ROCKWELL 21-122 milling machine REBUILD

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Harold_V
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Re: ROCKWELL 21-122 milling machine REBUILD

Post by Harold_V »

wally318 wrote: Fri Feb 26, 2021 8:08 pm so I could leave the head trammed and use the right angle head to act like the swiveling table.
I'm not convinced that's going to work. The angle you speak of isn't generated by swiveling the head, it's generated by swiveling the table, plus the cut would be taken with the horizontal spindle, not a vertical spindle.

If I'm missing something, please set me straight.

Very nice job of adapting the head, by the way.

H
Wise people talk because they have something to say. Fools talk because they have to say something.
wally318
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Re: ROCKWELL 21-122 milling machine REBUILD

Post by wally318 »

When cutting a helix with a horizontal mill the mil table is swiveled to center the cutter on the
intended helix. And the cut is taken on top. If doing the cutting with a vertical head the head
is tilted to the angle of the helix and the cut is taken from the side.
But if you mount a right angle head on a vertical mill head now you are cutting like a horizontal mill.
The cut is taken on top. But unlike a horizontal mill the right angle head can be indexed or swiveled
to the angle of the helix, basically accomplishing the same thing as the swiveling table.
So the vertical head stays in the vertical position only the right angle head swivels.
But putting the right angle head on the horizontal spindle basically turns that spindle into a vertical head,
so the head must be tilted to get the angle of the helix and the cut taken from the side.
The main thing this way achieves is the use of the back gear/lower speeds to suit the diameter of
the gear cutter.Am I understanding this correctly?
Harold_V
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Joined: Fri Dec 20, 2002 11:02 pm
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Re: ROCKWELL 21-122 milling machine REBUILD

Post by Harold_V »

wally318 wrote: Sat Feb 27, 2021 3:51 am Am I understanding this correctly?
I don't think so. Reorienting the head won't provide the angle you speak of. Tilting the cutter has nothing to do with the angle of the helix. The part must be set at the proper angle, not the head. You do that with the table.

Note that you can not generate a helical gear by plunging the cutter. Not even if the angle is set that you speak of. The centerline of the cutter must remain on the centerline of the gear, side to side, otherwise the teeth are generated with a concave configuration. They won't mesh with a like gear. You'd achieve some degree of success with exceedingly narrow gears (and improper clearance of the resulting teeth), but one with any width at all would have a form that simply wouldn't work.

if this doesn't make sense, place a ruler on the periphery of a cylinder, set at the angle you speak of. Notice how it touches only in one place, with the surface dropping away on each side of the contact? That represents the tooth you'd generate. The gear must rotate as the cutter traverses side to side, so that it is always on center at the contact point of the cutter.

Am I confused?

H
Wise people talk because they have something to say. Fools talk because they have to say something.
wally318
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Re: ROCKWELL 21-122 milling machine REBUILD

Post by wally318 »

The gear would still rotate(no plunging)
I did say it would be done with a universal dividing head which would be linked to the table movement
and geared for the apropriate lead.
The only difference is that the cut would not be done with a cutter that is in a vertical plane(horz.)
but in a horizontal plane(vert) with the cut happening along the side of the gear being milled instead
of the top. And the vertical head or right angle head tilted to the same amount of degrees as the
table would be swiveled on a universal mill. Cutter would still be at the centerline.
The cut happens exactly the same just 90 degrees opposed.
Harold_V
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Re: ROCKWELL 21-122 milling machine REBUILD

Post by Harold_V »

Unfortunately for me, I have almost no experience with gear cutting, so I may well be confused. Gears were never a part of my shop experiences, aside from a couple simple spur gears generated with a fly cutter. Helical gears are a totally different matter.

Is it safe to say you'll use a straight cutter to generate the tooth form? I now understand that you'll feed the gear and cut as it rotates. It is not clear to me if you'll generate an involute form.

Interesting project. I'm following with keen interest.

H
Wise people talk because they have something to say. Fools talk because they have to say something.
wally318
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Re: ROCKWELL 21-122 milling machine REBUILD

Post by wally318 »

If you use an involute cutter you will generate the proper form.
THe only difference being that the cutter you would use to cut lets say a 20T spur gear
would not have enough clearance when cutting a 20T helical gear. Ti would have to be
the cutter for several gear teeth bigger say 23 or 24 teeth.
There are tables and math formulas to get the right cutter.
wally318
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Re: ROCKWELL 21-122 milling machine REBUILD

Post by wally318 »

