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platypus2020
09-03-2007, 07:29 PM
About 3 years ago, I bought a Jet JVM 836-1 milling machine, a great machine for the price, but somewhat limited by having only 5 speeds, 240-1550 rpm. Based on a photo posted by Lane, made this milling machine "transmision", I now have 20 speeds, from 80-3100 rpm, much easier now to select the proper cutting speeds. At the same time I installed a 4" riser block in the mill column, a Grizzly piece for their G6760 mill, identical to the Jet mill.

Jack

http://i230.photobucket.com/albums/ee214/platypus20/MVC-863Fc.jpg


http://i230.photobucket.com/albums/ee214/platypus20/MVC-862F.jpg


http://i230.photobucket.com/albums/ee214/platypus20/MVC-861F.jpg

IOWOLF
09-03-2007, 07:34 PM
Or you could have bought a variable speed model. :)

Carld
09-03-2007, 08:18 PM
Very creative. I like the drive system and I have thought several times of making a riser for my mill.

IOWOLF
09-03-2007, 08:22 PM
Bad dog would have to make a doghouse on his roof for that mill. :)

lane
09-03-2007, 08:32 PM
Looks good .And besides a cheap way to gain the necessary speeds you need.

uute
09-03-2007, 08:36 PM
Studying second pic - wondered what in hell that big ass spring was for?? :confused:

Third pic splained all! :o

Pretty sweet change box, is the belt tension on an excentric?

platypus2020
09-03-2007, 08:51 PM
On one side of the plate there is is a pivot bolt and the other side of the plate is slotted with a clamp bolt going through, pull the plate back to the right tension, then tighten both bolts. The system is used on the transmission to the mill, then on the motor to the transmission. The tension on each section is set seperately.

Big a$$ spring is on the overhead door track.

Jack

IOWOLF
09-03-2007, 09:09 PM
In the famous words of Homer Simson ....DOH !
ROTFLMAO

JS
09-03-2007, 10:24 PM
Nice modification

BadDog
09-03-2007, 10:39 PM
Very nice job of of that. Been thinking about similar things for a different machine myself to get both faster and slower speeds.

Bad dog would have to make a doghouse on his roof for that mill. :)
The shop IS my dog house, or so says my wife. I could always dig a hole to put it in, my wife says I'm good at that too. Oops, here she comes, gotta go...

John Stevenson
09-04-2007, 04:34 AM
Why not fit an invertor or VFD ?
.:confused:

NickH
09-04-2007, 08:58 AM
Or a inverter/VFD and a speed increaser for really high rpm stuff?

7018
09-04-2007, 09:05 AM
Nice job on the transmission, Looks like it will do the job..

A.K. Boomer
09-04-2007, 09:57 AM
My question would be how does it like starting up in high gear? my jvm 836 doesnt even like starting up at 1550 rpm's let alone over 3,000, i actually leave the belt loose at 1550 so it allows the motor to get up to its speed quicker then I give it a tightening push after it gets going, other question -- how does the spindle do heat wise with those kind of rpm's,

I know if you go the 3 phase motor you can go 2 speed and get the rpms down to 120 from 240 (wich is my biggest concern) but it wont help the top speed at all...

platypus2020
09-04-2007, 10:14 AM
Sir John,

I'm not completely sold on the inverter/VFD systems, I have it on 3 pieces of equipment, all bought new, factory installed. One system (drill Press) has worked fine for 2-3 years without a hitch, the second system (belt sander) has lost 2 motors, all replaced under warranty, the third system (drill press) has been terrible, I've lost 3 motors and 2 VFDs, in a 3 year period, the factory tech has been here 4 times and says nothing is wrong, after the second motor failure, they completely replaced the control system, within 6 months, I lost another motor, after it was replaced, within a month the VFD failed. Since the drill press was new about 3 years ago, it has been unuseable for about a year. They keep extending the warranty, but what good is that if it doesn't run. I know the v-belt drive system is old fashion, but it works.

Jack

platypus2020
09-04-2007, 10:25 AM
A. K.

I've never had a start up problem at 1550 rpm before, and now at 3100 rpm. About a year ago, I had a slight bearing noise, so I replaced the spindle bearings, with the best I could find, I've run it at speed and haven't notice any excessive temperatures, the next time I run it I wll check it with a temp gun.

Jack

A.K. Boomer
09-04-2007, 10:37 AM
Its not as much as the motor bogging down as it is this very strange metalic sound --- I know this sounds strange coming from an electric motor but it resembles "pre-ignition" I dont think its related to the capacitor start switch or anything like that but I dont like it when it happens, I also use my mill as a lathe and with the R8 3jaw a start in high gear is even worse, anyways, sounds like a good upgrade on the spindle bearings, I really like my machine after i got all the bugs out of it, its very solid and the perfect size for my basement...

DR
09-04-2007, 12:44 PM
Wait a second.....the original post says the mill only had a speed range of 240 to 1550.

What kind of mill only goes to 1550rpm? Do you suppose there might be a problem running that spindle at 3000rpm?

Myself, I would have gone the VFD route.

Lew Hartswick
09-04-2007, 07:39 PM
Unless youre on the order of 8 ft tall what sort of stepladder do you
use to change speeds? :-) I have to stand on tip-toes to change
the belts on a Bridgeport.
...lew...

uute
09-04-2007, 11:20 PM
Yep, I see pivot bolts now. Spring must have been in the way. :D

Simple works great. I like the tensioning handle. This is what made me think of an excentric.

Personally, I can be way too lazy about changing speeds so it needs to be really easy. Just visiting this board helps me remember the importance of such things.

Looks like a good setup - easy to reach, quick belt change, and a proper speed for most any job.

A.K. Boomer
09-05-2007, 11:47 AM
Unless youre on the order of 8 ft tall what sort of stepladder do you
use to change speeds? :-) I have to stand on tip-toes to change
the belts on a Bridgeport.
...lew...



their slightly shorter mills, im only 5'9" and its perfect for me, I bet he leaves the top in mid range to cover most speeds and does most of his changes with the bottom, he could install two handles so he wouldnt have to pull the top all the time and use it regularly till he needs a drastic speed change then break out the foot stool...

platypus2020
09-05-2007, 08:52 PM
The centerline of the upper set of sheaves is only 72" off the floor, As I"m 5' 9'' there is no need of a step stool or ladder.

Jack

A.K. Boomer
09-05-2007, 09:50 PM
Even with the riser installed? i would have thought much taller:confused:

platypus2020
09-05-2007, 10:03 PM
A.K.,

Yes, thats with the 4" riser block, The height was one of the reasons I bought this mill, also it was floor standing, had a knee, had a good size table area and wasn't a huge iron chuck.

Jack