page 21

www.longislandindicator.com

Long Island Indicator Service Inc

Precision Tool Repairs, Sales & Spare Parts

Which contact point to choose?

Contact points are always available from Long Island Indicator Service. There are four components to take into consideration.

1. ball diameter
2. thread diameter
3. contact point length
4. ball composition

New indicators come supplied with .080" diameter balls as standard. We list the most common sizes below, but for special needs other diameters are often available. Thread diameters vary from manufacturer to manufacturer but are generally metric threads. Manufacturers differ in their method of measuring contact point lengths. It is imperative that the correct length point is used. Refer to the charts below for details on how the length is determined.

Our contact points are turned from #303 stainless steel and have carbide, ruby, Nylon or Teflon balls. We recommend carbide over chrome or steel for its durability. For special applications you may need the ruby, sapphire, teflon, nylon or some other exotic. Please email special requests.

The contact points listed here are home grown. They're every bit as good as the originals yet they cost less. We give you the manufacturer's ordering number for ease of reference. If you'd rather have the manufacturer's own contact points please send us a request for quotation.

When ordering specify indicator model and diameter point or use the ordering numbers provided on this page.

 

Ruby, Nylon and Teflon points

These contact points are used for special applications, typically in optics. The ruby point outlasts standard chrome points and does not expand or contract with heat and cold. It does not conduct an electric current so it can be used on your machines without creating interference. It is also less likely to scratch delicate surfaces. It's also the material that will hold up to silicon carbide surfaces. The Teflon point is softest made of a solid Teflon ball. It is least likely to scratch but is not as long lasting as the others. The smallest Teflon diameter available is 1/16" (.062"). Smaller points can not be manufactured in this material. The Nylon point is not as soft as Teflon but will last longer. It can also be used where surface damage is an issue.

If you buy any new test indicator from us, you may request one of these points to replace the standard carbide point. A fee applies to make up the difference in cost.

 

Longer contact points

You may wish to substitute a long contact point on short point models. If the point is exactly twice the length then the readings on the dial will be doubled. A .0001" indicator will now read .0002" and a .0005" indicator will now read .001".

The indicators were not designed with these long points in mind and you may see some problems with repeatability and hysteresis because these long points weigh more. The extra weight interferes with the hair spring and return spring and that may be noticeable in .0001" models.

Once this long point is installed, be sure to label the indicator with the new readings so no one else will make mistakes. These double lengths can be custom made for most models, although some are in stock (see charts below).

 

Cosine error

We know that the length of the contact point determines the ratio of leverage. In order to get accurate dial readings the length must be as specified by the manufacturer.

Changing the angle of the contact point changes the ratio just as if you had installed a somewhat shorter point. As a result, the readings on the dial will be higher than they should be.

To compensate for this cosine error it will be necessary to multiply the reading on the dial by the cosine of the angle between the contact point and the measuring surface.

How do you measure the angle? Most of us can intuitively judge an angle of 45° and, perhaps with a little less accuracy, an angle of 30°. Beyond that, we need help. A simple protractor like we used in grade school will suffice. Lay the straight edge on the measuring surface and, by eye, make a judgement of the angle. A few degrees one way or another won't be significant.

Where do you find the cosine? Use a scientific calculator or a printed chart. You can use an on-line calculator if you don't have one at hand.

Enter the value of the angle: for 20° enter "20" and press the COS (cosine) button. The display will read .9340 (allowing for rounding up).

Now it's simply a matter of multiplying the reading on your test indicator with this value.

For example: when the reading is .0006" you multiply .0006" x .9340 and the result is .00056"

This is just as expected. Your reading of .0006" was larger by .00004" than it should have been.

From this example you can see that angles of 20 degrees or less have relatively insignificant effects on the reading. But, when the angles are larger you'll be wise to make cosine error adjustments.

This same cosine error applies to all makes of test indicators regardless of contact point lengths and resolutions. Some Fowler test indicators feature "pear-shaped" contact points which compensate, in theory, for the cosine error. These may be a good choice if you frequently use a variety of measuring angles.

Interapid indicators pose a special problem. They're designed to work without cosine error at 12°. When setting up, use a protractor to make sure you're in the ball park. If you're off, then you'll have to compensate, just like the others. If the angle is 32° then the cosine will have to be of the difference between 32° and 12°, in other words 20°. Make the calculations as above.

 

Interapid

How are they measured? From the shoulder (not including the thread) to the center of the ball. Contact point thread size is M1.7 x 0.35 Those are the measurements given below.

