What am I doing wrong?

Been there, done that.

The scale on my lathe only goes to 55 deg, hence I foolishly assumed the 29.5 deg I could see on the scale was the one to use. Wrong. For some reason Grizzly decided to end the scale at 60 deg instead of 60 deg.

The 29.5 deg mentioned in other replies is an angle from the face of the chuck. My scale on the compound is with respect to the bed ways.

Since I have no scale to read and I wanted a consistent method to set the compound, I just cut a block of wood to 29.5 deg on my table saw, which has a decent mitre gauge. I epoxied a rare earth magnet in the face.

I then wrote the angle on the wood to remind me this was a jig and not a piece of scrap.

I now just attach the wood to the compound then swivel it so the block is flush with the chuck face.

Angle_block_to_set_threading_angle_7616.jpg
 
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to check that there is not somethin else going on dont use your compound and thread just with your crossfeed. set your toolbit square to your work piece and do a test thread with the cross feed. I know people are saying you cant do that. but you can. most people are taught to thread with the compound ,as was I, but I have cut many successful threads with this method then you know you compound if set wrong but if not then I would need to see your lathe to correct the problem bill
 
bfd said:
to check that there is not somethin else going on dont use your compound and thread just with your crossfeed. set your toolbit square to your work piece and do a test thread with the cross feed. I know people are saying you cant do that. but you can. most people are taught to thread with the compound ,as was I, but I have cut many successful threads with this method then you know you compound if set wrong but if not then I would need to see your lathe to correct the problem bill
Click to expand...
Thanks I'll try that, I added some additional photos
 
Dave Paine said:
Been there, done that.

The scale on my lathe only goes to 55 deg, hence I foolishly assumed the 29.5 deg I could see on the scale was the one to use. Wrong. For some reason Grizzly decided to end the scale at 60 deg instead of 60 deg.

The 29.5 deg mentioned in other replies is an angle from the face of the chuck. My scale on the compound is with respect to the bed ways.

Since I have not scale to read and I wanted a consistent method to set the compound, I just cut a block of wood to 29.5 deg on my table saw, which has a decent mitre gauge. I epoxied a rare earth magnet in the face.

I then wrote the angle on the wood to remind me this was a jig and not a piece of scrap.

I now just attache the wood to the compound then swivel it so the block is flush with the chuck face.

View attachment 247359
Click to expand...
Good idea!
 
JimDawson said:
Looks like a buttress thread :) I'm going to guess that your compound is set to 29.5° from the wrong start point. Start from the compound at 90° to the lathe centerline and rotate 29.5° counterclockwise.
Click to expand...
You are right, the compound needed to be set on the other side (59 1/2 - 60 degrees)
Thanks
 
matzo said:
My threads are not vertical but seem to layover to one side. Using a sharpe 60 degree cutter, compound set at 29 1/2 degrees, cutter at 90 degrees to work.

I have added some photos of my setup. The pictures of the thread were taken through a magnifying light. I am keeping the cross slide at zero and feeding with the compound.
Click to expand...
Thank everybody, the problem was the compound was incorrectly set at 29 1/2, should have been 59-60 degrees.
 
If you want to use the compound then it should be feeding at the same angle, to the centerline of the work, as one half of the thread angle. Different machine makers put their degree scales with the angle reading either from the centerline or off perpendicular to the centerline (ex; 30 degrees either side of perpendicular. Dave Pane shows a sure fire way to make sure your set up at the correct angle.

I have the compound removed from my lathe and the QCTP mounted direct to the cross slide to increase rigidity this means I must cut threads by feeding the cross slide. With a good sharp tool this presents no issues and I actually find I get better threads with the set up I have. Cross slide seems to be the weak link on a lot of lathes.

I cant see the insert tool you have close enough to tell so forgive me for asking, is that a specific threading insert or a standard 60* insert?
 
The above is correct, turn your compound to 59-60 and it will work out for you.
 
If you want to advance your compound in at 29.5º, you will have to set it to 60.5º.
 
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