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Fasttrack
04-14-2008, 11:20 PM
So as many of you know I was having issues with my beloved Mitutoyo 6" dial calipers. These are the "nice" jewled calipers that I've seen go for between 150 and 170 bucks, i.e. worth repairing!

So I started by disassembling the major stuff - i took the head off, the rack off and all the guards and plastic bits. Cleaned everything very well with a little WD-40 and a clean cloth. No luck ... still rough and clicky movement.
Here's a pic of the disassembled caliper:
(Notice the head is already disassembled in this shot)
http://i108.photobucket.com/albums/n22/fasttrack237/100_0147.jpg

To disassemble the head I first carefully pried the plastic bezel and crystal off. Just a flat blade screwdriver twisted at equall intervals about the bezel made quick work of that. Then I had to take the needle off.

This you have to be very careful with. I understand that it is easy to pull the shaft out and damage the brass plate that it rides in. Then your in big trouble!

Alright, so I decided to make a little puller to remove the needle. A quick, simple and worthwhile project! I used a piece of half inch aluminum rod, drilled, tapped and milled to the following shape. I also turned a 6-32 bolt to .020 at the tip to push on the shaft while the aluminum part pulls the needle. This is done by finger power alone - no wrenches needed. If you need a wrench, the point is probably too big.

http://i108.photobucket.com/albums/n22/fasttrack237/100_0152.jpg

http://i108.photobucket.com/albums/n22/fasttrack237/100_0153.jpg

http://i108.photobucket.com/albums/n22/fasttrack237/100_0154.jpg

Fasttrack
04-14-2008, 11:23 PM
Here is the needle removed using the handy-dandy little tool:
http://i108.photobucket.com/albums/n22/fasttrack237/100_0149.jpg


This is the picture of the head disassembled. Notice the anti-backlash gears that mesh with the gear that drives the needle. There are two small gears that engage the small gear on the needle spindle. They are connected via a spring and the spring works to eliminate backlash. In my case the spring had come loose and were interfering with the meshing of the gears.

http://i108.photobucket.com/albums/n22/fasttrack237/100_0150.jpg

http://i108.photobucket.com/albums/n22/fasttrack237/100_0151.jpg

All in all, this was a very satisfying project. After reassembly, the whole thing works like a charm. Just as silk smooth as I remembered. I did notice that the jewel was chipped slightly, but it seems to not affect it at all. Anyway, if you've got nimble fingers and good eyes, or some jeweler's glasses, repairing calipers is pretty neat. I wouldn't mind tearing into another one sometime.

Ken_Shea
04-14-2008, 11:53 PM
Nice work fasttrack,
Gotta love that little puller :)

DId you use any special oil for lube on movement / gears etc ?

Fasttrack
04-15-2008, 12:07 AM
:o Nope ... I was going to use some 3-in-1 oil or similiar light weight oil. Right now its got nothing but a very light coating of WD-40. I'm a little worried about the "gritty" nature of WD-40, so I'd like to get some other kind of light weight lubricant for it. Whatever I use, i want it to be light very light. I once made the mistake of using like 20 weight way oil on a precision measuring instrument. NOT A GOOD IDEA! :D

TGTool
04-15-2008, 10:25 AM
Starrett makes an instrument oil. I'm not a big fan of many of their measuring tools, but I use the oil and like it. A small squeeze bottle is a lifetime supply.

Mcgyver
04-15-2008, 10:41 AM
Fasttack, good stuff, I'm impressed. I tried to do so with a Mit caliper but there was so little clearance between the needle and face that i didn't think i could make the feet of the puller thin enough.....how thick are the ones on yours? how did the dial go back on the pin?

JCHannum
04-15-2008, 10:46 AM
Nice work, I have been tempted to try that, but managed to resist so far. Maybe I will give it a shot.

Another vote for the Starrett instrument oil. If not readily available, light sewing machine oil is a good substitute. Neither have additives or flavoring to leave a residue.

WD 40 has teflon added, and can gum things up. For cleaning instruments & such, I use plain lighter fluid.