Why do many catalogs have different lengths from those listed below? The Interapid carbide point lengths shown in the catalogs are the length of protrusion from the front of the indicator. A useful figure in some circumstances but not particularly helpful if you have a handful of contact points and you need to sort them out. We've given the actual length of the point from the shoulder to the center of the ball.

• $19.50 each (3 or more of one kind of carbide point for $15.60)
• Teflon or ruby points ... $29.50

Other ball diameters are available: .010" .093" .120 and other materials: ruby, teflon, nylon

Be advised that the Interapid look-alike called X-Test made in China does not use these same contact points. The threads are different and won't fit. See page 218.

Model

Contact point length

Order Number
(ø carbide ball)

Order Number
(ø special ball)

312B-1
312B-2
312B-3
312B-4
312B-20
312B-1v
312B-2v
312B-3v
312B-20v

.687"

105996 (.080")
105997 (.060")
105998 (.031")
116284 (.015")

131001 (.062") Teflon
131002 (.080") Teflon

131011 (.040") Ruby
131012 (.080") Ruby

MTC39-19 (.062") Nylon

312B-15

2.750"

111910 (.031")
111913 (.080")***

($29.50)

312B-15v

2.750"

111910 (.031")
111912 (.100")***

($29.50)

312B-15
312B-15v

5.5"
double length*

131020 (.080")

($55.00)

312-1
312-2
312-1v
312-2v

18.5 mm

105993 (2.0mm)
105994 (1.5mm)
105995 (0.8mm)

312-3
312-4

17.2 mm

110482 (2.0mm)
110491 (1.5mm)
110507 (0.8mm)

312B-1
312B-2
312B-3
312B-4
312B-20
312B-1v
312B-2v
312B-3v
312B-20v

1.450"
double length**

MTC39-34 (.060")

106361 (.080")
106363 (.031")

Indexable (bent) point

What is this?

Contact Point Wrench

018603-07

$7.00

* the use of these very long double length points on the .0005" indicator is not condoned by the manufacturer. The indicator graduations will now be equal to .001". Buy and use these at your own risk. For details refer to page 23.

** you can use these double length points on any of the models listed. The readings on the dial will be doubled as a result. The graduations on the .0005" indicator will therefore equal .001" and the graduations on the .0001" indicator will equal .0002". This only works if the contact point is exactly twice the length of the standard point.

***For a reason unknown to us, the manufacturer specifies that model 312B-15 must use .080" and model 312B-15V must use .100" diameter balls. In our estimation, there should be no difference whether you use one or the other.

 

Tesatast

Points are identical for inch and metric models. For that matter, these points are identical to Bestest points. For a larger selection of points, see the Bestest points on this page.

How are they measured? From the shoulder (not including the thread) to the center of the ball. Thread size is M1.4 x 0.3. Other materials: ruby, teflon, nylon

• $19.50 each
• $15.60 each for 3 or more (of one kind, carbide only)
• $29.50 ruby points (no discounts)

Tesa model

Contact point length

Order Number
(ø carbide)

Order Number
(ø ruby)

18.10005
18.10006
18.10009
18.10010
18.10013
18.10204
18.10304
18.20006
18.20007
18.20010
18.20011
18.20012
18.20013
18.20014
18.20015
18.20204
18.20304

.5" (12.5 mm)

018602-00 (.015")
018602-01 (.040")
018602-02 (.080")
018602-03 (.120")

018602-05 (.040")
018602-06 (.080")

18.10007
18.10008
18.10012
18.10205
18.20008
18.20009
18.20016
18.20205

1.436" (37 mm)

018602-11 (.040")
018602-12 (.080")
018602-13 (.120")

018602-14 (.040")

Compac

How are they measured? From the end of the thread to the center of the ball. Thread size is M1.6

• $19.50 each
• $15.60 each for 3 or more (of one kind)
• $29.50 ruby points (no discounts)

Model

Contact Point Length

Ordering Number
(ø carbide)

Ordering Number
(ø ruby)

214A + 214GA
215A + 215GA
224A + 224GA
225A + 225GA
234A + 234GA
235A + 235GA
245A + 245GA

.72"

018660-35 (.015")
018660-11 (.031")
018660-05 (.080")
018660-18 (.120")

018660-32 (.040") Ruby
018660-30 (.080") Ruby
018660-33 (.120") Ruby

213LA
213GLA
223LA
223GLA
233LA
233GLA

1.44"

018660-34 (.015")
018660-24 (.031")
018660-09 (.080")
018660-25 (.120")

