The small hand can be tricky to remove without tools and, if not careful, it is just as likely to launch itself into space, never to be seen again. Fortunately parts are available but they are expensive and you are much better off being careful along the way.

The hairspring can be an intimidating challenge. It has to float horizontally without touching the gears and, of course, it has to be immaculately clean so that it coils properly. Only fine pointed tweezers can deal effectively with the hair spring. You should also go easy on the caffeine.

Unless you can give the spring the correct amount of preload, the indicator hand will not repeat and the up-and-down contact point motion is probably only going to work one way. One-way is great for city streets but not for your Interapid.

Questions and Answers about the Interapid indicator

Q: I have a 312B-15V indicator and was hoping to use this for dialing in a rifle barrel in the lathe. I know most use the horizontal model with 2.75 long point. Will the vertical model still give me the same accuracy as a horizontal and work fine at 12 degrees?

• Simple answer: yes!

Q: I have a Brown & Sharpe Bestest model 7025-4. I need the tiny screw on the face, and a new crystal for it (1.5 inch approximately). I didn’t see that model listed anywhere on your site. Will you help me out with these?

• The 7025-4 is actually an Interapid 312B-1 indicator. For a very brief time, Brown & Sharpe had its name put on the dial. This only confused everyone, and it still does.

Q: We have a machinist with a Brown and Sharpe Dial indicator 7026-4. He is looking to replace the stem he uses in a collet/chuck in a CNC. Do you have this available?

• Model 7026-4 is the same as Interapid 312B-2. It was sold under the Brown & Sharpe name for a brief period of time in the 1970s.

Q: Is there a way to check and adjust the Interapid “stem” to contact point concentricity? The machinist in our mill department often uses the Interapid to centralize the spindle to the centerline of a hole in the part by sweeping the hole.

• There is no way this can be adjusted.

Q: What difference is there between the 312B-2V which lists as a .0005" model and the 312B-20V which lists as a .001" model? Is there any difference other than the additional lines (between the .001 lines) printed on the dial of the 74.111378 model?

• There is no difference except the one that you suspect. The indicators are identical in every other way.

Q: I was reading on your website that there are counterfeit Interapid test indicators. Do you know how to tell the difference or do you have any information on identification of the fakes.

• Although they look very much alike, the Chinese indicators DO NOT have the name Interapid on them. They are sold with names such as X-Test. All genuine Interapid indicators have the Interapid name printed on the dial.

Q: What are the most frequently used spare parts for these indicators?

• We have been asked this question by start-up repair shops and in-house repair departments. Here are the ten most frequently used parts which could be in their inventory: Crystals (both sizes), contact point (.080” carbide is standard), stem attachment, ball bearing spanner nut, pivot, movement fastening screw, hair spring (both .0005" and .0001"), rack lever for .0005" models, dial screw, and ball bearing.

Q: I have two Interapid indicators. Both of these indicators seem to not read as close as my Brown & Sharpe Bestest indicators. Both Interapid indicators are 99.85% good and clean but I would like them to be a little smoother and trustful in the reading of them.

• There are two differences between the Bestest and the Interapid indicators. You must keep these two points in mind when comparing them. They will never be equal in responsiveness nor in accuracy. The Interapid indicator is only accurate when the contact point is about 13-degrees to the work surface. The Interapid indicator has more moving parts meaning that it will be slower to respond and will have poorer repeatability, although these differences are almost negligible.

Q: My Interapid works fine but it has gotten very dirty. Don't tell me to wipe it with a paper towel because that won't work. Any suggestions?

• Dip a toothbrush in some Naphtha and scrub away. Avoid getting solution inside the indicator. If Naphtha doesn't remove stains, use Simple Green or Fantastik on a paper towel (!), just be doubly sure you don't get any of these cleaners inside.

Q: You mention that the large hand of an indicator should be at 9 or 10 o’clock. What if it rests between 12 and 1? Is that a malfunction?

• On the Interapid, the hand is at high noon when at rest. If it is slightly off, but is still accurate, then there is nothing to fret about. But, if the hand drifts or returns to various positions, then it should be checked out.

Q: Have you have seen any increase in warranty claims and/or quality issues with Interapid indicators 312B-1, -3, & -20?

• Just the opposite, over the past 12 months we have seen a decrease since the manufacturer fixed a "bug" which had recently surfaced.

Q: If I purchase a new Interapid through an eBay seller, is the warranty honored by the manufacturer?

• If the item is new when purchased, then TESA will honor the warranty. You would have to keep the purchase receipt to prove the date of purchase. It does not matter if the seller is an authorized distributor or not.

