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Long Island Indicator Service


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Roy Meyer and team


Premium Quality Swiss Test Indicators

It would be hard to give a reason why you shouldn't buy the genuine Swiss made Interapid indicator. It has quickly become the standard against which all other indicators are compared.

Contents of this page and related topics:

Caution! Beware of look-alike Interapid indicators made in China which can be bought cheaply even through reputable catalog houses like Fowler and SPI. The low price will give them away. If the dial reads "Interapid" then you can be sure that you are buying the genuine Swiss article.

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Horizontal Interapid Test Indicator

This genuine, Swiss-made Interapid indicator is undisputedly the best test indicator of its kind. The large hand makes two complete revolutions in either direction and the small hand helps you keep track which revolution you're on. The right hand side of the dial has a thin black half-circle in case you want to use these in a set-up involving mirrors.

The 4 mm diameter mounting stem swivels and can be replaced if damaged. The two dove tails (back and top) are mounted with screws and these can also be replaced or removed if they get in the way. These dovetails, by the way, are hardened metal and won't get squashed with wear like the brass dovetails on other indicators. If you don't want 4 mm, then you can easily slip on a 3/8" adapter.

Many different contact points, including ruby, Teflon and nylon are optionally available, and easy to install. The contact point operates on a friction clutch, so you'll have to apply a bit of force to get the point to swivel, which it does, from the front of the indicator to the back. New indicators come with a special "wrench" for removing the contact points. It's okay to use a pair of jeweler's pliers for this purpose.

Unless you know what you're doing, you should under no circumstances attempt to disassemble or adjust any of the screws or bearings on the indicator.

These indicators are designed to function when the contact angle is about 12° to the work surface (see details below).

These indicators come in a sturdy box, with a .080" diameter carbide point installed, a wrench for removing the contact point and a manufacturer's statement of conformance along with allowable errors (see bottom of this page). Calibration certificates are not available. If you require such, you will have to send the indicator to an accredited calibration lab in your area.

You can order online by clicking any of the links shown below. Purchase orders can only be accepted based on credit review or for established accounts. In most cases, ordering online (Your Internet Price) will save a considerable amount of money. Be advised that product photographs shown at Amazon do not always correspond with the indicator model. Read the descriptions carefully.

Special 1.45" long contact point to be used in place of any .687" point. When you install this point, the readings on your dial will be doubled. That is, the .0005" graduations will become .001", the .001" will become .002", and the .0001" graduations will become .0002"

Contact us if you need to place an order with a company purchase order. If a link on this page brings you to Amazon, be advised that we will receive a commission on any sales. We do appreciate it.


The angle to the measured surface should be about 12° regardless of the contact point's position on the indicator.

Graduations Range Dial Ø Point Length Horizontal Model No. Order No. (paid link)
.0005" .06" 1.5" .687" 312B-1 74.111370 check price and availability
.0005" .06" 1.5" 2.750" 312B-15 74.111965 $435.00 … order now
.0005" (.001") .06" 1.5" 5.5" (extra long) 312B-15x 74.111965x see page 230
.0005" .06" 1" .687" 312B-2 74.111371 check price and availability
.001" .06" 1" .687" 312B-20 74.111374 check price and availability
.0001" .016" 1.5" .687" 312B-3 74.111372 check price and availability
.0001" .016" 1" .687" 312B-4 74.111373 check price and availability
0,01 mm 1,6 mm 37,5 mm 16,5 mm 312-1 74.111366 check price and availability
0,01 mm 1,6 mm 30 mm 16,5 mm 312-2 74.111367 check price and availability
0,002 mm 0,4 mm 37,5 mm 15,2 mm 312-3 74.111368 check price and availability
0,002 mm 0,4 mm 30 mm 15,2 mm 312-4 74.111369 check price and availability

Vertical Interapid Test Indicator

Vertical, jig-bore type test indicator with one dovetail and an integral 4 mm holding stem which swivels in one direction. You can buy adapters so that the diameter of this stem becomes 3/8" or 8 mm. (See below)

The contact point (Ø.080" supplied) also swivels through a wide arc. These are available from a short .687" to a very long 5.5" length. Other diameter balls and other lengths as well as contact points made of Nylon, Teflon or ruby are optionally available.

A friction clutch holds them in a steady position so it might take a bit of effort to move the point. Do not use any tools other than your fingers for this operation and be sure that the point is securely fastened before attempting to move it.

