Cutting Internal 8 Tpi Thread

[taycat]

now i have my southbend 9" model c running, am planning on getting rid of chinese lathe eventually.
thing is have bought some decent chucks to use on chinese one so now need to swap them onto sb backplates.
can buy blanks but not ready tapped ones and set of taps here in uk will cost nearly £300.
wondering if i can mount blanks to faceplate and cut thread using lathe?
still learning screwcutting so will need explanation for internal.
what change gears would i need?

 

[janvanruth]

first you make a slug with the external 1.5 x8 thread on it
you copy the spindle, so to speak
you get it to a perfect fit, using the faceplate as a gauge
then you chuck the blank, and cut the thread using the slug as a gauge

as the leadscrew is a 8 tpi also, any set of gears will do as long as the spindle and leadscrew will turn 1:1

mounting the blank to a faceplate is possible but a lot more difficult than just chucking it in the 4 jaw

 

[pdentrem]

I can not help on the gear selection but look up "making a couple of threaded spindle backing plates for my lathe" on this site to see how I did mine.
Pierre

 

[mksj]

Wouldn't it be easier to get ones partially machined and threaded, such as from Grizzly. Even if they are shipped, still would be a lot easier. I have also seen a number on eBay, as well as many vendors that ship out of the US.

 

[janvanruth]

the stud gear and the screw gear must be the same
the intermediate gear can be any gear that fits

 

[spongerich]

I just bought a very lightly used 1-1/2 x 8 tap on eBay for $17 shipped. I bought it primarily to cleanup some old back plates I picked up and if I were making that thread from scratch, I'd probably still want to single point it part of the way and finish with the tap, but given a long enough handle, you could, in theory, tap it from the right sized bored hole. The most important part isn't actually the thread, it's getting the register just right.

 

[mzayd3]

Wouldn't it be easier to get ones partially machined and threaded, such as from Grizzly. Even if they are shipped, still would be a lot easier. I have also seen a number on eBay, as well as many vendors that ship out of the US.
View attachment 105775

This is the way that I went. Just cut the register for both the spindle and chuck

 

[taycat]

Wouldn't it be easier to get ones partially machined and threaded, such as from Grizzly. Even if they are shipped, still would be a lot easier. I have also seen a number on eBay, as well as many vendors that ship out of the US.
View attachment 105775

local foundry that make bits for model engineers as side line, do 8" blanks for equivalant of $15.
one of guys in club bought handful and they were good gear machined lovely they were for his myford and club as tap for that but not mine.

never thought of used of e-bay.