Reasonable Capacity for Lathe/Milling Machine

dcoates · May 15, 2018

Hi all,

I'm going to try not to make this question vague.

Given your typical machine shop with typical machines (not high-end machines that break the bank) and a 2" diameter bar of aluminum, for example, if you increased the diameter to 3", then 4", then 5", etc., at what diameter/dimension would you begin to run into problems?

The problems might be machining the bar to good quality, getting the bar into the machine, inspecting the part, storage space, etc.

I know that you can get anything for a price. On a size vs. price graph I'm aiming for the point just before the price starts increasing exponentially.

Thanks,

dcoates

DDoug · May 15, 2018

"Bar" as in shafting work "Between centers"

Or "Bar" as in "Barfed" work ?

Limy Sami · May 15, 2018

IMHO As a rough guide, 2'' bore lathes are easy to find, hence cheaper / reasonably priced, - 3'' harder and dearer, 4'' even more so.

You have bear in mind you have to be able to handle the material 1.5 M (<>5ft) of 50mm (<>2'') round steel weighs 23kg (<> 50lbs)- OK, the same in 75mm weighs 52 kg ( 114lbs) - bloody heavy, and 100mm 92kg <> 204 lbs - far more than any man can handle and load in to a machine safely without mechanical help.

Ever wondered why there are so many machinist with bad backs?

Here's a handy weight calculator for you Materials Weight Calculator

JRIowa · May 15, 2018

dcoates said:
Given your typical machine shop with typical machines (not high-end machines that break the bank) and a 2" diameter bar of aluminum, for example, if you increased the diameter to 3", then 4", then 5", etc., at what diameter/dimension would you begin to run into problems?

What's a typical machine shop? How many employees? How many square feet. Sales $/yr?

What's a typical machine? My bank and your bank are not the same. $100K for a machine is not that much.

Where I retired from, we never had problems with diameter, it was length. This sounds almost like a school project.
JR

edwin dirnbeck · May 15, 2018

I think a 16 inch swing lathe is a good dividing line. Any shop that I have worked at, that had a 16 inch or larger lathe had some sort of hoist over the lathe.Changing a 14 or 16 inch chuck and the work that fits it,is very hard to do without a hoist.Edwin Dirnbeck

steve-l · May 15, 2018

edwin dirnbeck said:
I think a 16 inch swing lathe is a good dividing line. Any shop that I have worked at, that had a 16 inch or larger lathe had some sort of hoist over the lathe.Changing a 14 or 16 inch chuck and the work that fits it,is very hard to do without a hoist.Edwin Dirnbeck

And dangerous!

Bill D · May 15, 2018

Any lathe can not swing a rod as big as the listed swing. faceplate work yes. but between centers the carriage limits swing to less then the stated size.
A milling machine by the time you allow for a vice thickness and tool length the distance under the endmill has been much reduced.
Bill D.

JRIowa · May 15, 2018

edwin dirnbeck said:
I think a 16 inch swing lathe is a good dividing line.

Putting an arbitrary number on something like this is really hard to do. I've worked in plenty of shops where you manually change the chuck on a 17" lathe. Last shop all lathes (down to 10") had a hoist above them. If you're geverned by OSHA, you'd better go with the later.

Like I said before, what's typical? Where I retired from, most of the manual machines are being replaced by CNCs. A 20" CNC lathe doesn't care about the bar size. It's got more RPM than a 12" manual plus flood coolant.

I think the OP might be asking a hobby shop question if not a project. He really needs to decide what he wants to do. Smaller machines like 15" and below have more spindle speed but less HP. So, if you're going to do a bunch of small work, buy a smaller lathe. The oposite applies too. Instead of capacities, he should be charting size vs quantity. IE, if 99% of my work was 1" and less, I wouldn't buy a 17" Colchester, it would be a 10EE. BTW, I've got a 15" lathe at home.
JR

dcoates · May 15, 2018

Sorry guys, I knew this question was going to cause problems. I guess it can only be answered by people that have worked in a lot of different places.

JRIowa said:
Instead of capacities, he should be charting size vs quantity. IE, if 99% of my work was 1" and less, I wouldn't buy a 17" Colchester, it would be a 10EE. BTW, I've got a 15" lathe at home.
JR

But to get good quantities you need to sell a lot. In most markets to sell a lot you need things to be cheap! For it to be cheap you need to make the manufacturing as easy as possible and use methods that most shops are capable of, so that the labour is competitive not specialist. If the operator has to use hoists to change things between jobs then I can see it ain't gonna be cheap.

How about this: If you were opening a new machine shop without any particular jobs lined up but you had to buy a lathe that would cover most of the jobs you expected to encounter (given your experience), what is the maximum size of lathe you would choose?

Limy Sami · May 15, 2018

dcoates said:
How about this: If you were opening a new machine shop without any particular jobs lined up but you had to buy a lathe that would cover most of the jobs you expected to encounter (given your experience), what is the maximum size of lathe you would choose?

So you're talking a job shop? still not enough information, the type of market you're aiming for is vital, it's no use being tooled up for say 1'' and below bar / 10'' max dia work, when all that's in your area is 3'' bar & 20'' max dia.

bryan_machine · May 15, 2018

OP seems to be asking "when is a machine Too Big" by its nature.

That almost never happens.

Rather, machines become Too Slow, Too Costly (to buy, tool up, build a foundation for, keep a roof over.)