Q: Contrary to my nature, I thought I'd ask for advice before I screwed up something. After all, you do say "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 [Interapid] indicator." However, on your "Do It Yourself" web page you say this about Interapid stem attachment: "You will notice that you can increase the swivel friction by tightening screw A." Can the swivel friction on the contact point be adjusted in the same way? The contact point on mine doesn't want to swivel, and I'm worried that I shouldn't push any harder on it. Also, should I put any oil on this friction clutch?

• This is a good question and I'm glad you asked. The contact point friction can not be adjusted in any way. The Interapid has fairly hard friction on the point. After all, you don’t want it to move on its own. Don’t be afraid. The contact point angle can be adjusted. Just use your thumb and the point will yield. A tiny drop of oil can be put on the “clutch” if you still feel that there is too much resistance.

Q: My Interapid seems a little jumpy, especially when changing direction. Is it in need of repair?

• Jumpiness is most often the result of a dirty hairspring. When the spring gets oily, it stops functioning and needs to be cleaned. This is easier said than done and should be put in the hands of a professional.

Q: We use the 312B series Interapid here on a daily basis. A few of them from time to time get abused by inexperienced or negligent machine operators. My question to you is, is there a way to zero out the small dial (rev counter) on these things? Repeatability does not seem to be a problem, I just would like to keep the needles in line as they were from factory.

• This should really not be happening. I suppose, if the large hand remains in its 12 o’clock position but the small hand has shifted, then the small hand might be loose on the pinion. You can unscrew the bezel and, if the small hand is loose enough, simply align it into the correct position and tap it down (we use a staking tool). If you feel much resistance though, I suggest you don’t play with it.

Q: The contact point moves up and down (forward and backward is a better description) but one direction is noticeably harder than the other. Shouldn't they be the same?

• Ideally—yes—and probably in a new indicator this will be the case. Interapid indicators have a spring mechanism that controls this force which is quite different from any other manufacturer's. Unfortunately it can not be modified without taking the entire indicator apart. Don't attempt this unless you already know how to put it back together! The spring can weaken in one direction over time but the problem is more likely the result of previous repairs. Just the act of taking the mechanism apart can distort the spring's shape. The difference in force shouldn't matter much but if it's imperative to your operation that they are identical, you should consider switching to a different brand. Bestest, Tesatast and Compac would be ideal substitutes.

Q: I know you have been asked before, but I really don't like the peeling paint on my Interapid. Isn't there something I can do?

• Of course there is. You will have to completely disassemble the indicator until you have just the body left. Use paint stripper if it still has bits of paint on it. Then spray with a primer followed by a color of your choice. Be careful you don't get paint onto any of the screw threads or you'll have a heck of a time trying to get the screws back in. Here's a handy hint: if you don't mind spending the money, just buy yourself a new body instead. Then your indicator will look like an original and the paint on the new bodies will last much longer.

Q: I have a model 310-B1. I see that parts are no longer available. The only thing wrong with the indicator is that the face comes off easily. The plastic split-ring that holds it on needs to be replaced and I was hoping that there might be another indicator that incorporates the same ring that I could purchase. Please let me know if that is the case.

• Those are exactly the parts that are the weak link on this indicator and those rings are long gone... no one else uses anything like it. The other missing item is the little horse-shoe shaped clip. If you really love this indicator, We suggest you try to improvise a way to hold the bezel in place. A properly shaped piece of spring wire might do the trick.

Q: We recently purchased a new Interapid 312B-3 indicator and noticed that the dial appears to slightly lift from the base. Is this common with these indicators ?

• The movements on the large diameter indicators are mounted on a spring washer which creates the friction to keep the dial from rotating unnecessarily. There is some wiggle as a result. You should notice it when you "pull" the bezel upwards. It should not be more than about 1 mm.

Q: I would like to know if the 2.75" #111913 indicator point can be used with the 312B-3 Interapid indicator? I believe that the divisions will now be 0.0005" instead of 0.0001" with this longer point.

• The readings would be very close to .0004" per graduation but the indicator will most likely stick, jump and hang with this size point installed. The hair spring can not handle the extra weight of this long point. It is not advisable.

Q: Can I get the small wrenches to change the Interapid contact point properly? The tips all have the small flat machined into the shank and a new indicator used to have one of these wrenches supplied with the kit but I haven't seen one with any of the new indicators we've purchased recently. It used to be a simple round disk with a notch that fit the flat on the tip shank. Without this a needle-nose pliers works but seems wrong putting a pliers on something so delicate.

