How do you check your threads when threading on lathe ?

[Arcane]

I like to use a thread die to do the last small bit of metal removal and that seems to ensure the thread is close enough for the girls I go with!

[old mart]

I like to find out the exact depth of thread from tables, and if possible, try the mating part frequently when approaching size. This method worked perfectly when I made a mill spindle out of two parts. The joint was a length of close fitting counterbore, (about 0.0005" clearance) and a close fitting thread. The parts were assembled with Loctite 620 which is slow curing. I produced the female thread first to standard thread dimensions and the counterbore in the same chucking. Then the male part of the counterbore and thread were produced together. I used the female part to gauge the best fit possible without the danger of the threads galling on assembly. The spindle runs better than expected, due mostly to taking 80% of the time checking before cutting metal.

[Mcgyver]

mating part when it doesn't matter (or if possible), thread mic if it matters, thread wires if an oddball form

[Bented]

As mentioned above, if making a small number of parts measure external threads over wires and internal threads using a plug gauge that is shop made over wires.

If hundreds of parts are required buy plug or ring gauges as needed, the time saved will pay for them.

Tomorrow I begin a job making thirty 2"-4 Internal RH Acme and thirty LH
Then one hundred ten 1 1/2"-4 acme RH and LH threads, we also make the externally threaded mating parts so I use drops as plug gauges.

This will be on a new Trak 1845 lathe that I have little experience with, there will be some bumps on the road I predict.

[DR]

If you're real serious into threading buy full profile inserts. For male threads simply measure the OD with a regular mike, once thread OD is on size all the rest of the thread is correct.

[wschoenbeck]

Just for completeness sake I did get to use my inexpensive set of thread measuring wires on the duplicate Ellis Dividing head spindle. MH says the pitch diameter should be 1.6688". I get 1.6644" so my thread is small by 0.0044". Not exactly high precision but the spindle duplicate worked for me. Next time I do this I'll try to pay closer attention to how much I'm removing.

[eKretz]

Mostly running manual machines, that is one reason I don't like using thread gages vs. wires. Wires give you a quantitative measurement so you know exactly where you are. A gage tells you if you fit or don't. When the thread is close to fitting you have to take a bunch of little cuts to get just to the right diameter without taking too much. IMO thread wires are better for individually cutting threads on a manual machine or initial setting up of CNC machines. Gages shine in post-machining QC or if you have a large batch on a CNC, since in that case, drift will be gradual with tool wear. Inserts that top the thread's O.D. might be good by the sound of it, I have never used them though.

[Tillie's in a bottle]

I'm lucky to have few good thread mikes. I haven't had to turn a (60 degree v thread) that I didn't have a mike for. I have wires too, haven't used them. The couple of times I turned an acme thread, I used a thread pitch gauge to get in the ball park, as well as setting an indicator on the toolpost and -with the lathe off of course- running the tool into the bottom of the tread and observing the difference on the indicator.
Of course any time I can use a die instead of single-pointing I do.

[nickel-city-fab]

When it's important, I use the thread mic.
If it's not so critical, I use a nut or the mating part.

[754]

Dont count on the die to give a good fit unless class of fit is marked on it,
some of you sounds like you use the pitch guage to check ? Is that correct ? I never tried that, but rather would make to nominal size, then cut to sharp vee , the file a bit off tops and deburr at the end.
i just find it handy to have the wires with nuts on them , for 90 % of the work..

[J Tiers]

When it's important, I use the thread mic.
If it's not so critical, I use a nut or the mating part.

Thread mics are good, but they need to be set to a standard, so you probably need at least a few gauges. And, mine, at least, do not read to tenths, so they are only rough measurements... many PDs are given to 4 places if you are trying to make them "absolutely right". Dunno how often that is the case, not often for me.

I have "almost" a full set for up to 1", and use them as well as the gauges. If it really has to be right, and I have a gauge, I use that. But I may use the thread mic to get close first. Otherwise I use the mic, or wires.

All of the methods need a clean thread first. Some materials cut so poorly that it is very hard to get decent threads single pointing on a manual lathe. But they usually work OK with dies. Adjustable dies can get whatever clearance you need, with care.

[MrWhoopee]

For non-critical fits we made our own test nuts by taking the next smaller size or a piece of hex and drilling and tapping. They would then be stamped with size and painted to identify them. Better class of fit than commercial nuts.

[nickel-city-fab]

Thread mics are good, but they need to be set to a standard, so you probably need at least a few gauges. And, mine, at least, do not read to tenths, so they are only rough measurements... many PDs are given to 4 places if you are trying to make them "absolutely right". Dunno how often that is the case, not often for me.

Fortunately my mics came with the setting standards (new) so I'm not too worried about it. I doubt I could hold the spec to 4 places myself. When it comes to class of fit I actually go by "feel" for the final decision. I'll use the mic to get close (to the 3rd place), and then take "spring passes" until it has the right feel. Most of the time I'm just doing a generic "hardware store" Class 2, but once in a great while I want a perfect Class 3 (Imperial measure). Hence most of the time I can get by with just spinning a nut on.

One thing I love about my dies is that they are fully adjustable. This also makes them a PITA since I haven't calibrated them to anything yet. I need a round tuit. These are the 2-piece with collet type made by Wells Bros and later by Greenfield -- see http://vintagemachinery.org/mfgindex...l.aspx?id=1269

They give me the ability to get a Class 3 fit with generic hardware store nuts.

[old mart]

I made a dummy 1 3/4 X 8W spindle nose for the Smart & Brown and simply used some ground pins and a micrometer and matched the two threads. They are within 0.001" of each other. The dummy nose is useful as a gauge when making something like a backplate, which works best when the threads are not too close fitting.

[eKretz]

I generally go for .001" - .002" under nominal pitch diameter with the wires for general threads. A little tighter for something like a bearing locknut.