After posting about Lee Valley’s new thread ID tool, we started thinking about other thread-identification tools that we’re familiar with. Identifying a thread is usually done in one of two ways – by matching an unknown thread to a fastener of known thread, or by measuring and comparing the diamater and thread pitch of a fastener.
Following are a few types of thread identification tools:
Pictured here is the (made in USA) Thread Checker by S&W Manufacturing. Loosely threaded about a wire, these beaded fasteners can be used to identify tapped holes, nuts, and bolts. This type of thread ID tool offers similar flexibility to Lee Valley’s ID tool, but eliminates the risk of losing a stud. S&W Manufacturing also offers a wall mounted Thread Checker.
You can purchase S&W’s Thread Checker via McMaster Carr, and an import version is available from MSC.
Nearly identical to the Thread Checker, Rockler’s Thread Detective Screw Gauge is as versatile, but a bit more economical. SAE and metric gauges are sold separately.
Then of course, you have bolt and machine identification gauges where you match fasteners to holes of known size. For these gauges to be used most effectively, you may want to have a screw pitch gauge handy to measure a fastener’s thread count. Of course, you could always hold the fastener up to a scale or calipers and count the thread density yourself.
Most hardware and tool stores will typically carry screw ID tools of this kind, and they’re quite affordable at $10-15, although you may be able to find a cheaper one. These types of gauges are available from several brands in a very similar layout (suggesting a common OEM).
Two examples of this syle of thread ID tool are the Empire screw ID tool (via Amazon), and the Screw CHEK’R (via Enco).
Some time ago we noticed a similarly styled ID tool by Woodcraft that can be used for sizing anchors and wood screws – Anchor & Screw Gauge (via Woodcraft).
Finally, a screw thread pitch gauge is used to measure the TPI, or threads per inch, of SAE fasteners. Metric thread gauges work in a slightly different manner and instead measure the separation between threads. Screw pitch gauges can be found at larger home improvement stores, and many well stocked online retailers.
Here are several gauges available via Amazon.
If you know of any great thread identification tool styles that we might have missed, please let us know via a comment!
Cool post. Great, now something else I need (want).
I have some Lowe’s and Home Depot gift cards; I’m going to check and see if they have the ones on the cable. I already have plenty of those gauge checking cards.
Would you recommend
1) wall mount vs. cable
2) inch/metric combo, or buying the inch and metric separately? It looks like if I buy them separately I get more sizes. I’m not sure how common these additional sizes are, and if it’s worth the extra cost.
To be honest, ideally it would best to have thread checkers of different styles. Absolute worst case scenario, if you find yourself unable to identify an uncommon thread size, you can usually resort to measuring and identifying it manually.
I’m trying to come up with good reasoning to help you choose between a wall mounted thread checker and a cable strung one, but it ultimately comes down to intended use. A wall mounted checker may be a bit easier for identifying loose nuts and bolts. If you think that you will occasionally need to check the thread of tapped holds or embedded studs, a loose thread checker would be more useful.
It does look that the combined Thread Checker has fewer sizes, but the excluded sizes are likely the rarest or least common ones. Again, should you find yourself needing those missing sizes, you can always measure the diameter of the fastener (calipers would come in handy) and then count the number of threads per inch.
I went back to check the Lee Valley version (Thread I.D.) and it’s still out of stock, now until 4/29.
I checked some reviews of the thread identifiers that are attached by cable. As suspected, seems like they are difficult to maneuver because of the cable (when trying to turn the male part). I anticipate needing to take the identifier to the workpiece (car), so I may not consider the cable-mounted versions.
Alternatively, I could cut the cable, so that each individual thread checker comes off, but I would prefer to avoid this.
Well, when in doubt, do as I do and get both. =)
In any case, Lee Valley’s new thread ID tool is once again out of stock, now with a 5/11/10 ETA. If that’s the one you want, it may be best to order now and just wait for it.
The major appeal of the cable-mounted thread checkers is the convenience of keeping all sizes in one place. You can cut the cable, but as you said, this should be avoided. OR, if you do cut the cables, simply come up with a way to reclose the cable, or replace it with one that you can open or close as needed.
This one was recently released.
Ultimate Metric Thread Checker now located at