Proxxon MF70 CNC Conversion

[Valentin]

Hello,

 

I've been trying to convert my Proxxon MF70 mill to CNC for a while. Three of the most important components are the flexible shaft couplings - they connect the stepper motors shaft (5mm in diameter) to the lead screw shaft (4.5mm in diameter).

 

Unfortunately, I couldn't find 5mm-to-4.5mm couplings so I purchased 5mm-to-4mm couplings, hoping I would be able to easily open the 4mm hole to 4.5mm hole using a 4.5mm drill. How wrong I was! I tried spinning the drill by hand, in a drill, but every time the result was disappointing: the 4.5mm hole was not concentric with the 5mm hole.

 

I think a lathe will be most useful to achieve the best result, but I don't own one. I tried to contact the nearest model engineering society (Canterbury & District Model Engineering Society), but I haven't got e reply in over two weeks. Does anyone know if there are any "lathe-on-demand" service providers in Kent who could help?

[michl080]

Valentin,

 

did you consider using a piece of flat sheet metal 0.25mm thick and wrap it around the 4.5mm axis?

 

You could use a matching feeler gauge sheet.

 

Michael

 

[Valentin]

Hi Michael,

 

Yes, I did think about this, but, to be able to roll the metal sheet around the 4.5mm shaft I would need a somewhat soft metal, and, because of that, the screw in the coupling used to secure it to the shaft will create a small depression, a dimple, in the sheet; this may lead to axis not being concentric? I may be wrong though...

 

Since I posted my message, I managed to have the couplings adjusted, but I still have to give them a try... I'll post how it goes.

 

Valentin

[didcot]

I thought Proxxon did a kits of parts for a conversion, but probably expensive.