Projects 6

Belt Conversion

I finally broke a gear in the head so it was time to make the change to a belt drive.
I made my own version of a design by J. Rollett posted on the GrizHFminimill Yahoo Group.
Download the PDF here. I made a few changes to make fabrication easier. No need for CNC,
rotary table, boring head or keyway cutter. Just need a conventional mill and lathe. I have the
hole locations for my Spindle Lock on the front of the base plate but it could be positioned on
the side like the original location. I modified one of the locking levers from the x and y axis to
use to lock down the motor. An easier solution would be to tap the center holes in the motor
plate spacer M6x1.0 instead of 1/4-20. A new lever can be found at Little Machine Shop.
I added a 1/2 in. hole in the base to clear the intermediate gear shaft. This way the head will
not have to be removed to take the shaft and gears out unless you want to. I just put the gear
lever in neutral and removed the handle. The belt is a 1/4 x 13 in. 40 degree V-belt from LMS.
Performed an RPM test with my Digital Tachometer (Search Ebay). The Motor on the X2 is rated for 6000 RPM. On low, the max is 2025 RPM, and on high, the max is 4250 RPM.
See the Video Here.

belt conversion parts

belt conversion parts 2

belt conversion assembly 1

belt conversion assembly 2

belt conversion assembly 3

belt conversion assembly 4

belt conversion assembly 5

belt conversion assembly 6

belt conversion assembly 7

belt conversion assembly 8

belt conversion lever mod

belt conversion lever mod 2

belt conversion locking lever

belt conversion motor clearance

belt conversion completed

belt conversion base plate

belt conversion motor plate

belt conversion motor plate spacers

belt conversion large pulley

belt conversion small pulley

Low Speed Max RPM

High Speed Max RPM

belt conversion small pulley for high speed

Overdrive pulley vs. stock

Max RPM with Overdrive Pulley

New X Axis

I extended the X Axis travel by replacing the stock table with a Z Axis column from Little Machine Shop.
The dovetail needed to have some stock removed to fit the saddle but other than that it was a good fit.
I added an extension for the motor mount in the bottom of the column. Also had to get a 24 in. length
of ballscrew from Homeshop CNC. The saddle needed a slot cut to give clearance for the ballscrew.
Travel is limited slightly by having to mount the ballnut outside of the saddle.
The new travel is 18 1/2 inches. This much exposes the gibs a bit , but 16 inches would be safer.
A lot better than 8 inches with the stock X2 table. I checked the table for flatness with a test indicator.
The Y direction varied only .001 and the X varied up to .004. I'll cut .010 off with a surface cutter to
make it all flat and true.

z column on stock x axis

dovetail milling vertical setup 1

dovetail milling vertical setup 2

dovetail milling horizontal setup 1

dovetail milling horizontal setup 2

dovetail milling horizontal setup 3

dovetail milling horizontal setup 4

saddle slot

new ballscrew

full travel left

full travel right

18 1/2 inches of travel 1

18 1/2 inches of travel 2

table flatness

Extended Y Axis and Spindle Head Attachment

I increased the travel on the Y Axis to 11inches (Soon to be 12.5 inches) by mating a replacement
base from Little Machine Shop. I had to cut off the extra and mill the end of the base to accept a
support bracket. Otherwise the dovetail at the open end would compress inward. I mounted the
mill and the extension on .625 inch thick steel. The extension had to be shimmed a few places to
keep the ways and dovetails even with the mills base. I used and indicator to get it within .0005.
I then used 320 grit lapping compound and the saddle to hone it smooth and true the entire length.
I reused the old X axis ballscrew for the new Y axis but it is 1 inch too short. I also need to modify
the new base casting as I did to the old one to get another .5 inch travel. thus I will end up with
12.5 inches of Y travel.

The stock mill has 6.5 inches between the center of the spindle and the column. To get more distance
I needed a spacer between the spindle housing and mount. I wanted to have some adjustment
capabilities to tram in the head, but went a little overboard. I created a rotating/tilting head attchment.
It will rotate 90 degrees to either side (technically 360) and tilt up 10 and down 95 degrees. I reused
the old fine adjustment worm gear to raise and lower the head. Possible uses will be surface grinding,
slotting or milling/drilling the end of stock too tall for the Z axis to handle.

I still have testing to do to determine if there is any/too much flex with the extension. I made an
engraving test to show the limits of the completed expansions.

Bottom line is, If I have to give up a little depth of cut and take an extra couple passes to get to depth,
That's a fair trade in my book to get 7 times the work area of the stock X2.

See it on Youtube or below. Also see the new articulating head in action as well.

Note: I performed several feedrate tests to make sure the head extension didn't hurt the rigidity.
It passed with flying colors. It cut with a .500 HSS Endmill @ 2000 rpm, .100 D.O.C. @ 50 IPM and .125 D.O.C. @ 30 IPM. These were done before I had flood coolant which would make it even better.
Check out the videos below, even more tests on Videos Page 4.