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"Do It Yourself"
Indicator, caliper, bore gage, & micrometer repairs

 

  • Anvil pressure on indicating micrometers
  • Calibration procedures on page 7
  • Changing contact points on your test indicator
  • Compac and Interapid bore gage clamp for 2-6" and 2-12" models
  • Compac: installing new-style ball bearings in older models
  • Contact Point Lengths: How to measure them
  • Creating a .0002" indicator with a long contact point
  • Crystal Insertion: Instructions and tools
  • Dial caliper repair: a Do-It-Yourself Guide
  • Etalon spindle locks: How to replace those awful plastic locks
  • Installing Indicator Hands: Use the right tools
  • Interapid stem attachments: How to replace them
  • Last Word Indicators: Some easy adjustments
  • Micrometer anvil pressure
  • Mitutoyo calipers: Zero-setting
  • Mitutoyo micrometers: Zero-setting
  • Mitutoyo Pocket "Last Word" style indicator repair
  • Mitutoyo pocket thickness gage: Adjusting the bezel
  • Q&A where customer questions are answered ... page 6
  • Standard Bore Gage: replacing the gaging plunger
  • Starrett calipers: Zero-setting
  • Tools for doing it yourself

Related topics: micrometers, calipers, dial indicators, test indicators

Note: for specs and calibration information on specific instruments refer to the contents page.

Make your own long point .0002" indicator

 

By replacing the contact point on Compac model 215GA test indicator with the 1.44" long point (part number 018660-09) you in effect change the dial graduations from .0001" to .0002". Additionally, each revolution equals .008" and the overall travel becomes .048". The indicator will be accurate but you must be sure to mark the tool so that it isn't used by someone else under the mistaken assumption that it still reads in .0001".

Similarly, you can replace the standard point on Interapid test indicators with the special 1.450" length point (see contact point list on page 21) to achieve the effect mentioned above.

If you need longer points, Interapid offers two models of .0005" test indicators which come equipped with 2.75" length contact points. There are no equivalent .0001" models available. See Interapid on page 23.

Additional contact point information - ordering information 

Contact point lengths

 

It is imperative that the correct LENGTH of contact point be used with dial test indicators. Test indicators rely on leverage ratios to amplify the readings. Changing the length of the contact point (from the center of the ball to the center of the pivot) will alter the ratio and result in incorrect readings. The common problem of incremental errors (ie, the readings gradually get worse from one revolution to the next) is most likely due to the installation of the wrong length point.

Most manufacturers specify the proper point length in their catalogs. It is not always clear how the over-all length of the point is measured.

Compac contact points should be measured from the center of the carbide ball to the far end of the threads even though the manufacturer's catalog shows otherwise (it's a misprint).

The standard method of measuring Interapid, Bestest, Tesatast, Mitutoyo and other contact point lengths sounds complex: one takes the overall length of the contact point, from end-to-end, then subtracts the length of the threaded portion of the contact point, and subtracts one-half the diameter of the spherical ball at the end of the contact point.

Some end-users purposely install extra-long contact points because their application requires it. This results in erroneous readings on the dial and is okay as long as the operator is aware of it. If the indicator is only used for centering, then this may be acceptable.

Most manufacturers make indicators designed specifically for use with long contact points. Compac test indicators have the letter designation "L" as a component of their model numbers. Interapid indicators can be fitted with long (1.45") contact points but all dial readings must be doubled to obtain correct readings. Even longer points (up to 5-1/2 inches) are available for Interapid indicators.

Catalogs which sell dial test indicators will often publish the proper length and method of measurement of the point which must be used with a particular model. For greatest reliability it is best to contact the manufacturer to obtain correct contact point information.

Click here for detailed information on contact point lengths

Contact points can have a variety of ball diameters typically ranging from .015" to .120" and are available in a variety of materials. For general work, it is highly recommended that contact points fitted with carbide balls be used, especially for .0001" indicators. The size of the ball diameter has no effect on the indicator's accuracy.

 

Crystal insertion

 

The crystals (clear plastic) for test indicators, dial indicators and calipers are typically larger than the bezel for which they are designed.

New crystals are also flat. They become domed once they are inserted, under pressure. An old crystal will appear domed because, after a long time, it will take on this shape. Unfortunately, at this point it will also fall out easily.

The crystals have a beveled edge which will fit into the groove on the upper part of the bezel, but must be inserted in a concave (domed) manner so that the crystal will remain in place under pressure, and so that the plastic clears the movable dial hand.

A crystal press is usually required to give the plastic lens its concave shape. (Bestest indicators and B&S calipers are some exceptions.) Place the crystal and bezel in the press, in the correct orientation (take into consideration the beveled edge) and while the press is bending the plastic, gently snap the bezel into place. Release the press and the crystal will be firmly seated and have the correct curvature.

