home built lathe idea's/concept

been looking into some of tony's pics and found some more interesting round bed designs

http://www.lathes.co.uk/kneller/index.html

http://www.lathes.co.uk/leinweber/

the idea i came to me for proper placement of the round ways would be to make a casting, sufficiently long so that both holes could be bored and honed to precise sizing of the way stock used. After which the casting could be cut into sections.

one section would be used to mount the head stock to.

one section to mount the end of the ways.

another section to mount the cross slide

and finally one section to mount the tail stock to.

provided the headstock mount and end mount casting are mounted to a base, (such as granite or cast iron,) proper alignment of the ways, and twist of the ways would be eliminated. it would appear to me that a highly precise bed/way assembly would be the result.

as for a head stock and the question of making a precision spindle assy, from what i have read, the plain brg design can be made very precise. The downside is one of limited speed of the spindle using the plain brg vs. roller or ball brgs.

could not a plain brg headstock be made with pressure lubrication to the plain brgs? this would allow high speed operation. Are there any commercial lathes that have pressure fed plain brgs?

additionally one could provide pressure lubrication to the slide brg surfaces to reduce wear on the round ways to nearly nill.

i know you guys are probably tired of this subject, but i am like a dog on a bone i guess.

with no usa manufactures of small bench top lathes left anymore that i am aware of, and everyone here seemingly against the chinese machines, it would seem like there would be some interest in developing one here.

might be a cool collective project for members of this board to work on. i would sure lend itself to many different folks working on different components of the machine, ie. casting the dual bore component, boring and honing, cutting, etc.

seems like there might be a market for a kit at least, allowing folks to assemble the pieces and have a useful machine when done.

what do you guys think?

bob g

Anotjher round-bed design to check out would be the Drummond. i've had my hands on one of those and they're good machines. As I had mentioned in an earlier post, one of the advantages of the round-bed design is the ability to rotate bits to other alignments (think milling).

I agree - it is a fascinating subject. A concrete-filled tube bed would be quite rigid - that basic design of machine with concrete as a structural adjunct was made extensively in the UK during WWII - the lack of steel prevented large cast sections, so light steel formers with poured concrete structural reinforcemnt was the order of the day and worked well.

Bravo - go for it.

Alan

Tubes are really good for making bicycles because they are good at resisting torsion. They end up really light. In a lathe we need damping and stiffness in many different directions. A deep webbed and diagonally braced casting has very high stiffness because of the amount of steel/iron in both bending planes.

Tubes also cause problems because they are by definition over constraining in terms of location. For a disk drive carriage to run on them we had to spring load one set of bearings. This is not cool for a lathe.

Another aspect is how to "scrape" them "in". How do you get rid of "dings" - difficult to stone on a round surface. If you refinish them by grinding you would need to match the tailstock, headstock and carriage to the new size.

You will note that all the round shaft machines seen so far are all "combination" machines for wood or metal.

Another item not discussed was how to get the tailstock to overlap the carriage. There seem to be too many items wanting to claim ownership to the two tubes to reach a compromise. If I clamp the tailstock doesn't that move the tubes so it might jam the carriage?

Chris P

I think from time to time about building a small lathe. Personaly I'd want to make it with enough adjustability to be able to dial it to perfection.
Round ways since I don't have a surface grinder.
I'd put CNC controls on it. Make the headstock out of a solid piece of steel. Put good bearings in it with a sufficient spindle bore that takes collets, perhaps 5C or something bigger so as not to have to use a chuck. It's always possible to make a small chuck that is held by a collet. Belt drive with VFD motor.

Certainly a fun project. A Taiwan import could probably be made a little better for not too much money. Some of them really aren't that bad. As much as I'm not the most pleased with the Taiwan lathe I bought. I wouldn't try to build it for the amount I paid for it.

Okay forget the tubing. Induction hardend, ground, polished chromed hydarulic shafting is relatively cheap, who cares about weight we'll dampen and maintain rigidity with sheer mass. 3" dia oughtta do it!
The ends would not need to be through holes. Precision grind vees and thru bolt to the head stock and tail end tie bar...think of sine plate rolls. They can be ganged up on a surface grinder and match ground.
Now as far as the tail stock it need only have a hole thru it on the far way. It could ride on top of the operators way bar and clamped at that bar only thus not attecting bar distance. A split cotter could also be used to clamp to the bar ways w/o deflection. This leaves the carraige as the only item requiring accurate hole work.
Go get 'em Bob, keep chewing on that bone

I think you'll get ringing (resonance) with steel rods, made worse by the length, and heightened at certain spots.

Cast iron has a wonderful damping coefficient that's highly desirable for machine tools.

Another thing to keep track of is the (L/d) ratio for any sliding ways. The L is the length of the collar, d = diameter of the collar. 2 or more is generally a good idea, keeps racking and jamming to a minimum when loaded off center.

