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Hi
I have converted two mills, a minimill X2 and an Optimum BF30.

Using stepper motors is balancing act that really requires an idea of what feed rates you need on each axis.

My experience...

Hi,
Here's a link to my 4th axis build thread using a harmonic drive and the old head of my minimill. The idea of using a lathe / small mill head stock saves a bunch of time if you go down the...

Cider press! Like that idea. Maybe there should be a competition for the best / most cunning up cycling of that box of bits that we all have at the back of the shed.

...and the sausage press works...

So it's been a while since I last posted. Mill is working great! But what to do with the old lead screws?

Seemed a shame skip them, in the end I decided to make a sausage press out of the Z screw...

Hi
No plans as such because the conversion was bespoke to the harmonic drive I found on ebay. Hopefully, the build thread gives enough detail on what I did.

Many thanks.

Here's a link to a video of a repeatability test of the axis.....
https://youtu.be/Khy2YQ3gYmY

Many thanks - LOL good point, I think it is probably easier to rotate the axis rather than the workpiece and the mill ;)

Sorry about some of the pictures, sometimes its difficult to predict which...

So after a bit of a delay, I've got round to building a brake for the axis. Its designed around a crane brake mechanism and sits between the chuck and the body of the minimill. I still have to add...

I put the 4th axis on the mill tonight after fitting it to a 20mm steel base plate. I mounted my test bar in the mt3 spindle and clocked the length. I measured 0.01mm over 3" or so, good enough....

I've assembled the whole 4th axis along with the motor and chuck. Here are some pictures of the assy.

Here's a link to a YouTube video of it.

https://youtu.be/x9MdNyrYQ54

I mounted the spindle and chuck in the minimill head last night as a trial fitup. The head has new angular contact bearings in it, heres a link to the video
4th Axis spindle trial mount in...

Bit more progress. I spent last night checking the lathe alignment, in the end I got it to turn parallel to 0.0003" over 6" at this point I decided to stop as I was at the limits of my micrometer. ...

Bit more progress... I've finished roughing out the chuck mount adaptor. This piece will be attached to the minimill spindle by press fitting and then
pinning with grub screws. I didn't want to...

I've now finished the nut and installed it on to the spindle. I have made two cuts across the nut to allow the nut to be clamped on to the spindle thread by tightening two M3 grub screws. Once...

Many thanks.
So here is the nut so far. the groove in it will allow the threads to be locked by tightening two grub screws from the front of the nut once installed. I still need to mil some...

Over the last night or two I've been making the clamp nut that retains the spindle and preloads the bearings. First off, I measured the spindle thread as M27 x 1.5. Not exactly standard but no...

A bit more progress. I made a jig plate to hold the housing and motor plate whilst I finished machining them. The motor plate and housing are now complete and the next thing I will do is make a...

Here's a link to a video of the mill hogging out the inside of the steel housing. I'm roughing it in the mill and will finish once mounted in the lathe.


...

More progress, outer housing and motor plate have now been part machined. The outer housing needs the bore opening out to take the motor plate locating spigot. I'll do the roughing on the CNC mill...

Anywhooooo...
I've been machining the outer housing from the 4" bar stock and made a start on the jig plate for machining the reverse side of the outer housing and motor plate.

Well a bit more progress. The part I made the other night now fits nicely on the spindle. I cut the keyway using a purpose made tool mounted in the CNC miller, and then wrote a simple loop to shave...

Torque specs are output and yes a 1Nm stepper theoretically can deliver 160Nm at the output and probably destroy the drive in the process! I plan to use the axis for light cuts / engraving rather...

Well after a bit of a break, I've started to make parts for the 4th axis. Tonight, I just about completed the connection between the minimill spindle and the harmonic drive (red part in 3d views...

Links added by site not by me. Harmonic drive came off ebay after a bit of waiting. Reference is here for the FB series drives.

Products | Component Sets | FB Series Pancake Component Sets ::...

So things have moved on a bit. I now have a working design that connects a Harmonic drive FB type pancake drive to the spindle of the minimill. Motive power will come from a small NEMA34 stepper...

It should be OK as long as it can drive the square section of the tap. A normal collet will slip as the tap gets larger and material gets stronger I.e. M10 in mild steel needs a very positive drive.

Sure, first off with large taps you really need a dedicated tapping chuck. Set the machine in to tapping mode, select low gear and slowest spindle speed. Experiment in free air with the quill down...

After upgrading from my minimill to an Optimum BF30 mill and doing the cnc conversion, I have been debating what to do with the minimill. Sell it? keep it as a mill? Hmmm. I have also been looking...

This is a bit of a sad follow up to this thread. The high speed spindle has been used in anger to create a memorial for our old cat who passed away recently. I ran a carbide engraving bit at 11krpm...

Yes their website looks like they only supply large quantities but a telecon revealed that they will supply small lengths of material. Guy on the phone was very helpful.