# Threading question for my pm1127.



## go4shoot (Jan 28, 2017)

I need to thread a 1.5mm thread on my pm1127 lathe but I can't find what number I should use on my threading dial.  Anyone have the answer? Anyone have a thread dial chart for the 1127?


----------



## rgray (Jan 28, 2017)

Without looking up specs I'll put this out there.
If the lathe has an imperial lead screw then when threading metrics you leave the half nuts engaged and reverse the lathe to get back to your starting point.


----------



## Bob Korves (Jan 28, 2017)

rgray is correct.  If you have an imperial lead screw then the threading dial is useless for metric threads.  You must leave the half nuts engaged while threading, though there is a workaround for that...


----------



## HBilly1022 (Jan 28, 2017)

Check your owners manual but if you don't have one you can get it on the PM website. Page 18 states that you must leave the leadscrew engaged at all times for metric threading. If your not sure what gears and settings to use check out the threading chart on page 27.


----------



## go4shoot (Jan 28, 2017)

Thanks for the help.


----------



## lpeedin (Jan 29, 2017)

The previous responses are correct.  I just did some 1.5 mm threading on my 1127 over the last week.  You will leave the half nuts engaged and then turn off the power when you are coming up to your stopping point.  Then you will back out the cross slide, reverse the motor, run the carriage back to your starting point, then set the motor back to forward, move the cross slide back to zero, dial in your infeed on the compound, and take another cut.   This is also what someone without a threading dial would do to cut threads.


----------



## go4shoot (Jan 29, 2017)

Made the cut yesterday and it worked great. Thanks again.


----------



## DrAsus (Jan 30, 2017)

3dshooter80 said:


> The previous responses are correct.  I just did some 1.5 mm threading on my 1127 over the last week.  You will leave the half nuts engaged and then turn off the power when you are coming up to your stopping point.  Then you will back out the cross slide, reverse the motor, run the carriage back to your starting point, then set the motor back to forward, move the cross slide back to zero, dial in your infeed on the compound, and take another cut.   This is also what someone without a threading dial would do to cut threads.



That's a lot of steps that one (me..LOL) could make a mistake on.

What do I need to look for in a lathe to be able to cut metric AND standard threads?
Thanks in advance

DrAsus


----------



## lpeedin (Feb 2, 2017)

You will need to determine if the lathe has either a quick change gear box capable of doing both types of threading, or if there are change gears that will enable the lathe to do both.  Many of the larger machines may require a single gear change to do metric.  For the smaller lathes like the 1127, it is done by changing all of the gears per the charts that come with the machines.  Also, you need to decide if you want a metric machine or an SAE / English machine.   My 1127 is a SAE / English machine and it uses the 63-tooth gear to convert to metric.  I just have to install the proper gears per the chart on the machine.


----------



## DrAsus (Feb 2, 2017)

3dshooter80 said:


> You will need to determine if the lathe has either a quick change gear box capable of doing both types of threading, or if there are change gears that will enable the lathe to do both.  Many of the larger machines may require a single gear change to do metric.  For the smaller lathes like the 1127, it is done by changing all of the gears per the charts that come with the machines.  Also, you need to decide if you want a metric machine or an SAE / English machine.   My 1127 is a SAE / English machine and it uses the 63-tooth gear to convert to metric.  I just have to install the proper gears per the chart on the machine.


Thanks. I have never cut metric threads....Only standard and ACME. When I get a machine, I want to be able to cut any thread I want.

DrAsus

Sent from my XT1575 using Tapatalk


----------



## qualitymachinetools (Feb 2, 2017)

Yes you can cut any thread you want, but on an Inch machine, you can not use a thread dial for Metric threads. This is not just on this specific machine, it is on ANY machine out there, no matter if it costs $1000, or $30,000.     It is just the way the math works out.       Other than once I actually did see a lathe that had a thread dial with a gearbox on it, and you could work it out and use it for metric and inch threads, but it was so complicated, its just easier to leave the half nuts engaged when doing metric.   Once you do it a few times, it is not hard at all.


----------



## mikey (Feb 2, 2017)

The thread dial indicator for the Emco Super 11 has three drive gears, one for Imperial and two for Metric. It allows you to cut metric threads on an Imperial lathe while using the half-nuts normally.


----------



## qualitymachinetools (Feb 2, 2017)

That is a Metric Thread Dial, on a Metric Leadscrew, which will work for Metric threads, but you can't do Inch threads with that one and vice versa. Inch leadscrew, no thread dial for Metric threads.                        All Metric thread dials I have ever come across have 3 gears on them, just like that one. 

     The only way I have ever know it to be possible is with the Metradial, which probably costs as much as one of these lathes:   Of course, there could be something out there that I do not know, but Ive never come across anything that will work other than this.


----------



## lpeedin (Feb 2, 2017)

To further what Matt said, if you don't have a threading dial, you can still cut any thread you want, metric or SAE, (assuming your lathe will thread) by leaving the half nuts engaged.  You will just have to reverse and back out each pass.  It is just a bit slower of a process than if you have a threading dial.


----------



## mikey (Feb 2, 2017)

Actually, the 16t gear is used on my Imperial leadscrew and cuts Imperial threads just fine. To cut metric threads on my lathe you use one of the other gears on the indicator and different marks on the discs on top to time the engagement.


----------



## darkzero (Feb 2, 2017)

Oh but you can use the thread the dial & disengage the half nuts with an imperial leadscrew cutting a metric thread & vise versa (metric leadscrew cutting an imperial thread). I use this method quite often & it works great!

Check out my post in this thread, post #12. http://www.hobby-machinist.com/threads/cutting-metric-threads.22504/#post-199388


----------



## mikey (Feb 2, 2017)

3dshooter80 said:


> To further what Matt said, if you don't have a threading dial, you can still cut any thread you want, metric or SAE, (assuming your lathe will thread) by leaving the half nuts engaged.  You will just have to reverse and back out each pass.  It is just a bit slower of a process than if you have a threading dial.



I understand this. Martin Cleve refers to this as the Complete Reversal Method in his book, Screw cutting in the Lathe. However, it is possible to back off the half nuts to cut metric threads as Darkzero points out. There is a video on this as well but I don't recall the author.


----------



## darkzero (Feb 2, 2017)

mikey said:


> it is possible to back off the half nuts to cut metric threads as Darkzero points out. There is a video on this as well but I don't recall the author.



Video link is in my post as well. Video by Tom Lipton. IIRC Abom mentioned the method in a video recently. Could be others too.


----------



## Bob Korves (Feb 2, 2017)

mikey said:


> I understand this. Martin Cleve refers to this as the Complete Reversal Method in his book, Screw cutting in the Lathe. However, it is possible to back off the half nuts to cut metric threads as Darkzero points out. There is a video on this as well but I don't recall the author.


Inch lead screw, metric thread to a shoulder.  Release the half nuts at the end of the cut, back out the tool, and IMMEDIATELY turn off the spindle before the position gets lost.  Now, put the lathe in reverse, start the spindle, and re-engage the lead screw on the same thread dial mark it was on for the cut.  Return to starting position.  You have only temporarily disengaged the threads and then re-engaged them, nothing is lost, unless you let the dial turn around too long and lose the original engagement position.  It works fine, I have used it several times...


----------



## mikey (Feb 2, 2017)

Thanks, Bob. I have a thread dial indicator that works for metric threads so no real issues. Well, it works for the pitches I've had to cut, which have only been a few of them.


----------