Bill Pace
04-15-2008, 10:47 AM
VERY innovative!! and the best part is that you got it back to life!

Alas, my Brown & Sharpe has not cooperated, defying efforts from Lane and I to to get it open. But from your descriptions -- rough & clicky -- mine may have a similar problem internally.

Since this is a pretty common B&S, I decided to check ebay and within a few mins had found the same model that wasnt getting any action, threw a bid on it and got it for $36 (in pictures looks like new), so I'll just back burner the dropped one for another day

rantbot
04-15-2008, 10:57 AM
I have done the same repair on an 8" Mitutoyo which I had knocked off a desk onto a carpeted floor, disturbing the pinions. I don't remember how I got it apart, though (must be the Brain Drain in action) - I'm sure I didn't make a puller. It took me a couple of tries to get the anti-backlash spring set just right, but the thing has been working fine for at least ten years now. I'm pretty certain that I didn't put any lubrication at all in there.

Fasttrack
04-15-2008, 11:30 AM
Rantbot - Yep, you don't need a puller, it just makes it go much quicker and less stressfully, imo. I read another post on here about someone who just pulled the needle off using screwdrivers and fingers but I've also read of people tearing the shaft out with the needle, so i figured I'd play it safe.

McGyver - The feet are .045 thick and the slot to slide around the needle is .070. I was actually shooting for .060 and thats the diameter of hole I drilled, but I had to file the slot because I didn't have any tools small enough to do it otherwise. The file was .070 so I figured it was close enough. You just have to be careful to locate the pin on the shaft since there is a little bit of play back and forth.

The needle looks a bit like a bolt with a reduced diameter that presses over the shaft and then a larger diameter that actually has the needle part on it. My puller fits around the small diameter section of the needle, not the shaft since, as you said, there is not much clearence between this reduced diameter and the shaft itself.

JC and Bill - Thanks! Good luck with that B&S, Bill.

TGTool - I will have to find some of that. I reckon Enco and MSC probably carries it?

<edit> to put the needle back on, i pressed it on with my finger! I think you could probably have pulled it off without damaging anything, but for no more time than it took to make the puller, i figured it was worth it.

Evan
04-15-2008, 02:25 PM
Excellent work Fasttrack. I really like the puller. Good solution.

There is no Teflon in WD40 so don't worry about that. This is an important consideration since PTFE particles can do a good job of clogging up bearings. To avoid any argument from Jim I will document my stated facts in advance.

From the MSDS for WD40



SECTION 3 COMPOSITION INFORMATION ON INGREDIENTS

Ingredient CAS Number Percent
Stoddard Solvent 8052-41-3 45-50%
Petroleum Base Oil 64742-65-0 30-35%
Non-Hazardous Ingredients Proprietary <10%


SECTION 5. FIRE FIGHTING MEASURES

EXTINGUISHING MEDIA: Use water fog, dry chemical, carbon dioxide or foam. Do not use water jet or flooding
amounts of water. Burning product will float on the surface and spread fire.
SPECIAL FIRE FIGHTING PROCEDURES: Firefighters should always wear positive pressure self-contained
breathing apparatus and full protective clothing. Cool fire-exposed containers with water.
UNUSUAL FIRE/EXPLOSION HAZARDS: Combustible liquid and vapor. Vapors are heavier than air and may
travel along surfaces to remote ignition sources and flash back.


OCCUPATIONAL EXPOSURE LIMITS:
Stoddard Solvent 100 ppm TWA ACGIH TLV
Petroleum Base Oil 5 mg/m3 TWA ACGIH TLV
10 mg/m3 STEL ACGIH TLV
Non-Hazardous Ingredients None Established


The proprietary ingredients are perfumes.

If the product contained PTFE it would be required to list certain very important warnings even if the PTFE were hidden in the proprietary ingredients. You can't hide a hazardous product in the proprietary ingredients without indicating it is hazardous.