For complete details and supplies (new crystals) please refer to page 233.

 

Etalon micrometer spindle locks

 

The very oldest lock for micrometers was made in the 1950's. They are metal and have an eccentric cam lock. These are no longer available.

The older model Etalon indicating micrometers (1960-1990) have plastic spindle locks which wear out rather quickly from over-tightening. These are no longer available. But there are metal replacements. You can buy this lock and install it yourself.

Fortunately the newest and most recent models have an improved metal locking device. This won't retrofit to your older model, however. The new diameters are different.


 

Left: #037905 replaces plastic lock - notice the rim - this is often a very tight fit* and may need customization. (made by Etalon) Refer to Etalon parts list

Right: #017857 new style lock (OD = .315") for new model micrometers only. Refer to Etalon parts list

How to replace: unscrew the spindle completely. The old lock usually pulls out easily.

After you've removed the old spindle lock, look for a step (counter bore) measuring .406" x .090" in the micrometer body. The presence of this counter bore indicates that this is a new style lock.

Insert the new lock and check to see that the inside of the barrel is clear so that you can screw the spindle back in. Don't force anything. And remember: hand tighten only. That's all there is to it.

*If you're trying to install #037905 you may notice that it won't fit. The lock diameter is over-sized and may have to be stoned slightly or turned down. You might be tempted to open the hole on the micrometer instead but we suggest you don't tamper with the micrometer body. If you attempt to force fit the lock you may ruin everything because you might not be able to line up the opening correctly, and you may not be able to remove the lock! Proceed with utmost caution.

**If you hand tighten these locks then there's no danger of damaging the expensive spindle. The spindle is made of hardened steel and it would take a major effort to cause damage by over-tightening of these stainless and aluminum screw assemblies.

 

Compac and Interapid bore gage clamp

 

The square shaped clamp on the 2-6" and 2-12" bore gage models which hold the extensions in place is part #040406 (see bore gage parts list). This clamp is sent unfinished. It doesn't have a thread. The reason is, the thread needs to be custom cut to match the thread already in your gage head.

If you want to do it yourself, you'll need a metric M12x1 tap. Remove the old clamp, put the unfinished clamp in place and using the thread of the bore gage head as a guide, insert the tap, cutting a thread into the clamp. Of course, if you prefer, we can install this for you.

Some customers can't understand that these clamps are sold unfinished and they put up quite a stink when they receive the parts. Be advised: that's the way it is.

 

Last Word indicators

 


STARRETT 52953 0.0005'' GRAD 0-15-0 DIAL READING LAST WORD DIAL TEST INDICATOR W/BODY CLAMP

Starrett Last Word indicators (model #711) have a contact point which swivels on a ratchet. Sometimes the ratchet doesn't fit well and the contact point will cause the lever arm to jam. You'll have to try another contact point. Sometimes the pivot screw protrudes too much and rubs against the contact point. Again, try another point until one fits. For proper operation make sure the reversing lever is fully engaged up or down and that the contact point is properly seated in the ratchet.

If the indicator hand jumps on a regular basis, try de-magnetizing the indicator. Spinning objects and motors can induce magnetic fields in the indicator. If magnetic fields are a problem in your shop environment it may be best to switch to a non-magnetic indicator. Bestest, Compac and Interapid are all suitable alternatives.

More details and suggestions are shown on page 117.

Contact points for these indicators are available in 3 ball diameter sizes.

 

Interapid stem attachments

 

If they're bent or broken you can replace Interapid stem attachments with a bit of care. When you remove the old stem, don't lose the other parts. Unscrew A, tap out the bushing E, pull out the old stem C, save the washer D which goes on the inside, remove B if necessary. Reassemble in reverse order. You will notice that you can increase the swivel friction by tightening screw A.

The replacement stem attachment and associated parts can be found on page 88.

See more information on Interapid or refer to our online parts list.

 

Zero setting Mitutoyo dial calipers

 

When the jaws are closed on a Mitutoyo dial caliper, the hand should point to zero at the 12 o'clock position. If it's off a bit, that's okay, you can rotate the bezel so that the zero and the hand line up. But if it's off by more than 10 divisions, Mitutoyo has provided a little adjuster (part #M142115) and the following instructions:

  • Rotate the bezel to bring the zero point to the 12 o'clock position.
  • Open the jaws by about 10 to 20 mm and bring the pointer to the zero.
  • Insert the adjuster into the groove which you'll find on the rear of the dial.
  • When you press down on the adjuster, the pointer won't move and you can slowly close the jaws.
  • When you let go, the jaws should be closed and the hand will remain at the 12 o'clock position.

note: on the 0.05mm and .2" per revolution models, you'll have to remove the bezel clamp in order to find the groove on the rear of the dial.

further note: zero setting on the "made in Brazil" calipers is not possible without disassembly.