• I'm surprised to hear that these wrenches are missing in some of your new gages. They really should have been included but they do tend to fall out. Someone may have opened the boxes at some point (even during shipping) and may not have known the significance of this little wrench. By the way, we use small pliers. They work very well. (The wrench is part number 01860307 and can be ordered on webpage 151.)

Q: I purchased a spring and gear assembly for the Interapid indicator (312B-3) and I am having a difficult time getting the indicator to return to 0 accurately (within .0001). Part of the problem is adjusting the ball bearing with spanner nuts. Will you please help me with this?

• Interapid indicators are difficult to repair. It takes most of us several months of practice to get it right. I suggest you send it to a repair shop for servicing.

Q: I have a model 310-B1. I see that parts are no longer available. The only thing wrong with the indicator is that the face comes off easily. The plastic split-ring that holds it on needs to be replaced and I was hoping that there might be another indicator that incorporates the same ring that I could purchase. Please let me know if that is the case.

• Those are exactly the parts that are the weak link on this indicator and those rings are long gone... no one else uses anything like it. The other missing item is the little horse-shoe shaped clip. If you really love this indicator, I suggest you try to improvise a way to hold the bezel in place. A properly shaped piece of spring wire might do the trick.

Q: I recently purchased an Interapid 312B-1V (used, no directions). In order to move the contact you state: "be sure that the point is securely fastened before attempting to move it." Would this mean to ensure point is tight in holder then run the contact against the stop? Then move to desired angle?

• As you've probably noticed, the contact will swivel (with a bit of force applied) in two directions. Just make sure that you've completely screwed in the contact point before you swivel otherwise you might break off the point in the process.

Q: I have an older Interapid test indicator, model # 311B-1 and I was wondering if by any chance you would still have parts for it? The part I'm looking for is the one that holds the bezel to the extension ring. It looks like a horse shoe, or if you know of any company that makes replicas such as this.

• We called it the horseshoe clip at the time. People have been known to improvise with a bit of copper wire which can pretty easily be bent into shape and filed down if necessary.

Q: I have a brand new Horizontal model 312B-15 with 2.75" long contact point. I ordered the wrong one, so I bought some shorter tips for this indicator, now it acts jerking and does not repeat with a shorter tip on it. Does this mean that I can only use the long tip?

• The long point models have a different hair spring to compensate for the weight of the point. Apparently replacing this with a short point causes the jerkiness you've noticed. The only thing you can do is stick with the long point, or have the hair spring replaced.

Q: The paint is peeling from my Interapid indicator. Can I do anything?

• This problem is seen more commonly among the older models. Certain solvents softened the paint and it eventually began to peel. We don't see the problem anymore on newer models. My suggestion is to scrape off the peeling paint. You'll end up with a shiny brass body which isn't so bad looking after all. Trying to repaint is usually an invitation to failure. For one thing, you'd have to disassemble the indicator completely and unless you really know what you're doing... please don't!

Q: How could I sterilize an Interapid indicator used in biological experiments?

• Surface cleaning with isopropyl alcohol can be used, just don't immerse. There is a small amount of oil in the bearings and we have to be sure that these don't dry out. Dried oil becomes gummy and that would be detrimental. For complete sterilization, Gamma radiation may work very well. I don't see how it could damage any of the gage's components as long as no excessive heat is produced. Having never tried this, though, it is only a guess. Ethylene oxide can be used if it doesn't dry the oil. I don't know if it would. If the crystal becomes fogged by the gas, you'd have to replace it, but that would be part of the cost of sterilization. Autoclaving to 120-degrees is probably too severe a method. The presence of steam would be quite damaging. I would avoid this method unless dry heat can be used. In summary, use the alcohol whenever possible, before resorting to any of the other methods.

Q: We have an Interapid 312B-2, the hair spring is currently not wound up, when you're looking at the dial and needle as if you were using the indicator, would you spin the needle clockwise to put tension on the spring or counter clockwise to put tension on the spring? The crown gear has a bent tooth which stops the large needle from turning more then 4 revolutions in the counter clockwise direction. Can the crown gear be removed and turned so the bent tooth doesn't hinder the movement?

• You will have to disassemble the gage in order to pre-load the hairspring. When it is apart, you will see the direction required. The crown gear can also be positioned so that the damaged tooth is not engaged.

Q: I have an Interapid indicator that has a little play side to side with the end. It will repeat fine as long as you don't move side to side on the part you're indicating. I was wondering if you could give me some advice on what I can do to fix the play?

• You would want to tighten the ball bearings just enough to remove the play. If you over-tighten, your indicator will start to stick or not repeat correctly.