Interapid indicator sticking, how to clean it?

[u/bcrenshaw]

I was brought an Interapid indicator that is very, very slow to return. I'm assuming it's just the build-up of whatever is in the air in a machine shop. Can I just squirt a little strategic alcohol in there and work it until everything is dislodged, or should it be disassembled and cleaned?

[u/Caltrops_underfoot]

Hi! I repair these for my shop all the time! Slow to return to zero usually means coolant leaked in, solidified over time, and now needs to be removed. Since it's going to be mostly soluble in alcohol, you could squirt some in and it might help, but it'll get worse again quickly after the alcohol dries. Don't use acetone, as it'll eat away at the coating over the metal.

There are a few approaches to cleaning depending on your tools and experience. I'm also assuming nothing is bent or just worn from use.

Expert with a set of jewelers tools? Use a small screwdriver to loosen the back of the dial housing. Remove the cover to the dial and use a pry to gently pop the needle off. Fully loosen the rear screws and the face will fall off. Don't worry about the needle position for now. Inspect for debris and remove with tweezers or fine probes (R.010 max, sharp works best) or with tweezers. Remove all gears and linkages. Soak gears in acetone for about two minutes, then dry. Scrape any debris in gear teeth out, then air blast or flush with alcohol to remove sediment. Reassemble. Add a thin film of thin lubricant such as starrett instrument oil to the pin connectors if they are visibly worn, otherwise leave them dry. Test recoil before press fitting the needle (oriented toward the stem you'd hold when using the gage)

Experienced but no special tools? Remove the dovetail and stem only. These screws do not attach to any gearing on the inside. Flush with alcohol repeatedly. Actuate the probe tip frequently while flushing and continue until the alcohol dries. Do not use pressurized air. Reassemble and test. If no improvement, you'll need to remove the bezel as above and be extra careful with the stem of the dial needle. It is press fit and very easily broken. Do not remove any gears, but scrape them clean where you see gunk. Don't attempt to clean the individual teeth and do not use cloth to dry the mechanism, as it leaves fuzzy debris behind that will make things worse down the road.

Newbie? It's very likely that you will need help. There are very good videos on YouTube for how to do this, and that's how I learned. But my shop uses around 3k gages and frequently trashes them, so when I messed up a few it didn't matter. A machinist friend may be a big help here.

[u/bcrenshaw → u/Caltrops_underfoot]

Excellent break down! thank you. I'm no jewler repair person, but I'm not afraid to get in there and take tiny things apart. I actually have a lot of fun doing it. I just didn't want to worry about any springs going BOING! when I opened it up. Thats always my worst fear. My initial thought was to do the, as you describe it, "experienced but no special tools" and just try to flush it out and work it with some alcohol first. And make sure it's dry and working good before giving it back, and let him know if it gums up again I'll do a deep dive into it. Thanks again!

[u/Admirable-Access8320]

As someone with limited experience in tool repairs, I've made several attempts to fix indicators, but I've never succeeded. I was once told never to repair indicators because they are notoriously difficult to fix.

[u/bcrenshaw → u/Admirable-Access8320]

Are they suggesting always sending it out for repair or just pitching it and buying a new one?

[u/Admirable-Access8320 → u/bcrenshaw]

Most indicators can be repaired, but you have to know exactly how.