WELL ...I'm finally back to working on the mill.
After a lengthy hiatus of making chips on the Chipmaster with various projects and
buying more tools. So first I needed to change the tool box situation to make room
for all the measuring instruments and tooling so everything is organized and efficient.
And then organize the shop to get everything out of the way. So could concentrate
only on the mill.
So here goes. I finally painted the base and column. The base had a coat of primer
on account of going to bare metal to get rid of the mess on the paint-dried coolant
and oil. On the column I decided to leave the paint-it was largely intact, so decided
to give a coat of primer first. As well as a second coat to the base.
First I wire brushed the existing paint and cleaned with thinner.
Next masked everything off the ways and all machined surfaces as well as threads.
Next I put down 2 coats of colour mixed to match 61 gray that was being used for smaller
items that went to powder coat.
I used Home Hardware Alkyd enamel paint with Valspar enamel hardener at a 16:1 ratio
and brushed on. I didn't want to deal with spraying the mill, my shop is very small(over-spray)
etc. But more importantly the health risks of atomizing hardener w/0 a full helmet/body
external air system. Even just brushing the shop stank to high heaven when I took the respirator
off after painting. Also my eyes were starting to sting on the last 25% of each coat.
For the most part the paint turned out pretty good. The enamel hardener is supposed to make
the paint dry quicker, cure harder and come out glossier.
The colour is real good and so is the gloss. But when it started drying on the 2nd coat lots of
tiny goosebumps(micro-bubbles) started showing up. Not sure if thats called fish-eyes. Didn't look
like that to me from what I saw on google.
Not sure what caused it. The paint I left underneath, or a reaction of the enamel paint and the hardener.
In any event its only noticable really close-up. So to mee I don't think its worth it to block sand and re-paint.
So now I'm stripping/cleaning and masking the last few items to paint. The knee/motor mount/gearbox
vertical head etc. I've got about 15 items off at the powder coaters. Should be back in the next week.
And I just got back 35 parts from getting fresh Black Oxide. Had already sent about 30 parts quick a while back.
So stay tuned in the next 2-3 weeks I'm hoping it should be finished.
Attachments
P1040419.JPG
wally318
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Location: Kelowna, British Columbia

Re: ROCKWELL 21-122 milling machine REBUILD

Post by wally318 »

Finish painting all the in shop painted parts.
Still waiting for the powder coated parts to get done.
Will start assembling tomorrow.
Attachments
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P1040422.JPG
wally318
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Joined: Sun Jun 05, 2011 1:06 am
Location: Kelowna, British Columbia

Re: ROCKWELL 21-122 milling machine REBUILD

Post by wally318 »

Got the knee/related parts assembled and set up.
Backlash is .002-.0025 thou.

I'm working on the horizontal spindle now.

If any Rockwell owners out there have questions
about certain specific aspects of the rebuild or
how parts go together, now is the time to ask.
Don't wait a year or 2.
Attachments
P1040423.JPG
wally318
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Joined: Sun Jun 05, 2011 1:06 am
Location: Kelowna, British Columbia

Re: ROCKWELL 21-122 milling machine REBUILD

Post by wally318 »

Well, spindle is in/sealed and ready for oil.
Gearbox is together/assembled and sealed-ready for oil.
Finishing the gearbox was some doing. The first time I already
had RTV on it and tightened but the engagement rod/lever for the
backgear gave too much mesh/too little backlash. So on-off on off
and adjust-check quite a few times till I finally figured out to mark
the eccentric shaft and where and which way to retard it to finally
get the backlash correct. After it was finally assembled/sealed
all I had to do was back off the set screws on the lever side all the
way-about 1/16" and I had the backlash dialed in.
Anyone doing a teardown/rebuild I recommend doing this before
using RTV sealant. Get the backlash correct. At this stage you can
observe the eccentric and mark points of reference to know where the
backlash point is good. Then when you pull of the gearbox cover
slide out the eccentric/backgear assy and advance or retard the eccentric by
1 or more teeth as required. Assemble and check. This needs to be
done with the gearbox cover in place so that both sides of the eccentric shaft are
fully supported. Otherwise the gear engagement rod may slide easily and feel
like optimal backlash, but when the rear cover is put in place it lifts up the
outer side of the eccentric and giving too tight of a gear mesh.

Tomorrow it's the rest of the pulleys/motor mount and motor.
Attachments
P1040424.JPG
P1040425.JPG
P1040426.JPG
Last edited by rmac on Sun Dec 04, 2022 9:09 am, edited 1 time in total.
Reason: Fixed minor typo
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Rex
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Location: DFW Texas

Re: ROCKWELL 21-122 milling machine REBUILD

Post by Rex »

Nice job! I rebuilt a similar machine - Centex - a few years ago. Enjoyed the process, and I use the mill often.
wally318
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Joined: Sun Jun 05, 2011 1:06 am
Location: Kelowna, British Columbia

Re: ROCKWELL 21-122 milling machine REBUILD

Post by wally318 »

You'll notice in the 1 st pic, that the lower(inner) pulley is significantly smaller than stock.
I turned this down in size so that 60 rpm becomes 39 or 40 rpm.
Pic no.2 shows a new custom made speed plate/chart the reflects this.
Pic no.3 shows the 5 step pulley in place. You'll notice that the largest
pulley on the 5 step is quite colse to the upper(inside) pulley.
In fact when I went to bolt on there was interference on account of going to a smaller
inner belt and so the pulley sits in a higher position.
So, I had to take it apart and take metal out of the hub for the upper pulley.

You might also notice that the 2 rear/largest pulleys are aluminum.
In fact 1 and a half are. There were 3 chips out of the cast pilley.
So I machined them off and made an aluminum ring which is bolted in place.
Then the pulley Vees were machined with the ring in place.
Attachments
P1040427.JPG
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P1040429.JPG
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