Click photos to enlarge

 

 This is my baby. It is a Homier, but is the same as many other names (Harbor Freight, Grizzly, etc.) made by Sieg. The shot below shows the area I built specifically for it with the stepped down layout bench. The lower area is 36 inches high while the mill mounting is 40 inches.

NOTE: It appears that Homier has discontinued this mini-mill.

 

    The higher mounting for the mill puts the work closer to eye level. This has been a very comfortable height to work. The lights are a home brew add-on. I got a couple of goose neck lamps at Home Depot and mounted them on a piece of plated angle steel. The angle is mounted on the back of the column through spacers into drilled and tapped holes. The rail was spaced back to clear the handles. They put light exactly where it is needed, but they do generate a bit of heat using small 50 watt spots.
  I got upset with the shove-it-through-the-hole stick provided as a spindle lock rather quickly. You can too easily leave it in the hole and start the mill thus eating gears. (Yes, I have). It also has the annoying habit of being somewhere else when you need it so I invented a better mouse trap. The following photos show the new spring loaded lock button.

 
 

  It is easily mounted with two recessed 1/4-20 socket head machine screws after drilling and tapping two holes. The resulting kit is available from Littlemachineshop.com. I hope you enjoy it as much as I have enjoyed the prototype.

Sadly, this item has been discontinued as I can no longer manufacture it.

 

DRO 

 

When I started this project I was going to digitize the X and Y table movements with modified digital calipers for a cost of $50, but the project kept going until I had digitized all three directions and then as a final touch I added the Shumatech DRO controller. What started out as a $50 project, ended up being a $200 project, but I had accomplished a controller that normally costs more than the mini-mill itself. It should be mentioned here that some people are not comfortable with the use of the converted Chinese calipers as scales for the Shumatech DRO, but I have had no problem with them and find them to be competely stable for this purpose. Click here for a discussion on their setup and use.

NOTE:  Since building my DRO, the models and prices for the controller have changed.

 

  The scales started life as Harbor Freight digital calipers at a cost of $15 for the 6 inch model (Y axis) and $35 each for the 12 inch ones (X and Z axes). I cut off the duck bill heads with a Dremel and dumped the thumb roller leaving just the stick and digital r/o head. I milled some aluminum mount blocks and powder coated them. The scale units were Gorilla glued to strips cut from .010 brass shim stock which are then screw mounted to table bases or moving head.

NOTE: all scale rails are mounted in locally milled aluminum blocks as befitted the particular mounting needs.  Click here to see them.

 I figured there would be a bit of movement, given that there are no perfect alignments. The lateral movements are rigid, but the readout can float a bit in and out from the rail as it travels from end to end due to the flexibility of the shim stock. The X table readout mounts to the extra length of the right side gib adjusting screws over the lock nuts with another outer nut . The Y table readout mounts to a new bracket screwed to the moving base. The Z scale mounts to two holes drilled and tapped on the right side of the head. The rail mounts screw to holes drilled and tapped on the back column. I bought the board and faceplate for the readout unit from Shumatech and the parts from Digi-key and Mouser. After assembly and programming, the finished unit appears as in the next photo down. The improvement all this makes in the operation of the machine is hard to describe. Everything is so much easier to operate and assures accuracy.

 

 

And here is the finished product with the Shumatech DRO-350 installed

(See motor drive below)

 

You may have noticed the small UPS in the upper left hand corner of the picture.  My power service seems to be plagued with small spikes.  This can sometimes cause scales on the DRO to shut down.  Restarting them is a bit of a headache.  A simple power-down does not always work.  The low cost UPS filters the spikes out and carries the system over from the occasional short-term power outage.  I have not had to wrangle the DRO at all in the two years I have had the UPS in place.  A small price to pay for peace of mind.

Another modification you may notice is the changeout of the original three arms and knobs for the course head movement.  My hands slipped off the skinny knobs provided and I often hit my knuckles on the light bar rail (a modification in itself).  I replaced them with slightly shorter rods made from drill rod and capped them with 1-3/8 inch knobs.  The shorter leverage is overcome by the grip on the larger knobs.

While we are on the subject of modifications, my mill has had the $40 air spring unit mounted to it (item 2258, littlemachineshop.com). It replaces the useless torsion spring counterweight. This is definitely a worthwhile expense. One suggestion: The kit has you move the plastic head stop up a bit. You still lose an inch of height. That can be important when using the drill chuck. Instead of that, throw it away and mount a small stop plate on the top of the rear column by drilling and tapping two holes right on top. The head stops against the plate as it reaches the full top of the column.

 

Motor Drive

 
   Since I do a bit of production work, I decided to reduce the effort of constantly cranking the X-table back and forth. The result is seen left and below. The drive is a Mazda pickup truck windshield wiper motor. Everything is stripped away except the worm gear output shaft and all electrical done away with except the common and two speed wires. I built a coupling with a 1/4 inch shaft that slides over the end of the lead screw which was conveniently slotted. It has a 1 inch pulley on it with a 1 3/4 inch pulley on the motor shaft. Drive coupling is by a quarter- inch wide, flat sewing machine belt. An external power supply capable of 18 volts @ 15 amps provides the power. It is an old unit scrounged from a junked out communications dispatch console.
  The red rocker switch seen on the control box goes left and right or center off. The drive direction is the same as the switch direction. It simply reverses the polarity of the voltage. The knob varies the voltage and a toggle switch, barely seen, below the knob changes speed ranges. All this allows a wide range of speeds. Decoupling of the drive for hand cranking is accomplished by slacking the belt. The natural mounting is slack, but is tightened by a roller on the small lever hanging down. It is set up in an over-center arrangement so it effectively latches in when the belt is tightened. This setup works quite well and makes very smooth cuts. An item not shown is the fast transit button. Whatever direction the table is set to run goes at max speed when the button is pushed.  

Short of going CNC, I consider this a fully upgraded milling machine.