change gear, quick change, and threading

[borjawil]

Looking around at lathes and was wondering what the difference between quick change and change gear are, the pros and cons, etc. Ive also noticed that threading is often mentioned with these terms. Is that referring to threading something to turn into a bolt?

 

[markba633csi]

A change gear lathe means you have to manually install the gears to cut a specific thread. A quick change gear box does the same function but has selector levers to select the various thread pitches you can cut. Quick change lathes are usually a bit more expensive, change gear lathes have a bit more flexibility, for example being able to cut metric and other special threads.
Mark S.

 

[Bob Korves]

A change gear lathe means you have to manually install the gears to cut a specific thread. A quick change gear box does the same function but has selector levers to select the various thread pitches you can cut. Quick change lathes are usually a bit more expensive, change gear lathes have a bit more flexibility, for example being able to cut metric and other special threads.
Mark S.

On most quick change lathes you can still change some of the gears to switch to metric threads or other special thread pitches. On some higher quality and mostly bigger lathes, you can do all of that without ever needing to mess with the gears at all, just move the handles to the correct positions per the chart for what you want to cut. Threads that are just as good can be done on all screw cutting lathes, it is more a matter of convenience and speed.

 

[borjawil]

Ah I see. So basically this wouldn't be a big issues (not having another set of gears) unless I'm cutting threads? I will need to thread steering stems but only at one end about 1" deep OD, and figure I can do so by hand. Is there another setback to not having another set of gears for other lathe operations?

 

[Wreck™Wreck]

Ah I see. So basically this wouldn't be a big issues (not having another set of gears) unless I'm cutting threads? I will need to thread steering stems but only at one end about 1" deep OD, and figure I can do so by hand. Is there another setback to not having another set of gears for other lathe operations?

Lathes come in several flavors, a very old machine will have change gears which requires a combination of gears for each thread lead.

A gearbox lathe has levers that choose the lead much like a manual transmission in a car, many will have a change gear change that gives the ability to do both inch and metric threads.

Some very specialized machines are for threading only.

A CNC control will make a thread with the programmed lead that you want, it is not dependent on a gear train.

Choose the method that you require for the work.

Good Luck

 

[Tozguy]

Ah I see. So basically this wouldn't be a big issues (not having another set of gears) unless I'm cutting threads? I will need to thread steering stems but only at one end about 1" deep OD, and figure I can do so by hand. Is there another setback to not having another set of gears for other lathe operations?

The gears that we change to cut threads also determine feed rates for other turning operations that involve power feed of the carriage or cross slide. My lathe has a gear box with shift levers but it also came with 5 change gears.

Change gears are easy to misplace so when buying a used lathe make sure that the ones you will be needing are with the lathe. If some gears are missing your options in thread pitch and feed rates are limited by as much.

 

[markba633csi]

If cutting threads "by hand" you meant using a die then be aware that when you get into larger threads like 3/4" and bigger it gets pretty difficult and you need to do it on a lathe.
In fact I wouldn't want to thread anything bigger than 3/8" by hand. Tapping is a little easier with large sizes but still tough.
MS

 

[12bolts]

If you are only likely to be threading the same pitch, (ie at x TPI) then you will not be changing gears. So the convenience of a QG box is negated. But there is nothing wrong with either type. Neither make the job any easier or simpler than the other. Just make sure you get the full set of change gears, or at least as many as you can.

Cheers Phil

 

[martik777]

If your power feed rate is controlled by change gears, it will be a PITA to change, say from rough to fine cuts. Some lathes have a semi QCGB where feed rates are controlled without needing to change gears.

You can also fit a lead screw hand wheel for more precise control of the feed rate.