narrow tool for sticking in places to measure distance - Page 1
Forum section: electronics / general

author: coppercone2
author_rank: Super Contributor
timestamp: May 24, 2025, 01:10:56 am
content: Like if you got a plate on a chassis and you wanna find how big the gap is and its like not accessible what kind of tool can you use for this?The closest I have seen is some tools for pipe weld inspection.Say there is a plate on the bottom of a chassis and you wanna know how much room is under it without taking it apart and trying to measure the standoffs. Like a really skinny caliper that you can extend, lock and measure, with a little ledge instead of a big beak. I thought about cutting a caliper but does this tool exist? Preferably it would be like nested tubes with a thing on the side 'Or like say some chassis fan, to measure how much room is under the fan, and you only have a tiny bit of access between the fan and a circuit board.The idea being is usually you only have line of sight access to some narrow hole or gap and can kinda tell there is some room there but its hard to say exactly how much.The best idea I had is to get a thin brass tube, solder a collet on top and a flange on the bottom, then put a rod in there, so you can push on the rod and pull on the tube to get it to expand in the narrow thing, then tighten the collet and try to get it out of there and measure it with a caliper.Like measuring the height of the wide part of a counter bore from the narrow side. Easy to measure from the wide side. From the narrow side you need some special toolLike a really really narrow height micrometer/cal;iper that you can stick into something to find a ledge to measure (with the measuring beak put on backwards)

author: TimFox
author_rank: Super Contributor
timestamp: May 24, 2025, 02:06:24 am
content: A set of feeler gauges?

author: coppercone2
author_rank: Super Contributor
timestamp: May 24, 2025, 03:11:25 am
content: that is way too thin

author: Kean
author_rank: Unknown
timestamp: May 24, 2025, 07:01:24 am
content: You can stack feeler gauges, maybe with a slight loss in precision. You can also get angled feeler gauges.Depending on the access and visibility you have, maybe you could use a taper gauge?You could make a custom taper on a rod, and coat it with Dykem layout blue to see how far it enters the gap.

author: coppercone2
author_rank: Super Contributor
timestamp: May 24, 2025, 07:19:40 am
content: its not like a gap, its measuring something behind a gap. It comes up sometimes. So you know whats going on before you take something apart and know if its feasible or not to doLike a bare caliper rodImagine you have a counter bored thing that is set on a table. What tool can determine the height of the wide part of the counter bore while only accessing it from the narrow side. If its big you can stick a height gauge in there and invert the part that makes contact with the work piece. Same ideaFor like ugly chassis mods. Not some mechanical thing that you can get on a nice bench. Stuff is always in the way. I thought this tool can tell me what I need without disassembly

author: Kean
author_rank: Unknown
timestamp: May 24, 2025, 08:03:22 am
content: While I am sure something exists, I've never seen anything like that in a standard catalog from the likes of Starrett, Mitutoyo, or Brown & Sharpe. It would likely be custom manufactured to order and very expensive.I'm guessing you don't need high precision for the use case you describe, so probably best to fabricate something yourself. I am not sure I am properly visualising what you are describing correctly, especially in terms of access. Some drawings or photos might help.It sounds like you already have a basic idea of how to make it, so give it a go and let us know how you get on.

author: darkspr1te
author_rank: Frequent Contributor
timestamp: May 24, 2025, 08:08:45 am
content: I think what you are looking for are expansion gauges , one type has a sprung section you insert into the gap, release the spring then lock it up then remove and measure, then theres needle gauges which you pull part to match the gap then remove and measure with calipers.Clickspring on youtube has some great videos on measuring & tooling to match.darkspr1te

author: TimFox
author_rank: Super Contributor
timestamp: May 24, 2025, 02:29:42 pm
content: The telescope gauges in the top figure are good for measuring inner diameter of circular holes.

author: jpanhalt
author_rank: Super Contributor
timestamp: May 24, 2025, 02:57:52 pm
content: Quote from: coppercone2 on May 24, 2025, 07:19:40 amIf you want a good answer, give a dimensioned example of what you are trying to do. All dimension below are in inches.1) Gaps (~ 0.01 or less): Feeler gauge & calibrated putty (used for measuring clearance on things such as crankshaft bearings)2) Holes: Mechanical gauges. There are expensive gauges based on air flow. Today, they may even be ultrasonic.3) An upside down counterbored hole: How did it get upside down? Measure it before turning it upside down.4) Undercut grooves at a blind end (e.g., something for an O-ring). There are gauges for reading such grooves.5) If you know the geometry of the access, then measure total depth , weigh, add a liquid of known density and weigh again.6) If you can see what you need to measure a calibrated ocular or comparator may work.7) As you mentioned, X-ray may work. Depending on materials, ultrasound can be used (e.g., measuring a mass inside a human body).Back to my original statement, if you want an answer to an actual problem, describe the problem. If this is just theoretical pondering, then it's a waste of time to be more specific.