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Strange old lathe - even stranger feed screw - any ideas?

fusker

Cast Iron
Joined
Apr 13, 2006
Location
Denmark
Got my hands on an oldish lathe in our museum (Flynderupgård, Elsinore).
Turning length abt. 700 mm (28 inches), turning diameter (swing?) 180 mm (7") over saddle, with bridge removed swing would be abt. 11 inches.
Quite good condition, not much visible wear although one tooth is broken on the back gear (can be repaired). Spindle hole 1 inch. Prismatic ways. The lead screw is in good condition. No Norton box but plenty of gear wheels.

No name to be found anywhere. Looks like a bit less than 100 yrs old. Handles turn the wrong way!

My question: I've measured the saddle feedscrew: 1/2" dia., movement 3.63 mm (1/7 ") per revolution. I would not mind working with inches - but can't imagine what a dial should look like. To my mind 1/7 inch is a most unpleasant figure.
AND there is no dial, has seemingly never been! Barely space for one.

I am able to make my own dial but would prefer one with nice integers on the scale. Any ideas?
Might have to put in a new feedscrew with, say, 2 mm or 1/8 inch per revolution and left hand thread. I know these can be bought but my boss is very concerned about the little money we have, and I feel I will use to much time in making a 1/2" screw and - especially! - a nut. I may have to, and I know how, but its going to take me more time than I have.

It will be a very nice lathe once it's repaired so I don't want to see it scrapped. We have many applications for it at the museum.

Who could have used a fine lathe with no scales? I'm baffled. Any ideas, Forum?

Best regards, fusker
 

mdshunk

Hot Rolled
Joined
Nov 14, 2015
Pictures! Pictures! :)

If this is a metal lathe used by an artist type tradecraft, like a jeweler, dials may be unnecessary. For some reason, it pains me a little bit to learn of a museum that wants to restore a lathe any other way besides completely original. Put this one on display and just put the word out that your museum workshop needs a functional working lathe and a good, useable one will find its way to you.
 

L Vanice

Diamond
Joined
Feb 8, 2006
Location
Fort Wayne, IN
My first metal lathe, bought new for me in 1954, had 3/8-24 feed screws and no dials. It cost $50 and was certainly not a fine lathe. I had earlier been given a wood lathe, so I was used to working with spring calipers and steel scales (or yard sticks) to measure my lathe jobs. I did eventually get a micrometer and learned to guess how much of a crank turn would get me to the desired dimension. It was 11 years before I got a lathe with 10 TPI screws and dials. What luxury that was.

I don't know what metric trapezoidal taps you may be able to get. But 1/2-10 Acme taps, right or left hand, are readily available in the USA and maybe in England. I look at Victor Machinery first for odd taps. Right Hand Tandem Acme Taps - roughing and finishing

Generally, you make the screw on a lathe, but there are places that sell Acme threaded rod. The 1/2 inch size is standard with 10 TPI, which is handiest for feed screws. Some lathes use 200 division dials for the cross feed so that the dial reads in diameter change with 10 TPI screws.

Larry
 

fusker

Cast Iron
Joined
Apr 13, 2006
Location
Denmark
mdshunk, a lathe this size for a jeweller? And no, we don't really care about restoring the thing to original, this museum is about agriculture. It's just that I would like to have a working machine on site instead of 300 pounds of old iron. I have to watch out for the scrap dealer

Larry, I can buy ACME rod and nuts here - I suppose - but the problem is getting the museum to pay for it! Thanks for the link though.

Could I ask you to consider why 7 TPI has been used?
Thanks, fusker
 

Conrad Hoffman

Titanium
Joined
May 10, 2009
Location
Canandaigua, NY, USA
I used an Italian mill once that was 1/8" per turn, but no idea how somebody could come up with 1/7". If it were the main leadscrew I could imagine they might have some permanently installed gear pair that would make it more normal.
 

franco

Hot Rolled
Joined
Jul 8, 2003
Location
Cairns, Queensland, Australia
I used an Italian mill once that was 1/8" per turn, but no idea how somebody could come up with 1/7". If it were the main leadscrew I could imagine they might have some permanently installed gear pair that would make it more normal.

Some time ago I made some missing parts for a small, old unidentified (English?) lathe to get it going again for a friend of mine who found it completely dismantled in a box in an old abandoned shed. It had no dials, the cross slide handle turned the "wrong" way, it had a dovetail bed, and the leadscrew was 7 TPI. When I worked out a threading chart for him to identify some missing change gears I was surprised to find it was theoretically capable, if it had the power and rigidity to do so, of cutting all the common fastener threads from 8 to 44 TPI with a reasonable range of change gears. It did not require any permanent gear combination to do this. It only needed a 21T gear on the headstock spindle and various other change gears with tooth counts divisible by three to cut all the threads in the range.

franco
 
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fusker

Cast Iron
Joined
Apr 13, 2006
Location
Denmark
I used an Italian mill once that was 1/8" per turn, but no idea how somebody could come up with 1/7".QUOTE]
Yes, Conrad, that's precisely the point.
It seems impossible to design a simple scale with continuous 'nice' figures, say 2.0" per full revolution (or 8.0 mm as on my lathe) with the existing screw. As is the scale would go 0 ..... 2/7" (0.... 7.26 mm) which makes it very awkward once you go on turning the handle.

Larry, a digital read-out would be just fine, only I don't want to change the looks too much (apart from the price).

