Time to add a mill. Knee or vertical?

+1 to make sure you have enuf vertical travel todo the work you need to do. Some- maybe most knee mills have very limited vertical travel distance.

Don't buy a clapped out machine just because it is big. Big and worn out won't make you any parts you would want to pass on to customers.

Glenn
 
PM935 is a GREAT machine to look at. I love mine. This is assuming you want a new machine. If you are ok with old you have other options but honestly the PM935 is still better than any of those options aside from a BP (which you said you don't have room for).

To add to what was said above, the difference between the cheap import vertical milling machines and a knee mill (any type, import or domestic) is rigidity which is EVERYTHING on a machine tool whether it be a lathe or a mill.

In my opinion, if you have the money and space for a knee mill, even a smaller one, buy that. That said I don't think that Grizzly 8x30 model you linked to is worth it, too lightweight for the money. For not much more you can get the PM935 which weighs 2000 lbs and has incredible features for its price.
 
RandyWilson said:
I'm not looking to compare the two specific machines. I am looking for comparisons of the two types, Knee mill vs dovetail column vertical mill. I just don't see the big difference between moving the head up or the work down if they are both on dovetails. So far the only things I've found is a knee mill has gravity working for you rather than against when dealing with backlash but it is harder to install a DRO. There has to be something else to justify the 50% higher price.
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I'll share my point of view & experience. As mentioned, rigidity is the main difference, & IMO it's a big difference. When I refer to a knee mill below, I'm talking about a BridgePort style mill & not a benchtop knee mill or a Clausing 8520 style knee mill.

Columns flex. Mill/drills don't have a means for adjusting nod, knee mills do. You have to shim the column when you have to adjust for nod. Knee mills have a worm drive. The column may sag over time from the weight of the head.

Difference in moving the head up & down on a column mill & the table on a knee mill is important if you have to plunge a cutter or drill. With a knee mill, you crank the table up taking up backlash on the screw. Knee mill also has a dial for the knee & the handle is in the front. On a column mill, if you lower the head, the weight of the head may not be enough to overcome backlash depending on the size of the mill/drill, it can hop when you first make contact with the cutter & workpiece. Many column mills don't have a dial for the head. Fine if you have a DRO but column mills usually have the Z handle somewhere on the column. Kind of awkward to turn the handle & watch the work piece or fight to look at the DRO if the DRO is not mounted on the same side of the mill as the handle.

Knee mills also have have a ram & turret. The ram allows the head to be advanced forward & back giving you additional Y travel. On a column mill the head is fixed. The ram is great if you don't have enough table Y travel to get the spindle where you need & can't mount a part on the table where you need. The turret allows you to rotate the entire head left & right (not talking about tilt), again allows you to position the spindle over areas that would be impossible to reach with a mill/drill. These features might not be used that often or imporant for small hobby guys but there were times I sure wish I had them.
 
Thanks DZ, that's the type of generalized info I was looking for. The issue is I can't put my hands on these mills easily. I'm making a multi-thousand dollar decision mostly blind. I did have access to a BP almost (groan) 20 years ago. But that experience was limited to not much more than being allowed to push the button and watch the bit go 'round. Never seen a dovetail column mill in person, and there are no local dealers.

The PM935 looks like a dandy chunk. But alas it's twice the cost of the ones I'm considering. And the weight is getting well beyond my capacity to handle. I really don't want to have to hire a rigging company every time I need to move it.

Thanks all!
 
moving a 2000 lb mill is not bad. I can be accomplished by one person but having a second is better. My 12 y.o.a. Daughter helped me move my 645 Index when I got it.
 
Another shop owner years ago I talked to when I was considering a small VMC told me you can put a small job on a big mill, but not a big job on a small mill.

He also said buy something you can grow in to and not out of.

So I bought a 4020 Fadal. Less than 6 month later I got a job that required 37" of travel on X. I ran that job for over 3 years. That job helped me build my business until it was sent to Mexico.

I also modify transmissions but from your description it's nothing like what you do. I'm always looking for another product to add to my little business and having a big mill allows me to have multiple setups on the table. (my manual is about 1-1/2 times the size of a Bridgeport) and I love it. Very rigid, the table locks actually lock the table, 3HP controlled by VFD, DRO.

Buy the biggest mill you can and at some point in the future you will be glad you did.
 
The wife helped me move the 2000lb South Bend lathe. I don't want another project, and I can't afford a divorce. So I'll stick to something I have a chance of moving myself. :)
 
alloy said:
Buy the biggest mill you can and at some point in the future you will be glad you did.
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That, sir, is sound advice. When my wife wanted a small embroidery machine to help with her business, I insisted we get a commercial grade monster rather than a consumer toy. But at least I can move that one.
 
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