The MSDS for PTFE from Dupont includes this information:




HAZARDS IDENTIFICATION
----------------------------------------------------------------------
Potential Health Effects

ADDITIONAL HEALTH EFFECTS

Before using read the Fluoropolymers Safe Handling Guide published
by The Society of the Plastics Industry.

The primary hazard associated with these polymers is the
inhalation of fumes from overheating or burning, which may cause
"polymer fume fever" (see HUMAN HEALTH EFFECTS below).

POLYTETRAFLUOROETHYLENE Inhalation of PTFE dust may cause
generalized irritation of the nose, throat and lungs with cough,
difficulty breathing or shortness of breath.

Heating PTFE above 300 degrees C may liberate a fine particulate
fume. Inhalation may produce polymer fume fever, a temporary
flu-like condition with fever, chills, nausea, shortness of
breath, chest tightness, muscle or joint ache, and sometimes cough
and elevated white blood cell count. The symptoms are often
delayed 4 to 24 hours after exposure. These signs are generally
temporary, lasting 24-48 hours and resolve without further
complications. However, some individuals with repeated episodes
of polymer fume fever have reported persistent pulmonary effects.
Protection against polymer fume fever should also provide
protection against any potential chronic effects.

Exposure to decomposition products from PTFE heated above 400
degrees C may cause pulmonary inflammation, hemorrhage or edema.
These more serious consequences of exposure may occur from extreme
thermal decomposition of PTFE which can liberate fume particles,
and toxic gases (carbonyl fluoride, hydrogen fluoride, and other
fluorinated gases) especially under conditions of poor ventilation
and/or confined spaces. These decomposition products may
initially produce chest tightness or pain, chills, fever, nausea,
with shortness of breath, cough, wheezing and progression into
pulmonary edema. Edema may be delayed in onset and requires
medical treatment. In severe cases, if medical intervention is
delayed, pulmonary edema may become life threatening. Recovery is
generally complete within a few days; in some rare cases,
persistent lung function abnormalities have been reported.

In particular, PTFE (Teflon) decomposes to a very toxic gas when exposed to fire. This gas, Perfluoroisobutene, is about ten times more toxic than the poison war gas phosgene. For this reason a product that contains PTFE MUST list information regarding this hazard in the MSDS even if it doesn't list the actual ingedient responsible.

JCHannum
04-15-2008, 03:54 PM
Whatever. WD40 does contain a finely divided white particulate material which is not dissolved, and which does leave a gummy residue when the volatiles evaporate.

John Stevenson
04-15-2008, 04:31 PM
It's probably the remains of the MSDS sheet..................

.

Fasttrack
04-15-2008, 05:46 PM
Thanks Evan - like I said, this ended up being a very satisfying and fairly quick project. I'm just ecstatic to have my good old calipers back. I used them for about a month with their rough and clicky movement ... it sucked!

I figured I might get some crap for using WD-40. I figured it wasn't the best choice ever but being on a college campus with only a wal-mart... well the pickin's are slim :) Next time I'm home I'll probably put together an enco order to get some other stuff and I'll get some of that instrument oil. Can't be too expensive.


Edit - Hey JC, what kind of lighter fluid do you use? Are you talking about like kingsford bbq lighter fluid or something else? What about clean kersosene. Thats what I would usually use to clean machines and etc (like i said, WD-40 is all i have while at college)

Evan
04-15-2008, 05:54 PM
WD40 does contain a finely divided white particulate material which is not dissolved, and which does leave a gummy residue when the volatiles evaporate.
Not that I can detect, and I have tested it. Nor do the listed ingredients support that claim. We already had this discussion before and I gently evaporated off a few grams of WD40 and it left exactly zero residue. I wouldn't want you to make people think I was advising them to use a product that might cause a problem with their machines. In Xerox we learned the hard way (and expensive way) not to use products with PTFE in them. Many years ago somebody tried a product called Triflo which is loaded with fine PTFE. The initial results were very promising so the company issued it to all techs and indicated that it should be used on sleeve and oilite type bearings. Within a year nearly all of those bearings were beginning to gum up and all eventually had to be replaced. I wouldn't use a PTFE loaded lubricant on any sort of bearing and I most certainly wouldn't use a PTFE loaded product as a cutting oil for aluminum.

