Single Point Threading on a PM-1030V?

[erikmannie]

It looks like the desired dimensions for an internal thread are just taken off a reference chart. The reference chart that I have been using lists 2A and 2B.

Hopefully I should use the 2B figures because that is how I am proceeding.

 

[erikmannie]

Looks like I bore to between .8650“ and 8797”.

 

[Nigel123]

The 0.75 divided by the number of threads is the formula for the amount for the infeed of the compound set at 30 degrees
8 tpi would be 0.09375
The 0.742 divided by the number of threads is the formula for the compound set at 29.5 degrees
I just go by the drill size for that particular thread seems to work
I always feed with the compound never the cross feed
A little less than 30 degrees lets the cutting tool to only contact on the front edge
Feed in the direction of travel
I never have got into minor or major diameters but will monitor your progress
I am not too old to learn

 

[Downunder Bob]

If you want to make high quality single point threads, Joe Pisinski has an excellent YT Video on how to it properly

 

[erikmannie]

I almost have the bushings ready for the internal threading practice. I had to have everything perfect for the small lathe to part this 2” mild steel.

I tried to upload a picture using my phone, but the file is too large.

 

[erikmannie]

Here is a picture of the 3 bushings that I will use to make 3 nuts:

 

[erikmannie]

I made one nut today, and I want to tell everybody the 2 mistakes that I made:

(1) I should have done the precision boring and internal threading in a single chucking, and
(2) I should have made the groove before this chucking, and approached the groove from the groove side. I part off this grooved area, so it does not need to be concentric with anything. It only needs to have enough room to both support the bushing as well as allow the threading tool a safe area to stop work after a pass.

Pictures to follow...

 

[erikmannie]

I bored the first bushing to .879” for this 1", 8 TPI female thread.

.879” is near the point where one would overshoot it & scrap out the part, but it is officially in the specified range.

I had planned for my groove to be a generous .500”, but the taper induced by my misuse of the boring bar increased the length of this groove.

 

[erikmannie]

I ended up with this .001” runout after I took the workpiece out of the 3 jaw chuck. Like I said, next time it will all happen in a single chucking.

 

[erikmannie]

Carbide insert tool centered and Dykem applied to bore: