Bench top mill questions?

[Charles scozzari]

Hello John, I agree that the round column mills are a good choice for the money. I see them on line for around $1.500. When it's all said and done we have to do what's right us, at that time. Enjoy and I'm sure you'll make good use of your mill. Thanks for the reply.

 

[Larry$]

I've got a 9x49 Jet knee mill. I traded for it with no use in mind other than a desire to see "if I could make /repair things."
By far the biggest machine limitation has been Z-axis space. I have swung the head over the side of the table, & I have rotated the head to horizontal to overcome the Z limitation. The vice is usually the easiest work holding device and eliminating it in a setup will save you 2+" of Z.

Other work holding devices also eat up Z space: rotary tables, adjustable angle plates, indexing heads etc. BTW accessories and tooling will cost more than the machine! Go 3 phase if that is an option.

If you have a decent size lathe you can more easily drill/ bore deeper holes there if the part will fit on your face plate.

With sufficient self control you can limit the depth of the rabbit hole. You can always move up to a 6 axis CNC later.

 

[thequintessentialman]

Lot of new terms here, trying to figure the difference between knee mill, mill-drill, and mill. If it helps any, I already have a free standing variable speed drill press (have to change belt/pulley though.)

 

[Charles scozzari]

I've got a 9x49 Jet knee mill. I traded for it with no use in mind other than a desire to see "if I could make /repair things."
By far the biggest machine limitation has been Z-axis space. I have swung the head over the side of the table, & I have rotated the head to horizontal to overcome the Z limitation. The vice is usually the easiest work holding device and eliminating it in a setup will save you 2+" of Z.

Other work holding devices also eat up Z space: rotary tables, adjustable angle plates, indexing heads etc. BTW accessories and tooling will cost more than the machine! Go 3 phase if that is an option.

If you have a decent size lathe you can more easily drill/ bore deeper holes there if the part will fit on your face plate.

With sufficient self control you can limit the depth of the rabbit hole. You can always move up to a 6 axis CNC later.

I believe the BP head spacer will fit on your Jet mill. I have a Bridgeport 4" spacer and it has saved me a lot of trouble on set ups over the years. If you look on my site you'll see that I relocated my on/off switch lower to accommodate the use of the spacer and for safety reasons. Thanks.

 

[Aaron_W]

The Rockwell and Clausing small knee mills can't swing the head to access long work. I have a Rockwell...

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Rockwell can't because of its origin as a horizontal mill. Clausing 8520 / 8530 can, the head swings 360 degrees and extends on its ram giving several options including securing something to the edge of the table.

 

[Aaron_W]

Lot of new terms here, trying to figure the difference between knee mill, mill-drill, and mill. If it helps any, I already have a free standing variable speed drill press (have to change belt/pulley though.)

Bench mill the head moves up and down on the column, and often the head may also tilt side to side to work at an angle. The term bed mill may also be used this style of mill, usually those on the larger end, I guess because they are to big to fit on a bench.

A knee mill has the table move up and down instead of the head. The head can usually tilt side to side, and many can swing (pivot on the column) and extend allowing it to reach more of the table, or even off the table. Some also can nod the head tilting in or out. The Bridgeport mill is the classic example of a full featured knee mill.

Mill drill is kind of a vague term. Often applied to round column mills, but also used for many square column bench mills. Round vs square refers to the column the head attaches to. Round allows the head to swing, but generally has less positive control of the head position so requires the user to adjust more frequently. Square uses dovetails to control the movement of the head up and down, so has more positive control, but trades some flexibility in movement and costs more.

Square column is generally preferred, but Round has some benefit.

 

[GT-6 Racer]

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[thequintessentialman]

Bench mill the head moves up and down on the column, and often the head may also tilt side to side to work at an angle. The term bed mill may also be used this style of mill, usually those on the larger end, I guess because they are to big to fit on a bench.

A knee mill has the table move up and down instead of the head. The head can usually tilt side to side, and many can swing (pivot on the column) and extend allowing it to reach more of the table, or even off the table. Some also can nod the head tilting in or out. The Bridgeport mill is the classic example of a full featured knee mill.

Mill drill is kind of a vague term. Often applied to round column mills, but also used for many square column bench mills. Round vs square refers to the column the head attaches to. Round allows the head to swing, but generally has less positive control of the head position so requires the user to adjust more frequently. Square uses dovetails to control the movement of the head up and down, so has more positive control, but trades some flexibility in movement and costs more.

Square column is generally preferred, but Round has some benefit.

So what are the pros/cons of a knee vs a bench mill? Just a different approach to the same thing or does they have some different advantages?

 

[Jim F]

So what are the pros/cons of a knee vs a bench mill? Just a different approach to the same thing or does they have some different advantages?

Size and power required.
A knee mill requires about 5-8 ft of room and usually 3 phase power.
A bench mill/ mill/drill cen fit on a worjbech and run off of 120V.

 

[GeneT45]

Size and power required.
A knee mill requires about 5-8 ft of room and usually 3 phase power.
A bench mill/ mill/drill cen fit on a worjbech and run off of 120V.

I've got to disagree. There are many knee mills that are single phase (220V) and several that are much smaller than a Bridgeport Series 1 (that's the "small" Bridgeport). Precision Mathews makes a very nice mini-Bridgy, there are the A1SA style made by Grizzly, Jet and others, Hardinge made some table-top knee mills, and I'm sure there are others.

A knee is typically much more rigid because it is uses the large vertical ways and carries the weight of the table. A knee generally has more Z-travel than a benchtop square-column mill and certainly more than any quill. Because gravity works against it there is virtually zero backlash. This is not at all true of most quills. A head that is geared to a square column might provide a similar benefit with respect to backlash. I think a knee is a worthwhile advantage, but after that things are very much about size - bigger is usually more rigid, more powerful, and with a larger work envelope.