Never attempt to make adjustments to the ball bearings located on the side of the body, or you'll have a repair bill on your hands.

This superior vertical style indicator is well worth the invest-ment. We offer a full repair service as well as warranty repairs if there is ever a problem. Spare parts are available for anyone skilled in the repair of these admittedly difficult gages to repair. Simple "do-it-yourself" projects include replacement of the mounting stem, the dovetail and the bezel with crystal.

Vertical Interapid test indicator

The vertical models have just one dovetail.

Graduations Range Dial Ø Point Length Vertical Model No. Order No. Insist on genuine Interapid
.0005" .06" 1.5" 2.750" 312B-15v 74.111958 $435.00 … order now
.0005" (.001") .06" 1.5" 5.5" extra long 312B-15vx 74.111958x see page 230
.0005" .06" 1.5" .687" 312B-1v 74.111377 check price and availability
.0005" .06" 1" .687" 312B-2v 74.111378 check price and availability
.001" .06" 1" .687" 312B-20v 74.111379 check price and availability
.0001" .016" 1.5" .687" 312B-3v 74.111957 check price and availability
0,01 mm 1,6 mm 37,5 mm 16,5 mm 312-1v 74.111375 check price and availability
0,01 mm 1,6 mm 30 mm 16,5 mm 312-2v 74.111376 check price and availability

Complete Interapid Indicator Sets

Several models are available in complete sets. They will also include the following:

  • 74.106331 height gage bar with clamp
  • 74.108943 adapter sleeve 3/8"
  • 74.108942 adapter sleeve 8 mm
  • 74.106931 axial support 3/8" Ø stem
  • 74.106026 axial support 8 mm Ø stem

These parts are described individually on our indicator attachments page.

Interapid Model No. Style Complete Set Order No.
74.111370 312B-1 .0005" horizontal 74.111508 place online order
74.111371 312B-2 .0005" horizontal 74.111509 place online order
74.111372 312B-3 .0001" horizontal 74.111510 place online order
74.111377 312B-1v .0005" vertical 74.111513 place online order

Important calibration information

Unlike other test indicators, Interapid indicators do not have serial numbers on them. Perhaps someday the manufacturer will remedy this situation but for now you'll have to assign your own unique serial number to each indicator if you intend to keep track of their calibration. It's easy to scratch a number into the painted body using a sharp tool. A permanent marker with a super fine point will also work. Do not use an electro-engraver because it creates sparks which have been known to damage the pinions on the gears.

Interapid series 312 test indicators are designed to permit a true reading when the angle between the stylus and the reference surface is 12° as shown in illustration A and B.

In the rare cases when axial measurement is required with the stylus at 0° with respect to the reference surface as in C and D in the illustration, (for instance: small diameter bores) the readings must be multiplied by a factor of 1.022

It also follows that incremental calibration discrepancies can be corrected by adjusting the contact point angle.

Interapid contact point angle setting

Interapid indicator features

These indicators have a very light measuring force: just 0,12 N for .0005" models and 0,25 N for .0001" models.

The indicator is designed to measure with the contact point held at an angle of 12° to the measuring surface. (Some sources list this angle as 13 degrees. The difference is not significant.) This allows you to take measurements down a hole or in a bore.

The .080" diameter carbide contact point is easily replaceable with other diameters (from .015" to .120") and other substances (ruby, teflon or nylon). Under some circumstances, you can even install a longer point. See contact points.

The dial hand makes two revolutions in each direction. The small counter hand keeps track of the revolutions.

The dial has balanced numbering: 0-4-0 (.0001" indicators) and 0-15-0 (.0005" indicators). The right half of the dial features a thin black band which will help identify the plus or minus side when using a mirror.

The novel tapered shape tilts the dial towards the observer. Both Mitutoyo and Starrett have recently copied this design. This makes for easier reading with less likelihood of parallax errors as well as a reduction in glare from overhead lights.

If you need to slip the indicator into an opening then you may be interested to know that the width of the body at the stylus (contact point) is 10,3 mm which is broader than Bestest, Tesatast or Compac.

The holding stem is 4 mm (5/32") in diameter. The stem swivels and is attached to the body, although it can be removed and replaced. Simple instructions for this procedure are available on our Do-It-Yourself page. If you need a holding stem with a different diameter, use one of the following adapters show on our spare parts list:

  • An elegant 3/8" adapter fits over the 4 mm stem. Order no. 74.108943
  • For metric set-ups, use the 8 mm stem adapter. Order no. 74.108942

The dovetails are hardened metal, screwed onto the body. These can also be removed and replaced. See our spare parts list for replacement parts.