-Matt

One other issue that comes to mind after a day of boring long small dia holes is that if you are intending to bore the holes in all parts of the casting before separating them, the job is probably best done in a line-boring setup (horizontal boring mill with outboard/tailstock support), or on the carriage of a super-sized lathe.

-Matt

People who seek alternative designs in machine tools are like most innovators: often obsessed, frequently frustrated by reality, and responsible in a Darwinian way for the progress of the human race. I highly encourage people to explore new ways and means of making things. I know many of them thanks t o years in manufacturing and I frequently pour cold water on plans tried before without success for the reason that most things have been tried in the past, failed to be forgotten to be thought of anew by the coming geberation of innovators.

Round ways are attractive to would be machine tool designers because they appear to solve several fitting and assembly problems with conventional way systems. The harsh reality is the chips still fall one them sooner or later getting past the wipers and accellerating wear. Round ways do not self compensate like prismatic ways. Round ways are limber if the carriage is fully enveloping.

So go with my blessing.

What I would like to see is a practical, easily manufactured machine tool whose ways, way bearings, and sealing system are not subject to chips, scale, coolant, and shop debris. A slant bed CNC turning center design comes close but how do you efficiently interface hand cranks to it?

Here is a "conventioal" slant bed lathe, complicated damn thing, well not really its a hydraulic tracer

thanks all for your ideas, thoughts and input.

as for tube ways:

i was thinking relatively large diameter for the given length, for instance i have some test bars that are precision ground 2.250 od with a 1/4 wall.
if i was to use them i would fill them with polymer cast iron to make them dead.

as for the carriage, and sealing out the debris:

if one was to machine the ends of the carriage to accept chevron seals of a very stiff compound such as those used in fracturing pumps from common in oil field service. these seals are subject to sand/gel mix at high pressures (over 10k psi) and have a good life.

as for wear take up on a round way, if the brg is sized properly to start with and pressure fed with lube, the thing should wear virtually forever in a carriage environment. Consider IC engines with plain rod and main brgs turning at high speeds, millions of cycles, at high temperature, being pounded by explosive forces, both normal and detonation, and often not service very well. Most of which have crank journals that are not hardened, and usually don't wear down a thou in several million revolutions.

just more thinking on the subject

bob g

There was a suggestion in a book I was given as to how lathes could be improved. The strangeness is that current lathes have all the mass at each end of the bed which leads to what I call the "bridgeport problem" - large masses hanging out in the breeze.

It might be that they were better if they look like a girder railway bridge with most stiffness in the middle - at least tapering towards the tailstock. I think one of the Myfords was this way.

Chris P

Consider IC engines with plain rod and main brgs turning at high speeds, millions of cycles, at high temperature, being pounded by explosive forces, both normal and detonation, and often not service very well. Most of which have crank journals that are not hardened, and usually don't wear down a thou in several million revolutions.

Click to expand...

Except that none are assailed by wet, rust, hot,hard sharp chips and the worst of all, metallic dust. All of above IC bearings are fed pressure oil from a filtered and closed system, and none of the IC engine round bearing surfaces are frequently exposed to trash attacks outside the lubrication envelope.

John

"Except that none are assailed by wet, rust, hot,hard sharp chips and the worst of all, metallic dust. All of above IC bearings are fed pressure oil from a filtered and closed system, and none of the IC engine round bearing surfaces are frequently exposed to trash attacks outside the lubrication envelope"

this is all true

but would it not be easier to provide way guards that telescope on a round way to preclude much of the damage caused by these troublesome byproducts?

and if one was to go to the trouble of providing pressure lubrication, wouldnt it be prudent to have the oil well filtered in a closed loop system?

with sufficient oil pressure and decent seals such as the chevron style units i mentioned, and incorporating a telescoping way protector it would be difficult for much to get into the way slide brgs. i won't go so far as say impossible but surely it would be better than most conventional means.

keep the critiques coming, i hope you see where i am going with this.

an idea is profered and critiques follow, which thought is given and possible solutions are brought forward. with give and take a better idea can be formulated and then committed to paper as the next step.

thanks guys

bob g

Plain bearings work on a priciple called the "oil wedge". This happens from the rotation rolling the oil into the tight or loaded area of the bearing constantly. You aren't going to get an oil wedge from very slow linear movement.

As far as completely covering the ways:
That will just make a place for dirt & swarf to collect out of eyesight so it can be rubbed into the ways over and over.

Graziano had covered ways that looked like they might work well.

It is going to be tough to come up with better lathe ideas than the very best efforts of the world over the last 200 years or so.

"Plain bearings work on a priciple called the "oil wedge". This happens from the rotation rolling the oil into the tight or loaded area of the bearing constantly. You aren't going to get an oil wedge from very slow linear movement."

the oil wedge will occur if the oil is pressure fed in at the pressure or contact point. most machine tool ways are engineered to have under 35 lbs per square inch of way contact. oil pressure in excess of 35 lbs should provide the needed cushion or wedge even under very low linear movement.

