Denford Micromill & Microturn blog

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The Denford MicroMill & Denford Microturn have very similar electronics so this page exists try to stop repetition of that information.

I'm not too bothered if some common mechanical to dos find there way onto here, prioritise non-repetition.

Setup/ Information

From Kascper when he donated these "I believe they machines have been converted to run with a Mach3 enabled PC via the parallel port of the included PC (AFAIK without spindle control). As well as that, the previous owner has provided original Denford PCB's and a GRBL conversion kit for both."

[Datasheet for newer, but mechanically similar version]

Some handwritten notes

Electronics Setup

These have two main boards in them, a Baldor board and a parallel stepper breakout board

Baldor Board

Both Baldor F391 boards, believe an issue 2 in the lathe and Issue 1 in the mill but may have that transposed

possible Pinouts

Stepper breakout board

potentialy this one or similar

Micromill specific

Possible Wiring Diagrams

Conversion process to Mach3]

Problems/ to do

To both machines

  • conduct a full mechanical check over, cleaning and maintenance - In progress - Steve & Andy
    • axies and rods cleaned and lubed. ISO 220 way oil would be ideal
    • for greasing the rods molly grease or white lithium would be the best materials
  • spindles under computer control - In progress - Paul
  • new bearings on spindles to run faster Not needed - Steve
  • post processing software for fusion - Andy
  • mount secondry power supply in casing running off same main supply, but isolated from each other - Not needed with GRBLs
  • Find stable place in lab for them and sit on something heavy for dampening


  • Need to fix incoming 5v DC jack - Not needed - Steve
  • Currently has an emergency signal always running - Fixed - Steve
    • Steve - OK as far as I can figure for the E-stop stuff on the mill, you need to find a pair of normally-closed contacts on the E-stop switch, and connect them between terminals TB1-6 and TB2-11 on the baldor board, that'll eliminate the false "emergency" signal


  • New version of GRBL for 2-axis control

Found resources

Maintenance Log


  • E-Stop problems were found to be a mis-configured pin in Mach-3, no hardware changes needed.
  • We like having a microcontroller on board, and the GRBL boards seem to work better than the parallel boards (and I blew up one parallel board) so forget the parallel boards we'll stick with the GRBL ones from now on
  • The GRBL boards already have firmware loaded and partially configured for the Denfords
  • The mill GRBL board has all it's pin assignments set right, all it's step and direction parameters and it's axis sizes mostly set. We did have to reconfigure the Y axis travel as the stock value (65mm) was much smaller than what the machine seems capable of. We also enabled soft limits as they were default off. Still to set
    • Spindle control parameters
    • Axis Kinematics tuning
    • Full Kinematics tuning will require a dial-indicator gauge and ability to clamp to the mill table, are these available? According to IanM yes, there's enough basic equipment around to do it
  • Both machines will need a USB-B panel connector fitted, we should cut it's +5V line to avoid dual-powering the GRBL boards. PaulE has ordered some panel connectors.
  • We need to put the spindles under GRBL control, this requires something that converts 5V PWM to 0-10V analog, preferably also providing isolation. We should check to see if this is a product that already exists before we try to roll our own. If we do decide to make our own then we can probably integrate the spindle over-ride control on the front panel. PaulE has emailed the maker of the GRBL board to ask some advice.
  • Do the GRBL boards have any analog inputs that could be connected to the front panel dials to provide spindle and feedrate overrides in software? Probably not, at least not without some changes to firmware, PaulE is discussing with GRBL devs
  • Both machines still need thorough mechanical going-over, especially the Z-axis on the mill
  • Lathe needs to have it's GRBL fitted and all parameters checked.
  • Spindle speeds need calibrating and if possible increasing on both machines, need to get bearing type codes off machine to check datasheet then check health and play/preload of bearings. If they turn out to be cheap ones then consider replacement with taper-roller or angular contact types
  • Need to define machine setup and write post-processors for fusion360 for both machine
  • UGS works as a G-code sender but also investigate other options like LinuxCNC and CNC.js. Drop Mach-3 as too expensive



  • Paul E made and attached a small converter board to apply a variation of the modification listed above, which lets the GRBL board control the optoisolator on the Baldor board, generating a 0-10V control voltage signal.
  • The original "R29" from the board (and 0805-sized 220 ohm resistor) has been saved and is currently taped to a small piece of paper attached inside the machine.
  • The original link cable has now been restored to join the Baldor board to the (unknown name?) spindle controller, meaning that GRLB now has total control of the spindle speed - tested with variations of `M3 Sxxx` and `M5` to stop it.
  • The front panel override pots are now totally disconnected, and the wires screwed back into their original (though unconnected) terminal blocks. The wiring is
 134 red  = "spindle" pot wiper
 135 blue = "feedrate" pot wiper
 136 red  = pot +ve end
 137 blue = pot -ve end


  • Paul E began working on the lathe. Removed the old conversion, added the GRBL board. X axis works fine. Found that the other axis was wired as Y, but the Baldor board seems to have a short and does not pass the Y axis limit switch. Have adjusted wiring to connect the other axis as Z, avoiding that problem and putting it where GRBL / users will expect it to be.
  • It seems we may need a custom build of GRBL to be in lathe mode, as by default it still expects to see three axes and gets upset when it can't home the Y axis.
  • Fuse was left out of the lathe spindle controller for safety for the moment
  • Steve R has done a full examination of the mechanics of the micromill with the following conclusions
    • The main column is indeed cast iron. The bed, X and Y carriages, and the table are all aluminium extrusions, this includes the ways and may limit future machining. If the machine gets long-term use then an upgrade by fitting Turcite on the ways may help.
    • The machine uses tapered gibs, made of Delrin! to take up slack in the ways, they are retained with wire clips
    • The head is rotatable at 2 places with locking keys for both horizontal and vertical milling
    • The spindle uses 6004C3 deep-grove roller bearings which aren't ideal but are probably good enough. Could be replaced with 7004P4 precision angular contacts if someone wanted, but expensive and probably overkill for this machine
      • Maximum rated speed for the bearings is 24,000rpm so the plan to increase spindle speed can continue
      • The spindle belt runs on plain pulleys which are easily made to custom size, so the plan to increase spindle speed can continue
      • The belt type is MB-330 N1
    • The spindle is currently fitted with an ER11(?) collet retained with a drawbar and taper which means other tooling is possible if we can ID the taper
    • The spindle bearings are correctly adjusted and just need a proper run-in to be seated. There is a pre-load adjustment nut that's already set right
    • The machine is USA made and uses imperial threads and fasteners in most places
    • All 3 axis use standard leadscrews, which look like they might be 1/4-20 UNC but need to check. Upgrade to ballscrews might be possible in future
    • Leadscrews are supported only on the motor bearings and the slide movement nuts, this is a candidate for future upgrade
    • The Z-axis uses a detachable bronze nut
    • The X and Y axis use press-in brass insert nuts in the carriage, this is a candidate for future upgrade
    • There's something caught in the X-axis slide that needs attention but full disassembly is required to do that, we ran out of time
  • Steve R disassembled, cleaned, and re-lubricated all Z-axis parts and the head is running smoothly on it's ways now. Re-tightening of the gibs will be needed in a few hours of run-time.
  • Kinematics tuning cannot be properly completed until the X and Y axis are serviced
  • The mill is now partially functional, it's slow and has a compromised X-axis rigidity, and the spindle speeds aren't scaled properly, but it's usable by someone with good machining skills and low expectations.
  • Andy H discovered that RML has a working microwave
  • Instant coffee that's gone white tastes weird