A Mill "Transmission" For The New Rockwell Mill

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Buffalo20

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I have decided at this point, to run the new Rockwell mill, with a single phase motor. Whether its going to be 120 vac or 240 vac, I'm uncertain, the 3/4 hp motor I have can go either way. With the 1725 rpm of the motor, I'll end up with 6 speeds, 370 rpm in low and 6300 rpm in high.

I've decided to build a "transmission", like I did for the Jet mill, adding a 4 step layshaft between the mill head and the motor. I'm building it to be a cartridge, to allow the mill to be returned to original configuration, within about 15 minutes, drilling no holes, using the manufacturer's original holes. Also reusing the original motor drive sheave.

So today I went to Graingers, for (2) sheaves (pulleys) and (2) 5/8" plate bearings. Then to the local machine shop supplier, for 5 feet of 5/8" ground and polished shafting. Then to the metal suppler for some tubing, then to the industrial supplier for some nuts and bolts.

I cut out (2) 10-1/2" discs, one of of 1/4" plate, and one out of 3/8" plate, then trued them up on the lathe. I laid out the bolt placement and drilled the holes on the 1/4" plate. Transferred the hole to the 3/8" plate, then threading the required holes in the 3/8" plate. Took a piece of the 5/8" shafting and set up the Jet mill, to cut a 3/16" keyway.

The cut up some 1/4" pipe nipples, to 3" long, the bored them out to 25/64", so some 3/8"-16 B-7 allthread would pass though to make the spacers.

Then assembled the "transmission" set, placed it on the mill and set the correct sheave height, so the belt was aligned properly. Set the new drive sheave height and tightened the bearing collars and shaft collars.

So today, I used the lathe, the Jet mill, the Jet drill press with the tapping head, the Franken-Drill, the belt grinder and finally the new saw. The shop was quite a mess.

Here are a few pictures of the work so far, next up is the motor mounting brackets and the wiring.shop work 026x.jpg shop work 030x.jpg
 
Nice job , I think you could have added the motor mount as part of the plates or do you have another reason for vibration or something. Still think it's a great idea . I'm in need of doing a planer I have , with flat belts. I have to build a complete super structure over it for the drive shaft and motor , I may need to slow the speed so ill build that too. An extra Jack shaft , two hp motor will do it easy but heavy. Yes I m using isolation mounts.
 
Working the rpm numbers this morning, the original spindle rpms with a 1725 rpm motor, were a low of 370 rpm to a high of 6300 rpms, I have some options, each give 24 different speeds.


Option #1

low of 185 rpms, to a high of 12,600 rpms, with average steps of 230 rpms between speeds

0ption #2

low of 111 rpms, to a high of 10,080 rpms, with average steps of 150 rpms between speeds

Option #3

low of 111 rpms, to a high of 8190 rpms, with average steps of 78 rpms between speeds
 
Couple thoughts; I would be cautious about running the spindle up into the higher ranges- you might want to replace the bearings also. Secondly, there may be belt slippage as your ratio goes up, especially if you plan to use large flycutters for example.
Nice job though, gives me some ideas for my mill.
Mark S.
 
At slow speed you can power tap , the slower the better. Just my thoughts, even for boring head use its better.
 
I would be inclined to maintain the lowest speed on the bottom end and go as high on the top as you can while doing so. You may have to ditch the existing link belt, as it may not like the higher speeds, and could be potentially dangerous. Once hooked up and running, monitoring the temp and sound on the bearings will tell you if the bearings are adequate. If you have the bearing #'s you may be able to find the allowable rpm. My gut says you will probably be fine. Next up, CNC conversion to make use of that velocity. :) Mike
 
Let me know if you decide to ditch that 3 phase motor. I may be interested :grin:
 
The option thread was somewhat tongue-in-cheek, Option 3 is the only real option. I made up a motor mount, mounted the motor and ran the mill at about at 500 rpms for about an hour, the ran the unit at 5000 rpms for about 15 minutes, constantly checking the head temperature, hardly any temperature rise.

As I have 2 other larger mills, I seriously doubt the Rockwell will ever see a end mill bigger than 3/8". Probably a lot of keyway cutting and lots of small jobs.

I picked up a used 4" vise and have ordered a handles to replace the existing ones.

One thing I'm going to have to do is build a riser platform to rise the mill higher, I'm only 5' 8" and even setting on 2 x 4s, I looking directly into the Rockwell logo, bottom of the quill is about mid-chest.


As for the link belt, I put the link belt in, everything in the shop runs a link belt, about 95% of the equipment we service, all over the Northeastern US, uses link belts, I wouldn't run anything else
 
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Link belts compared to normal V-belts are:

a) more expensive if of acceptable quality
b) wear out pulleys more quickly
c) slip at lower torque for the same tension
d) handy to have on hand if you break a real belt and don't have a spare on hand.
e) quicker to change on a lathe if you break a belt in the middle of a job
f) were never intended to replace V-belts
g) it's your machine so do to it as you wish.
 
Norm (a friend and fellow Chinese Buffet fan) came over yesterday, and helped out with the preliminary motor bracket, we mounted motor and ran it off an extension cord for a little while.

This morning, I rounded up all of the parts to wire the mill, the Square D on-off switch, forward-reversing switch, the plug and some SO cable. Wired up the mill, to operate on 230 vac, single phase. Wonder will never cease, I had a 50/50 shot on getting the rotation right, on the direction switch and damn, I got it first time. Usually when wiring a motor, you get that 50/50 chance and I'm usually wrong about 80% of the time. I ran the mill under no load for 1-2 hours at various speeds, motor got to about 110 degrees, mill head assembly remained at about 85 Degrees.

The UPS truck arrived at the end of the driveway (strange for a Saturday, at least here) and I got 3 boxes. My order from Grizzly came, new table handwheels and folding safety handles. Grizzly did screw up the order, the packing slip showed a dozen 7/16" t-nuts, but none were in the box. At least they are consistent, they have screwed up my last 5 orders, is someway or another. They have made them right, just takes time.

My HSS end mill order hit, all was correct.

My new Shars 4" vise arrived, I bought from a guy in Rochester area, he bought it brand new, opened the box, said looks good and then 3-4 days later got a hell of a deal on a much bigger mill, then retooled for that, this has set for about 6-8 months in his garage, so I snapped it up for $75, which included shipping. I set the vise on the table, will probably remove the swivel base, but vise look very nice.

So this afternoon, I started to change the handles on the mill, I did the knee and the Y- axis handle, and started to work on the table end handles, ran out of daylight. Placed my nut bolt order for the shop and ordered the 4" x 4" x 3/8" box tubing, to start my riser/base. The tubing and the adjusting feet should get the mill about 6" higher than it is now.
 
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