Feeling a little restricted.

[MattH]

Do a little short thread, maybe 10 threads. There's nothing to learn letting it run so much.
Cut a relief for the thread tool to run into at the end of the threaded portion, this means that you can stop the lathe without pulling the bit back.
It's all about the sequence.
Engage halfnut, cut, disengage halfnut, wind out cross slide, wind out carriage, wind in cross slide, advance compound, engage halfnut.
Rinse and repeat (based on having a appropriate thread dial).

If you don't have a dail indicator or you are trying to cut a metric thread on a imperial machine (or vise versa) the you would leaving halfnut engaged and the stop and reverse the lathe at the end of the cut, again requiring a relief.

 

[Brad93]

Does your lathe have a thread dial Richard?

 

[Brad93]

Ok so tonight I tried a bit of thread cutting. In doing so I found a few things that perhaps are not so great about this lathe as it is.
1) I don't think it's slowest speed at 48 rpm is the best for this. It does fly across when the feed speed is changed.
2) changing all those wheels around is a pita and took me a good 25-30 mins.
It wasn't a disaster though. I went for a 2.0mm pitch on some steel tube to practice. The first one was a train reck as I cut straight over the thread deeming it useless which is the one on the right. The other two dispite needing a little clean up would probably work as the thread stayed in line with the tool. Not easy I must say. Used cutting oil and watch a db vid for some tips on it. Cheers @doubleboost your lathe vids are very nice to follow.

Now you can see why the Super7B's (screwcutting gearbox) go for so much. I think the cheapest gearbox alone on ebay at the minute is £500 and its fairly used.

 

[Richard.]

Do a little short thread, maybe 10 threads. There's nothing to learn letting it run so much.
Cut a relief for the thread tool to run into at the end of the threaded portion, this means that you can stop the lathe without pulling the bit back.
It's all about the sequence.
Engage halfnut, cut, disengage halnut, wind out cross slide, wind out carriage, wind in cross slide, advance compound, engage halnut.
Rinse and repeat (based on having a appropriate thread dial).

Sort of what I was doing but with more fumbling about lol. I was engaging the dog drive on the left so that the manual gear on the lead screw stayed where it was not changing the position of the slide in accordance with the lead screw if that makes sense.

 

[Richard.]

Does your lathe have a thread dial Richard?

Don't know mate. Which one is that.

 

[Bill Edwards]

Does the lathe reverse?

 

[Bill Edwards]

Don't know mate. Which one is that.

It's a dial attached to the carriage near the leadscrew which spins as it travels along the bed. The idea is that it indicates where you are on the leadscrew, so if you stop threading at number four when you wind back you stop with the pointer at four again and engage again and it'll be in the correct place.

 

[MattH]

Sort of what I was doing but with more fumbling about lol. I was engaging the dog drive on the right so that the manual gear on the lead screw stayed where it was not changing the position of the slide in accordance with the lead screw if that makes sense.

That dog will be the halfnut lever, it clamps a set of Half Nuts around the leadscrew to connect the saddle to the screw and therefore drive the carriage along the ways. The dial indicator will be a small wheel with graduations on it that rotates when the halfnuts are disengaged and then stays still when engaged. It allows you to re-engage the halfnuts and the same position on the leadscrew. Without a dial you need to leave the halfnuts engaged throughout the entire threading operation. At the end of each cut you have to reverse the lathe to drive the carriage back to the start of the cut.

If you do have a dial it will be either Metric or Imperial (probably Imperial) and can only be used to cut the threads that it is matched to. To cut he other type of thread you would need to leave the halfnuts engaged again.

 

[brightspark]

heres one http://modeleng.proboards.com/thread/6007/myford-dial-indicator-problem

 

[WorkshopChris]

Cut a relief for the thread tool to run into at the end of the threaded portion, this means that you can stop the lathe without pulling the bit back.

Very good advice, it's practice, practice, practice.
I very rarely have to cut threads but when i do its always after a good mock up first.