018660-31 (.080") Ruby
 

244A
244GA

.67"

018660-26 (.015")
018660-10 (.031")
018660-07 (.080")
018660-17 (.120")

244LA
244GLA

1.65"

018660-12 (.031")
018660-08 (.080")
018660-19 (.120")

213 + 213G
215 + 215G
216G
223 + 223G
225 + 225G
233 + 233G
235 + 235G
242 + 242G
245 + 245G

18 mm

018660-14 (0.8 mm)
018660-03 (2 mm)
018660-21 (3 mm)

212L
212GL
215GL
222L
222GL
232L
232GL

36 mm

018660-16 (0.8 mm)
018660-04 (2 mm)
018660-23 (3 mm)

243L
243GL

45 mm

018660-15 (0.8 mm)
018660-06 (2 mm)
018660-22 (3 mm)

Girodtast (Fowler)

There are two generations of Girodtast in circulation. The oldest models (without identifying numbers on the dial) will use Bestest contact points.

The parts listed here are for the new ones with an M1.4 thread size. A set screw is used to adjust the length of these points. This gives you control over the calibration. Actually, this just gives you a headache. Always calibrate before use when changing Girod contact points. See page 19 for more information on calibrating this indicator.

In Switzerland these are also sold with the name SISO (SISOtast test indicator).

• $19.50 each
• $15.60 each for 3 or more (of one kind)

How are they measured? From the shoulder (not including the thread) to the center of the ball

Fowler Model

Contact point length

Ordering Number
(ø carbide)

52-562-253
52-562-272
52-562-273
52-562-453
52-562-473

.500"

52-567-101 (.031")
52-567-102 (.080")
52-567-103 (.120")

52-562-474

1.50"

52-567-104 (.031")
52-567-105 (.080")
52-567-106 (.120")

52-562-252
52-562-452

.780"

52-567-096 (.031")
52-567-097 (.080")
52-567-100 (.120")

Starrett

Starrett indicator points are available in carbide. The Last Word points snap in place. See our "Do-it-Yourself" page for suggestions if you're having problems with these points. The other points have 1-64 threads which screw in.

Click on a linked number to order online.

• $19.50 each
• $15.60 each for 3 or more (of one kind)

Model

Contact Point Length

Ordering Number (ø carbide ball)

711F "Last Word"

5/32" carbide

PT07137X (.030")
MTC58-12 (PT07136X) (.060")
PT07087X (.120")

711-T1

.49" carbide

MTC58-22 (.080")

709A, 708A and
709MA (0-40-0)

13/16" carbide

MTC58-02 (.031")
MTC58-03 (.060")
MTC58-04 (PT23914) (.080")
MTC58-06 (PT23943) (.120")

811

5/8" carbide

PT23062X (.032")
PT22315X (.078")

Mitutoyo

Mitutoyo measures their contact points from the pivoting point to the center of the ball. This makes it difficult to figure out what's what. To make it easier, we've included, in parentheses below, the length from the shoulder above the threads to the center of the ball. We only supply carbide or ruby points for Mitutoyo test indicators. These points are for current models with M1.7 threads. Other size ball diameters are available on request.

• $19.50 each
• $15.60 each for 3 or more (of one kind)
• $29.50 ruby points (no discounts)

Model

Contact Point Length

Ordering Number
(ø carbide ball)

Ordering Number
(ø ruby ball)

513-203
513-253
513-403
513-405
513-443
513-453
513-463

.59"
(.455")

M 136076 (.040")
M 136075 (.080")
M 136077 (.120")

513-104
513-128

.73"
(.606")

M 131314 (.040")
M 103019 (.080")
M 131315 (.120")

513-202
513-242
513-282
513-402
513-406
513-442
513-452
513-462
513-472

.78"
(.643")

M 133196 (.040")
M 133195 (.080")
M 133197 (.120")

MTC51-16R (.040")
MTC51-18R (.080")
MTC51-20R (.120")

513-118

513-518

1.04"
(.900")

M 103008 (.040")
M 103007 (.080")
M 103009 (.120")

513-212
513-412
513-446

1.33"
(1.198")

M 136291 (.040")
M 136290 (.080")
M 136292 (.120")

MTC50-03R (.040")
MTC50-05R (.080")
MTC50-07R (.120")

513-112
513-512

1.47"
(1.336")

M 131316 (.040")
M 131324 (.080")
M 131317 (.120")

513-404

M 103006 (.080")

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14 Sarah Drive — Hauppauge NY 11788 — USA
 

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This page's most recent revision: 24 June 2010
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