For more information on Mitutoyo refer to our contents page. 

 

Zero setting Starrett calipers

 

If the hand is no longer set on zero then the gear jumped a tooth because the gage was dropped or hit. It doesn't necessarily mean that there's internal damage. If the caliper still moves smoothly then everything's probably okay. Resetting the hand is a bit tricky but it can be done. Remove the bezel clamp and then tilt the bezel off carefully like the plastic lid on a take-out cup of coffee. (Pretend the coffee's hot.) The hand can then be pried off using a hand lifter or two smallish screwdrivers, one on either side of the pinion. Do this with caution so that you don't break the center pinion in the process. Now realign the hand to zero and tap it back on, gently but securely. Reassemble and you're all set. Don't attempt to play with the movement or to remove it. The gears are preloaded and you'll have a heck-of-a-time trying to get things to work again. If you're squeamish about all of this, send the gage to a repair shop (we no longer repair Starrett calipers). For additional instructions on dial caliper repair, refer to page 44.

 

Zero setting Brown & Sharpe calipers

 

If the hand is no longer set on zero then the gear jumped a tooth because the gage was dropped or hit. It probably means there is a broken tooth, or the gears have slipped. Unfortunately there's no way to deal with this other than attempting a repair. Refer to page 103 for additional information.

 

Changing contact points

 

It would seem to be such an intuitive procedure - changing contact points on your test indicator - that writing instructions is almost trivial. There are some pointers which may be of interest, however.

The points unscrew or, in the case of Starrett Last Word, Gem, Alina 88 and a few others they snap in place. To unscrew them, you may use fine nosed pliers for this job. If the contact point has a small hole drilled through it, then you may push a pin through this hole and use that to screw and unscrew the point. If the point has two flat spots near the base, then a contact wrench can be used. These come supplied with Bestest and Interapid indicators. They're the circular black disks located in your indicator box and the slots fit perfectly onto the contact point for easy removal. When you put the new point on, don't over tighten. It's a small thread and you may break the point. Also be careful not to damage the carbide ball at the end of the point.

If you need a replacement contact wrench for your Interapid or Bestest, check on the parts lists for the ordering number.

On the snap-on style test indicators you swivel the contact point holder to the side so that the point can be removed and replaced. You may want to use a small screwdriver to help you swivel the metal plate because it can damage your fingers. You'll also want to make sure that the point sits properly on the ratchet when you're done. 

 

Mitutoyo pocket thickness gage adjustment

 

The bezel on Mitutoyo pocket dial thickness gage no. 7308 and 7309 is designed to rotate a little bit to the left and a little bit to the right so you can set the zero. The bezel should stay put, however, and not rotate on its own. If it's loose, carefully peel off the plastic back just enough to expose one of the two holes. A small Phillips head screw driver will allow you to loosen the screw which you'll see inside the case. Loosen it just enough so you can slide the brass clamp a little, then tighten. You'll notice that you can adjust the friction which holds the bezel in place by sliding this clamp in or out. For additional information refer to page 12.

 

Compac new ball bearing design

 

Although redesigned more than 15 years ago, there are so many "older" Compac indicators still in use that we have to refer to these as "new". In 1999 COMPAC redesigned the ball bearings and the pivot assemblies (contact point support) for their 210-220-230-240 series test indicators. The old ball bearings case (ID 3,6 mm) was black while the new ones (ID 2,0 mm) are stainless. Similarly, the pivot assembly comes in old and new styles to match the ball bearings case inner diameter. You will still be able to repair the older models because the new ball bearings and pivot assemblies can be installed in the old indicators. COMPAC claims that adjustments will now be easier and that accuracy will be improved with this change.

Series 210-220-230-240:

part #044256 adjustable ball bearing (old)
part #044259 adjustable ball bearing (new)
part #044257 fixed ball bearing (old)
part #044260 fixed ball bearing (new)

Refer to a new parts list which identifies these parts.

 

Zero setting Mitutoyo micrometers

 

Before use, even with a brand new micrometer, be sure that it is set to zero. The manufacturer admonishes us to "observe the following points to correctly zero adjust the micrometer."

  • Rotate the ratchet stop 1-1/2 to 2 times to exert a constant measuring force.
  • Allow sufficient time for the micrometer [to become] thermally stabilized, especially when moved from a significantly different temperature.
  • Zero adjust the micrometer in a posture in which measurements are actually performed.
  • Use a calibrated standard bar (micrometer standard).

