I have seen a couple of Hand cranks on Lathes.

[Huntinguy]

Okay. I am .... ??? confused... to say the least.

I have seen a couple of pictures here and mentions of hand cranks on lathes to be used for threading... My lathe has an electric motor ;D and my power bill is paid

I was also taught never to leave a chuck key in the spindle for safety reasons...

This leads to the question... Why do some of these folks have hand cranks bolted to the drive gears behind the head stock and how are they used?... Or is this something the wife did to get some money and a second go at a hubby that doesn't spend all the time in the garage ;D

 

[Deanofid]

One of them you may have seen is the one I have on my small Atlas. For most turning operations, it is not used, and is stored away.

When I need to cut metric threads, it's used because the half nuts have to remain engaged at all times, since the lathe has imperial threads. That means after a thread pass is taken, the carriage has to be returned to its starting position by running the lathe spindle backwards. My lathe motor does not reverse to provide this function, so the crank is used.

The power to the lathe is cut when doing this kind of threading, so that crank is not spinning under the power of the motor.

Dean

 

[mklotz]

Huntinguy,

For a more in-depth discussion of lathe cranks, their construction, use and safety issues, you might want to read...

http://www.homemodelenginemachinist.com/index.php?topic=1502.0

 

[tmuir]

I don't have a hand crank so I may be jumping in the deep end here but my lathe slowest speed is 180RPM which to me would be way too fast for short course threads, so I would think a hand crank would be the only safe option in those situations.
I should also mention I'm yet to cut a thread with my lathe.

 

[Lew Hartswick]

I don't have a hand crank so I may be jumping in the deep end here but my lathe slowest speed is 180RPM which to me would be way too fast for short course threads, so I would think a hand crank would be the only safe option in those situations.
I should also mention I'm yet to cut a thread with my lathe.

We have the students do 3/8 - 16 threads at 118 rpm with a 0.100 stop groove on
their beginning project. So with a very little practice you should be fine at 180.
Just pay close attention to what youre doing.
...lew...

 

[kvom]

A little arithmetic show that 16 TPI @ 118 RPM gives .81 seconds to cover the .100 inch groove. As Lew says, that's plenty of time if you pay attention.

Obviously, with finer threads you have more time; with faster RPM and/or smaller groove you have less.

My first shop project was 1/2-13 at 80 RPM, which I though was fast at first. For subsequent parts I was OK at 160. My home lathe goes down to 40 RPM in back gear, so I'm a bit spoiled now and do it slow. 8)

 

[Huntinguy]

So, the jist of what I am hearing is that the handle is used to run the lathe by hand power.

It seems to me that this would create some very low feed rates. I suppose with HSS and light cuts it would work.

My lathe is a little iffy on the half nut, I may just have to try this.

Thanks.

 

[Deanofid]

You get the same feed rates, it just seems slower because the spindle only goes as fast as you crank it. I've cut 1-8tpi threads using a crank, and cutting right up to a corner is a lot less stressful when you crank it, too.

Dean

 

[Blogwitch]

I would also like to remind you that for very course threads, to reduce the strain on your drive train, you can use a handle on the end of the leadscrew as well.

Some machines come fitted with them as standard. If they are fitted with a scale as well, you can use it for very accurate feed of the saddle for say facing cuts, or turning to a specific length.

Bogs