PM Mill Types?

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RedOak

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I'm an old timber framer, so please excuse the novice metal working questions...

I see, on their website, that Precision Matthews (PM) has three types of milling machines: Bench Type, Knee and Bed. The only type of mills that I'm familiar with at all are the Bridgeport mills I've seen, which resemble the "Knee" mills depicted on the PM website.

Can anyone give me a primer on what the difference is between these different type of PM milling machines?

Thank you for your time.
 
Beginning, the "bench" type mounts on a work bench or independent base, but the table is stationary in Z. cannot move up and down relative to the head.

The "Knee" type resembles the "bench" type but the table can be moved vertically.

The alternative perhaps "bed" type, would be like the BridgePort, in that the table can be moved vertically.

Not absolutely sure of the above, just know from personal experience that the bench mill table won't move vertically, that's what I have.
 
Why don’t you read the attached. It might help understand the differences. The term “Bed Mill” is used in all kinds of ways, but when PM uses it, it’s just a larger version of the “Benchtop” category.
 

Attachments

  • Benchtop versus Compact Knee Mill 12-2021.pdf
    1.8 MB · Views: 56
@RedOak
If you are going to purchase one, I suggest one that is made in Taiwan. They are more $$$ but QC is much better and these seem to have fewer problems.
 
The designations kind of overlap- you can have a bench mill with a knee, for example. A bed mill has a movable head- the table usually doesn't move vertically- that essentially covers all the low cost import bench "mill/drills" out there as well. Some industrial bed mills weigh thousands of pounds. I think when you reach a certain size, a knee is not practical and it's easier to move the head.
Example: a horizontal bench mill with a knee (shown without a motor)
B12pic.jpeg
 
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Originally, a milling machine referred to a horizontal mill. Nowadays, they have mostly been superseded by the vertical (Bridgeport) type.
They are more versatile, can do a wider variety of jobs (milling, drilling, slotting, tapping, gear cutting)
 
RedOak said:
I'm an old timber framer, so please excuse the novice metal working questions...

I see, on their website, that Precision Matthews (PM) has three types of milling machines: Bench Type, Knee and Bed. The only type of mills that I'm familiar with at all are the Bridgeport mills I've seen, which resemble the "Knee" mills depicted on the PM website.

Can anyone give me a primer on what the difference is between these different type of PM milling machines?

Thank you for your time.
Click to expand...
On the PM site the Bench top mills are small and can be mounted on a stationary work bench, they are limited by their work envelope (movement in the X, Y and Z axis) and the amount of weight they can work with on their tables and generally they do not come with some of the features which the larger mills do. The Bed mills appear to be a larger version of the bench mill, but they are different in a number of ways. The only bed mill offered by PM currently is the PM940 in the V (belt driven, variable speed, 3 phase AC VFD controled, not a DC motor) and M (a gear driven head) versions. The bed mills have a large work envelope and are rated for up to 400 pounds centered on the table. On the bench top and bed mills the head moves up and down to provide distance between the table and the quill whereas on the Knee mill the table moves up and down to provide that clearance.

I know of a couple individuals that have had real issues with the PM940's and if I am not mistaken they were the gear heads (M version), I have a V Version and I am very pleased with it, it has 26" of movement in the X axis, 12" of movement in the Y axis and at max height 22" of clearance between the table and the quill, a very large working envelope, and with the base the machine weighs 1200 pounds, mass rules.

The best advise I personally can provide is look at how much room you have to put the machine in, what type projects you want to do (work envelope related) and the budget you have to spend.

Hope that helped.
 
verbotenwhisky said:
On the PM site the Bench top mills are small and can be mounted on a stationary work bench, they are limited by their work envelope (movement in the X, Y and Z axis) and the amount of weight they can work with on their tables and generally they do not come with some of the features which the larger mills do. The Bed mills appear to be a larger version of the bench mill, but they are different in a number of ways. The only bed mill offered by PM currently is the PM940 in the V (belt driven, variable speed, 3 phase AC VFD controled, not a DC motor) and M (a gear driven head) versions. The bed mills have a large work envelope and are rated for up to 400 pounds centered on the table. On the bench top and bed mills the head moves up and down to provide distance between the table and the quill whereas on the Knee mill the table moves up and down to provide that clearance.

I know of a couple individuals that have had real issues with the PM940's and if I am not mistaken they were the gear heads (M version), I have a V Version and I am very pleased with it, it has 26" of movement in the X axis, 12" of movement in the Y axis and at max height 22" of clearance between the table and the quill, a very large working envelope, and with the base the machine weighs 1200 pounds, mass rules.

The best advise I personally can provide is look at how much room you have to put the machine in, what type projects you want to do (work envelope related) and the budget you have to spend.

Hope that helped.
Click to expand...
@verbotenwhisky

Thank you very much for taking the time to write up a very informative post. There was nothing here that I couldn't comprehend, so, as a novice, I especially like that...and, yes, it did. :grin:
 
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