In lathes, the famous line "you can do small work on a big lathe and not vice versa" isn't quite true - if the work needs high spindle speeds for surface finish or just to be economic, your 20x80" monster will have a hard time competing with a little swiss/screw machine class lathe. But that's not really "too big" - it's Too Slow.

[There ARE cases where hucking the very small part in and out of a very large machine becomes a real drag - don't hear about it nearly as much as 'any clever ideas for how to stuff this part into this too small machine?']

Conrad Hoffman · May 15, 2018

I used to work in a shop that had a "Bertha". I'll be most do. In that case it was an old Warner Swasey, can't remember the size, but this thread is interesting-
http://www.practicalmachinist.com/vb/general-archive/w-s-turret-lathe-sizes-90168/

DDoug · May 15, 2018

dcoates said:
Sorry guys, I knew this question was going to cause problems. I guess it can only be answered by people that have worked in a lot of different places.

But to get good quantities you need to sell a lot. In most markets to sell a lot you need things to be cheap! For it to be cheap you need to make the manufacturing as easy as possible and use methods that most shops are capable of, so that the labour is competitive not specialist. If the operator has to use hoists to change things between jobs then I can see it ain't gonna be cheap.

How about this: If you were opening a new machine shop without any particular jobs lined up but you had to buy a lathe that would cover most of the jobs you expected to encounter (given your experience), what is the maximum size of lathe you would choose?

Yup, a student for sure.

What college you make of this Limy ?

To the OP, how are you going to load/unload a part into the machine when it exceeds
40 lbs ?

TDegenhart · May 15, 2018

Recapping what has been said. You need to define your business plan and skill set before buying equipment. You want to service the oil fields, one type of machine. Farm equipment, another and so forth. Did I mention watchmaking? You don't start out to service Freightliners or Big Pets with a shop equipped for Chevies.

Tom

PeteM · May 15, 2018

dcoates said:
. . . How about this: If you were opening a new machine shop without any particular jobs lined up but you had to buy a lathe that would cover most of the jobs you expected to encounter (given your experience), what is the maximum size of lathe you would choose?

A hobbyist might look at it that way - what machine will do 90+% of my work. That usually ends up with a lathe in the 9" to 14" swing arena. 12" probably most common in today's market. A money-making shop would be looking more at the paying work that's available and the time required to complete a job. They wouldn't be caring about such things as "Oh, I'll need a hoist" if that hoist would quickly pay for itself. Beyond CNC, I suspect for most job shops that means at least two manual lathes. One towards the HLV-H or Monarch end. Another to handle much larger work.

Once up and profitably running, a shop will often buy a machine just to get or keep a single customer's business.

dcoates · May 15, 2018

Honestly guys I'm looking at this from a product design point-of-view. I want to be able to go to the majority of shops and for them to look at the drawing and think "no big deal." I don't want them to turn me away because it's too much work, or for them to charge me an arm and a leg because they need to cover a new machine, or to have to travel to Timbuktu to find someone that has a big enough lathe.

digger doug said:
To the OP, how are you going to load/unload a part into the machine when it exceeds
40 lbs ?

You're literally the expert. You tell me! Perhaps like this?

PeteM said:
That usually ends up with a lathe in the 9" to 14" swing arena. 12" probably most common in today's market.

This is the sort of answer I was looking for. Today's market is 12" swing. Got it.

PeteM said:
Once up and profitably running, a shop will often buy a machine just to get or keep a single customer's business.

But they probably wouldn't buy a machine for a new customer. As a product designer you would need to find a shop that fits your product, correct? I was trying to find out what sort of product size would give me the largest selection of shops.

HuFlungDung · May 15, 2018

dcoates said:
Sorry guys, I knew this question was going to cause problems. I guess it can only be answered by people that have worked in a lot of different places.

But to get good quantities you need to sell a lot. In most markets to sell a lot you need things to be cheap! For it to be cheap you need to make the manufacturing as easy as possible and use methods that most shops are capable of, so that the labour is competitive not specialist. If the operator has to use hoists to change things between jobs then I can see it ain't gonna be cheap.

How about this: If you were opening a new machine shop without any particular jobs lined up but you had to buy a lathe that would cover most of the jobs you expected to encounter (given your experience), what is the maximum size of lathe you would choose?

If you only have small machines, you won't get the larger work. You don't have to cram in as many large jobs to make it pay as you do small ones.

I started out with about a 14" and that was too small, for farm and light industrial. Got a 19" swing with 4" spindle hole and that was entirely the proper machine for me. Then I got another one, same thing. Then and even larger one for occasional use. Then finally, got a 15" again.

If you are going to do a lot of small work, I still think it might be better to go with a small cnc as it reduces the tedium of small part manufacture. While you're killing yourself trying to crank out cheap widgets on a manual machine, you'll get to the point (rapidly) where you'll wish you bought cnc in the first place. Still, a small manual is good for a polishing and fitting machine to touch up parts coming out of the cnc.

Limy Sami · May 15, 2018

digger doug said:
Yup, a student for sure.

What college you make of this Limy ?

University of the bleeding obvious ?

dian · May 15, 2018

you need three lathes. a big one, a small, fast one and a third to keep the first two running.

DDoug · May 15, 2018

Limy Sami said:
University of the bleeding obvious ?

That would be Cambridge then.....

Reasonable Capacity for Lathe/Milling Machine

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