[jimbo]

This is kind of long, but here goes.

I putting together parts for a mill using the r8 mini mill spindle. Uses linear slides instead of dovetails. Expecting to have 20"X 10"Y 12"Z travels. I am planning to modify the spindle to use a belt drive similar to jfettig's setup. The spindle motor is 0.5hp 3 phase AC motor with a 1.6 service factor, will control it with a VFD drive and run the motor at 0.8 hp for a 1.0 service factor. Plans for spindle rpm are 3000-5000 rpm.

Intended use is cutting variety of aluminum parts. No plans for steel parts.

Below is the progress so far. How can I make this more rigid? Just kidding. This is a mockup just to get a feel for size and travels. The bottom and vertical pieces (the chipboard pieces) are going to be 2x8" steel tubing with 0.25" wall thickness). The table surface and the part joining x and y together are going to be 1" thick steel plate milled flat. The vertical supports will be 1/2" aluminum with several cross braces. The rest will probably be misc aluminum plates.

Some questions:
1. table surface is 30"x10"x1" thick. I can get this at Misumi for $160 for 1018 steel, flat to <0.05 mm per 100mm. See http://www.misumiusa.com/usacatalog/...tric/p1421.pdf. Are there cheaper alternatives? Is this an overkill? Can I put a cadmium coating on it to prevent rust?
2. A big question I really havent worked out is the part holding, I could have a series of threaded holes or make an aluminum tslot plate that bolts over the steel. The threaded holes will allow contaminates to pass through the table.
3. do I need the ability to lock the table? How would I do this with the linear slides?
4. Are linear slides okay for this application?
5. I am planning about 12" z travel, is this adequate for most uses? Shown is a 4" vise. I have plenty of room to take out the r8 endmill holder. Otherwise I can move the table away from the spindle to get more room.

I would like your critiques, please.

[ViperTX]

How accurately do you want to mill the aluminum stuff that you plan to mill.....what size are these pieces usually? I'm asking because your table top has a variation of about 0.020 for every 4 inches ....do you plan to mill it flat? I'm not sure that cadimum plating is the way to go....check with your local plater....I believe that it will not electroplate as well as using chromium.
What is the travel of a mini-mill? You might consider using that as your base.

[balsaman]

What sort of tools do you have?

Eric

[Torsten]

I noticed how close to a Mill/Drill Dovetail Machine this is.
24" x 9" x 18" envelop, start at about $1400.00.
Have you done some comparisons build versus buy.
Dovetails versus Linear Rails may need slightly bigger motors to push.
Overall weight concerns?
You may find a few modifications to a bought solution would give you
a better overall value.
Good Luck

[jimbo]

viper,
Originally it wasnt intended to be this big, I was going to use a chinese cast iron xy table found on ebay, with about 11" x 7.5" travels. But I was afraid it was going to be junk. The travels of the mini mill that this spindle came from is even less than the xy table. It seems it would be difficult to work with a small table. Another thought was to take the base of a chinese round column mill along with its xy table and adapt a square column and spindle to it. As for the steel plate, I made a mistake when typing, it should be <0.05 mm per 100mm. So it is .002 over 4 inches, still not super. Any better ideas? I will correct the first post. And cadmium was just a thought.

Balsaman,
I have all woodworking tools and a old metal lathe that needs a new drive belt. No access to a big mill. I may be getting in over my head, the plan was to purchase the plates already flat and drill/tap holes for the slides.

torsten,
You are right, I had forgotten about those. I looked at the lathemaster one, and the size is pretty good. One issue I have is the spindle speed, <2000rpm. Will this be an impediment? I expected to have less than a thousand in my setup, this is with a much lighter spindle and less mass. For $1400 I could also find a used bridgeport. I should probably think about this a bit more. Do you have one of these sqare column mills?

[ViperTX]

Just my few cents:
IMHO you need at minimum a mill with assorted tooling. A lathe will also help.

Without those tools you'll most likely need to have the other stuff machined for you. Things like the ends of the ballscrews / acme screws, bearing housings for the ends of the leadscrews...so unless you know a machinist this will be costly. Some time back I tried to have some stuff machined....minimum charge was over $100....I had a simple delrin piece with 4 holes ($114) and I supplied the delrin...and the specs for the holes and the size of the plate were so loose.

Since then I've acquired a Rong Fu 30 and a Lathemaster lathe and I'm still collecting tooling. I chased old American Iron for 6 years...most was well worn the rest was overpriced...I live in Texas and machinery is not as readily available as in the Northeast.

[jimbo]

that is good advice. I have come to the realization that the lack of a milling machine has been a big obstacle. I hate the idea of buying chinese since nearly everything is made there. But it is in a size that is convenient. I know where 3 bridgeports sit, one is clapped out for $800 and the other two are $1800-2000, with redone chome ways. But they are going to be difficult for me to move.

[ViperTX]

jimbo,

Check with a rigging company...I believe most will charge about $400 it will save your back, trailer & lift truck rental...I'd opt for the bridgeport that has been factory rebuilt unless you can run some basic tests on the others. Negotiate for tooling with the bridgeport...they are selling it for some reason.

Check out http://www.makeitsimple.com check out the Metal working suff under Sections....he shows some nice ways to move the heavy stuff around the shop (which is another problem).