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

"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.

Quote:

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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

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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.

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

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?

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

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

https://diqn32j8nouaz.cloudfront.net...department.jpg

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

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...)

Wire mesh machine. American Steel and Wire Co. Donora, PA. Circa 1915.

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

https://diqn32j8nouaz.cloudfront.net...hine_input.jpg

Too bad this photographer wasn't in charge of the Brazilian line shaft shop...Line shaft driven factory and workers. Brazil, 1880, post 2613.

Post #585 shows the other side of that machine...