Even then on the part that matters the first pass just kisses the work lets you double check the job before you commit.

 

[MattH]

Richard, PM me your address and I will pop this in the post for you. It's an old book but is required reading for anyone starting out with turning.

 

[addjunkie]

Without a dial you need to leave the halfnuts engaged throughout the entire threading operation. At the end of each cut you have to reverse the lathe to drive the carriage back to the start of the cut.

If you do have a dial it will be either Metric or Imperial (probably Imperial) and can only be used to cut the threads that it is matched to. To cut he other type of thread you would need to leave the halfnuts engaged again.

I dont screw cut very often, but find i have less scrap bin additions leaving the half nuts engaged, and reversing the machine.

Your serious about mastering machining, I know guys with decent lathes owned for years, who have never screw cut anything.

 

[Richard.]

Does the lathe reverse?

Yes

 

[Richard.]

It's a dial attached to the carriage near the leadscrew which spins as it travels along the bed. The idea is that it indicates where you are on the leadscrew, so if you stop threading at number four when you wind back you stop with the pointer at four again and engage again and it'll be in the correct place.

Yes got one of those too. I kept it at zero.

 

[Richard.]

That dog will be the halfnut lever, it clamps a set of Half Nuts around the leadscrew to connect the saddle to the screw and therefore drive the carriage along the ways. The dial indicator will be a small wheel with graduations on it that rotates when the halfnuts are disengaged and then stays still when engaged. It allows you to re-engage the halfnuts and the same position on the leadscrew. Without a dial you need to leave the halfnuts engaged throughout the entire threading operation. At the end of each cut you have to reverse the lathe to drive the carriage back to the start of the cut.

If you do have a dial it will be either Metric or Imperial (probably Imperial) and can only be used to cut the threads that it is matched to. To cut he other type of thread you would need to leave the halfnuts engaged again.

Yep I have a thread indicator dial it's metric like all dials on the lathe. I kept the half nut engaged and used the dog drive on the far left for the feed. This way the thread indicator never moved and I didn't have to reverse feed.

 

[Richard.]

Richard, PM me your address and I will pop this in the post for you. It's an old book but is required reading for anyone starting out with turning.

View attachment 85088

Will do and thank you Matt that's really kind.

 

[Richard.]

I dont screw cut very often, but find i have less scrap bin additions leaving the half nuts engaged, and reversing the machine.

Your serious about mastering machining, I know guys with decent lathes owned for years, who have never screw cut anything.

Very serious , I've turned down all my private work this weekend just so I can learn and play. You fellas are simply awesome and may this thread never end because every post is enlightening.

 

[Bill Edwards]

Yes

In that case I would suggest reversing rather than disengaging to wind back. It's a foolproof method which can't go wrong and although a little tedious it's not all that bad provided the workpiece is short.

 

[MattH]

Yep I have a thread indicator dial it's metric like all dials on the lathe. I kept the half nut engaged and used the dog drive on the far left for the feed. This way the thread indicator never moved and I didn't have to reverse feed.

There's something amiss there then mate, if you kept the halfnuts engages then you shouldn't be able to cross cut your thread. When you say the dog drive do you mean the tumble reverse lever I.e. Reversing the leadscrew in relation to the spindle? To wind the carriage back with the halfnuts engage you should be reversing the motor to reverse the spindle and leadscrew. If you just reverse the leadscrew you can then lose the relation between the work and the leadscrew.

 

[Richard.]

There's something amiss there then mate, if you kept the halfnuts engages then you shouldn't be able to cross cut your thread. When you say the dog drive do you mean the tumble reverse lever I.e. Reversing the leadscrew in relation to the spindle? To wind the carriage back with the halfnuts engage you should be reversing the motor to reverse the spindle and leadscrew. If you just reverse the leadscrew you can then lose the relation between the work and the leadscrew.

I only cross threaded the first one Matt while sussing what the levers do. After that I cut 2 more that would of worked out ok.