# New to me Covell 14 Comparator- What have I gotten myself into



## silverforgestudio (Jul 28, 2019)

OK guys- Stumbled on to a FB Marketplace item- it led me to a sale at the old "Arrow Tool and Die Company" outside Philly... Guy there has already sold the building, and is having a bit of a "Fire sale" on remaining items- I bought some drills and micrometers... Went into the Quality control room and there sat a Covell 14 comparator- with a few extra lenses and plates. Machine powered up fine... Ive always wanted one- even though I cant USE one (Im still new in the grand scheme of making chips...)

Anyway- machine is home... I feel like I got a steal on it- and for it to sit, I figure I will have time to learn it...

My questions are: 
1- I eventually want to make clock gearing and watch gears and smaller parts- Did I just go "WAY OVERBOARD" for this?
2- Any recommended old school texts or books on the care and feeding of these beasties?

Yes, I run the "Orphanage for Old Iron and Home-Shop Misfit Tools" If you have to ask... 

Pics to follow


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## benmychree (Jul 28, 2019)

Should be nearly totally useless.


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## T Bredehoft (Jul 29, 2019)

You'll be able to see every flaw in your gearing.  Or, conversely, how perfect you got it.


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## Bob Korves (Jul 29, 2019)

Sure beats squinting at little parts or using a magnifying glass, just have to have the extra money and a place to put the thing....


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## pstemari (Aug 9, 2019)

If you want to gauge all of the features on an external thread, not just pitch, pitch diameter, and major diameter, it's the way to go. You should be able to measure the flank angles, minor diameter, root size/radius, and even how straight the flanks are.

Not really needed for hobbyist use, but if you're trying to see how perfectly you can make a thread, that's the way to do it.

Sent from my Pixel XL using Tapatalk


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## silverforgestudio (Aug 11, 2019)

benmychree said:


> Should be nearly totally useless.



Dude- you dont know me- I dont know you. You have some interesting content but generally are a crusty one liner guy- teach or help or pass the thread over. You are a spirit killer for new guys and toxic. 

Im not a machinist- I am a hobby guy. But I am taking my hobby to the level of second income. That is why I am here. To learn.



T Bredehoft said:


> You'll be able to see every flaw in your gearing.  Or, conversely, how perfect you got it.



Thanks T- Im really hoping it helps with taking apart some older clocks so I can make accurate drawings to work to. Plus As I can mathematically know the "original" pitch diameters of the gear train- I can see how much the clocks have worn over the years.



Bob Korves said:


> Sure beats squinting at little parts or using a magnifying glass, just have to have the extra money and a place to put the thing....



As always- sage and true Bob! I had to move a few things and re-arrange the "grinder room" wall- but the thing is IN place and hopefully she will be at home for awhile! I work out of a small garage- space is TOTALLY at a premium... but for the price- I couldnt pass it up! 

What is funny is I had been lamenting my passing on the purchase of a JnL "Benchtop" last year- I went to the going out of business sale for an item TOTALLY unrelated to the Comparator. The fellow literally said "Make me an offer"... I did and I apologized and openly told him I know its way too low- and he said "Sold...." and I looked at my buddy who came with me and asked "How are we going to get this thing OUT of the truck when we get home?" 

We managed with only one injury to the Comparator (see photos) that will be on the "learn as you go" process. (The X-Y table came apart)



pstemari said:


> If you want to gauge all of the features on an external thread, not just pitch, pitch diameter, and major diameter, it's the way to go. You should be able to measure the flank angles, minor diameter, root size/radius, and even how straight the flanks are.
> Not really needed for hobbyist use, but if you're trying to see how perfectly you can make a thread, that's the way to do it.



Thanks PST- You are totally right- it is a bit overkill but for the clock gearing and rebuilds of fine geartrains (where I hope to be in the future) I am hoping this will assist me in specs for original sizes and to show the flanks and angles too. Plus the ability to compare my "Shop-made" parts to "Original" specs will allow me to have a bit of self-teaching in the shop. 

At least I can see how flawed my own work is! HA! 

