CNC Arboga U2508 Mill Conversion

[Swarfing]

Hi Geoff the short answer is yes and it is not the easiest conversion on the planet if you want to do it right. There is not a lot of space for 20mm ballscrews under that table. I've dumped the gearbox on top and going for two speed direct drive on VFD. Expect to do a lot of machining of the table. Not really a job unless you have access to another mill. I have had to build a complete new inner spindle to give tool release (it will accept R8 as well).

The project has been on hold for a while due to other circumstances, i will get back to this thread properly as soon as i can.

[Swarfing]

About time for an update and a drip feed of pics. Tonight I finished rebuilding the spindle for this machine in readiness for the Poly v pulleys i need to make. I dumped the original inner and used an old spindle from a lever lock collet closer. I re machined it to take new bearings and machined it to use R8 tooling (before you ask why?....i have loads of it already). I ended up with a 28mm id bearing on the top and needed a lock nut, apparently they don't do them? So i ordered a 28mm x 1.5 pitch hub nut for a citron/ Peugeot that fitted the bill and sunk a capcrew in the side and slit it. It locks lovely



The next job is to make the pulleys and machine the rest of the spindle so it all looks good.

[Swarfing]

Another pic of the R8 end

[Ross77]

What size and type bearings did you use if you dont mind me asking? Still collecting info for my spindle project and its good to build up a data base of existing arrangements.

You are probably aware but the pinch bolt in the top lock nut could cause vibration and imbalance at high speed, since you mentioned vfd I'm guessing you are looking to increase top speed? If not ignore my comment

[Swarfing]

Hi Ross

The lower bearing is 35 x 62 x 18 and the top bearing is 28 x 52 x 12. I've left enough room to double the top bearing should i need too. It's all about making things fit, it does not work out then i shall build a complete new spindle and housing. The locknut should be fine as used that arrangement before on another project. It's all heavy duty so will have to see how it works out. Just made a new adjustable burner for the furnace, so will get some Ali blanks cast at some point this week to make the pulleys. I can then start getting the motor mounted etc.

[Ross77]

The locknut should be fine as used that arrangement before on another project.

Fair point, just seems a shame to do all that work and then risk an imbalance problem

Cheers for the bearing info, are they AC or deep groove?

lastly why would you want to put 2 bearings at the top? most of the cutting force is in the lower bearing, hence the lower one being bigger.

Cheers

[Swarfing]

The top are just deep groove, having two just helps with stability. As for the nut i could always replace that without too much effort. Thamesdown bearings said they could get me proper locknut but only on as a special order for a ton of money. I will learn a lot more from what does not work, i'm happy to just plod along

I did my casting today for the pulleys as one of the kids had a teacher training day. I had the first pulley on the lathe tonight and ruffed out. Need now to switch to the 4 jaw for the finishing cuts. Before i can do that i need to make a new mount for the lathe theres always one more job that gets in the way......

[Ross77]

Hi Swarfing, apologies I seem to have ended up critising your design when you didn't ask for help. duh

I just have an inquisitive mind and when I see something different I have to ask just in case they know a special trick

Based on what I have read from other threads I think you might have problems with using deep groove bearings preloaded against AC, but I wont mention anything about that.

with regard to the lock nuts can't you just get 2 more of the wheel nuts and face them down to 4/5mm thick on your lathe?