Thread Checking Gauge

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sign216

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What's a quality set of thread-checking gauges? So when getting a replacement bolt, I know exactly what I need.

I've suffered long enough with a plastic set. It's too easy for the plastic to get deformed when checking, and I need something that has a greater variety too.

What do people recommend?
 
I've got two types: one on a roughly yard-long board with male/female gauges in different sections (like you'd see at a hardware store), and another with double-ended male/female gauges threaded on a wire cable.

The cable type gets a LOT more use, since it's far more portable. Sometimes the thread you want to check is on a large assembly that you can't take to the board (which is only useful for checking loose nuts and bolts).

Something like this, for example.

1714758974404.png
 
Amazon has a plethora of thread gauges. I've found the foldout metal ones are quite accurate and inexpensive. The ones above are fine for identifying bolts and nuts, but not of any real use on the lathe. Mike
 
Since @sign216 mentioned wearing out a plastic one, I assumed he was talking about a Screw Checkr

The types I referenced above are superior to those, especially compared to plastic ones.

I disagree that they aren’t useful for lathe work. Many things I make in the lathe have standard threads for common nuts and bolts.

Thread pitch gauges are also useful on a lathe, of course, for non-standard threads.
 
Seems a little problematic using them on the lathe attached to the cable, and should you take them off they are small enough to disappear, as small round things are prone to do. But to each his own. Always more than one way to skin a marsupial. Cheers, Mike
 
Apologies for prolonging this, but I'm bored so I'll clarify.

The OP asked about thread checking gauges for identifying bolts. The cable-type thread gauge I linked to is a great tool for that.

By "fold out metal one", I think you were talking about a thread pitch gauge (to measure the number of threads per inch, or the pitch in mm for metric threads). One of these:

1714763884755.png

A pitch gauge is useful to verify that you've set your QCGB or change gears correctly when cutting threads on the lathe after a scratch pass. (It's much easier on external threads than with an internal thread, though!).

A pitch gauge only measures pitch, however, and does not tell you anything about the major and minor diameter of a thread. sometimes it isn't feasible to bring the mating part to a thread you've just cut in the lathe. A cable type set of thread gauges is very handy in that scenario if you don't have a bolt or nut (or go/no-go gauge) of the correct size at hand. It's particularly easy to screw up the diameter of an internal bore. A cheap set of thread gauges like I showed above usually suffices, but, of course, if you really care about class of fit you'll need go/no-go gauges (which are quite expensive or require a lot of time and effort to make in advance).

I've never had to remove a gauge from the cable. The cable can be a bit of a nuisance, but you can usually bend the cable away from the one gauge you're using sufficiently for it not to foul with the work.

In short: I'd highly recommend the $30 tool I linked to. I find my set quite useful and use it all the time. I also have pitch gauges, but I use them much less frequently.
 
Rex and Fomogo,
Thanks for responding. Rather than the fold-out gauges, I'm looking for a "screw in" style, like you linked to Rex, in your first post. However, that plastic style is... not the best. The metal bolts abrade the plastic threads, so it's hard to check it if the diameter or pitch is close, but not correct.

I'm looking for a metal one, for more positive, more certain results.

Joe
 
Rex,
Pardon me, That one looks good, thanks. Re the plastic one, I was referring to the one in your second post, but I think we all agree that the metal one is better.

I'm working on a rifle built in the 1800's, on the cusp of thread standardization, and several recent items (frig and a vise) were supposed to be metric, but turned out SAE. Who would have thought?
 
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