 threaded rod
but the tapped hole in hot rolled bar stock was only 0.005" over the tap
drill. The labels on that auction lot of 12" USS and SAE rod don't admit who
made it.