Bought a Rockwell 21-120 Mill

Discussion on all milling machines vertical & horizontal, including but not limited to Bridgeports, Hardinge, South Bend, Clausing, Van Norman, including imports.

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JPar
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Bought a Rockwell 21-120 Mill

Post by JPar » Mon Oct 02, 2017 4:54 pm

I've been looking a long time for a milling machine, and finally found this Rockwell 21-120 combo not too far from home. It seems to be in really good shape. The PO used it for hobby/maintenance work. He thought it was originally in a school. The owner previous to him bought it from the school, and just stored it for 20 years or so. So overall, I think it's had little use. It came with an assortment of 14 horizontal cutters, most of which look like they've never been used. PO says he never used the horizontal feature.

I'm not planning a full-on restoration; I just to want to clean it up, get everything properly adjusted and lubricated, and then start making some chips. I've got a lot to learn. I have some lathe experience, but not much milling experience. Any/all suggestions and advice will be much appreciated!

John
Front.JPG

Glenn Brooks
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Re: Bought a Rockwell 21-120 Mill

Post by Glenn Brooks » Mon Oct 02, 2017 5:10 pm

Iam not familiar with the Rockwell. Yours in the photo looks nicely cared for. Congrats- you've earned some tool gloat stars, I think!

Couple of questions re: horizontal milling. How do you set up the vertical head for horizontal milling? Does it come off, or swivel?? Seems like a lot of weight on the head, hanging sideways, if it swivels.

Also, most horizontal mills have some sort of overarm support that reinforces the end of the arbor, outboard of the cutter. The top of the overarm support usually slides over some sort of 2" round shaft, protruding through the upper mill casting - whichnitself can be pushed into, or pulled out of the mill to accommodate the support arm.

Did you get these arbors and support arm with the cutters? If so, your on your way to some interesting aspects of machining.


Edit: just looked again at your photo again. The horizontal milling arbor appears to mount directly into the upper casting - into the spindle mounted between the vertical head and the table. Then the head apparently comes off the mill, and an overarm support mounts in its place - on the apparently gigantic round column running through the top of the casting.

I could see the need to fab up a small dedicated gantry and electric hoist to hand over the mill to swing the head out of the way! :wink:
Regards
Glenn
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Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

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JPar
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Re: Bought a Rockwell 21-120 Mill

Post by JPar » Mon Oct 02, 2017 5:20 pm

For horizontal milling, the vertical head (including ram) is removed from the machine, and replaced with an overarm and outboard support as you mentioned. The arbor is powered by a second motor, which is behind the column. I've attached a picture that shows this. I believe I have all of the necessary parts, including the overarm, support, arbor, and drawbar.

John
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SteveM
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Re: Bought a Rockwell 21-120 Mill

Post by SteveM » Mon Oct 02, 2017 8:36 pm

I believe that the 21-120 is a horizontal only. What that might be is that someone took the head from a vertical Rockewell and put it in the overarm mount.

Best of both worlds!

Steve

Glenn Brooks
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Re: Bought a Rockwell 21-120 Mill

Post by Glenn Brooks » Mon Oct 02, 2017 9:35 pm

John, Awesome!

Great find. Even better that you have the overarm support and arbor. What Size is the arbor? Lots of smaller H mills are either 7/8" or 1" - and hard to find cutters for. 1 1/2" ID cutters seem to be more plentiful.

Tony's UK machining site indicates you might actually have a model 21-122, a Universal vertical/horizontal Mill.

See the bottom of the page: http://www.lathes.co.uk/rockwellmillers/page2.html

Looks identical to yours.


Glenn
Moderator - Grand Scale Forum

Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

Ahaha, Retirement: the good life - drifting endlessly on a Sea of projects....

choprboy
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Re: Bought a Rockwell 21-120 Mill

Post by choprboy » Tue Oct 03, 2017 1:32 am

As others have noted, it looks like someone has combined two machines into one (guessing via the mismatched paint and the lack of worm gear for turning the head orientation). Looks like it has the 3phase motor option and someone has put a VFD on it? The belt cover plates show they were using the VFD to control speed... Mine sit in the spare parts bin and many machines are missing them, far to much trouble to remove/reinstall every time you change the spindle speed.

