Threading Problem

D

ddickey

H-M Supporter - Gold Member
H-M Supporter Gold Member
Joined
Apr 21, 2016
Messages
3,570
So I need to turn some 5/8-32 threads. I set up my gears and place my change gears in the correct position. I check double and triple and then check again. Everything is correct according to this chart.
I measure the threads to be about 11tpi.
Any idea what I should check?
1496846639935-1885198914.jpg
 
I was wondering what that meant. It appears then I can't thread 32TPI?1496848832325-386469004.jpg
 
In the upper chart it shows 16, 8, and 4 TPI, which are in the same ratio group for 32 TPI, would need to reduce the drive train ratio by a factor of 2 (slow down the lead screw by 1/2) and otherwise use the setup for 16 TPI. If we knew the lead screw pitch and the tooth count on all the gears in the train to make 16 TPI, along with what additional change gears you have available, we may be able to come up with something that would do 32 TPI.
 
Before threading check the lead, this is easily done on a small lathe that allows rotating the spindle and gear train by hand. Put the gear box in the desired lead, in your case .03125, close the half nuts then rotate the spindle until the lash is gone, place an indicator on the carriage and rotate the spindle by hand 1 revolution and the motion of the indicator will tell you the actual lead. Most people do not have an indicator that will resolve to 5 decimal places so 16 revolutions of the spindle will yield .500" of travel for 32 TPI.

On lathes with an automatic spindle brake this is more difficult, you will not be able to rotate the chuck by hand with the brake on.
 
ddickey said:
So I need to turn some 5/8-32 threads. I set up my gears and place my change gears in the correct position. I check double and triple and then check again. Everything is correct according to this chart.
I measure the threads to be about 11tpi.
Any idea what I should check?
View attachment 235018
Click to expand...

I'd try the 10 selection or the 104 selection.
 
Do you have the change gear set for your lathe? If not, is it available?
 
I have all the gears.
 
What Bob said, also, the 6,12,24 group might provide a path- depending on the gearset.
Mark S.
 
Things that will be very helpful in getting a good response:
A decent pic of the change gear set up.
A list of the gears that are already installed.
A list of what gears you have on hand.

I agree with the others, no reason this can't be done easily enough since you can turn 16TPI.
Some lathes have wonky set ups, your lathe is already a bit unusual in that it gives a plate for DP (a nice feature IMO).

Typically, a lathe will have a gear at the spindle, a gear at the gearbox, and an idler gear in between. All you have to do is get the gear at the gearbox to run at 1/2 speed for the 16TPI setting.
 
You must log in or register to reply here.
Back
Top