Thanks folks- now on with the show


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## silverforgestudio (Aug 11, 2019)

OK so I made one horrible discovery today- 1960s era frosted glass plates are NOT etched- they are INKED... the plates for the comparator had been stored for years in a shipping box with straw and were filthy to touch... I went and got my lens cleaner I use for the microscopes and camera lenses and wiped down the first plate- and no problem... Figured this was the SAFEST cleaner I had- its designed to not remove the AR (anti-reflective) and other coatings on the microscope lenses and the photo optics.

Plate one- CLEAN! I was happy to see years of grit/grime and crud melting off the glass...

The SECOND plate however... CARNAGE!  The degree lines dissolved and the lint free lab-wipe went from sooty black to a pale blue with the ink...  AAARGH! 

So I have ONE plate that is clear of any printed lines but is totally clean and use-able!  When I saw the lines gone- I just kept on wiping- cleaning up the murder scene till it was nice and fresh... no fingerprints... nothing to see here....

No other plates were harmed in the making of this post! HA! all received a thorough dusting and brush down with a light water spritz and sponge. I cleaned out the box and lined it with flanel and bubble wrap- each plate has its own layer of insulation and will live there till I have better storage for them.


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## silverforgestudio (Aug 11, 2019)

So pictures were promised a WEEK ago- c'mon slacker- where are they!???

OK... OK... OK... So here they go.

So it was bought and delivered in March 1960... I love having the "Original" paperwork- Just me? Maybe- but I enjoy knowing a tool's history.


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## silverforgestudio (Aug 11, 2019)

Here she is- I cut the Plywood face to cover her until I can get the interior cleaned to keep stuff from the mirror.

Talk about tool-room porn... Shes got no DRAWERS on! 

Her drawer is removed and was undergoing a bit of an industrial clean... it was full of grit, grime, spooge, smut, (insert any word for machine-shop detritus here)... 

So fear not- she has her drawers back on guys and is in a decent state after this pic was taken.




Here is the Mirror and Light assembly. The Mirror has a few dots and smudges on it so I will be researching how to clean these- This is not just a plain glass mirror- the underlay glass is as close to "optically flat" and abberant free as they could get- and these mirrirs (as far as my reading/research suggests) were mercury-silvered so very high index of refraction.



So I have 4 different plates and measuring screens- the mounting ring is in good condition and there are about 50 mylar "blanks" to overlay/write on or print or trace profiles to measure to.

Outside the one "casualty" to the cleaning fluid- all is good! Spare bulbs are a plus too!


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## Boswell (Aug 11, 2019)

While I don't know, I would suspect that the mirror is a front surface mirror where there reflective coating (Silver?) is laid down on the front surface of the glass. household mirrors it is on the backside and so the glass protects the mirroring surface.  A front surface mirror is very easy to damage.


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## Choiliefan (Aug 11, 2019)

I too would be very careful cleaning your mirror and it may be best to remove it before proceeding.
A mild dish soap with gentle rinse and pat dry.
I had a Scherr-Tumico comparator and found the 10X lens the easiest for transposing measurements.
Also came with a set of centers which iirc replaced the XY stage and a useful surface illumination light fixture.


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## silverforgestudio (Aug 11, 2019)

Heres the 10x that was installed in the Unit- I have placed a cap over this workhorse so She doesn't get dinged...



Here is the "steal" of the day- the drawer held a series of lenses- R to L:
20x 31x 50x 62x

There are fractions on the 31 and 62 (1/4 and 1/2 respectively) And I would assume the math for the lenses is magnification based so Im interested in knowing if anyone has the magnification equations (or knows where they can be sourced from)



The BnS Micrometer dial for the XY table- it is in good shape cosmetically and works smoothly throughout its travel.



Here is the major casualty of the move- the XY table fell apart when we tilted the cabinet- nothing major dinged or scratched- but the ball bearings went all directions and the brass gibs went another- so I now have a "fixer-upper" portion to this ol gal.

This is the bottom of the table




Here is the underside of the "Top" of the table with the parts found- the 2 rectangular tabs and the washer are parts to the observation rotating ring. As you can see- Im missing a ball bearing...


