Lathe operation, feed rod vs leadscrew

[grhm]

I have an Enco lathe (model 110-2031, of which I own possibly the only example), and I do not have the manual. I have been reading the manual for the Grizzly G9249, which is clearly somewhat similar, but definitely not the same. In the manual, in the section "Power Feed", is described the operation of the feed rod. I have a couple questions:

1. I had been previously familiar with the lead screw, used for power feed (of the carriage) as well as threading operations. I wondered why it is necessary to have a second rod that performs nearly the same function (with the additional function of driving the power cross-feed). Wouldn't it be possible to eliminate the lead screw and use the power feed for threading?
2. The manual is not entirely clear on whether I can engage the power feed (in either cross-feed or carriage-feed mode) while the machine is operating. It says not to "change gearing" while the machine is running, but under "to engage the feed rod", step one is to turn the spindle off, and step two is engage the feed rod (start the spindle isn't until step 5). Is it actually necessary to completely stop the spindle before engaging power feed, or is it like the half-nut where I can engage it while the spindle is running (assuming everything else is set correctly)?
3. Is there any way to know what change gears I'm supposed to be using and what my feed rates would be based on the various quick-change settings? There's a table in the G9249 manual, but I don't know if it applies to my lathe. While there is a threading chart on the quick-change gearbox, there is no feed rate table there.

 

[JimDawson]

It would not be possible to thread with the feed rod because there is no connection between the thread dial and the feed rod.

You would not want to change the gears while the spindle is running. But engaging the carriage or cross feed while running is normal.

It's odd that there is no feed chart on the QC gearbox.

 

[ttabbal]

Having a separate feed rod limits wear on the leadscrew to threading operations. You can't eliminate the leadscrew as the thread is more accurate and you need accuracy for threading. It's also used to drive the thread dial and use the half nuts to run the thread itself. I suppose you could achieve most of that in other ways, but there's really no reason to.

I've never heard of a lathe that you can't engage the feeds while running. It does engage a gear, but it's designed to work that way. They usually mean the gearbox when saying not to shift while running. "Engage the feed rod" likely means to set the machine to feed mode. This makes the feed rod spin while disabling the leadscrew drive. That is generally part of the gearbox, so that's why they want you to do it while off.

Even lathes that look the same often have different gearing. It might at least give you some idea though. The best way if you can't find a manual or chart on the machine for it, is probably to just measure it. Zero an indicator on the carriage, rotate the spindle by hand 1 turn, and see how far it moved. Feeds are generally in thou per rev, so it's pretty easy to determine. I would say it's more important to be repeatable than a particular rate though.

 

[grhm]

Awesome, thanks!

 

[Mitch Alsup]

Having a separate feed rod limits wear on the leadscrew to threading operations. You can't eliminate the leadscrew as the thread is more accurate and you need accuracy for threading. It's also used to drive the thread dial and use the half nuts to run the thread itself. I suppose you could achieve most of that in other ways, but there's really no reason to.

Correct:: save the lead screw for threading, and use the notched drive for everything else.

Some 10" lathes have a notch cur out of the lead screw so there is only on part, but most turning operations still use the notch and not the lead.

 

[T Bredehoft]

Some 10" lathes have a notch cur out of the lead screw so there is only on part, but most turning operations still use the notch and not the lead.

Thats the way my MP10-40 is, the lead screw has a slot running lengthwise. if threading, the half nuts are engaged, If turning, the feed levers are used, engaging a gear driven by the key in the slot, no wear on the threads.

 

[markba633csi]

South Bends and Logans use the slotted leadscrew, among others
-Mark

 

[RJSakowski]

My Atlas/Craftsman 6 x 18 and Grizzly G0602 both use the lead screw for threading and for power feed. While it is cheaper to build a lathe like this, it has certain disadvantages.
1. For most users, they turn far more often than threading. Threading is also a relatively light duty operation. Using the lead screw and half nuts for power feed places additional stress and subsequent wear on the lead screw and half nuts.
2. The gearing required for threading and power feed is usually very different and changing from threading to power feed is bothersome at the least. In my case, I underused both power feeding and threading because of the hassle involved in changing gears.
3. Threading is usually done at a relatively low speed compared to turning. Running a lead screw at higher speeds creates additional wear on the bushings used for lead screw bearings. For the OEM configuration of the 602, the lead screw is always engaged which means it either has to be configured fot power feed or the gear train has to be dropped out. If the operations consist of turning a shaft to diameter followed by threading and multiple parts are being made , this becomes old very fast.

Using a slotted lead screw and worm for power feed these concerns are removed, although you are limited in the selection of feeds if your lathe doesn't have a quick change gear box and don't want the bother of changing gears. An independent power feed system provides the the convenience of rapid selection of both power feed rates and threading pitches along with the increased sturdiness for heavier cuts.

I solved some of my problems by installing an electronic lead screw. I can switch between threading and power feed or change deed rates at the push of a button. this has made the use of the lathe much more convenient and enjoyable. It hasn't eliminated the wear problem for the lead screw and half nuts though.

 

[Steve-F]

"I solved some of my problems by installing an electronic lead screw. I can switch between threading and power feed or change deed rates at the push of a button. this has made the use of the lathe much more convenient and enjoyable. It hasn't eliminated the wear problem for the lead screw and half nuts though."

More on this please

 

[ttabbal]

"I solved some of my problems by installing an electronic lead screw. I can switch between threading and power feed or change deed rates at the push of a button. this has made the use of the lathe much more convenient and enjoyable. It hasn't eliminated the wear problem for the lead screw and half nuts though."

More on this please

This was my take on the process. You have to adapt it to your machine, but some of the stuff in there might be useful for you. I don't recall how RJ did it off hand, I'm sure he'll mention it later.

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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