Rule of thumb for pairing a lathe and mill?

[Aaron_W]

Some of the discussions on 3 in 1 machines has had this bouncing around in my head. Not at all a jab at combo machines, they are just the inspiration for the question.

Obviously if you have specific jobs in mind then you can just pick machines that are sized for the needed work, but in the case of setting up a generalist shop how would you match up a lathe and mill? No cheating and say buy the biggest of each that you can find.

Perhaps I'm biased coming from mini-machines, but at the small end it seems the obvious intended parings place the mill at slightly larger capacity than the lathe so anything you can work on the lathe will probably fit on the mill with some room to spare. This makes sense to me, but it is also possibly explained as simply as maybe it is possible to make a functional lathe of a smaller size than you can a functional mill.

Now when you look at the 3 in ones, you typically see a 12-14" swing lathe, with a relatively small mill, sometimes a mill that alone would be considered in the mini class, and even if not still definitely on the smaller end of the scale.

To me this makes about as much sense to me as matching a Grizzly 7x14 lathe with a Bridgeport mill. Sure there are some that this will work, for but I think most would find the lathe lacking in this case.



So back to my question, if you were starting from scratch how would you match a lathe with a mill? By size, not brand specific.

 

[ttabbal]

I wouldn't say I chose to do it this way, but I have a PM1127 and a Bridgeport. On one hand, anything I can turn can be milled, but I can't really go the other way every time. I think I would say an "ideal" pairing would be a larger lathe, perhaps 12x36. Much longer, and even the 42" table on the mill isn't enough.

Of course, nothing says you have to be able to mill the entire length of something you turned...

The combos have various tradeoffs to make them combined and to keep costs down. The sizes reflect that reality. Particularly the type that just bolt a mini-mill to the lathe bed. The type like the Smithy seem a bit more evenly matched, though the mill capacity is still a fair bit less than the lathe.

 

[P. Waller]

There is no rule of thumb other then purchase each machine sized for the work being done.

One may turn 6" Dia. shafting 96" long on a 20" X 100" lathe, if the only mill work required are key ways 3" long on each end a very small mill will do that part of the job.

I turn a few of these parts per year, 5" diameter 1045 steel round 92" long in a 24" X 110" lathe, offset centers are first drilled in each end then once finish turned a short key way is milled in each end. All of the milling is done on a Bridgeport 42" wide table knee mill.

The lathe work is large and the mill work is small, choose a machine that fits the work for each.
The saddles clamp on to the part, this is how it is held in the mill, the offset centers in each end need to be concentric and the key ways have a radial position with the cam.

 

[francist]

Maybe instead of looking at physical size or space characteristics you might look at the rate that work can be done on each machine. In other words, is the power that each machine can give to removing metal more or less in step with each other or will one outpace the other dramatically?

It wouldn't account for different sized machines for different types of work, but it may reflect the general type of work done and be somewhat of a guide for determining if the machines were well-suited and complimentary to each other or not.

-frank

 

[Shootymacshootface]

All that I have at work is a Lagun mill, and I have used it to turn simple parts. There is always a way to do something with what you have.

 

[ThinWoodsman]

if you were starting from scratch how would you match a lathe with a mill? By size, not brand specific.

When I got fed up with the benchtop machines and started preparing a space for full-sized ones, i.e. starting from scratch, I planned on a Bridgeport-sized mill and a 14" lathe. In doing a spreadsheet (OK, I lie, it was graph paper) of the new machines within a price range, there were a few undersized (e.g. 10" lathes and Grizzly G0704-sized mills) machines, but nothing larger.

Decided to get the beefiest lathe I could, and skimp on the mill if necessary. With a mill, you're basically talking about limitations of table size and depth-of-cut (i.e. rigidity of the lathe). I figured I'd hit the table size limit eventually regardless of what size mill I buy, and improving rigidity/depth-of-cut gets very expensive very quickly. The lathe seemed to offer more bang for the buck, at least at an enthusiast's price point.

Ended up buying used and not having to skimp on either.

 

[magicniner]

Obviously if you have specific jobs in mind then you can just pick machines that are sized for the needed work, but in the case of setting up a generalist shop how would you match up a lathe and mill? No cheating and say buy the biggest of each that you can find.

That's not cheating, it just needs a caveat, there is a tendency for Max RPM on mills and lathes to reduce as the size increases so go for the biggest thing you can get which will still handle the smallest jobs you want to be able to tackle.

 

[ezduzit]

The only pairing that makes sense to me is to have 2 lathes (1 small, 1 large--like 12" and 18" swing)) to go with a mill.

 

[ThinWoodsman]

The only pairing that makes sense to me is to have 2 lathes (1 small, 1 large--like 12" and 18" swing)) to go with a mill.

And a shaper! And... and... a surface grinder! And...

 

[magicniner]

If your skills run to it a friend of mine made a mount for a small headstock that he could then drop on the bed just in front of the chuck, it allowed him to do the small work which the large lathe didn't have the RPM for