Photos: Will post as soon as possible. Thanks for the responses everyone and please forgive my clumsy English.

fusker
 

JST

Diamond
Joined
Jun 16, 2001
Location
St Louis
it isn't even an exact 1/7,as that divides to a lot of decimal places. you are correct, the dial would be very ugly to use.

maybe it was a patternmaker's lathe. That would look a lot like a metalworker's lathe, but would have no particular need for dials, since everyting would be done to a "shrink rule" with calipers. Whatever was being made would shrink at a specific rate, different fro other materials, so dials would be little help. The shrink rule would have inches (or whatever) marked on it, but they would be longer than standard by the shrink amount. So dials would only be confusing.

I had probably the same type machine as L Vanice many years ago, with 5/16"-24 screws. It was 0.04166666.... inches per turn, and no better in mm. So a dial would leave a fraction extra with any common unit. Virtually useless. Makes a person wonder why they didn't use a 20 tpi thread, which would have been a nice 0.050 inch per turn, and no more expensive.

By the way, your English is very good, no need whatever for apologies. Far better than my German, and I know no Danish at all.
 

Spruewell

Hot Rolled
Joined
Sep 8, 2015
Location
Northern California
You could always go the poor-mans route and mount a set of calipers on the cross feed rather than spending the money on an expensive DRO. Would also eliminate the need to replace the lead screw or come up with some crazy dial. A decent set of digital calipers (or even a used pair) could be modified and fitted to the cross feed quickly and discreetly. As far as the carriage travel goes, it's not likely you will need much more than a dial indicator mounted to a magnetic base (and you probably won't need it very often).
 

Matt_Maguire

Stainless
Joined
Oct 17, 2011
Location
West-Central Illinois, USA
If the 1/7" lead is on the the "leadscrew" it can be dealt with. If it's on the cross slide that would be very hard to deal with...

If you are not certain of your measuring mark the screw & turn it 7 times & it should move 1" (25.4mm) - need better resolution 28 turns = 4", 56 = 8" etc.

Good luck
Matt
 

fusker

Cast Iron
Joined
Apr 13, 2006
Location
Denmark
Measuring the cross slide screw

Yes, Gentlemen, it's quite possible to miss a revolution or two or even a whole section of a ruler. But I have measured six times, each time counting 27 revolutions, reading the ruler's divisions every 3 turns, over a period of two weeks. I believe in my results now to the extent that I dare bother the exalted members of this august forum!

Thank you for your ideas and suggestions, I'm learning a lot from them. Will soon post photos.

Unless I find I've made a stupid mistake - then I will commit ritual suicide, i.e. I will scrap my forum name and start over with a new nom-de-guerre. But hopefully this is not going to happen ......

fusker
 

k3vyl

Stainless
Joined
Feb 13, 2008
Location
newark DE USA
For a 7 pitch lead screw you need a 28 tooth gear. The inch screw is for making inch threads. The dial is for tracking that screw. That dial won't work if you put metric transposing gears on the machine.
 

fusker

Cast Iron
Joined
Apr 13, 2006
Location
Denmark
k3vyl: you are right as far as lead screw goes, but my problem is the cross slide screw.

enginebill: Yes, this would work - partly! It would not allow any figures to be engraved for more than one revolution. When one reaches the last division, the next one will not correspond to zero.
But if I have to, I can work within only one revolution, that is 2x1/7 inch = 18.3 64ths (7.26 mm) on diameter. Not impossible but still a PITA. By the way, I got the same idea from the german forumspanbude.

I think I'll see if I can find space for a 16 mm left-hand rod as I own a tap and die, albeit in standard thread only. If I can get this working I might convince the museum to buy a proper rod and nut.

An interesting problem in applied mathematics, don't you think? Thanks all for your comments.

Spruewell, thanks for your idea. It would work, of course, only I don't think I can lay my hands on a 'measuring clock' which would allow forty inches travel .....

As Piet Hein said: An expert is someone who can tell you just how nothing can be done.
Regards, fusker
 

JST

Diamond
Joined
Jun 16, 2001
Location
St Louis
As you KNOW the current pitch, there is nothing but some annoyance between you and having the CRANK, if not the screw, turn 1 rev per X mm or X inches. Probably inches, given that it is a fractional inch per rev now.

Simply add a pair of gears of the appropriate ratio between crank and screw, and there you are. IF you care that much.

My own impression is that it may be un-productive to do that, as the machine itself may really not be designed for metalworking, unless VERY old. And if that old, it is a better display somewhere (else) than it is a tool.
 

Matt_Maguire

Stainless
Joined
Oct 17, 2011
Location
West-Central Illinois, USA
Well the 7TPI crossfeed screw is a nutball pitch. From an engineering view you can use pitch to translate a distance in a given number of rotations...

Something like "I want 100 turns to travel 5' (60") length" so that works to 60/100 which would be a .6" lead... I can't thing any reasonable reason why 1/7" lead is there except it was at hand.

Good luck
Matt
 

k3vyl

Stainless
Joined
Feb 13, 2008
Location
newark DE USA
When you said saddle feed screw,I assumed you meant the leadscrew. A 7 pitch cross feed is truly off the wall. A 1/2-7 screw is a strange looking object in and of its self. If you are going to use it on a lot of small things,you could use 1/2-20 rod and tap the nut so a 50 div dial will work. The cross feeds on 7" instrument lathes were 20 pitch. A feed like that has a very different feel.
 








 
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