High-quality black-and-white photographs of large old machines and tools

**Isambard** · Jun 2, 2022, 07:42 PM

"For those who don't know doing a 3 start *TPI thread you only make the cuts as deep as if you were doing a 24TPI but you must be precisely 120° between starts"

Memory fade Frank?
Thread depth is as normal. However the lathe must be capable of thread cutting at 1/3 of the tpi. i.e 3 start 12 TPI would cut at 4 TPI.

**Toolmaker51** · Jun 2, 2022, 11:05 PM

Originally Posted by Frank S

Making large diameter threads is not much of a task. I've made both internal and external 18" diameter threads 4 TPI on a 16" gap bed lathe using a homemade 20 inch diameter face plate instead of a chuck to take advantage of more of the gap Obviously not hex stock. One of the strangest threads for me at least was when I made a 3 start 8 TPI thread full length on a 4inch diameter bar and the nuts to go with it.
For those who don't know doing a 3 start *TPI thread you only make the cuts as deep as if you were doing a 24TPI but you must be precisely 120° between starts

All the more reason to have a degree wheel, or degree tape prepared in advance; it'd be utterly correct to have a vernier or some means to locate quadrants accurately. Something tells me a Pi tape (easily determines .001 -.0005 accurately) and a fine tipped pointer is just the ticket. Not much reason beyond 2-3 and 4's.

**old kodger** · Jun 3, 2022, 06:17 PM

I recently had to go the other way and produce a 2tpi mandrel 50mm in diameter to make a coil in 10mm stainless tube

**Toolmaker51** · Jun 3, 2022, 06:28 PM

10mm stainless? Coil? 50mm x 2 TPI?
It's OK, you can tell us.
Ain't heard tell'a revnu-oors here bouts.

OMG! Have I committed a serious bit of stereotyping?

**Jon** · Jun 5, 2022, 02:32 PM

Furnace from the Mesta Forge Department. West Homestead, Pennsylvania. Circa 1915-1925.

Fullsize image: https://diqn32j8nouaz.cloudfront.net...t_fullsize.jpg

**bruce.desertrat** · Jun 5, 2022, 02:44 PM

Wow, didn't know Mesta had a line of miniature machines :-) That looks hardly taller than a worker!

**Toolmaker51** · Jun 5, 2022, 04:04 PM

Awful good estimation by bruce.desertrat.
Perhaps MESTA acquired it via auction lot; didn't know something so small was included?

Common brick is 2.25" high. Foundation is 5 courses with 4 mortar joints @~.6 (judging by the stack of 6 at left front corner) or kind of 13-5/8". Furnace box about 4x that 13.6, or 61"; 61"+13.6= ~74.8" (74.8/12 = 6.2').

Noooo, didn't stay at Holiday Inn last night, did employ Gerber Vari-Scale though. Enjoyable device, once in awhile wish it wasn't two feet long.
(drumroll please, cue for marksbug...)