Hello all. I've been lurking here, well, for years actually. I'm a woodworker for the most part, but also do some metal working for various projects. I have a bridgeport clone and a south bend 9" that is in various stages of reconditioning. I also have an old 22" Voest that sorta scares me to death...

I used to work with a chair maker who built his own huge cnc router, and I found the idea of building your own machinery fascinating. That was years ago, and since then I've spent a great deal of time reading the posts here, collecting random parts, and have finally decided to plunge into a small build. I figure that materials and components are relatively inexpensive and abundant for a small machine, making this a good learning experience. Y'know, before I get to work on the 5-axis gantry router I'd love to have ;)

I've decided to get to work on a small CNC mill, and would rather start from scratch rather than convert a chinese mill. My intent is to roughly follow the same build on 5 Bears website (www.5bears.com/cnc.htm) because I happen to have access to some heavy extruded aluminum columns and somewhere in one of these boxes I have an assortment of THK HSR25 & 30 linear bearings and rails. I also have a new set of Keling 382oz/in stepper motors that I acquired last year and I'm hoping the G540 drive will poke it's head into the market soon!

I need some spindle advice however. I've searched this forum over and over, and it seems like the search leaves me even more confused. I have the majority of the build figured out, roughly, but don't really know what I need in a spindle and motor. I'm not certain what size or speed I need, what type of controls are required, etc. My intent is to use the machine primarily for brass, and primarily small parts, hinges and whatnot. I build custom furniture and it's not unusual to have to make a custom set of knife hinges or tansu drawer pulls. Usually I make such hardware by hand, a timely process. In the past I've used bronze, aluminum, silver, and occasionally cast iron or mild steel, so I need this machine to be beefier than an engraver, but due to the small runs of parts I don't exactly need a 50,000rpm production oriented machine.

Also, and excuse my noob ignorance, but why does a spindle motor require a controller? Why not just a step pulley like a larger machine?

Any help y'all can send along will be much appreciated!

Also, and excuse my noob ignorance, but why does a spindle motor require a controller? Why not just a step pulley like a larger machine?

Any help y'all can send along will be much appreciated!

Most are replacing the stock motors(single speed/step pulley) for variable speed motors which require a controller and pot to adjust the speed.

Looking forward to watching the build....

Cheers,
Jack

Right, that makes sense. I suppose spindle motors are typically DC then?

Depends how big the mill is. If it's tiny, DC is easy, I use a DC suds pump with a speed controller. If you have any size an AC motor is best, but without a zero crossover switch it can occasionally pull the mains circuit breaker if you switch on with your pulleys set for speed. That's a real pain if the computer is on the same circuit.

I think the best big solution is a digital phase converter, that way you get full power from slow to twice normal speed, soft start and braking, plus, you can set the speed from within the G code. OTOH the motor may need another motor to keep it cool when you run it slow.

The spindle is tricky, needs to have a taper inside for collets and chucks. A good reason to start with a non-cnc mill then convert it.

You can get ac controllers too. A lot of people use an ac controller to control a 3-phase ac motor from a single phase circuit.

Hopefully somebody who is smarter(electronics) then me will chime in here and help explain.

Jack

Depends how big the mill is. If it's tiny, DC is easy, I use a DC suds pump with a speed controller.

I think the best big solution is a digital phase converter, that way you get full power from slow to twice normal speed, soft start and braking, plus, you can set the speed from within the G code.

Ah yes, my Bridgeport has a Hitachi VFD, which I initially installed because I lacked 3 phase power, but it has proven very handy for speed control, braking, and acceleration/deceleration.

Without running any calculations, I would say I'm looking for 3/4 to 1 HP, 5000RPM tops. So if I have a 1.5HP, 3500RPM motor, and a 2:1 pulley setup I could control it with a VFD...

Any thoughts on the feasibility of buying a super X3 spindle from littlemachineshop.com and machining a boss for it? Obviously this would be an R8 taper, would it be more wise to pursue a spindle with a different taper? I remember looking into the Tormach R8 system, it looks like it's much more repeatable than standard R8 collets.

I saw a router build a while back with a X2 head on it. I believe was bought through LMS.

Whiskeykid,
Take a look at LeeWay's Thread #32609.
He used a lot of 80-20 with quality Linears & Screw's.
His thread may give you some idea's.
Good luck!!!

Instead of trying to modify a complete headstock, especially if you are already planning on replacing the mount and the motor assembly, you might look into just getting a cartridge spindle (its basically just all of the spindle guts self-contained in a tube, aligned, pre-loaded, and ready to go. There is usually a pulley shaft on one end and collet nut on the other). Mount it to the Z with a simple clamp and go. After that you can very simply build whatever type of mounting system and boss you want, and whatever motor. A lot easier than having to modify and use an entire head assembly casting off something else just to get the spindle guts, especially something like an X3 which has a whole lot of extra (and heavy) stuff you won't be needing like the quill.
I recently went to using a Hitachi VFD for one of my spindle motors, and it is extremely handy, especially as it is easily controlled from software. Haven't had it installed for long now, but I haven't had any complaints at all yet and will likely do the same thing again.

Instead of trying to modify a complete headstock, especially if you are already planning on replacing the mount and the motor assembly, you might look into just getting a cartridge spindle.

I've been thinking along these same lines. I was considering building the cartridge around an R8 spindle from a super X3 machine, but am definitely keen to buy one pre-built if it's reasonably priced. As far as motors go, after reading some similar posts I ordered a 2.5 hp, 10,000rpm dc motor and a suitable controller from surplus house. It was cheap enough that if it turns out that it's underpowered I can find something else, chalk up the motor and controller costs to 'R&D'.

I've also started building the table. I looked at salvaging a cast table off a small mill or a cheap XY drill press table, but decided to mill my own from a piece of 1" mild steel. I'll post some pictures when I'm a bit further into it.

Does anyone have any ballscrew sources? I'd like to stay away from rolled screws and the pickings on e-bay seem to be thin. I'm thinking about 16-20mm diameter and one each of 24", 12", and 8" of travel.