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## gradient (Aug 11, 2019)

A very good and old method of cleaning mirrors, especially first surface mirrors is to use collodion. 









						Collodion Optics Cleaning - How to . . .
					

Cleaning the optics of our telescopes is something most of us dread ? and with good reason: aside from dropping the OTA on your driveway, nothing has a greater potential for damaging the optical surfaces   Cleaning Modern Antireflect...




					www.cloudynights.com
				




I have used this with great success on mirrors and ruled gratings for telescopes and other optical surfaces.


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## silverforgestudio (Aug 11, 2019)

Boswell said:


> While I don't know, I would suspect that the mirror is a front surface mirror where there reflective coating (Silver?) is laid down on the front surface of the glass. household mirrors it is on the backside and so the glass protects the mirroring surface.  A front surface mirror is very easy to damage.


Very true and thus the "cover and wait till I know more" philosophy- Thanks for the tip! 



Choiliefan said:


> I too would be very careful cleaning your mirror and it may be best to remove it before proceeding.
> A mild dish soap with gentle rinse and pat dry.
> I had a Scherr-Tumico comparator and found the 10X lens the easiest for transposing measurements.
> Also came with a set of centers which iirc replaced the XY stage and a useful surface illumination light fixture.


Thanks Choil- Im afraid to even mild dish soap this one as it has a few schmutz areas I can not tell if it is de-laminating or if it is surface grime... Nice to know the 10x is the "workhorse" lens- I have a feeling I will be starting with it as well!

Thanks for looking and contributing to the knowledge guys!


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## silverforgestudio (Aug 11, 2019)

gradient said:


> A very good and old method of cleaning mirrors, especially first surface mirrors is to use collodion.
> 
> 
> 
> ...


AWESOME and thank you! However this article says the fellow did NOT have good results- I will continue to look at Collodion- and the thought of primary mirror cleaning is now in the hunt as well (off to a telescope forum!)

I truly appreciate the assistance. Thanks folks!


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## Choiliefan (Aug 11, 2019)

It's possible your mirror is polished on both sides.


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## gradient (Aug 11, 2019)

The collodion article was to give you full disclosure  As I say, we have had good luck with it on really critical front (first) surface mirrors and gratings. Try it on a small corner of the mirror as a test. The nice thing about it is that you don't have to do any rubbing on the surface. Pour it on, let dry and peel it off. The dirt and munge sticks to the collodion. But as they say, "your mileage may vary".  Good luck with a nice instrument.


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## silverforgestudio (Aug 11, 2019)

Understood Gradient- and I hope to be doing some ore research this week as well for this method- I have several "vintage" SLR cameras with silvered mirrors that were stored in an open face container- their mirrors may be a great way to practice- thanks!


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## C-Bag (Aug 14, 2019)

I've seen OC's on CL, some real cheap. And after picking up a stereo microscope for $40 it has made a huge difference in my bit grinding technique. This thread has been very enlightening, thanks.


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## silverforgestudio (Sep 13, 2019)

Update for the folks about town- So the Comparator is functioning and I will be upgrading the lights to LEDs. 

The Table mechanism and ball bearings will be "tabled" (pardon the pun) until the lights and mirror are addressed.  Thanks to Paul and Rodger (neighbors I didnt know prior to this adventure) for inviting me into their shop for a test drive of their Johnson Comparator.

This item will have more use than originally thought as I am now the proud owner of a large box of watch/clock gearing to "learn" on! 

In other news I WILL be painting this ol'girl as I have found she likes her new home by the door and my TOES are suffering! (One day I will learn!- HA!)

@gradient - the Collodion will be the next foray as well. I am thinking this fall as my "shop" area doesnt get to a decent relative humidity and temp sustained until October/November timeframes

Stand by as she gets up and running!


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## silverforgestudio (Sep 23, 2019)

gradient said:


> A very good and old method of cleaning mirrors, especially first surface mirrors is to use collodion.