Triflo works well to prevent snow from sticking to snow shovels and plows.


Fasttrack,

Lighter fluid is naptha, the same as "white gas" used in camping equipment. It's pretty flammable. Deodorised lamp oil would be a better choice. Watch makers use benzene or at least they used to. It's highly carcinogenic and I doubt you can buy it if you wanted to.

Lew Hartswick
04-15-2008, 06:12 PM
Very nice repair. NOW The big question is HOW di you get the
antibacklash gears engaged with the spring tension?????
I took (part way) apart an inexpensive (probably Harbor Freight)
caliper to try and rid it of chips in the gear/rack and couldn't figure a
way to get the spring loaded gear set against the rack. It's still setting
here on my desk. :-)
...lew...

JCHannum
04-15-2008, 07:10 PM
I use Zippo or other cigarette lighter fluid. It is lighter than kerosene or gasoline and evaporates more quickly.

This is a photo of a bottle of WD40 I filled about two hours ago that clearly shows the heavier component settling. It might be a wax or some such, I have no idea what it may be, but it is an insoluble that requires agitation to keep it in suspension. The can instructs to agitate before use. This is bulk material, aerosol possibly does not have this material as the instructions do not include agitation.

http://members.aol.com/jchannum/wd40

Fasttrack
04-15-2008, 07:14 PM
The anti-backlash gears engage the single gear on the "out-put" shaft that the needle is pressed to. To get them tensioned and engaged, I went ahead and assebled the brass part of the caliper head. Then, I gently tilted the shaft with the pinion gear. This disengages one of the two gears that drive the "out-put" shaft. While keeping pressure on the shaft with the pinion gear, I used a jewelers screw driver to carefully wind the gear. The trick is to get the whole brass plate assembly put together before trying to wind the gears. I tried several times before putting the brass plate assembly together and was unsuccessful.



p.s. If anyone knows the correct terms for all these little bits and pieces, i'm all ears! I'm kinda making them up as i go :)

Fasttrack
04-15-2008, 07:17 PM
JC - Thanks!

Thats interesting with the WD-40. I've never noticed that effect with the aersol type. I've often emptied aersol cans that ran out of propellent into a glass jar for soaking parts in. But I'm always careful to make sure there is no pressure left in the can when I pierce it ;)

I'll have to see if the bulk variety does the same when its in a glass jar. Regardless, I don't think WD-40 is the right choice for caliper lubricant, it was just what i had handy.

Evan
04-15-2008, 07:36 PM
That is certainly different than the aerosol and the 4 litre can of WD40 I have. It looks like an emulsion of water is in the product, a lot like vinegar and oil. Is it possible that your can has been subjected to temperature changes and has inhaled water vapor from the atmosphere like a car gas tank is prone to do?

Murphy
04-15-2008, 08:45 PM
I've used a variant of watchmaker's lube; 1 part of Pfluger's Speed Oil for spinning reels with 50 parts of 1,1,1-trichlorethane.

Yes, I know it's banned and all that BS, but for some things you can't just beat it!:eek:

The local hardware store had solvent on sale, and I got two gallons of Sunnyside Carbo-Sol for $12 each! I've turned down $40/gallon for it, good luck getting anymore of that!

Allen

JCHannum
04-15-2008, 09:00 PM
It is from a tightly sealed one gallon can that has happily resided in my climate controlled basement shop for a month or so since purchase. It is typical of the product and every can I have ever used has displayed the same characteristics.

BTW, that is not phase separation as an oil water mixture, it is the material itself settling. It had only sat for a couple of hours in the photo, by the morning, the majority of the bottle will be clear liquid with a layer of white residue at the bottom.

Evan
04-15-2008, 09:54 PM
My bulk supply doesn't have anything that resembles that. It's water clear but for the color. It also doesn't mention anything about shaking the can.

I have a good idea what it is and why mine doesn't do it. Our product isn't the exact same product since it must be packaged differently due to our language requirements.

