Internal Threading Problems: Carriage Moves

Here's a pic of my tool. Best way to sharpen it I could figure was to hold the flat top face against the grinder and just touch it up a little bit. The arrow points to the wear/damage. Any ideas?

That doesn't look like enough front clearance.

dbassing said:

You said that you set the compound to the same angle as when you thread externally. When threading internally the compound is set so that the handle is on left side. External the handle is to the right. Same angle different direction of feed.

Click to expand...

For some reason, I don't understand this statement. I read it , thought about it and still don't understand. I must be missing something. ( sometimes I have a brain fart and things don't always sink in since the last stroke. )Would someone help? The handle is on the left or right side of what?.

When single point cutting a 60° external, right hand V thread the compound is set at 29.5° with the feed handle to the right hand when viewed from the operator's position. By setting the compound like this and feeding in the edge of the cutting tool that is toward the headstock does most, if not all, of the cutting. The direction of the carriage is towards the headstock.

When single point cutting a 60° internal right hand V thread the compound is set at 29.5° with the feed handle to the left when viewed from the operator's position. By setting the compound like this and feeding out the edge of the cutting tool that is towards the headstock does most, if not all, of the cutting. The direction of the carriage is toward the headstock.

In both cases the work is turning in the normal direction and the tool is square to the work and exactly on center.

Hope this helps.

Ahhhh....... Thank you.

What about cutting a left hand internal thread where you are feeding the carriage away from the headstock? The same scenario apply?

In the case of cutting an internal left hand thread the compound would be set over 29.5° to the right as viewed from the operator's position. Feeding out would allow for the cutting edge of the tool, which in this case is the one away from the headstock, to do the cutting. As you note, the carriage direction is from the headstock towards the tailstock.

For an external left hand tread the compound would be set over towards the left.

The basic principal to remember is to set over the compound in such a way as to have the leading edge of the V tool be the one that, when advanced, in the case of an external thread or retracted, in the case of an internal thread, is the one that does the cutting.

The front part of the carriage of a sb 9 can always be lifted a bit.
There is no provision for holding down the front part.
The "brake " on the right hand side of the carriage is meant for locking the carriage down when parting off.
So no, it is not a problem lathe.

Where did you get the tool from?
It looks like it has no front clearance at all, which would be consistent with your problem.