lathe thread question

Um, fine feed? Sounds like around 2 thou/rev..
Tim
-- "I've got more trophies than Wayne Gretsky and the Pope combined!" - Homer Simpson Website @

Instrument threads and optical apparatus. My ancient "Machinery's Handbook" mentions Lowenherz threads, metric, with an equivalent pitch of up to 101.6 tpi. HTH --

My latest copy of Nasa Tech Briefs has an ad for 200 tpi leadscrews.

Its for slow feed, you get a real nice finish. I have just gotten a heavy 10 and look forward to the nice finish the 460 tpi will make. My 10K goes to about 260 TPI and will make a nice finish at that.

Yes. The company simply decided to put both the feed per turn and the number of TPI the change gear position would give. I *do* use the finer settings on my 10L gearbox - but for feeds as you say.
Jim
================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ==================================================

I think the 480 tpi setting is more bells & whistles than anything else. I have Southbends with the standard and wide range gearboxes, and rarely go slower that 224 tpi setting. If you can't get an acceptable finish at 224, you probably need to take a look at the setup or tool. To turn something at 480 tpi, even at high spindle speed, takes too long.
Tony

They provide a slow advance for the cutting tool when turning.
Harry C.

Harry C.
Seen threads like that for adjusting the paint output.
You got this 3 inch square box full of epoxy paint, steel pickup roller that it attaches to.
You control the thin film of paint by the finely threaded knob that moves a blade in and out.
Your painting thousands of small (inch or less) rolling pins, the colors are a color code, that specifies their characteristics for aircraft industry...
ceramics, heat, non magnetic, etc...
my 2 cents

I cut 100tpi threads for a customer. That job is coming up again next month. I suspect they are supposed to be .25mm pitch, but at only 4 or 5 pitches, they'd probably interchange anyway
I read someone in this group looking for info on 5/8-27, I had to laugh, I own that tap...
5/8-27 is the top of a microphone stand.
like camera tripod mounts have always been and will always be 1/4-20.

I saw that, and also a cool article about passivating stainless steel.
cheers T.Alan

[ ... ]
You probably read me mentioning cutting that thread, and that fairly few quick-change gearboxes include that thread. I was mentioning that because it is sometimes nice to have a quick-change box which covers the less common threads. My Clausing does, FWIW.
I also own the taps (starting, plug, and bottoming), and the die. But I usually cut it with the Geometric die head and the right chasers, because I then don't have to stop and reverse the spindle to back it off. The Geometric die head (as do other brands) opens when it reaches the preset stop position, so you can pull it back off even when the spindle is still rotating forward. (One of the benefits of doing repeat jobs on a turret lathe. :-)
Exactly why I cut it. Usually in batches of eighty at a time. To adapt microphones to non-standard support systems.
But it is not the *only* microphone mount thread. There is a common smaller metric one, as well as other special threads typically for very expensive recording microphones. I've had to make such adaptors from time to time.
Just like it -- since not all have *that* thread either. Larger cameras (such as my 5x7 view camera) have a larger thread -- 3/8-16 IIRC. And you can get screw-in adaptors to the 1/4-20. But if you are hanging an 8x10 (or larger) view camera on a tripod, you really want something bigger than 1/4-20. :-) Same for big heavy TV or movie cameras.
Also -- FWIW -- the lightweight telescoping light stands also tend to have the 1/4-20 thread on the top -- and can reach up to something like 18 feet -- nicely above the crowd for a microphone for a live recording.
Enjoy, DoN.

Given a nice hefty depth of cut, a feed of .002 per rev. could be very useful.
Probably on larger machines (more HP?) I've taken cuts from 1/4 to 3/8 deep using a slightly lower feed.

Actually it is 1/4" BSW not 1/4-20 (UNC). similarly the 3/8" thread is 3/8" BSW rather than 3/8-16 (UNC). The other camera and telescope mount sizes tend to be Whitworth as well.
Doesn't make much difference in this application since they tend to be made more than a bit sloppy, but it's best to get it right!
Mark Rand RTFM

You should qualify that statement with US cameras and more recent world wide. My Exakta, circa 1955, has a 3/8 16 and I believe many other european cameras of that vintage were the same. ...lew...

"To turn something at It is usefull sometimes. I was making a valve for a model engine and used .0005 feed per rev as a finish pass on the stem. It was the only way I could get it to hold the required tolerance +or- .0001 on a .125 stem 1.3 inches long made out of nitronic 50.
Charlie