How do you check your threads when threading on lathe ?

[alanganes]

If I can't just try the mating part on the part I am making I use thread wires. A set of them is not overly expensive and they really are not very difficult to use. As a hobby shop, generally my requirements are only that the thread fits reasonably well, I rarely need to make parts to some defined spec or standard. And in my experience anyhow, if a thread I cut measures OK with wires, it will fit and fit nicely. That's usually as close as anything I make needs to be.

[Doozer]

I hope your picture does NOT give anyone the impression
that these are thread gauges, which of course they are NOT.

-Doozer

[DR]

Something else to consider....... the topic of this discussion is threading on the lathe. To me that implies single point threading, but it might also cover threading from the tailstock using a die.

Threading with a die held in the tailstock quill and pushing the tailstock along can be a big problem. The common problem is the pitch of the thread is not guaranteed to be consistent since it relies on an even pulling/pushing of a relatively heavy tailstock. Without an even feed of the tailstock you get shaving of the thread flanks causing uneven pitch.

I picked up a good customer when I made some adjusting nuts to fit their screws. They returned my nuts saying they didn't fit their screws. My nuts were correct according my thread gages. It turned out their screws were made with a button die tailstock method. Checking their screws in the optical comparator it was obvious the pitch varied over a one inch segment. I got the long term job of making both the screws and nuts.

An optical comparator can check all aspects of an external (male) thread.

[nickel-city-fab]

Something else to consider....... the topic of this discussion is threading on the lathe. To me that implies single point threading, but it might also cover threading from the tailstock using a die.
........
An optical comparator can check all aspects of an external (male) thread.

I love optical comparators, Can't afford em yet.
Often when threading with a die in the tailstock, I leave the tailstock loose
and just shove on the end of it until the die and threads start feeding themselves.

[polaraligned]

I often finish with a die. Just easier for me.

[754]

Few things are as satisfying as cutting a Nice thread by single point... with insert tooling.. it gets very easy ..
may as well learn it, you wont always have a die handy..

[Doozer]

I often finish with a die. Just easier for me.

I never understood this but I have seen it too many times before.
If you have a nut, why not just cut with the lathe until the nut fits ? ? ?

-D

[Doozer]

Few things are as satisfying as cutting a Nice thread by single point... with insert tooling.. it gets very easy ..
may as well learn it, you wont always have a die handy..

I agree. Very fun to cut threads in the lathe.
And for finer pitches, I often times use a triangular carbide insert.
If it is a coarse pitch and I need side rake, I have no issues grinding a HSS toolbit.
Now I have graduated to a better lathe than most have access to.
My Hardinge, my Hendey, and my Pratt & Whitney lathes all have single dog threading.
But I often thread on the big LeBlond lathe at work, still fun as can be.

-D

[JRouche]

I hope your picture does NOT give anyone the impression
that these are thread gauges, which of course they are NOT.

-Doozer

Nope, didn't imply that either.

They are what they are, thread checkers. JR

Edit: Here is my answer to the original post

"I'm not good on threading on the lathe. The way I check my cut threads is to test it on the either male or female part I am making the thread for..

When cutting threads on the lathe I am almost certainty cutting it for an already cut thread. So I try to match it as best as possible for my skill."

[old mart]

Thats exactly what I would do if the mating part was available, then the two can fit as tightly or loosely as I want. I once made a 1/2" ACME two start male thread for a copy of the lathe toolpost. When I got to the size according to the charts, it was not even close to screwing into the top slide. Luckily the female thread was available and I kept taking a bit off each start until it fitted. I have no idea why the lathe manufacturer made the thread 10% undersize.

[Fasturn]

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

Ring gage

Thread mic pitch diameter

Wires, last resort or when it's an odd one.

Mating part if it's a one off.

[eKretz]

Thats exactly what I would do if the mating part was available, then the two can fit as tightly or loosely as I want. I once made a 1/2" ACME two start male thread for a copy of the lathe toolpost. When I got to the size according to the charts, it was not even close to screwing into the top slide. Luckily the female thread was available and I kept taking a bit off each start until it fitted. I have no idea why the lathe manufacturer made the thread 10% undersize.

They may not have. Did you buy the lathe new? It is common for users of a machine to true up a worn screw to a uniform lead then cut a custom nut with "just so" fit to get rid of wear. Also, how were you measuring the "size according to the charts?" If you were just feeding in a double depth number you were out in left field to begin with. You really need to use wires or something similar to get an accurate size. My wire measurements never agree exactly with the double depth after I touch off with the tip of a threading - or at least rarely do.

[nickel-city-fab]

I agree. Very fun to cut threads in the lathe.
And for finer pitches, I often times use a triangular carbide insert.
If it is a coarse pitch and I need side rake, I have no issues grinding a HSS toolbit.

-D

I have a similar policy, but it really depends on the situation.
I prefer lathe-turned threads, they are just a lot better.
But where it doesn't matter, or if I can't justify the time spend
I'll just buy a box of bolts or whatever.

I very rarely use my dies any more, mostly for repairs nowadays.
But I love the adjustability, I have the antique 2-piece Greenfield/Wells Bros dies.
Like this set: https://www.ebay.com/itm/32472185672...UAAOSwvRBg901X

You can get any kind of fit you want with them.

[polaraligned]

I never understood this but I have seen it too many times before.
If you have a nut, why not just cut with the lathe until the nut fits ? ? ?

-D

At least with running a die for the last bit, I know the fit is correct for the class of fit I need. If I just have a nut, I have to fumble with wire gauges to see how much the last cut should be before trying the nut, or I might be wasting time taking light cuts to work up to getting the nut to screw on. Either way, the die is faster and the fit is always right on.

[JoeLee]

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

Same here. Nice thing about threading on the lathe is you can get any fit you want.

JL...........