[pleasedontcrash]

I'm needing a little help on turning threads on our kent lathe. Ive never done it on a manual just cnc. Ive watched some videos online and get the basics but I haven't found anything that involves a kent lathe. The settings on this lathe look a little different then what ive seen in the videos. If someone could help with just a basic outline that would be awesome!! By the way I need to turn 7/8-14 thread.

[SchachtSpindle]

On a manual lathe you want to turn you major diameter and then setup your tooling for your thread. Cut a standard tool for threading and set it into the tool hold dead square to the stock with the compound 30 degrees away from the direction of travel. On the kent lathe you look for the the diagram that has a 1 inch picture and thread and next to it you will find a letter (mine is a v) one of the knobs, mine again is all the way on the right has that setting change it to this knob. then under that picture are all of the threads per inch that the lathe can do find the 14 and you should see a code next to it, mine is LB8T. Set the lathe to low range (L) the first gear lever to b the transmission to 8 and the second lever to T. You want to set the rev's to 90ish. Set the compound wheel to zero and align to the start of the thread with the tool just touching the thread. With everything on there will be a larger lever on the apron and a wheel to the upper right of that. With the unit on the wheel turns pick a number and engage the lever on that number. When you get to the end of the cut disengage the lever and back the crossfeed out two turns (oops make sure to set this to zero as well). Crank back to to in front of the threads by a little and take the cross feed back to zero. Now advance your compound by 5-10 thou and repeat and repeat and repeat until the minor diameter matches spec. I don't thread often and will usually take a scrap piece and get a feel of the motion before i do. If you can cut a should to feed into at the end of the thread. this means you just have to stop the advance of the threading (the larger lever on the apron) and not try to back out at the same time. If some one else could jump on board and explain the threading dial I would much appreciate it. I believe though with a standard thread that you can start the thread with any whole number and catch the existing thread but there is a art on this look in your manual for better direction on that if no one else will explain it or just use the same number every time (like I do, a little slow but works). Also slow turn it slow and take light cuts to get a clean thread. at the end repeat the last cut to clean up and i usually run a stone over the top of the threads and in the v to remove the burrs. Before you unchuck it test you thread with a nut to make sure it works.

[MetalCarpenter]

Using the Threading Dial

[pleasedontcrash]

Thanks a bunch!! I got the standard threading figured out but what about metric threads. Is it the same process then just use the metric chart or is there a different process?

[SchachtSpindle]

I believe standard process just with the metric chart but have not cut metric threads.

[handlewanker]

Hi, if you want to cut metric threads you need to keep the half nuts engaged all the time and just reverse the spindle when you get to the end of the thread.....going back and forth as you dig deeper.

If you disengage the half nuts with Metric thread cutting you'll lose the synchronisation......that applies to odd pitches too with Imperial leadscrews....(or Metric leadscrews).

It is a case of with manual lathes you're cutting threads relating to the leadscrew pitch which is in threads pert inch.

Metric threads are in mm pitch.....like .75mm.....this does not relate to the leadscrew pitch and you "can" cut Metric pitches with Imperial leadscrews if you know the formula and have the right change wheels fore your lathe or can cut a few extras.

We can write an essay on screw cutting, but it's an acquired hands on skill.......these are just a few tips, and there is a bag of info if you search for it.
Ian.

[SchachtSpindle]

One note on the Kent lathe there is a brass(Ibelieve) pull knob on the apron that will reverse the travel direction when you pull or push it.

[handlewanker]

ABSOLUTELY NOT........that is for reversing the gears inside the apron to reverse the auto feed, not for screw cutting.

With screw cutting, the lead screw pulls the carriage along by being directly connected to it with the half nuts when they are closed on the lead screw..

When the screw cutting tool reaches the end of it's cut (with metric threads) you must IMMEDIATELY retract the tool and reverse the motor that drives the lathe.....nothing else....keeping the half nuts engaged at all times.

An ideal screw cutting speed is 80 rpm....this gives you time to do the reverse trick without drama.
Ian.

[SchachtSpindle]

Opps.. Sorry I learned something as well thanks Handle. Never would have thought about that until way too late.

[handlewanker]

Hi, we live and learn....LOL.

BTW.......on my old Colchester Bantam lathe dating from 1930.....I don't have a reversible motor.......it's dangerous to have that option with screw on chucks......so I fit a winding handle into the end of the spindle bore and use this to wind the carriage back when screw cutting......it gets removed when normal turning is resumed.

It sounds agricultural, but at a forward screw cutting speed of 80 rpm, and as long as nothing is in the way of the rotating circle of the handle, it works and has been for the last 35 years.
Ian..