"It is going to be tough to come up with better lathe ideas than the very best efforts of the world over the last 200 years or so. "

agreed that it is going to be tough to make a better lathe, but i am not sure that is necessarily the goal, but rather a functional and accurate machine that can be made or assembled by a home shop guy.

machine tools like all else in life are a series of comprimises (ie. functions, accuracy vs cost)
are they not?

my idea of a useful lathe would be one that could swing 12", have a between center distance of perhaps 24", have a spindle hole that would take 5c collets and be able to attain .0005" tolerances, and be a basic manual machine.

that should be a good starting point, don't you think?

bob g

Mobile-Bob, you have described the Monarch 10EE.

You know, along the lines of what Forrest said, the carriage should hang from underneath the lathe bed and the lathe bed should be over top of the spindle center.

Chips, coolant might get slung up but the vast majority will fall harmlessly below.

I take no responsibility for claims about the ergonomics of such a setup tho.

I was finishing hand tapping some holes started on the machine tonight, I was doing this "upside down" with the tap pointed straight up in the air...seemed perfectly logical to let the chips fall down/out of the flutes and avoid being trapped in the newly forming threads.

-Matt

Interesting machine here from one of the links at 'lathes.co.uk' in the beginning of this thread:

http://www.oldengine.org/members/hammink/web/indexWSI.htm

I thought I was the only nut who fantacized about making a home-brew round way lathe. I can't decide if it is good or scary to see so many other folks afflicted with this disease.

Here is my own particular deranged vision:

1) Hard chromed, largish round ways finely ground. The 'tubes' would have sufficient stiffness from both the wall thickness and the diameter for the size lathe intended, probably about 13 x 30-ish specs. Why round? Because they can be simply made, that's why. Plating and grinding tubes to run straight and true ought to be much simpler, cheaper, and do-able than casting and grinding a typical lathe bed, yes? Also, you can imagine that with a top-notch grind, they should be REALLY straight. The kick would be mounting them to run parallel. Fill 'em up with some kind of dampening material if necessary.

2) Pressure-fed plain bearings in the carriage and headstock. Simple to replace when they wear out, with replacement a planned event. Same concept with the ways when they get worn - easy to re-grind.

3) Oil recirculation system would have big-time filtration to suck up whatever grit gets past the way covers.

Such a lathe would never supplant a big, heavy machine for deep cuts. Forget that - this is just an alternative way to make a small-to-mid sized shop lathe that uses cheaper ways and cheaper bearings. Skip the huge cost of castings, skip the huge cost of standard headstock-quality bearings.

Issue - could pressure fed plain bearings run true enough in the headstock? Or do you have to have precisely machined hard seats of some kind in the bearings to make it run true?

I don't believe it is practical to design and manufacture a desirable lathe as envisioned here in commercial volume using raw materials and new components. I'd sure be pleasantly surprised to be wrong.

I DO believe there is room for good new home shop machine designs that CAN be made both cost- and time-effectively on a limited basis, using salvaged or unconventional materials, and slower fabrication techniques, that would not be practical on a commercial scale, but can be dealt with on a one-or-two basis by individuals.

For example, IIRC, there was that horizontal mill in HSM a while back that incorporated a small engine block in the design.

I like the CONCEPT of the Gingery series - make machine tools by casting scrap aluminum, with only minimal hand tools.

I never liked the time and value tradeoff - for all that time, while a great learning experience, the result is a novelty not a useful tool.

I'd love to see someone cook up a series that assume you have more to start with - such as a capability to fabricate from steel plate and angle, and perhaps incorporate salvaged hydraulic cylinder rod, cheap granite surface plates, concrete, epoxy, automotive wheel bearings and hubs ... you get the idea.

For example:

Serendipitously scrounged steel plate @ $.05/lb, vs new steel @ $.45/lb.

Salvaged ground, polished, hydraulic cylinder rod for $.05 to $.25/lb, vs. $3/lb or whatever.

Free or cheap used auto or truck parts, vs. $100 bearing sets.

Bob

One design that may be worth considering is the old Unimat. This uses two steel rods for the bedways and crosslide ways.
These little machines are not bad. If scaled up a little, a lathe could be built without alot of work.
My DB 200 Unimat
http://www.clubchopper.com/photopost/showphoto.php?photo=16033&password=&sort=1&cat=500&page=4

Well I gues my problem with threads about making lathes is that it disgusts me watching decent older American lathes getting scrapped because nobody wants to bother with them. Seems like those should be save and fixed before people build home made substitutes. I've seen so many good lathes get given away and scraped.... I can't save them all myself....

It just seems like you guys should look around and find a nice old USA lathe that needs saving instead of trying to start from scratch. Read some of the threads on the Antique machine section. You'd save yourselves so much time and money and energy and would have something better and saved a piece of our great history.

Sorry to rain on you design fun. I'm just grumpy about all the waste of old tools I see.