[Adam Baker]

Im looking for suggestions on what to use for a spindle and motor. Its looking strongly like Im going to probably build a CNC from scratch.

I think my chances are pretty good on being able to score linear bearing rails and ball screws at work, so I think it would be better for me to build my own instead of spending the money on a manual system and converting it.

So b/c of that, Im going to have to find a spindle and a motor to use in my build. I suppose its possible that I might be able to get one from work too, but Im pretty sure that anything they might have at work, would be extreme overkill and just physically too large to work w/ what I would want or need.

The vast majority of the work on the machine would probably be aluminum w/ occasional brass & copper. It might see an occasional steel job, but that would be rare, b/c of what I have in mind for the machine.

Milling, Drilling and Tapping obviously would be the operations run on the machine, so that would need to be kept in mind. I dont imagine I'd need more than 2-3k RPM's since most of the tooling is likely to be smaller, 1/2" mills and smaller. Occasionally might see larger boring using boring bars and such, but I wouldnt expect it to happen often at all.

[fatal-exception]

A large servo motor/driver/encoder combo works well for me, and is fully controllable through mach3. I've geared it up so that I have about 7k rpm at the tool.

Paul

[Adam Baker]

Hmmm, that might be something I could get from work then. They use pretty good sized motors to run the axes' on the machines they build. I'll see if I can get a picture of one when I go back to work on the 4th.

[serriadh]

I dont imagine I'd need more than 2-3k RPM's since most of the tooling is likely to be smaller, 1/2" mills and smaller. Occasionally might see larger boring using boring bars and such, but I wouldnt expect it to happen often at all.

Remember that for a given spindle speed, small diameter tools have a lower surface speed than larger diameter tools. Because you're not cutting materials that need low surface speeds (ie, steel or cast iron) you may want to be looking at 6-10krpm spindle speeds rather than 2-3.

[Hans_G]

A large servo motor/driver/encoder combo works well for me, and is fully controllable through mach3. I've geared it up so that I have about 7k rpm at the tool.

Paul

What size motor are you using, and for what type of machine? I'm considering upgrading to a Nema34 (660W) BLDC motor from Keling as an upgrade for my Sherline spindle, geared 2:1 to get 6krpm. thanks.

[Adam Baker]

Yea, your right. For some reason I was thinking smaller tools needed lower RPM's, but thats backwards.

Remember that for a given spindle speed, small diameter tools have a lower surface speed than larger diameter tools. Because you're not cutting materials that need low surface speeds (ie, steel or cast iron) you may want to be looking at 6-10krpm spindle speeds rather than 2-3.

[Starleper1]

Just throwing it out there but I retro-fitted an X2 head onto my custom mill. I get 4500RPM at full speed with my belt drive kit. I've yet to find an issue with this setup. Its a cheaper solution but still effective.

[serriadh]

Oh yeah, if you're in the US, its easy enough getting an X2 or X3 head from somewhere like littlemachineshop. Not so convenient on the other side of the Atlantic :-/

You could also get a sherline ER16 spindle relatively cheaply almost anywhere and power that with your own motor/beltdrive. In theory those things are good to 10k, though that's probably pushing it a bit.

You probably don't want a router, though. General consensus seems to be that they're pretty noisy, don't have great runout, and probably don't have great bearing life either.

[rc-monster mike]

The Sherline spindles are great, rugged little units(aside from their mounting strategy). Once properly affixed, they are good for 10k+ rpms and quite rugged and true for their size and weight. X2 spindles are a bit larger/beefier units and are also a great value - for 1/4" smaller tools and higher rpms, the Sherline gets my vote - if more work will be done with larger tools, the x2 head is likely the better candidate.

[Adam Baker]

Is it possible to buy just the head for the X2? Unfortunately the machines we build at work dont have spindle heads on them. We build Grinder, Laser Welders & Water Jet machines, so I cant get one there.

[rc-monster mike]

http://littlemachineshop.com/product...ory=-269978449 - r8 head

http://littlemachineshop.com/product...ory=-269978449 - MT3 head

[Adam Baker]

Thanks Mike. I looked and they sell the entire head w/ motor for 299 which I could do.

Im not overly familiar w/ the tooling, which one is better/ larger number of accessories available?

[rc-monster mike]

I think most people go with the R8 setup - R8 tooling is fairly cheap and easy to come by. If you use a Tormach style tooling strategy(recommended for ease of use), then either is as good as the other - the Tormach style tooling uses a 3/4" modified collet, which is also available at LMS for either spindle. I use the R8 currently, but also have the MT3 head(may swap some day). The MT3 version has a shorter spindle(protrudes less from the bottom of the mill head), which moves the cutting tool almost an inch closer to the spindle bearings, and also will move the whole head almost an inch lower on the Z axis when cutting a given part - should theoretically increase rigidity, but is generally good practice anyways. The mill heads are identical aside from the spindle and upper bearings, so either one is fairly easy to "swap out".

[serriadh]

I'd be tempted to go for R8... both tapers have a fair bit of tooling available for them (especially on ebay, where they are very common), but I vaguely recall that R8 is easier to eject than MT, facilitating quicker and easier tool changes.

I can't actually provide any links to back that up with, however.

[Adam Baker]

Ok, next question then. Eventually I plan on building an automatic tool changer similar to what Hoss as built, and would have a power draw bad to facility the tool change. Is either of the options easier to do that w/?

[rc-monster mike]

R8 tools eject more easily than MT tools, but if you are planning a power drawbar/tool changer like Hoss's machine, then you would be using a Tormach-style system. In this case, tool ejection from the spindle is irrelevent, as the modified 3/4" collet stays in the machine spindle during tool changes - either style is likely just as good as the other.
I have only used the R8 version myself thus far(with power drawbar and Tormach tools), but the MT3 spindle/mill head would theoretically function exactly the same. The only advantage I see to the R8 would be on the occasional(if such occasion exists) use of tooling OTHER THAN a Tormach style, as R8 tooling is generally more accessible. Having said that, I don't own any R8 tooling myself. I only use the Tormach style tools that work with a power drawbar.
I have actually considered switching to the MT3 head simply because the mechanics seem advantageous - the shorter spindle puts the head lower on the Z axis during cuts and also puts the tool closer to the bearing, as mentioned previously. I also found a set of AC bearings rated to 15k rpms for the MT3 spindle head for pretty cheap, while the R8 uses a different lower bearing that is difficult to find in AC style(without giving up a body part in exchange).

Sorry for the rant - the short answer: either style spindle should work just as good as the other with a power drawbar and Tormach style tooling strategy.

[Adam Baker]

Thanks for the info Mike.