Choosing the basis for a small CNC mill

My first post on this forum - did some searching but didn't find the suggestions I was looking for so here is my (hopefully not redundant) question:

Applications - small parts - up to 3" X 6" X 1" in brass and aluminum (occasionally mild steel) for working model racing cars - tolerances are not tight, +/- .001" generally works - mostly linear cuts with 1/32" - 1/8" end mills

Current tools: Unimat PC lathe with Unimat CNC fitted, Grizzly Sieg X2 with inch screw conversion and DRO (helps with layout and compensates for aging eyes)

Motivation: - Went to the "Cabin Fever Expo" last week and was intrigued by the CNC mills on display - like the idea of doing two things at once!

Will probably buy motor mounts and might invest in upgraded screws - will buy or build drivers and am currently leaning toward Mach 3 software

So - after all that, here is the question: I've looked at 3 mills as the basis for the system and see +'s and -'s for all - looking for comment or suggestions:

Sieg X1: (+) - sturdy, cheap, motor mounts available, solid column mounting - probably the most stable (-) - getting high speeds appropriate to the cutter size is an issue, heavy head with offset screw presents problems

Taig mill: (+) variety of conversion hardware available - large screws, high spindle speed off the shelf (-) single bolt column fastening, spindle limitations - either a threaded spindle (questionable for high speed) or the ER16 spindle useful for collets only

Sherline mill: (+) variety of conversion hardware available, many sources, (-) limited spindle speed off-the-shelf, single bolt column fastening, (relatively) expensive.

[I]At the moment[I], I'm leaning towrds the Taig but am very much in the learning mode.

comments and suggestions would be greatly appreciated

Thanks

EM

EM,

Any reason not to convert your X2?

Later,
Tim

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Originally Posted by Tim Wiltse

EM,

Any reason not to convert your X2?

Later,
Tim

Actually a couple - some spindle speed limitation - I have the Little Machine Shop belt drive conversion but that still gives me only about 4000 RPM - I'd have to re-do my DRO set-up that I use fequently for one-off precision drilling operations and/or just a handy drill press.

thanks

EM

Hey There,
If you do decide to cnc your X2 this could help.
http://www.cnczone.com/forums/showthread.php?t=30385
I'm in the process of adding a dewalt laminate trimmer attachment as well.
I'll get 30,000 rpm and it has a 1/4 collet to handle plenty of tooling options.
I'll post it soon.
Later Hoss

Quote:

Originally Posted by Pretorien

My first post on this forum - did some searching but didn't find the suggestions I was looking for so here is my (hopefully not redundant) question:

Something new always has the possibility of turning up.

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Applications - small parts - up to 3" X 6" X 1" in brass and aluminum (occasionally mild steel) for working model racing cars - tolerances are not tight, +/- .001" generally works - mostly linear cuts with 1/32" - 1/8" end mills

The occasional mild steel bothers me. If you really intend to work with steel I think you will be better off in the long run with a larger mill. Of course with CNC you can set the mill up to take almost an infinite number of small cuts. So that is good but the other issue is being able to set the right spindle speeds and have the right power available at those speeds for steel.

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Current tools: Unimat PC lathe with Unimat CNC fitted, Grizzly Sieg X2 with inch screw conversion and DRO (helps with layout and compensates for aging eyes)

Seriously if you have a X2 why not get another one for conversion to CNC? This way you end up with common parts, common work envelopes and common tooling. Nobody in this world says that you can't have two of something.

The other side of this is that the X2 is not significantly larger than the other machines you are considering. Well at least foot print wise.

The big negative is the spindle speeds in the ranges you may need.

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Motivation: - Went to the "Cabin Fever Expo" last week and was intrigued by the CNC mills on display - like the idea of doing two things at once!

Spent some time there my self. CNC is very interesting to me also as I use to play with such at work. That is gone now but my goal is to build up a CNC machine.

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Will probably buy motor mounts and might invest in upgraded screws - will buy or build drivers and am currently leaning toward Mach 3 software

I like what I saw in Mach3, but it isn't the only game in town. Many people are making use of EMC.

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So - after all that, here is the question: I've looked at 3 mills as the basis for the system and see +'s and -'s for all - looking for comment or suggestions:

Sieg X1: (+) - sturdy, cheap, motor mounts available, solid column mounting - probably the most stable (-) - getting high speeds appropriate to the cutter size is an issue, heavy head with offset screw presents problems

The spindle speed issues can be overcome with a little work. At least to some extent. At the small sizes you are working with I doubt you will reach ideal speeds though.

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Taig mill: (+) variety of conversion hardware available - large screws, high spindle speed off the shelf (-) single bolt column fastening, spindle limitations - either a threaded spindle (questionable for high speed) or the ER16 spindle useful for collets only

Of the really small machines I think the TAIG strikes the best balance, of capability, features and stiffness. As to the ER16 spindle I see that as a very positive thing for the TAIG and is one of the reasons I looked towards that machine at first. The only taper that really offers up an advantage is R8 and that is really only suitable for lager mills. It is not like you are going to mount a huge boring head on a TAIG, or for that matter any of these micro mills, and get good results.

By the way the ER16 spindles does not force you to make use of collets. You could turn your own arbors and make a suitable nut. The question in my mind is what would you mount on it. It is not like you will be able to make good use of a full size Jacobs Chuck and jobber length bits.

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Sherline mill: (+) variety of conversion hardware available, many sources, (-) limited spindle speed off-the-shelf, single bolt column fastening, (relatively) expensive.

Sherline certainly has a nice system, though somewhat light for my tastes. The good thing is that they can sell you a machine with a CNC controller (EMC) ready to go.

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[I]At the moment[I], I'm leaning towrds the Taig but am very much in the learning mode.

That would have been the way I went if I had convinced my self to go the micro route. Instead I will take the time to think a bit with the goal of getting a larger machine for my first mill. Obviously we have slightly different goals. I'm looking for something that can handle steel well and a larger working area. The trick in my case is being able to move it into my cellar.

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comments and suggestions would be greatly appreciated

At the hobbiest level, every machine is a huge compromise with respect to the spindle. You might seriously want to consider two spindles. One for high speeds and one for torque. The imports suffer from poor spindle bearings and a lack of speed range. The US made machines have significantly lighter spindles, though in this case I don't see it as a problem for you.

Leadscrews are important, this is almost like stating the obvious, so you need to consider the adjustability of the nuts, and potential future replacement with ball screws. Even if you don't make use of ball screws initially I would not invest in a machine that could not be easily upgraded to ball screws in the future.

There is something to be said for a canned system. That is buying a machine already set up for CNC. Of course that takes a lot of the fun out of it.

There is a very real possibility on the imports of having to rework the ways and such. I've gotten mixed messages about how bad the mechanics on these machines can be. Equally though I've gotten comments from people indicating that they have never seen a need to touch the mechanics. Just realize that people see these small imports as kits, that may or may not be justified but is something to keep in mind.

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Thanks

EM