Sherline or mini-mill spindle?

[AK_Five-O]

I am looking for advice on spindle selection for a DIY CNC router / mill. I mostly am looking to mill aluminum, but would also like the ability to work with steel, wood, and plastics. To me, accuracy is more important than speed. I see many people construct a DIY router / mill using a traditional "hand router" but after doing much research that is not the direction I want to go. I initially set my budget at around $1000 for this project, but am willing to spend a bit more for better results. That figure does not include the computer or monitor.

Please correct me if I am going about this the wrong way, but I would like to select and purchase the motor / spindle first, then design the rest of the machine around that. The two that I have found that may not completely blow my budget are the Little Machine Shop mini-mill spindle box assembly and the Sherline Industrial spindles. I am leaning towards the Sherline because of the greater RPM range (10K) with a slightly looser preload setting. The LMS spindle just looks cheap.

Is cog belt drive preferred over V-belt? Is the #1 Morse (same as R8?) preferred over ER-16? As far as the motor to drive the spindle, I would like to stay with a 120VAC source as I don't have 240VAC into my garage but could add it if needed. Are there any load calculations to estimate motor and pulley sizing? Does anybody have any suggestions for a particular motor, or specification range?

One snag is that I don't currently have access to a lathe or mill. I do have a nice drill press and can weld and cut aluminum. For those reasons 80/20 is attractive but I'm sure deflection is it's downfall, especially cutting aluminum / steel...right? Thanks a bunch.

[microcarve]

A mini mill head will need a very strong welded steel frame...some
expensive linear rails....and likely very high quality ballscrews with
zero backlash. Along with some very strong motors with high holding
power.

If you were to put a 6" long 3/4" rod in the mill head and using it as
a handle.....if you're able to push/pull on it and you get any deflection
at all anywhere in the machine, that'll be a sure indication that you'd have
so much chattering as to make metal milling useless. It takes extreme
amounts of force to use those milling heads at their lower speeds.

I'd go with a router like everyone else and just take it slower and easier.
That's proven to work on a well built, tight machine....which is *maybe*
do-able within your budget.


John

[corderbo]

I have to agree with John's post. When it comes to the harder materials and accuracy, weight and rigidity are the prime aspects required for the successful machining results. Unfortunately, with respect to a machine of this caliber, cheap equates to vibration, chatter, material 'push off' and a variety of other results that will leave you unhappy and I guess this is why standard sized lathes and milling machines need a fork lift to move them. Sorry...

[DonFrambach]

I would also consider a Taig spindle. I'm putting a Taig spindle on my DIY router. The "CNC" Taig spindle has a motor rated for continuous use and I've done more than 24hr runs with the Taig on my metal mill. The Sherline motor gets pretty hot. I've used both the regular speed and the 10k Sherline spindles and feel the Taig is much better for CNC. Even when the preload is adjusted my Sherline spindle also got very hot at 10k rpms.

I made a mount that will accept Taig as well as other spindles. You might want to consider that too.

BTW my router is small with a fixed gantry made mostly of 8020 extrusions. It seems fine to cut aluminum have not tried steel.

some photos:

[AK_Five-O]

The pictures DonFrambach posted are similar to what I am looking to build. I would like a machinable area at least 2' x 2' and the fixed gantry makes a lot of sense structurally I think. I had not looked at the Tiag spindle before....is this the correct one - "200-00ER Complete headstock with ER Spindle $117.50"? That was from the Tiag Tools web site. Is that a dovetail mount? Does someone make an adapter that will fit it?

Thanks for the responses about using a router. I do have one of the larger Porter Cable routers mounted in an inverted router table I use for wood. I could always use this as a backup I guess, although as I said before I want to stay away from that if possible. I don't think I will have a problem building a strong frame, the issue may be the rails and such.

[DonFrambach]

Yes that's the spindle that I'm using (ER-16). It has a dovetail mount. Taig makes a mount. I also have the Taig motor, pulley's, mounting post and mounting plate . I bought my parts from A2ZCNC.com. Here's a linke for the Taig accessories at A2ZCNC.com: http://www.a2zcorp.us/store/Category...Accessory+Mill

Here's a link for the Taig spindle mount:
A2Z Corp E-Commerce Store

[AK_Five-O]

Thanks! Is there an advantage or disadvantage to the ER-16 system versus the R8 or something else?

[UUU]

The ER16 system works very well - it grips the cutters just fine. The disadvantage over an R8 or similar is that when you change tool on the ER16, you'll have to re-zero your Z setting. Unlikely you can get the tool to sit in exactly the same place every time. On an R8, or similar, you could have several tool holders (gets expensive) so you can pre-measure the z-offset of all the tools for a job and then just swap about as the job proceeds.