Leadscrew TPI?

Standard headstock spindle gear size?

Edited By Hopper on 18/01/2018 23:24:19

Whatever gear train you go for make one gears teeth divisible by the number of starts then you can use that to index each start. Crank the leadscrew not the spindle and make sure you have clearance under the tool to clear the steep helix angle

I am in the (very extended) course of doing a similar thing. My thread started as 0.75" pitch, 4 start 1" OD but has become 0.6" pitch, 3 start, 1" OD – it is for a steering box and I decided for other reasons to give the box more ratio. I decided to go down the thread milling route and have done the job on my TS mill. I am using a modified gear cutter (No. 1 which is near to rack form) to cut an ACME form thread. The nut (which I think is the more difficult job) is to be cast in whitemetal inside a bronze housing. There are some pictures on Flickr starting here:

Hope that helps.

Martin

Prof. Chaddock gave a detailed description of producing a large pitch thread in a lathe for his Quorn construction series in ME and book.

IIRC, he chose milling with a toolpost mounted spindle. The leadscrew was driven by adapting the lathe drive, using a large, home-made plywood pulley to get an overall very low ratio. I think that he discounted "handraulic " drive because of the time traverses would take on the fairly long thread.

I think machining an internal thread would be tricky. The Quorn uses a peg to engage the thread.