With the spindle closed on the 0-1" micrometer, or closed onto a micrometer standard for larger micrometers, the zero of the barrel should coincide with the zero on the rotating thimble. For instance, on a 1-2" micrometer you must insert a 1" standard and close the thimble. If the zeros don't line up, use the wrench which came with your tool, hook it around the barrel so it fits into the small hole and gently turn the barrel until the zeros line up. If the barrel won't budge, use the back of a screwdriver to gently tap the wrench. Old micrometers may have become corroded and the barrel won't move. In this case you'll have to send it in for reconditioning. Micrometer wrenches are available if you've lost yours.

 

Installing Indicator Hands

 

This should be no problem if you have the right tools. You'll want hand lifters to remove the old hand, a fine reamer, and a small hammer. If needed, check the index on this page to find information on removing the bezel (indicator crystal insertion). See repair tools.

New hands usually have holes that are too small to fit onto the pinion. If you try to hammer these on, you'll only bend the pinion and be worse off than before. A very fine reamer is used to open the hole just enough so that the hand can be hammered on with a fit tight enough so that the hand won't come loose. Please don't use glue. This invariably seeps into the works and you'll have wasted both time and money.

On dial indicators, according to AGD standards, the hand is set at 9 o'clock. Kafer metric indicators, made in Germany, have the hands set at 6 o'clock.

Bestest and many other test indicators are now set at 5 o'clock. This allows you to use the indicator "upside down." Compac long range indicators and some Starrett models are set between 10 and 11 o'clock; those with the standard (one revolution) range are set at 5 o'clock while Mercer short range sets the hand at 11 o'clock. Interapid indicators are set at 12 o'clock. New Mitutoyo model 513 indicators are set at 11 o'clock. Starrett Last Word and some older Mitutoyo indicators need to be set at 6 o'clock so that the hand moves equally in both directions.

If the hand is inadvertently set in the wrong position, it will affect neither the indicator's functionality nor its accuracy.

 

Standard Bore Gage Do-it-yourself

 

How easy is it to replace the gaging plunger yourself? Fairly easy, according to our experience as long as you’re not all thumbs. A guide pin has to be adjusted so the new gaging plunger doesn’t stick yet doesn’t turn side to side. The guide pin is then secured with Loctite® so it doesn’t work itself loose - but use the removable kind! If you need a new gaging plunger, check our parts list.

 

 

Indicating micrometer anvil pressure

 

To calibrate or adjust the anvil pressure on an indicating micrometer you'll need a spherical steel ball smaller than 1" in diameter and a Correx gram force gage which has a range that will include your desired setting. Remember that 100 cN equals 1 N. The micrometer must be in a micrometer stand. Insert the steel ball between the anvil and spindle and turn the spindle so that the indicator hand is at zero. Press the surface of the anvil with the tip of the Correx gage until the ball falls. Take a reading on the force gage at that point. Repeat this process many times until you get consistent readings. It takes a bit of practice. For one thing, you must keep the Correx feeler at right angles to the micrometer anvil.

You can lessen the anvil pressure on an Etalon indicating micrometer by removing the end cap on the micrometer and loosening the large lock nut. The micrometer spanner wrench is used to do this. You'll find that you can bring the pressure down to about 1 N (=100 cN) without affecting micrometer function. This is particularly useful if measuring flexible or thin-walled tubing.

 

Mitutoyo Pocket ("Last Word" style) Indicator

 

The old model Pocket Style Mitutoyo indicators such as model 513-128 are not worth repairing at this point. Some parts are no longer available and replacing them with the new, better designed Pocket indicators would be a wise move. However, some folks just can't leave a broken gage alone and wonder how to get the "movement" off the body. Here are the simple steps:

  1. Remove the bezel. It pries off with a flat blade screwdriver.
  2. Remove the hand using a hand lifter.
  3. Remove the dial.
  4. Unscrew the two larger (usually) philips head screws, and remove the two locating pins, if they are present, with needle nosed pliers.
  5. The movement now lifts off, but do it gently (don't force, or you may damage the teeth on the crown gear).
     

For additional information on the Pocket Style indicators refer to page 137.

 

Dial caliper repair - a Do-It-Yourself Guide

 

Dial calipers are now quite inexpensive to buy and often times the repair cost, from a repair shop, is more than half the new price. Many folks want to try their hand at fixes, both simple and complex, and we have devoted a page to this process with tips, hints and instructions. Please refer to page 44.

 

Books by René Urs Meyer

The Companion Reference Book on Dial and Test Indicators … page 178
Repair Manual for Swiss-made BesTest and TesaTast Indicators … page 177
Starrett 711 Last Word Indicator Repair Manual … page 199
Interapid Indicator Repair Manual … page 208
 

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14 Sarah Drive — Hauppauge NY 11788 — USA


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This page's most recent revision: 27 JULY 2016
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Original photographs and content copyright 2016 by René Urs Meyer

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