Power Feed to Make Threads (English or metric threads) Curiosity

[B2]

Hi Folks,

I am just curious. Does anyone use the Power Feed feature on their lathe to do threading? You might ask why bother, but I am curious for a "Universal" Threading chart/spread sheet I have been investigating. What are the issues and problems? Is it ever useful? Clearly you give up the thread dial as you are not using the lead screw. There may also be some looseness or backlash, but is this really an issue for fine threads where you have gotten a running start? Clearly an "Electronic Lead Screw" would make this a moot point, but if you do not have one....

By "Universal" I mean any of a large number of lathes. The thread chart would include all of the change gears etc in all combinations. Clearly on many lathes there are far more possible "custom" threads that could be made. Does anyone make custom threads or ever run into odd ball threads that they need to make? If and when I finish it I will post it for folks and I am trying to decide if I should include the additional threads that you could possibly make using the Power Feed rather than the lead screw 1/2 nut.

Dave L.

 

[matthewsx]

I’m probably the last person who should answer this but I think you wouldn’t end up with anything repeatable. That’s the point of a lead screw, to be physically linked to the spindle.

For custom threads a lot of folks are happy with electronic lead screw conversions, look at the Clough42 project. It’s a fair bit of work but for machines where the change gears are missing or just a PITA probably worth it.

I’m looking forward to other answers here but just don’t see how simply power feeding would work for threading.

John

 

[RJSakowski]

The Clough42 ELS is great and I really like it. One shortcoming is that the feed table for power feed and for treads has preset values. You can cut a feed or thread that isn't in the list but it involves going back into the source code, modifying it to include your desired feed or thread and reflashing the Launchpad. A feature that I wold really like to see added is to be able to jog the feed rate or thread pitch via the user interface. There is an unused button on the user interface that could be used to toggle a jog mode and use the + and - buttons to jog. It is a fair amount of modification of the source code and I am not familiar enough with it to do so (or I would have already )

As to the need for this, winding springs or electronic coils would be the obvious ones. I could also see where a custom thread might be desired.

 

[B2]

Thanks. I am a ware of Clough42 and may some day build one, but not yet. Anyway, the Power feed rod is "physically connected" to the spindle via the power feed rod in a predictable manner, so I am a little confused by your phrase.

physically linked to the spindle.

At least on my PM lathe and others that I am familiar with the power feed rod is the one below the lead screw which has a slot in it running its length. The Apron attaches to this rod via the power feed lever but uses a gear box at the apron to move the apron along the lathe bed.

 

[B2]

jog mode and use the + and - buttons to jog

Since I do not have and ELS yet, I am not for sure what you are getting at in your quote. My lathe, with my VFD conversion has a nice spindle jog and so would move the threading tool along at a slow pace. Maybe you mean at a fast pace? Or maybe this + and- is a feature on the ELS for changing the thread number? Do you ever cut threads using the Power Feed on the apron?

VFD conversion using solid state electronic components

However, I am not for sure what I would use it for, but I have thought that being able to cut a spiral where the pitch is changing with distance along the bed.... might be interesting. I am thinking toys. I suppose a ELS could be reprogrammed to do so. Or maybe one should just have an entire CNC lathe!?

 

[matthewsx]

Sorry, probably should have “geared to“.

The gear in the apron which drives the feed screw does move the carriage at a consistent speed but with backlash it’ll be hard to get back to the starting point for the thread and it wouldn’t be as consistent as direct gearing through the lead screw.

I might be wrong about this because I’m a total novice with threading but if someone has done it successfully done it I’m sure they’ll chime in here.

John

 

[B2]

By the way, I do use my lathes to wind coils. I find that I usually do this at extremely slow speeds so as to keep the wire nice and neat. But I usually guide the wire by hand.

 

[B2]

Sorry, probably should have “geared to“.

So on the PM1440GT and the PM1340GT the feed rod is geared from the spindle. It is connected to the knobs that control the 2x factors on the threading gear box. So its number of possible speeds does not include all of the levers that select the fundamental TPI values. but is is also varies by the possibilities of the change gears. So there are a lot of them. In the PM1440GT there are 4 sets of factors of two plus the WXYZ threading settings, but is not connected to the final set of threading gears, PQR(I)T. In the 1340 I think there are 5 factors of two but because it has a Norton style gear box and I am guessing that these are not connected to the feed rod it so it would be more limited in its possible feed rates. By the way, the best I can tell the feed rates provided on the 1340 face plate are inaccurate and inconsistent with the factors of 2.

 

[RJSakowski]

Since I do not have and ELS yet, I am not for sure what you are getting at in your quote. My lathe, with my VFD conversion has a nice spindle jog and so would move the threading tool along at a slow pace. Maybe you mean at a fast pace? Or maybe this + and- is a feature on the ELS for changing the thread number? Do you ever cut threads using the Power Feed on the apron?

However, I am not for sure what I would use it for, but I have thought that being able to cut a spiral where the pitch is changing with distance along the bed.... might be interesting. I am thinking toys. I suppose a ELS could be reprogrammed to do so. Or maybe one should just have an entire CNC lathe!?

The jog refers to setting the lead screw speed and is separate from the spindle rotation. The ELS has no control over the spindle. It just monitors the spindle rotation via the encoder and syncs. the lead screw to the spindle, eliminating the gear train.

 

[B2]

On my old South Bend 10 there is no separate power feed rod. Just the lead screw. So you do feeding and thread cutting are the same function and use the 1/2 nut for both. However, the Norton gear box is fantastic. It has 10 fundamental thread gear positions, but 7 factors of two. So there are both lots of threads up into the several hundred TPI values and corresponding sloooow feeds.