Some time ago they were forced to change the formula for WD40, at least in the US. In order to meet the restriction on VOCs they replaced a portion of the Stoddard solvent with paraffinic long chain hydrocarbons that have a very low VOC rating. These compounds are very much like a liquid wax and of a higher density than the other components in WD40. I haven't seen the product here as we don't have the same regulations on VOCs, yet. I can still buy 5 gallon pails of oil based paints here unlike in California.

I am pretty sure that the milky substance is simply the long chain low VOC material separating. This would be very similar to the wax formation that occurs in diesel at low temperatures.

JCHannum
04-16-2008, 07:36 AM
I have no idea what it is, but perusal of the MSDS's of the various penetrants shows they all have very similar makeup, including 70%-80% volatiles, which would indicate a rather significant percentage of non-volatiles which would remain as a residue. This is what can accumulate and gum things up.

Also, as to the teflon requirements on the MSDS, Tri-Flow is advertised as containing PTFE, yet no mention is made of it in the MSDS. This is for the aerosol and includes the propellants, but no flourocarbons. Note the date, it is quite recent.

http://www.paintdocs.com/webmsds/webPDF.jsp?SITEID=DBS&prodno=032053200090&doctype=MSDS&lang=E


The MSDS is not always a reliable document to determine the actual composition of a material.

Evan
04-16-2008, 08:27 AM
You have to know how to read the MSDS and what is required by law and why.

The Tri-flow PTFE content is responsible for this health warning:




UNUSUAL FIRE AND EXPLOSION HAZARDS
Containers may explode when exposed to extreme heat.
Application to hot surfaces requires special precautions.
During emergency conditions overexposure to decomposition products may cause a health hazard. Symptoms may not be immediately apparent. Obtain medical attention.

Also the PTFE is the reason that contact telephone numbers are given in the MSDS.



I have no idea what it is, but perusal of the MSDS's of the various penetrants shows they all have very similar makeup, including 70%-80% volatiles, which would indicate a rather significant percentage of non-volatiles which would remain as a residue. This is what can accumulate and gum things up.

Oils are considered to be non volatile. Light machine oil is one non volatile component of WD40. There are many possible non volatile liquid components that will not cause gumming, especially various silicone compounds such as diimethylsiloxanes which do not evaporate. The major non volatile component in the penetrants now are the paraffinic hydrocarbons I mentioned. They do not form gums precisely because they are non volatile and so do not evaporate.

I checked my browser history and the MSDS for WD40 that I downloaded from WD40.com was for the Canadian product. There is a difference and the difference is paraffinic oils I mentioned. This is the composition of the US product.




3 - Composition/Information on Ingredients
Ingredient CAS # Weight Percent
Aliphatic Hydrocarbon 64742-47-8 64742-48-9 64742-88-7 45-50 percent
Petroleum Base Oil 64742-65-0 15-25 percent
LVP Aliphatic Hydrocarbon 64742-47-8 12-18 percent
Carbon Dioxide 124-38-9 2-3
Non-Hazardous Ingredients Mixture <10


The other components can be determined from the CAS numbers and are the same as the Canadian product but with different percentages.

The LVP Aliphatic Hydrocarbon product is described as this by one manufacturer:




http://www.penreco.com/images/trans_spacer.gif http://www.penreco.com/images/trans_spacer.gif Penreco 150-B Solvent is a broad boiling range aliphatic hydrocarbon solvent derived from highly refined kerosene. It is composed primarily of C9 - C15 cycloparaffinic, isoparaffinic and aromatic hydrocarbons. Penreco has determined that 35% of this product meets the low vapor pressure (LVP) VOC exemption for consumer products as set by the California Air Resources Board.


Benefits

Controlled flash point and boiling range
Sulfur and nitrogen content of <0.5 ppm
Water-white appearance
Higher solvency than comparative aliphatics
Low reactivity


Applications

Chemical processing
Degreasers
Household and industrial cleaners
Insecticides

JCHannum
04-16-2008, 09:31 AM
Evan, I do know how to read MSDS's and what is required by law and why. I wrote MSDS's in one of my former lives as a matter of fact, so I do have a bit of expertise there.