Put two cans or jars in the bottom of the cabinet, one under the table jack screw, a second under a ~4-6" piece of 3/4" NPT pipe in the drain holes. Catches the drips of way and cutting oil before they leak across the bottom plywood and out onto the floor.

If your not bolting it down, I mounted mine on a couple pieces 2x3 lumber about 32" long, stabilizes the mill and keeps it from walking about.

earlgo
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Re: Bought a Rockwell 21-120 Mill

Post by earlgo » Tue Oct 03, 2017 8:19 am

With some thought and additional tooling, you can do odd things with a horizontal that you can't with a vertical. Since you have both heads, you could mill from the top and the side in the same setup. I use my horizontal with end mills and drills more than with arbor mounted cutters.
side milling.jpg
Good find.
My buddy has a Rockwell vertical and it doesn't look much like the one you found.
--earlgo
Before you do anything, you must do something else first. - Washington's principle.

JPar
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Location: Mayoville, MN

Re: Bought a Rockwell 21-120 Mill

Post by JPar » Tue Oct 03, 2017 3:31 pm

Thanks to everyone for the comments so far. In answer to some of the questions that were raised:
1. Re the model number, I agree that it probably left the factory as a horizontal-only machine, and the vertical head was added later on. I think I read somewhere that the vertical head could be purchased from Rockwell and retrofitted to horizontal machines.

2. The machine does have the worm gear tilt adjuster. I've attached a picture that shows this more clearly.

3. The diameter of the horizontal arbor is 1 inch.

4. Both motors are 3-phase. The PO fitted the machine with a GE/Fuji AF300 Mini VFD. The vertical head motor is 3/4 HP; the horizontal is 1 1/2 HP. The PO didn't wire up the horizontal motor, so I didn't get to see it run before purchasing. Keeping my fingers crossed that it's OK!

John
TiltAdjuster.jpg

choprboy
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Re: Bought a Rockwell 21-120 Mill

Post by choprboy » Tue Oct 03, 2017 9:18 pm

Interesting, the worm gear tilt is on the back side of the over arm support and faces to the right on the vertical mill. The tightening bolts are also on the right hand side. Must be a difference between the vertical/horizontal column castings.

Jchevy
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Re: Bought a Rockwell 21-120 Mill

Post by Jchevy » Wed Oct 04, 2017 7:10 am

I have one of these mills as with yours it sat unused for many years .You will very happy using this mill my only complaint is the short quill travel .

JPar
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Location: Mayoville, MN

Re: Bought a Rockwell 21-120 Mill

Post by JPar » Wed Oct 04, 2017 1:20 pm

Made a little progress today. I tested the horizontal spindle motor with the VFD, and the motor runs smoothly and responds to the VFD. It was nice to see that. Also, I figured out how to engage the back gear. The bracket that the VFD is mounted on interferes with the movement of the backgear lever, so it can't be moved completely to the position where it can be pulled out to engage the gears. After moving the bracket out of the way, I was able to engage the gears. I need to rework the bracket for a more permanent solution.

The VFD is rated for 1 HP, which is plenty for the 3/4 HP vertical motor. However, the horizontal motor is 1-1/2 HP. Can I get away with using this VFD for the horizontal motor, or do I need to start looking for a VFD with a higher rating (i.e., 2 HP)?

spro
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Re: Bought a Rockwell 21-120 Mill

Post by spro » Thu Oct 05, 2017 7:43 pm

As you suspected, running the 1 1/2 hp under load, may be too much.
The note about quill travel; The Rockwell quill is 3" diameter , 7 1/4" long. It is wide for the R8 spindle. Down feed rack length is 3"
The Bridgeport M head quill is 2.56" diameter , 8 3/4" long. It uses B&S 7, MT#2 or B3 . Down feed rack length is 5 3/8".
This is comparative measurements of the rack and not the actual travel.

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