Thread Triangles Vs. Thread Wires Vs. Thread Mics?

Bob Korves said:
BTW, you can take your threading work to the mating part to test it if you thread it between centers. A verified fit always trumps a fussy measuring method in the H-M world... 8^)
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Hi Bob,

That's my normal method. Have also frequently gotten close then chased it over with a die (when a standard thread).

Bruce
 
BGHansen said:
Hi Bob,

That's my normal method. Have also frequently gotten close then chased it over with a die (when a standard thread).

Bruce
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I have done that, too, Bruce. Whatever gets it done to your satisfaction. There is no use messing around with a lot of fussy measuring when your part is essentially going to be a bolt. If it really needs a precision thread, then and only then go the extra mile. Of course, there is also practicing for the really difficult ones, but I seem to do better under pressure... 8^)
 
I recently got a 1" thread mike (buying the anvils seperately as projects come up where I "need" others - right now I have anvils for two pitch ranges). Of course, I still check the fit with a nut. I find the measured pitch diameter from Machinists Reference results in a very nice fit of the nut.

I actually ended up with two 0-1 Mitutoyo thread mikes: no sooner did I trade work for a new mike, then at a recent auction I bid/won on a bunch of mikes - including a like new thread mike (same as the new one I just got!). Anyway, makes for a good story. If anyone has a "spare" 1-2" I'd be interested in talking to them.
 
I just made a little lead screw - 15" of thread. Even with a follower rest, it is tough to get the thread dimension correct all the way along. However, with a by measuring every inch or so and marking the locations - it was pretty straight forward to complete the task. Using the thread micrometer is a pretty quick way to determine the progress - certainly measuring over wires would work, just a bit fussy to manage the wires for that many measurements.
 
Thanks for all of the tips and suggestions. Yeah, had a little money burning a hole in my pockets so I bought a 0-1" Shars for $55 off eBay. Did the web searching today on pitch diameters (easier than typing everything from the Machinist Handbook) and made up the chart below. Figure there's not a lot of need to extend past 1" if the mic only goes that big! I checked a number of fasteners and found the hardware store bolts to be a bit under these numbers so these are for a tighter class thread than hardware store bolts. I'll show my son how to read with the 3-wire method and let him chose which way to go. Whatever gets him enthused being in the shop!

Thanks again, Bruce


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While we're on the subject of thread measurement, I will pass along the formula for an over-wire method used on 29° Acme and Stub Acme threads.

(4.9939 x Wire Diameter)-(1.9934 / TPI) + PD

This will give the over-wire target, or if you work it backwards, obviously give you the PD. You choose the Best Wire size yourself, if you don't have a chart for that. The closer you get to contacting the flanks of the thread at the pitch point, the better, but you must be able to contact the wire before the crest of the thread. That's the only real constraint. Of course, you can use a huge wire and not even get down into the thread and this is useless. But getting as close to mid-point contact is helpful.
 
Attached is a photo of the replacement lead screw I made (for an old meat slicer). The thread mike came in handy. The threaded portion is 15" long. The main challenge was in learning to use a follower rest.

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Chipper5783 said:
Attached is a photo of the replacement lead screw I made (for an old meat slicer). The thread mike came in handy. The threaded portion is 15" long. The main challenge was in learning to use a follower rest.

View attachment 122079
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Nice job there! It takes a little learning to use the follow rest, but once you get it adjusted, works like a charm!
One rule of thumb, once you get it adjusted at the tailstock end, loosen the tail stock to where the center is barely touching. Doing this will allow the material to follow the FR while it is cutting. If done right, you should get a even reading on the thread wires from end to end.
Ken
 
mmcmdl said:
Nothing wrong with the wires . They work on any diameter threads and not limited as mics are . You get used to them over time after dropping them into your chip pan . But if ya like to spend money ......
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Believe Victor sells a set
 
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