The only point is that even though Tri-Flow contains teflon, it is nowhere mentioned on the MSDS, and is not required to be mentioned specifically, as are many ingredients, and the MSDS is not the be all end all when it comes to determining the ingredients of a material.

My bad, I should have said in the ingredient listing.

Evan
04-16-2008, 09:46 AM
The only point is that even though Tri-Flow contains teflon, it is nowhere mentioned on the MSDS, and is not required to be mentioned specifically, as are many ingredients, and the MSDS is not the be all end all when it comes to determining the ingredients of a material.
No, it doesn't say Teflon, which is a brand name. It does say PTFE which is the same thing.

http://vts.bc.ca/pics3/triflo.jpg

Herm Williams
04-16-2008, 10:56 AM
I use clock oil. It stays where you put instead or running. google has a lot of sites that sell and explain how that works.
re

ACF
04-16-2008, 09:14 PM
Jim H.

You may be able to keep your WD-40 in one phase by addding a small amount of xylene or toluene to the batch, as this will "sweeten" up the solvent system.
I doubt there is any teflon in WD, but you won't be able to tell from the MSDS. The TRI-Flow with teflon MSDS doesn't even list it in the ingredient section, so the teflon is in there in a small concentration. I also saw under the hazardous decomposition products for Tri flow only CO and CO2, no mention of anything else.

I doubt that WD-40 has any perfume compounds in it, simply becase I don't smell any, and those types of chemicals are usually used in concentrations less than one percent, because they are very potent (smellly) and very expensive.

As a chemist, the smell and toxicity of xylene and toluene don't bother me, but I suggest you "Travel at your own risk". I love the smell of solvent in the morning. :)

Chris

Evan
04-16-2008, 09:50 PM
WD40 has perfume. None of the ingredients listed together or in combination have the characteristic odor that WD40 has, not even close. It is very common to use aromas and fragrances to distinguish a product from other similar products. In the case of WD40 the fragrance has even earned it's own name, WD40.

The probable fragrance is estragon oil which accounts for the yellow color. It also accounts for the warning in the Australian MSDS for WD40 not to use epinephrine in response to bronchospasms (allergic reaction) caused by excess inhalation of the product because of potential myocardial sensitisation to catecholamines. Estragon oil is an industrial fragrance that has the potential to stimulate the production of catecholamines in the body when inhaled in large doses.


I also saw under the hazardous decomposition products for Tri flow only CO and CO2, no mention of anything else.


The decomposition warning in the Tri-Flow MSDS is specific for flourocarbons, not CO or CO2


Application to hot surfaces requires special precautions.
During emergency conditions overexposure to decomposition products may cause a health hazard. Symptoms may not be immediately apparent. Obtain medical attention.

Those are not symptoms associated with CO2 or CO. The reason for the phone numbers is that the PTFE is not listed.

JCHannum
04-16-2008, 10:22 PM
Chris, thanks for your reply and comments. The component goes back into solution or suspension with little trouble, and it merely requires a quick swirl to accomplish. I only mentioned it as it does make WD40 inappropriate for lubricating instruments.

I do agree with your statements, but do not wish to see Fasttrack's post hijacked any further. The information he has presented is pertinent and very informative and it should be allowed to stand on it's own merits.

Evan
04-17-2008, 01:10 AM
Here is an excerpt from the Australian MSDS for WD40. They are much stricter there and everything must be listed.



Section 3 - COMPOSITION / INFORMATION ON INGREDIENTS
NAME CAS RN %
solvent naphtha petroleum, medium aliphatic 64742-88-7 >60
petroleum base oil as
paraffinic distillate, heavy, solvent-dewaxed (severe) 64742-65-0. 15-25
corrosion inhibitor unregulated 1-10
wetting agent unregulated 1-10
fragrance unregulated 0-1
carbon dioxide 124-38-9 2-3

http://www.wd40.com.au/msds/ChemWatch%20MSDS%20WD-40_Aerosol.pdf

Fasttrack
04-17-2008, 01:35 AM
Hey now, JCHannum has addmitted that he wasn't sure that it was teflon after you corrected him. :) Regardless of the exact chemical composistion of WD-40, its not the right stuff for calipers.

