Thread cutting dilema?

Great thread going here, I need this info as I have not cut any threads yet.
Recommended minimum tooling/measuring for this single point threading?
Currently looking at some screw pitch gauges, but not sure whats needed.
 
My standard recommendation for anyone learning how to run a lathe is to download and study South Bend's "How to Run a Lathe". There are other books and resources available as well, but this one is my favorite.

Just Google it and you'll find many sources and different versions to download. Or, if you're so inclined, you can order a paper copy from Amazon.

There are also a lot of threads on this site about this very topic. This subject has been discussed several times and there is a lot of good information already posted which will help.

Ted
 
Just a comment on the 29.5 degree thing when feeding with the compound.....
The protractor scale on most compounds is not absolutely accurate. However the actual angle of the compound for feeding must NEVER be over 30 deg. So to hedge on inaccuracy of the scale we set with a safety margin of 0.5 deg. or 29.5.
In fact any setting of something less than 30 degrees would work but 30.1 deg would not.
 
Great thread going here, I need this info as I have not cut any threads yet.
Recommended minimum tooling/measuring for this single point threading?
Currently looking at some screw pitch gauges, but not sure whats needed.

Depends on how accurate you want your threads to be. At minimum, you need a thread pitch gauge to make sure you've identified your thread pitch correctly. It is also used to make sure your first scratch pass conforms to the thread you're cutting so that you know your gearing is correct. You also need a fishtail or centering gauge to correctly orient the threading tool to the work piece; a Starrett C391 is common but many others make them. With these tools you can cut threads to fit an existing female piece or thread internally by cutting the thread and checking for fit.

If you want to cut threads to some spec then you will need a more accurate way to read pitch diameters. The cheapest way is to buy a set of pitch diameter thread wires and use your micrometer; read up on the 3-wire technique. Thread micrometers that read pitch diameter directly are also popular and nowadays are pretty cheap. There may come a time when you need to cut a Class 3 thread and you need to be able to read pitch diameters accurately; that is when you need these tools.

Lastly, you need good thread cutting tools. These are available in carbide, HSS or you can grind your own tools. The cleanest threads I can cut are done with a shop-ground HSS tool so that is what I prefer.

Threading is not hard to do but you sort of need to know what you're doing. Read, ask, try and try again. It will come.
 
And don't let anything distract you're attention lest you end up with a nice crash like this. 3.5"- 4TPI on a shaft worth probably $800-$1000. Saved the shaft after ordering a new threading tool (probably $250). What's really bad is the boss and his son and the company owner and a customer where standing in the middle of the shop when I crashed it. :oops: Still not sure how I got my timing/rhythm whatever off so bad, but it only takes a heartbeat.

IMG_0240.JPG IMG_0241.JPG
 
Just Google it and you'll find many sources and different versions to download. Or, if you're so inclined, you can order a paper copy from Amazon.

...or choose a PDF copy from one of several hosted right here:
https://www.hobby-machinist.com/res...a-lathe-for-beginners-1914-15th-edition.3217/
https://www.hobby-machinist.com/resources/sb-how-to-run-a-lathe-1966-27th-edition-56-pdf.2909/
https://www.hobby-machinist.com/resources/sb-how-to-run-a-lathe-1914-3rd-edition-pdf.2890/

-brino
 
And don't let anything distract you're attention lest you end up with a nice crash like this.........................Still not sure how I got my timing/rhythm whatever off so bad, but it only takes a heartbeat.

Ouch! Kinda hard to hide something like that when it goes bad.
Glad you saved the shaft.

-brino
 
My SB9A compound degree markings are very small and difficult to read, so I made a 29.5 degree jig that lets me reset to that angle for threading whenever I have moved the compound to some other angle such as cutting an R8 taper on a piece. A one time gauge is much easier for me to reset to == Jack
 
I read the SB book. I watched videos. I read forums. But there seem to be exceptions and variables depending on the thread and the machine and who's doing it. But nobody explained that in order to get the correct angle I can't go by the markings on the machine.

To me the one tip I got early on was you're just going to have to do it. In this case I had so much other stuff like a proper grinder and gage to hold the tool at the correct angle, didn't understand what I was looking at on the gear chart to set up the feed, the cluster that is the gear train on the 9x20, my machine just doesn't go slow enough so I had to make a hand crank, the real way to use the fishtail and on and on. There was a ton of side trips and detours so by the time I was actually ready to cut the threads it was kind of anticlimactic. But finally getting how to not go by the deg on the compound, but using my Starrett gage I was able to get the correct angle. There is still a lot I need to learn but after three tries I got it done. I have another project, a graduated carriage stop, that needs to be threaded. Hopefully I'll be able to get to that before all this fades. I feel like it will stick though because each try taught me a lesson and those stick with me more.
 
Excellent info again!!

I am still gathering the devices specific to threading. Any suggestions on thread gauges and fishtails and thread mics? Are the gauges and fishtail ok to get new cheap ones or does the quality vary enough to warrant a name brand set? Are the Mics for threading good bad, where to start with equipment?

Thanks
 
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