I should have pointed out the the Machinists Workshop MiniMill belt-
drive modification uses double pulleys on both the motor shaft and
spindle. The diameter of the both sections of the double pulley on
the motor shaft are the same diameter. The pulley sections on the
spindle are of different diameters or in other words a two-step
pulley. With this arrangement, the author of the MW modification
article uses two different sized belts to retain the two-speed
feature of the original MiniMill gear drive. The MW modification has
the the two double pulleys and belt out located in a manner that
appears to provide easy belt changing capability. Furthermore the MW
modification does not do anything to the MiniMill that would prevent
it from being restored to its original gear drive arrangement if one
However, before I move ahead I am going to try to determine if by
using a two step, two-diameter, pulley on the motor shaft it is
possible to use a single belt for the two speeds.
--- In GrizHFMinimill@y..., "klauszietlow" <klauszietlow@y...> wrote:
> --- In GrizHFMinimill@y..., "nplaks" <nplaks@n...> wrote:
> > One of my `to do projects' is to change the gear drive in my
> > MiniMill.
> > Brett Flemming's MiniMill belt drive modification is on Ty
> > site at:
> > http://warhammer.mcc.virginia.edu/ty/7x10/vault/Mills/G8689-
> > MiniMill/Projects-Mods/DriveBeltMod/MillBeltMod.html
> > Brett Fleming's description indicated the need for an electrical
> > reversing switch for the motor to restore proper spindle
> > required after his modification.
> > As noted previously on this list, the June/July 2002 issue of
> > Machinists Workshop included an article for a belt drive
> > of the MiniMill. The MW modification uses two pulleys and a
> > One pulley is on the motor shaft and the other pulley is mounted
> > the spindle. With this arrangement, the spindle will rotate in
> > same direction as the motor.
> > On My MiniMill, the spindle rotates in the same direction as the
> > motor. This means that for the MW modification, the motor will
> > have to be reversed for proper operation of the mill.
> > I went back and carefully checked out the Brett Fleming
> > modification. It also uses two pulleys and a belt. The first
> > is mounted onto the motor shaft. It is not clear onto what the
> > second pulley is mounted. It is not mounted onto the spindle!
> > appears to possibly be mounted onto the transmission shaft, which
> > so suggests that there still is a pair of gears between the
> > transmission shaft and the spindle. This in-turn would explain
> > spindle reversing that results from this modification.
> > Have I missed something? Would there be any advantage of the
> > modification over that of the MW modification, even with the loss
> > motor torque that results from reversing direction?
> > Norman Plaks
> > Raleigh, NC
> The one advantage of Brett's conversion that I could see is that
> still have the hi/low speed selector. I don't know which gears
> most often. In my case (as it was for Bratt) it was the gear that
> driven by the small metal motor gear.
> However I decided to go without any gears in my conversion which
> be seen in the photo section of the mini_cnc_mill group:
> You might have to join to see them.
> I also changed the motor to the famous treadmill motor and used 2-
> step pulleys. I used a flat belt with a spring loaded tensioner.
> This setup has a great range of speeds and huge torque compared to
> the original mini-mill. Because of the spring tensioner the head
> only run in one direction. This is only a small part of the
> modifications I have made to the mill. It's very easy to get
> away, which is what happened to me.