I knew that when I used it, but its all I had available to clean and lubricate. Using the wrong oil makes a mess of calipers, quick! So JC, along with TGTool and Herm Williams were correct to suggest a tried and true lubrication for precision measuring devices. They were just offering a helpful suggestion, albeit with a minor technical error that your corrected. I say we all let it go and be friends again :D


<edit> ahh I see you've edited your post, thanks! And thanks for all the information from everybody. Learned alot about WD-40 that I wouldn't have otherwise known.

Tony
03-01-2012, 10:18 AM
Success! Success, Success!
(3 stooges fan anyone?)

what an ordeal this has been! took the calipers to a watch repair
to have the lens and needle removed. he proceeded to take everything
apart with a 4' pry bar and linemans pliers. :(

after the lens and needle where out (all I asked of him) he insisted that
the calipers opened up (casework) by pulling the little bent shield that keeps
chips from falling down into the rack. his linemans pliers did a quick job of
just tearing that thing out.

anyway I took it home (figured it was a goner anyway right?) to discover
the plastic/metal "gibs" were gone.

went back and he pleaded ignorance.

in the parking lot outside the lumberyard (waiting for some hardwood to
get cut to size for me) I managed to (carefully!) take apart the rest of the
calipers with my pocket knife of all things.

now I realize this all sounds very scary.

Got everything home, cleaned the calipers meticulously.
Using a loupe I found 2 small (alum?) chips in the pinion teeth.
picked those out with hypodermic needle.
made a new gib from green UHMW.

had to reassemble 3 times trying to figure out the backlash spring.

now its zeros every single time!

still doesn't feel silky smooth but maybe there's some real small
stuff in there? good enough for now!

I feel like a guy who's just found $150.

Thanks for all your help esp Fasttrack w/ the encouragement.

Tony

ps I shot the needle across the room twice I still don't know
how I found it.

Black_Moons
03-01-2012, 11:26 AM
Tony: Good story... Remind me not to go to that watch repairman..

legendboy
03-01-2012, 12:46 PM
I took a sticky last word to a local watch guy and he fixed me right up

Oldbrock
03-01-2012, 03:35 PM
All that trouble could have been avoided by using good vernier calipers. Gave up on dial calipers eons ago. Gave my dials to the kids to play with. Peter

Tony
03-01-2012, 03:53 PM
What do you consider good vernier calipers? $50 mitutoyos or $300 B&S?

Oldbrock
03-01-2012, 05:21 PM
I have Helios, Mitutoyo and Starrett. The Mit. has prisim beam, scales are flush, no parallex error. Peter

Fasttrack
03-01-2012, 05:37 PM
OldBrock's a purest! I feel the same way about digital calipers as he seems to feel about dials :D

I save my vernier reading skills for the mic, when I just need a quick measurement, I use the dial calipers. Reliable, reasonably accurate and quick.

Tony - Glad you were able to get your calipers working again, although your experience sounds pretty scary!

Clevelander
03-02-2012, 12:11 AM
You said that the movment wasn't smooth...did you inspect the gears under magnification? Perhaps one (or more) of the teeth on the pinion gears got a little distorted, or perhaps the pinon shaft is slightly bent making the movement of the gear eliptical.

Fasttrack
03-02-2012, 12:18 AM
You said that the movment wasn't smooth...did you inspect the gears under magnification? Perhaps one (or more) of the teeth on the pinion gears got a little distorted, or perhaps the pinon shaft is slightly bent making the movement of the gear eliptical.


Hmm? This thread is several years old. The calipers have been fixed and working beautifully for a long time... Or was this aimed at Tony? He, evidently, had success in repairing his caliper, too. :)