So- just thought I would offer a "Poor Mans" version of Collodion- This is a parallel discussion in a Microscope forum I belong to- I would figure teh mirror has no AR or coatings so this may be a good test piece!

Here is the body of the text-
<<Figuring that I had little to lose testing with a simple microscope slide, I got a dirty microscope slide and wiped it off with my shirt, which left a nice oil film and some cotton debris. I painted some generic *Walgreens Liquid Bandage* on the slide and dabbed a small strip of mosquito netting into the goo to help lift it.

After the *stuff** had dried, I lifted the tab of mosquito netting that I had left outside the puddle of goo (it was more viscous than I had expected) and it popped right off. I looked at the slide with only a stereo microscope but from all I could tell, the surface was pristine. All evidence of the oil smear and all particulate matter was gone in the area where the Liquid Bandage had been applied. I could see a very definite edge between where the puddle of Liquid Bandage had been and where it hadn't. The material came off so easily that I don't see adhesion to surface coatings being a problem. I can't vouch for the safety of any of the solvents involved though.

Any suggestions for a more stringent test?

** Acetone, amyl acetate, castor oil, ethyl acetate, nitrocellulose, and specially denatured alcohol (SD 40)*>>

The reply was for our folks across the pond:
<<
Well done, a great test. The next step in more stringent testing would be, I think, to try it on antireflection-coated optics. Possibly not your finest planapo but maybe an old or scratched eyepiece.

In the UK I can find "Liquid Skin" which seems to be made of cyanoacrylate (superglue), so probably not at all the same as yours, and various very cheap preparations from China. Plus there is *something called New Skin that seems to be American*.

Then I found a home grown product (*Germolene New Skin*) containing

Ingredients

*Ethyl Acetate
Alcohol Denat
Nitrocellulose
Ricinus Communis
Isopropyl Alcohol
Amyl Acetate
Isobutyl Alcohol
Camphor
Parfum (includes Benzyl Alcohol, Citronellol)*

Would this be similar to what you use? It's £5 for 20ml so a no-brainer if it works. But it does contain castor oil (ricinus) which someone said was a no-no.>>

So- the consensus is to try it- As the working area of the mirror is central and projected onto a circle- And the Mirror itself is a SQUARE... I figure the edges are safe to "play" with and experiment!

The replacement used mirror runs about 350 USD- a bit steep for a home shop- but then again- Im hoping to invest in the equipment to be able to grow moving forward!

Hope this helps- I will post the results here and try to remember to put this in a WIP thread or tips/tricks forum as well- if it works... Im excited as I have rifle scopes, binoculars, prisms and a few other glass lenses/mirrors I desperately need to clean!

Thats all for now! The quest continues!


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## Dabbler (Sep 23, 2019)

what a find!! I'm green with envy!  You will finds tons of use for it!  Especially to easily check cutters for wear, and touching up your carbide cutters.  Without good magnification it can be tricky to get a really good edge on carbide.  I wish I had one while I was learning...


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## silverforgestudio (Sep 24, 2019)

Dabbler said:


> what a find!! I'm green with envy!  You will finds tons of use for it!  Especially to easily check cutters for wear, and touching up your carbide cutters.  Without good magnification it can be tricky to get a really good edge on carbide.  I wish I had one while I was learning...



Well Dabbler- if you get south ( a LOT south) come on over- if the truck is in the driveway just bang on the garage door- Im there... maybe in the back- but Im there... Always fresh coffee on and a snack in the fridge!

I like the use for cutter grinding as well- had not thought of that! Thanks!


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## Dabbler (Sep 24, 2019)

I have some long distance friends in Virginia... Perhaps one day!


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## silverforgestudio (Sep 25, 2019)

Well unless you hate puppies/cats and sitting with folks listening to music and chatting... Add one more to your list of the "Down South-ers"... 

Just be prepared to teach me a few tricks or at least get a chuckle out of my misfit patchwork hobby cave!

Cheers!

BY THE WAY FOLKS... ILL BE PLAYING WITH THE HOME COLLODION IN THE NEXT POSTS... STAND BY!


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