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Questions about lathe power feeds.

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SillyOldDuffer06/06/2020 13:45:17
5798 forum posts
1235 photos
Posted by Andrew Johnston on 06/06/2020 12:04:01:

I think SoD is getting confused between surface speed and feed rate. When facing ideally one would increase spindle speed to keep surface speed the same as the tool approaches the centre. ...

Andrew

Oh poo, Andrew is right! But as spindle speed and feed rate are geared together on most lathes my point about cutting speed still stands. I hope...

Dave

Mick B106/06/2020 16:13:11
1580 forum posts
84 photos
Posted by Bazyle on 06/06/2020 11:45:09:

Who wouldn't want a finer feed on the surfacing? Do you want a crappy finish for some reason?

...

Yes, but I'm grateful for it on my Warco because powered crossfeed enables fine milling on the vertical slide. The machine would be materially less versatile without it.

Edited By Mick B1 on 06/06/2020 16:13:57

Bill Davies 206/06/2020 16:23:56
190 forum posts
11 photos

Clive, looking at lathes.co.uk, the Ikegai A-20 (for example) has some very nice features and seemed to incorporate these quite early on, including the recirculating ball leadscrew. But then it is described as a toolroom lathe.

It almost breaks my heart to imagine what it might have cost new, and after a google-search to see the second-hand prices at the end of its life.

Bill

Howard Lewis06/06/2020 18:08:22
3288 forum posts
2 photos

Driving the power feed(s ) on the Apron from a key way in the Leadscrew is a cost saving exercise.

Many lathes use a separate feed shaft to power both sliding and facing feeds, with the sliding feed via the rack. Certainly most Industrial quality lathes do this.

Even hobby machines, with Norton boxes, such as the Warco BH600, BH900, Chester Craftsman, and Engineers ToolRoom BL12-24 do this. There is a lever to engage either the Feed shaft or the Leadscrew, so the Leadscrew is spared the wear resulting from providing the sliding feed..

Unless the cost cutters have got to them, most of their Geared Head offspring seem to have the same professional features.

I think that the Raglan, which has a multi speed gearbox, does this also.

Howard

ega06/06/2020 18:16:35
1716 forum posts
150 photos

My rather agricultural Willson slantbed has one thing in common with the superb Ikegai, namely, the roller shutter enclosing the lead and feed screws, a feature which I had thought might be unique.

By the way, the Willson cross slide feeds away from the chuck when the gear lever is set for sliding to the headstock; this suits me as I mainly use the power cross feed for parting off from the rear toolpost.

old mart06/06/2020 20:23:34
1795 forum posts
138 photos

The Smart & Brown model A has a feed shaft which can be used for both sliding and facing in both directions, but I cannot say which is faster. The facing uses the cross slide screw and sliding uses the rack to move, so there is probably going to be a difference. I usually use the leadscrew for ordinary turning which goes down to 76tpi, good enough for most things, especially if using a large nose radius insert.

not done it yet06/06/2020 22:03:19
4662 forum posts
16 photos

Ega,

the Willson cross slide feeds away from the chuck when the gear lever is set for sliding to the headstock; this suits me as I mainly use the power cross feed for parting off from the rear toolpost.

I now do parting the same way, but more facing than parting. The only down-side is that (to leave the rear tool-post in situ) it needs to reside in one slot further back, thus the cross slide is much closer to its end-of-travel to reach past the centre of the chuck. To counter this problem means extending the parting tool holder in the tool-post. Compromises, compromises!

I rarely faced off with my Raglan Little John - too slow, even with the QCGB to raise the feed rate - plus it needed a tumbler change to face towards the centre. The 5” was a revelation. Much faster facing - and it feeds towards the centre without altering the tumblers.

Howard,

I think that the Raglan, which has a multi speed gearbox, does this also.

The raglans do have a separate feed shaft, but as above, the difference (between the earlier models and the 5&rdquo cross-feed speeds is remarkable.

ega06/06/2020 22:40:59
1716 forum posts
150 photos

NDIY:

I meant, of course "feeds away from the" work as I expect you spotted.

When designing my rear tool post I positioned it so that the tool tip would just reach centre with the cross slide fully towards the operator so as to give as much room as possible for my tailstock turret.

I have yet to check properly but am fairly sure that the cross slide feeds are less than the carriage feeds.

John Reese07/06/2020 01:45:55
842 forum posts

I had a Pratt & Whitney 14 x 30 that had identical feeds in X and Z.

My other lathes, 13 x 30 Clausing Metosa and Nardini 16 x 40, had X feed equal to half the Z feed. All three machines had a drive rod for the power feeds separate from the lead screw.

