LeBlond Regal Feed Mismatch

I have a 19" LeBlond Regal (1967 vintage) with a puzzling issue on the feeds. I was wondering why I kept favoring feeds much lower than what my brain tells me is appropriate and I decided to do some sleuthing.

Set up a bar in the chuck and made a nice little spiral around it with the leadscrew at a couple different TPI. They all checked out OK per the feed rate chart on the headstock. Then I engaged the cross slide feed, and what should have been 0.0172 IPR (cross-listed with 12 TPI) fed the carriage about 0.045" after rotating the head one revolution. I thought about needing to divide by 2 to get the actual size since it's listed diametrically on the cross slide, but that is still not correct. It's a factor of 2.6 off.

It makes me wonder if the lathe was changed to metric feeds or something, but it's very puzzling because the leadscrew still feeds TPI and that's what you'd really want to change if you needed metric.

Anyone know what might be going on here?

Feed rod for feeds, lead screw for threads.

The 2.6 diff is the apron gearing

BOTH long feeds AND cross feeds are controlled by apron gearing and any clutches involved

Thread pitch of lead screw simply has nothing whatever to do with FEEDS - it only comes into play when using the Half Nuts when threading

(Yes, I know SB Model C used lead screw and half nuts for long feeds, but it is important to understand that only the lowest of the low would only do that for ECONOMICS)

Handy pub to have around

http://vintagemachinery.org/pubs/2102/6811.pdf
http://vintagemachinery.org/pubs/2102/6810.pdf

Are the long. feeds off by the same factor? I find it interesting the lead-screw is right but cross-feed is off.

John,

Thanks for the documents, there's some great information in there. I know the leadscrew and feed rod are separate mechanisms (even a dunce like me can figure that out since they're operated with different levers ), but the feed rate and thread pitch are both controlled together by the same quick change system. I was simply puzzled that one was off, and the other was what it said it should be.

CountryBoy19 said:

Are the long. feeds off by the same factor? I find it interesting the lead-screw is right but cross-feed is off.

Click to expand...

Checked that this morning, and it actually appears to be correct. This changes my question to: "why is the cross slide feed a factor of 2.6 greater than the longitudinal feed, and not double to account for the diametrical markings?" Is this something that is simple to change, or at the end of the day is it even meaningful?

I suppose the mystery is solved, and it didn't even take too much effort or thinking (refer to dunce comment above ).

I don't have a LeBlond book anymore, but if nothing is amiss that is just the gear ratio that LeBlond put in the apron. You posted about threading leads being correct, are the feeds/rev correct for OD turning? Is the diameter lead screw the correct pitch for the dials?

Yeah, the leadscrew pitch and longitudinal feeds both agree with the labels on the headstock, it's just the cross slide that is different by a factor of 2.6 which I guess I could simply account for when I select a feedrate for facing, parting, etc. It just seems odd to me that it wouldn't be double to just account for diametric vs radial distance.

I saw a YouTube Visio Adam79 I believe he has a lathe that’s like this . He was dividing by 2 for the cross slide


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