Roughing cuts on Standard geared lathes

[Glenn Brooks]

Hi all,

I've been experimenting with bit geometry, finishes, and speeds/feed rates for my old, restored 1919 Dalton 7 x 36 flat belt lathe. ThE Dalton does not have a quick change gear box, so one must resort to changing the gear combinations on the banjo end of the lathe for screw cutting, etc.

With these old style gear lathes, is there a gear combination that can be set up on the banjo-stud-lead screw that will produce fast, efficient roughing cuts?

If so, which gears do I want to experiment with? e.g. Gears mounted on the stud, banjo, or lead screw- or all three???

Note: I do have a screw cutting chart showing what gears are,required for a variety of threads. But don't understand how those combos translate into roughing feeds...

BTW: The Dalton will produce a feed rate of .001" with a 24-24-96 gear combination. But that's all I have been able to uncover so far. And this is OK, nice indeed for a finishing cut, but takes a LOT of time to take a cut along any length of shaft.

Any tips would be greatly appreciated.

Thanks
Glenn

[spro]

I could be wrong as our lathes are slightly different. The main thing is to see if the lead screw has a traversing slot. A slot indicates a sliding worm in the apron. From the traversing worm wheel other gears by lever position and clutch are engaged to feed from the "rack". The same hand wheel rack is a different ratio than the lead screw / clamp and that is the finer feeds. So I don't recall having that feature on mine but I am losing my memory.
Hey what about that SB ? The Patriots turned it upside down in the last quarter. Amazing and remarkable. I was never into this before. Uh Oh !

[spro]

My Dalton is remote now but have looked at pics on the net. When the lead screw is engaged, the worm is also running . Any traverse across the bed, the worm key is there. So this slot should be kept clear and the inside elements of the worm and associated gears lubed. When the lead screw is engaged the option is to engage it with the clamp nut lever OR tighten the clutch knob. It can't be both. The power rack feed is the same as very controlled hand feed of a different ratio and doesn't wear out the lead screw threads.

[Glenn Brooks]

Spro, this is interesting about the slot in the lead screw. I do have that feature on mine, but never knew what it is used for. My carriage does traverse along the bed, but so far haven't figured out if it should traverse across the bed E.G. Towards the center line as in a facing cut across the end of the work.

So, reading the SB How To Run a Lathe Book, there appear to be some change gears that will allow, say .008" feed for roughing cuts. I,don't remember seeing any gear settings for for this on my Dalton thread cutting plate. So hoping some one knows which gears are appropriate to change, and what the gears should be.

Yep, the Super Bowl sure turned into a comeback. New England fans must be exstatic. We're on the left coast so root for the Hawks, poor things....
Glenn

[earlgo]

Glen, If you wish I can send the gear combinations from the Atlas non-QC lathe. This will mean that you may not have all the gears required, but should give you some Idea of what to use.
For giggles here is the chart from the Sebastian and May Lathe:

--earlgo

[Glenn Brooks]

Earlgo,

Sure, if you have the chart at hand, be interesting to study it.

Thanks
Glenn

[earlgo]

Glen, this may not make it thru Chaski's forum as the file is 1.54Mbytes, but here is a try.
Nope, failed.
PM me your email address and I will send it outside of Chaski.
Anyone else is welcome to have a copy, too.
The ATLAS lead screw is 8TPI so it may not be relevant.

--earlgo

[Hopefuldave]

Hi Glenn,
I don't know your lathe, but I can make a guess...

If the 24-24-96 is spindle (or tumbler) - idler - leadscrew then you have a 1:4 reduction, suggesting you get a 0.004" feed per revolution of the leadscrew (you could check with a dial gauge), so going 24-96-24 will give you that 0.004" medium-fine feed. 96-24-24 will give you the 4:1 in t'other direction and (if the gears can be fitted that way) will give you 0.016" per rev, still fairly fine for a medium feed - just a guess, mind!

Dave H. (the other one)

[Glenn Brooks]

Hi Dave, yep, you are right regarding the standard turning gearing on the Dalton: 24-24-96.

I will go count my TPI on the lead screw - probably 8, maybe 10 TPI.

I am trying to visualize how the math works out. I understand the 1:4 gear ratio easy enuf. However, how does one interpolate the .004" feed rate? Iam sure it has to do with the relationship to the leadscrew threads (TPI), but never thought about the math before...so,drawing a blank.

Once I understand that, probably could factor in different available gears to get possible coarser feeds.

Thanks much,
Glenn

[spro]

The "power feed" is not dependent on the lead screw pitch. The slot in the lead screw is driving the captive worm and from there a worm wheel.
The clutch of the worm wheel is tightened by the large knurled "knob" on the apron face. It works the same as the South Bend "star shaped" knob. It is really best to inspect this area as best as you can before trying to use it under power. Even an inspection mirror can show you the general state of things back there. Obviously, if it is full of chips etc. it needs cleaning and lube. Clean out the rack and any teeth with a small wire brush. My Dalton power feed is only carriage feed, no option for cross slide feed.
So back to the "knob".. it should be tight at CCW now. See if it will turn CW and make sure the split nuts are not clamping the lead screw. As the knob is further tightened, the worm wheel is fully engaged to the handwheel gearing. This is very much like any lathe but the others have a separate lever (idle, bed feed, cross feed) and interlocks to prevent the split nuts clamp. You can turn a pulley by hand and see how it works. Again; Don't clamp the lead screw.

[spro]

It just occurs that maybe the Dalton is different about its "knob". If it appears there are two sections of knurled rings, this may be the one. Whichever lathe had these rings and possibly a hole for a hook spanner, it was an early way. The outer ring was the lock ring and it had to be loosened first. Then the second ring adjusted the "clutch" ... There was some procedure.. then it was locked with the outer ring. That knob, when grimey, looks like one piece but there is something more to it. Sorry about my lapse of memory and hope you figured it out okay.

[Glenn Brooks]

Spro, thanks, I will look at it tomorrow. I've been confused about what the star knob actually does. The apron does have a lever on the right side that engages the half nuts for the power feed. If I understand you correctly, the star knob also engages the power feed? But Do not engage both. That much I picked up on, as it jambs the lead screw and locks up the machinemwhen twking a cut. So I have been leaving the star knob loose, and closing the half nuts with the lever.

Still not,sure what the knob actually does.

Glenn