My South Bend 10K has a keyway the full length of the leadscrew. That allows the lead screw to act as a drive rod for the feeds. There is an interlock to prevent the half nuts being engaged when the feeds are being used.

I am in the US and the Pratt & Whitney lathe had a Buck and Hickman property tag on it. I am guessing it was shipped to England in the early 1940s. What surprised me is that it made it back to the US.

Ron Laden07/06/2020 07:30:33
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1939 forum posts
383 photos

Out of interest how useful is a driven cross feed, my old Warco doesn't have one so I have no experience of it. I can see it being good for facing larger diameters and providing a constant feed for parting, what else is it good for? Also this maybe a stupid question but does the Cross feed have reverse.

Ron

jimmy b07/06/2020 07:33:34
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639 forum posts
38 photos

I have power feed on the cross slide on both my lathes. Just about the only time I use it, is for facing soft jaws.

Jim

JasonB07/06/2020 07:35:00
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Moderator
18151 forum posts
1998 photos
1 articles

I would not want to be without my power X feed now for the two points you mention and even facing small stuff.

I can run mine either way at the flick of a lever so you can face outwards if needed which is handy for things like the bottom of a recessed hole

Mick B107/06/2020 07:35:41
1580 forum posts
84 photos
Posted by Ron Laden on 07/06/2020 07:30:33:

Out of interest how useful is a driven cross feed, my old Warco doesn't have one so I have no experience of it. I can see it being good for facing larger diameters and providing a constant feed for parting, what else is it good for? Also this maybe a stupid question but does the Cross feed have reverse.

Ron

As I said above, it's extremely useful if you do milling in the lathe. If you reverse the feed knob it retracts the crossslide just as the sliding feed would work towards the tailstock.

Ron Laden07/06/2020 07:46:54
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1939 forum posts
383 photos

Thanks Jason/Bill, it would be good to have especially the reverse as I always part off using the rear tool post.

Edited By Ron Laden on 07/06/2020 07:48:26

ega07/06/2020 10:19:56
1716 forum posts
150 photos

Parting off under power gives you a spare hand - useful for applying cutting oil, speeding up the lathe as the cut progresses and catching the work when the cut completes.

Bazyle07/06/2020 10:52:38
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5235 forum posts
201 photos
Posted by not done it yet on 06/06/2020 22:03:19:

Ega,

the Willson cross slide feeds away from the chuck when the gear lever is set for sliding to the headstock;

this makes sense when you think of an older lathe without multiple quick change tools. After doing some longitudinal cutting if you want to trim the end you can spin the same tool round 90 degrees and face off whereas if going inwards the geometry would be wring.

Ron power feed is 100% non essential just a nice to have like electric windows in a car. Millions of people get on just fine without either.

not done it yet07/06/2020 13:25:49
4662 forum posts
16 photos

The only problem with starting at the centre, as I see it, is getting the cutter the wrong side of the centre and rubbing, in my book. Possible chipping of carbide tips, too?

I usually adjust my tool post by around 16 degrees to change between long and cross feeds.

Edited By not done it yet on 07/06/2020 13:26:03

ega07/06/2020 13:51:51
1716 forum posts
150 photos

It is certainly possible for a conventional tool both to surface and face without changing its position but it is something of a compromise.

Has anyone mentioned the very desirable auto cut off that many lathes offer? And are there any that provide this for either direction of the cross feed? I believe some lathes combine this feature with the slipping clutch which also gives some protection in the event of a jam.

Howard Lewis07/06/2020 18:42:15
3288 forum posts
2 photos

Approaching retirement I rejected a Super 7 Sigma, because it did not provide PCF.

I would not be without it, since it produces a constant feed rate (Which can be changed , if I so wish )

And, I get better results using PCF for parting off, with the tool in the back toolpost.

Changing from Inward, through Neutral, to Outward only entails stopping the lathe and moving a lever.

If I ever need to cut a Left hand Thread, or to bore away from a shoulder, the reversing facility provided by the tumbler gears allows the tool to traverse away from the Headstock.

Industrial lathes provide PCF, so why should hobbyists be denied such a useful facility?

Howard

Ron Laden08/06/2020 12:36:12
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1939 forum posts
383 photos

Yesterday evening I found myself looking at the cross slide drawings in the lathe manual with a view to how feasible it would be to build and fit a power feed, initial thoughts are that it is doable.

I wouldnt attempt to fit it to the front apron as that would mean some serious surgery but it looks as if it could be added to the rear of the saddle without too much trouble, so shall I or not..?

What do you guys think, well worth having or leave as is, seems a number of you think it a very useful feature to have.

Ron

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