small mill for machining steel. Max spend £500 including computer

[M250cnc]

As an idea could you not mount the nut into the base of the knee and use a belt to turn the screw in the configuration you have now? a bearing block could be placed under the plate you have the motor mounted to. a couple of pneumatic rams like used on hatchbacks would help with the weight if you use them upside down and a light spring over the ram section?

I think Andrew has the best solution now as maybe he maybe would need a hole in the table to do as you suggest.

I went through 4 different Z builds on my mill so i know the frustration after a lot of effort it is all in vain.

Like the amp meters in the control box, i would like to see an Estop placed on the machine when the wiring is finished, in case the worst happens.

Phil

[Andrew Wilding]

on with the mechanical build:

new gibs machined, teflon glued on then remachined. I prefer using the shaper rather than the manual mill.



Spindle started. Spindle rough machined and drilled



taper set on the top slide (female centre drilled)



taper set using existing more 2 centre



taper in the end of the spindle was finished with a mores 2 reamer. TIR was less than 0.0002.

[Andrew Wilding]

rough machined spindle and housing



pulley key machined



spindle exploded assy

[Andrew Wilding]

I thought I would post an update on the mill progress. I have been a bit busy fitting a kitchen, drawing tractors for my son and somwhere along the way had time to make anther sprog - due soon!

As you can expect progress has not been great on the mill front, however I have the spindle operating and have made some cuts in delrin then steel . The machine performed ok but I am now making improvements. The next few post will bring you up to latest progress

[Andrew Wilding]

These shots show the spindle drive pulley arrangement. Tensioning of the high speed belt is achieved by rotating a block in which the counter shaft is mounted (eccentrically). The low speed (v belt) is tensioned by rotating the pulley assembly.



note that no guards have been added yet but are on the list before the mill is complete.

[Andrew Wilding]

The anti backlsh seemed to work ok but I had an idea how to improve them. I modified the design so that the two nut halves are radially fixed to each other but axially free. this was acheived using 4 off 3mm rods in close fitting holes in both nut halves. The slave nut is threaded with a fine thread and an outer collar threaded on. this is biased with a tprsional spiring to take up any backlash. hopefuly this greasy sketch might help - it was used when I was machining the parts so it is not the clearest:


drilling the holes for the rods in the nut halves

[Andrew Wilding]

machining castelations in the collar


some surgery to the bed to fit the larger diameter nuts in - I love machining cast iron!



X axis nut in position but biasing spring not fitted over collar (lash up wiring shown!)

[BillTodd]

Nice build :)

Bill

[Andrew Wilding]

one more picture showing x axis nut