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Mounting dial indicator directly in line with mill spindle?

Terry Keeley

Titanium
Joined
Oct 18, 2005
Location
Toronto, Canada eh!
I needed to mount an indicator directly in line with my mill spindle. The clamping area is under the dial but I noticed the tip had the same thread as the plunger, so I put the tip on top of the plunger and mounted it upside down in a collet. The plunger is now spring loaded up so I put a rod down the spindle with enough weight on it to hold it down. Of course it reads backwards but it's gonna work.

I've never seen or heard of this before, anyone? Is there an accessory to screw on the top? I see threads there but couldn't find anything on line.


DSCN5829.JPG
 
A lot of dial indicators come with a screw-on cap, long enough to cover the travel. That would mount in a collet and should be concentric with the tip within a few to several thousandths. You'd preserve the proper orientation of the dial and plunger.

You could of course make a fixture to hold the indicator (flat back mount might be best) and contrive a concentric spindle mount to whatever accuracy you wish.
 
Lots of drop indicators are supplied with a closed tubular cover (attached at the threads you mentioned) to protect the back end of the plunger. They're light gage metal and suitable for your purpose, with care. A quick look into the Mitutoyo catalog suggests that the current offerings are molded plastic and tapered, so not good for what you're doing.

Depending on your talents and priorities:
Option #1, call Mitutoyo Tech Assistance/Parts and see if they could help with a replacement part.
Option #2, buy another indicator with the appropriate configuration.
Option #3, make what you need.
 
Just to add, I'm pretty sure the covers on the longer throw (say 2" and up travel) versions of both Starrett and Mitutoyo still have the metal caps. Maybe a good excuse to buy one . . . they're handy if you don't have DRO's on all your machines. And a same brand 1" to 2" long cap should still fit your indicator's thread.
 
Thanks for the reply's.

I found the cap, as mentioned another brand might be better to mount in the spindle but I don't think those threads are really meant for a mount:

Mitutoyo, Product: Dial Indicator Spindle Cap

I could make something, but as Pete said there's no guarantee that the finished mount would be concentric to the plunger if I just attached to those threads. Something that clamped to the bottom with an arm that went around the dial would be better (again as Pete said).

There's probably a specialized indicator somewhere that mounts the way I want but for this little project my "hillbilly" set up will do.
 
OT but is that a 8525 or 8530 Clausing? I haven't been able to find anybody else with one.

-Ed
 
The cap or cover for those indicators are about a standard diameter but not really designed for mounting. The guys I used to work with thought it was a good idea to put them in a ER collet chuck and would crush the cover, it can be done tightening by hand only!
Dan
 
I don't see a problem with what he's done... indicators are spring loaded, will read accurately in any position. I've had one mounted in this position for years as the depth stop on a sinker EDM with no ill effects.

Yeah, having the trade name upside down looks funky, but it gets the job done.

Dennis
 
Not Kyle, but my recollection is that the Mitutoyo uses a non-standard metric rather than ANSI thread. You'll have to measure the diameter and pitch. The pitch might be something like .5mm.

Whatever metric thread it is, just guessing by its nice companion Clausing mill, that you might not have metric threading on your lathe -- and while an approximation (like 48 tpi) might work in a short and loose thread -- you might lose a bit of concentricity??

Could be Ebay will have a Mitutoyo or other longer travel indicator with a good metal cap? If you grip gently and down toward the threaded portion of the cap it should be fairly concentric and with little danger of crushing the cap. Not too different, just a bit thinner and with close fitting threads, than the adapter Kyle made.

Not sure what back is on your present indicator, but I've seen a variety -- including one that has precise adjustments for centering. Again, might find something used and cheap; just for the back? That's if you make your own holder.
 
Not Kyle, but my recollection is that the Mitutoyo uses a non-standard metric rather than ANSI thread. You'll have to measure the diameter and pitch. The pitch might be something like .5mm.

Whatever metric thread it is, just guessing by its nice companion Clausing mill, that you might not have metric threading on your lathe -- and while an approximation (like 48 tpi) might work in a short and loose thread -- you might lose a bit of concentricity??

Could be Ebay will have a Mitutoyo or other longer travel indicator with a good metal cap? If you grip gently and down toward the threaded portion of the cap it should be fairly concentric and with little danger of crushing the cap. Not too different, just a bit thinner and with close fitting threads, than the adapter Kyle made.

Not sure what back is on your present indicator, but I've seen a variety -- including one that has precise adjustments for centering. Again, might find something used and cheap; just for the back? That's if you make your own holder.


I have an Emco Super 11 lathe so I can do any inch/metric threads but I think I'd still want to check if the plunger was concentric with the mount if I did Kyle's mod.

Better to make a mount that grabs it under the indicator as designed or on the back lug I'd think, not sure gripping a metal cap would work out well.

I still like Kyle's solution tho, or mine!
 
Cool! Do you recall what the thread was?

Ø7.24mm x 0.5mm, at least that is what I came up with.

I cut a Ø0.285" x 52 as the little HLV was ready to go. Sometimes the world ain't perfect. :D

I had to measure an odd shape similar to your other thread, http://www.practicalmachinist.com/vb/general/o-t-creating-cad-file-simple-template-344304/, not too long ago, that is why I piped up in the other thread. I indicated the indicator tip in the spindle and it was close enough for me. Wasn't sure if I would go back in time or create a glitch in the matrix indicating an indicator, but I seem fine.

Edit: I see Pete had the same thoughts on the thread size.

attachment.php
 
Ø7.24mm x 0.5mm, at least that is what I came up with.

I cut a Ø0.285" x 52 as the little HLV was ready to go. Sometimes the world ain't perfect. :D

I had to measure an odd shape similar to your other thread, http://www.practicalmachinist.com/vb/general/o-t-creating-cad-file-simple-template-344304/, not too long ago, that is why I piped up in the other thread. I indicated the indicator tip in the spindle and it was close enough for me. Wasn't sure if I would go back in time or create glitch in the matrix indicating an indicator, but I seem fine.

Edit: I see Pete had the same thoughts on the thread size.

attachment.php

Sweet! Thanks! Just starting to take some measurements on the template. I see you suggested this method 1st and it went right over my head.

I might take you up on your offer if I have trouble drawing the part once I got the numbers...
 
I also had a similar requirement and made the quick/dirty adaptor in the photo. The eccentric end of the adaptor is slit for a clamp screw. There is a short, non-threaded stem on the indicator over which the adaptor fits. (The rod was drilled deep enough to accommodate the one inch of indicator travel.)

1-P1070356.jpg
 








 
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