Todays silly question

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cooper1203

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What is a feed screw on a lathe? Is it the lead screw for the top slide or cross slide or none of the above.

The micrometer dials on my atlas for the cross slide and top slide are completely illegible The dials on my friends myford seem to be approximately the same size (outer diameter) and the dials on both lathes read 0-100 ie 10 tpi but we aren't sure of the diameter of the top and cross slide screws on the myford.

I have tried google and it keeps coming up with a feed screw for it that is 8 tpi and clearly shows increments from 0 to 125 on the dial so i am confused.com

many thanks
coop
 
A couple pictures of your machine would help. Many lathes only have a single lead screw. Both my Seneca Falls machine and my Sheldon machine are in that category.
 

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ithink this is where my confusion is coming in.... im on about the leadscrew in the cross and topslide that allows the top and cross side to move ie if you were doing a facing cut you would wind the handle to move the tool across the face of the work piece
 
My understanding is the feed screw is the threaded rod that the half nuts lock on for threading.
 
There are terms for machine parts that everyone agrees on, then there are parts the names of which differ by country/region (for example, US - compound slide/UK - top slide), and then there are parts, the names of which don't seem to have any agreed upon fixed nomenclature and people use all sorts of terminology for.

As far as I know, the cross slide and top slide screws are "leadscrews", as are the screwcutting feed screws (and if the surfacing feed, AKA facing feed, uses a separate screw to the cross slide screw, don't know if any do, that would be a leadscrew too). I don't know if the separate, keyed, longitudinal traverse shafts that some lathes have, are considered "leadscrews" as they aren't threaded.

The term "feed screw", I think tends to be used for the powered lead screws

[warning, minor thread hijack: what I'd like to know is if there's an official term for plates that hold the saddle to the bed, generally from the underside of the bed; I've seen "saddle shear plate", "saddle retaining plate" and even "saddle gib" (although the latter doesn't seem right to me). The reason for my question being is that I struggle to know what to call the extra assembly I've added to my mini lathe that bolts to the underside of the saddle, in the middle and uses the underside of the bed, in between the ways, to hold the saddle down for extra rigidity]
 
Okay, there is a difference.

The cross slide and compound have feed screws, they are used to feed the compound or cross slide. Because of the known thread per inch on the feed screws, we know how far the compound or cross slide will move with each turn, or partial turn of the crank. We use the dials on those screws to determine how far the compound or cross slide moves.

The long screw on the front is a lead screw. It also has a keyway cut in it. By changing the gears that drive the lead screw, or changing the quick change gearbox, you can cut threads with different "leads", that is different Threads Per Inch. Thus the name "lead screw" This is done by engaging the half nuts into the lead screw. If you are just turning a part, the keyway in the lead screw drives a gears in the carriage that engage the gear rack that is under the front ways, to drive the carriage along the ways.

That is all
Richard
 
Generally most bench top machines have just a feed screw for turning and threading, larger machines have separate feed and lead screws and control handles. The feed is for turning and lead is for threading.
 
Almost all lathes, you will see a threaded rod called the lead screw. That is basically reserved for threading. On the more expensive lathes, there is a slotted rod the same length underneath the lead screw. This rod is used for power feeding. This will save wear and tear on the lead screw. The confusion is on the cheaper lathes, the lead screw is used both for threading and power feed. There is no feed rod. That is why it can be called both a lead and/or a feed screw. Cooper, this is an excellent question.
 
markba633csi said:
I usually think of the long screw that moves the carriage up and down the bed as the leadscrew. All the others- feedscrews.
As for the last piece I would go with "saddle retaining plate" not gib
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Ah, so I have the words 'feed' and 'lead' arse about face then? Every day's a school day eh?

It's weird, for such a critical part, I mean it holds the saddle in place against lifting forces, it feels like it should have a more, oh, I don't know, distinctive name.
 
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