WM210V how to cut perfect threads

[weston1968]

I have no experience cutting metric threads using a full metric lathe with a metric lead screw. I have only just googled a few recent things that I was able to find. Not interested in arguing about various merits, was only stating that apparently there are metric dials, but they are not universal with pitch settings. I also found that some metric dials have gear sets that can be used on the dial to do certain pitches. This is all I know about it. Trying to be supportive of what you are doing, but it feels as if you are being a little combative.

I don't think you can willy-nilly change pitches and have things work. Take a 1.5mm pitch and 1.25mm pitch. If you moved your stop perhaps it could work. However, neither pitch lines up satisfactorily on a 2mm thread. You can move your initial position, however, so it will line up for that single pitch. There may be other work arounds. I applaud you for trying to make this work, and hope you continue this in this thread, despite any nay saying. Keep on plugging at it!

I have over 25 patents here and abroad. Almost always it is a matter of looking at something differently and then others look at it and go, that is obvious. Once the obvious is seen you wonder why everyone did not see it. Just like it is obvious that if you add a 20T gear between the spindle gear and the next gear on theWM210V you can cut left handed threads, but the manufacturer has never looked at it that way.

 

[benmychree]

I just realized that the red herring here is the use of the stop, which is entirely unnecessary for the normal threading process, in which you locate the carriage to any point convenient for starting another cut and wait for the appropriate number to come around and re engage the half nut. On my lathe there is a four thread per inch leadscrew; even numbers of threads can close on any numbered or un numbered line, odd threads must close on any numbered line, half threads on opposite numbers, and quarter threads must close on one number only, and pitches that are a factor of the lead screw can be closed anywhere. when cutting metric threads or special leads, the half nuts must be kept closed.
On lathes with metric screws, change gears on the thread dial must be used to cut certain pitches, one cannot cut all pitches with just one gear, as has been already stated. I think on the metric machines that I have seen, 4 gears were used, usually mounted back to back with a movable thread dial that can bring them into play.

 

[weston1968]

I just realized that the red herring here is the use of the stop, which is entirely unnecessary for the normal threading process, in which you locate the carriage to any point convenient for starting another cut and wait for the appropriate number to come around and re engage the half nut. On my lathe there is a four thread per inch leadscrew; even numbers of threads can close on any numbered or un numbered line, odd threads must close on any numbered line, half threads on opposite numbers, and quarter threads must close on one number only, and pitches that are a factor of the lead screw can be closed anywhere. when cutting metric threads or special leads, the half nuts must be kept closed.
On lathes with metric screws, change gears on the thread dial must be used to cut certain pitches, one cannot cut all pitches with just one gear, as has been already stated. I think on the metric machines that I have seen, 4 gears were used, usually mounted back to back with a movable thread dial that can bring them into play.

Exactly, it is the end stop that makes it work.

 

[mksj]

The issue is not the relationship of the carriage and the threading dial is in the same position when you engage the half-nut, it also has to do with the position of the chuck/start of the thread when you reengage the threading dial. The relationship is only to specific marks on the threading dial, for the particular pitch. Some lathes come with different threading dials depending if you are cutting a metric thread vs. imperial for a specific pitch lead screw, but they are not the same. So all three would need to be in-sink, I assume you could probably index the chuck position, and manually align everything up. Typically what is done is to not disengage the half-nut unless it is specifically indexed to the thread you are cutting.

 

[weston1968]

you are right, thanks for taking the time to understand what I was doing. I see that the position of the chuck also matters, well now that you said it it is obvious

 

[benmychree]

Exactly, it is the end stop that makes it work.

I do not see how the end stop could have any effect when cutting metric threads on a metric lathe with the spindle rotating during the return of the carriage, it would be analogous to an imperial lathe cutting imperial threads and using the thread dial to time the closing of the half nuts; we manage to cut threads just fine without an end stop.

 

[weston1968]

I do not see how the end stop could have any effect when cutting metric threads on a metric lathe with the spindle rotating during the return of the carriage, it would be analogous to an imperial lathe cutting imperial threads and using the thread dial to time the closing of the half nuts; we manage to cut threads just fine without an end stop.

Yup, mksj pointed out that I failed to take chuck position into account. Once said it was obvious. Back to the drawing board

 

[WobblyHand]

The issue is not the relationship of the carriage and the threading dial is in the same position when you engage the half-nut, it also has to do with the position of the chuck/start of the thread when you reengage the threading dial. The relationship is only to specific marks on the threading dial, for the particular pitch. Some lathes come with different threading dials depending if you are cutting a metric thread vs. imperial for a specific pitch lead screw, but they are not the same. So all three would need to be in-sink, I assume you could probably index the chuck position, and manually align everything up. Typically what is done is to not disengage the half-nut unless it is specifically indexed to the thread you are cutting.

View attachment 436431

Thank you for stating this so clearly. I was attempting to say something similar, but I failed to convey the information. The spindle angle, lead screw angle and carriage position all need to be taken into account for successful threading via a thread dial. The only way to get the correct relationship for a metric/metric setup is to introduce these extra gears into the thread dial.

 

[weston1968]

We all get tunnel vision when working out a problem. In my case it led to not taking all of the variables into account. The forum is great for this type of exercise. I was working out the design of an 8T gear to mesh with the lead screw, that would be a lot of wasted work. I appreciate all the people that took their time to review my design.

 

[mksj]

Given that you do not have a threading gearbox, I think the best approach to take would be an ELS type of system where you can dial in pretty much any thread you want, the relationship of the leadscrew is indexed to the spindle. Wobblyhand just designed one (nicely done) and quite a bit on the Clough42 version. There is also a kit version which integrates positional information.

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Electronic Lead Screw

I'm going to attempt to adapt clough42's ELS to my PM1127. I figure I might as well do it publicly in case it ends up being useful for someone else. I have most of the parts now, and have the electronics and servo running on the bench. The first thing I decided to mess with is the rotary...

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