Interapid repair

Long Island Indicator is an authorized repair service for Interapid test indicators.

Top-of-the-line Interapid test indicators are probably the most challenging of all to repair. Absolute cleanliness and the replacement of critical parts is essential to a quality repair. We've been trained by masters in the craft, and having an ample supply of fresh parts directly from the manufacturer are able to return any Interapid test indicator to A-1 condition.

To make things easy, we have fixed repair costs. It's our policy to replace any damaged or worn parts necessary for the full function of the indicator. This way you'll be sure to get an instrument that's as good as new and one you can rely on. And, if you request it, you'll get a short-form certificate of calibration, NIST traceable, for free; after all, when you get your indicator back you need to know that it's accurate. If you pay with a credit card, turn-around is less than a week.

Is the indicator damaged beyond repair? If the body is damaged in any way (the front end is squashed, for instance) then we'd have to replace the body and you'd have to pay about $190 for the repair. Not usually worthwhile. If the whole face has come off because it was ripped off - that sounds serious, yet happens regularly - it's probably repairable for the normal cost quoted in the paragraph above.

Do you only need a new crystal installed? We charge $45 and that includes return shipping. Just enclose a check and we'll do a 2-day turn around. To make it easy, print out a packing list.

Sorry, we can't repair old models such as the 310B and 311B series. Parts for these indicators are no longer available. If have one of these, then you've gotten your money's worth since they were discontinued about 40 years ago. If you just bought one on eBay, then you've been had.

Is Interapid any good?

We rate them among the very best. If you'd like to compare the good points and the not-so-good points of the Interapid indicator with other manufacturers then take a look at our indicator comparisons page.

Using the correct contact point

While various diameter balls do not affect readings, the correct contact point length is critical. (Refer to model information on this page.) Use only points designed for Interapid indicators. Any deviation will result in reading errors.

When ordering new points, take note of the indicator's model number and decide on the ball diameter you'll need.

Problems with repeatability

According to the manufacturer, the Interapid test indicator is allowed a repeatability error as shown in the reference chart above.

Repeatability must be checked against the measuring surface. When the contact point is resting against the measuring surface, turn the bezel so that zero is directly in line with the pointer (hand). The indicator's "at rest" zero reading must not be used to verify repeatability.

Swiveling the contact point may cause the zero setting to change slightly. If this happens, reset zero by turning the bezel.

Zero readings may also be off when comparing contact point up and contact point down motions. Reset the zero by turning the bezel as needed.

Furthermore, repeatability can only be assured if the indicator is securely fastened to a good test stand or other fixture. Fastening by the dovetail as close as possible to the front of the indicator is the preferred method.

Interapid older models

Current test indicator models begin with the number 312. Previous models dating to the 1960s were number 311 and these are often still repairable, depending on the damage. The oldest models were number 310 and you can assume these are beyond repair simply because spare parts are obsolete. If the horse-shoe shaped clip which holds the bezel in place is missing, then you may have to improvise with a piece of spring-wire bent into the correct shape. You might be tempted to say "It only needs a cleaning," but that's almost never the case. None-the-less, if you want us to have a look, it costs you nothing but shipping.

For a brief period of time Brown & Sharpe had put its name on the Interapid indicators. For example, B&S model 7025-4 was actually Interapid model 312B-1. These can still be repaired because they were not imitations but genuine Interapid indicators made in Switzerland.

Interapid dove tails and stem attachments

It would appear that one of the advantages Interapid indicators have over other brands is the replaceable dovetails. Each of the 1 or more dovetails (depending on models) is fastened to the body with several screws. Dovetails are made of hardened steel and they won't break or wear down like those which are integral with the bodies of Bestest, Mitutoyo, Compac and others. Because they're hardened, they probably will never have to be replaced. Unless... the entire dovetail has been ripped from the body through some misadventure. In this case, the screw holes are usually damaged beyond repair anyway.

The feature of replaceability is not particularly important. However, the hardened steel is. These dovetails will outlast any others.


Caution if buying from Amazon: their product images sometimes do not match the product description. Read carefully!

Companion Reference Guide for Test Indicators
$19.50 Now available at

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