What size drill bit

T

trapper

Active User
Registered
I'm about to start a face plate project for my wood lathe. I need to drill the hub so an 8tpi x 1inch thread can be cut can someone give me guidance as to size of drill hole. I'm guessing the usual metric deduct thred pitch from diameter wont work.

I'm intending to make a 6" diam plate with T-slots I'll make the thing by making a wood buck and then caste or have it caste in allumininium
 
Assuming your threads are the same as US standard 60 deg class 2a threads, the threading program on my computer sayd 1inch /8 tpi internal threads have a minor diameter of 0.8716 inches, if that's any help. A tap drill for a 75% thread would be 0.8750, it says.

I cut threads like that for a chuck mounting plate on my dividing head, made in Asia, and found their male thread was way off spec, and I cut the internal thread to match it. So the theoretical measurement may not match what you really need to cut, you might want to measure the male thread and calculate from there....
 
Video_man said:
Assuming your threads are the same as US standard 60 deg class 2a threads, the threading program on my computer sayd 1inch /8 tpi internal threads have a minor diameter of 0.8716 inches, if that's any help. A tap drill for a 75% thread would be 0.8750, it says.

I cut threads like that for a chuck mounting plate on my dividing head, made in Asia, and found their male thread was way off spec, and I cut the internal thread to match it. So the theoretical measurement may not match what you really need to cut, you might want to measure the male thread and calculate from there....
Click to expand...

In my case the Lathe is a Sheppach made in Austria. Yesterday I turned up some wood and drilled the centre at 22mm....... happened to have that size bit........ I used Oak and was able to cut the thread with a tap sourced here in the Uk. The wood one I've made up I'll retain as a glue chuck for wood turning.It fits up on the headstock spindle ok.
So I'll now repeat that exercise to make up the faceplate.
Thanks for the input
 
You must log in or register to reply here.
Back
Top