What to look for when buying a milling machine.

[Apples]

After a milling machine that can do good clean accurate cuts. Somthing around the 3-5hp area.

What do I look for when buying one, either new or old?

dovetail ways of box ways, box are stronger???

R8 30INT I beleive or 40INT, should be stronger???

ETC etc.

Cheers
Peter
Australia

[Caprirs]

Depends a lot on what you intend to cut. Can you give some ideas about your application? Is tool change time important? What materials will you be cutting? How much travel do you need? Can you service the machine yourself?

A job shop doing small aluminum parts can run lightweight Haas and similar machines with linear guides. By contrast, someone in a mold/die shop working heavy chunks of steel would be better with a heavy box way machine. There are lots of different machines because there are so many different applications.

[Apples]

Well I guess you caould say that I'd be after a high end hobby machine. Something bigger that a Tormach. There is a tread on here about a bloke from Australia as well who has a HAFCO brand knee milling machine. But I think he said that there was a bit of slop in it.

So I'd be after something a bit more rigid than that. Apparantly that model has a R8 which I think is a 30INT. I was also speaking to a machine shop in town who said that his machine is just really a great drill press.

That is why I be after something a bit stronger than that size, which I think will be the next size up with a 40INT taper?

What do I want to use it for? I'd like to be able to knock up some small CNC machines as a sideline hobby thing. I did make a CNC plasma table ages ago, which I have a thread on here as well. It was only made with common tools.

I did not have a milling machine or lathe to use and thus the quality was not that great.

In particular I'd like to be able to fly cut or face mill a length of hot rolled box or flat steel to make both sides parallel to run bearings on as a rail for x or y etc. Another issue here is the bed on a mill might be only have 3-4ft travel but my rail will need to be 4,5,6ft long. In this case It might just be easier to take it to a machine shop as it will need to be milled, flame hardened and then re ground for accuracy.

It would be nice to do as many jobs at home as possible.

And one last thing, I'd probably look at doing a CNC retrofit on it as well.
Either an old mill or new mill. An old mill would be cheaper if going to CNC myself. What wears on an old mill?

Peter

[Caprirs]

Other than the rails you intend to make, what is the next biggest part you might run? If you only need the long travel a couple days a year, it might be better to out-source that portion of the job. At 6 feet, you'd need a big machine.

(If I'm wrong on this part, hopefully someone will correct me.) R8 is different from 30 taper and 40 taper. Further, for 30 taper, there are NMTB, CAT and BT toolholders. Same for 40. R8 is what is most commonly seen on Bridgeport-style knee mills. The 30 and 40 taper tools are similar to what is used on VMCs like Haas. There are some knee mills with 30 taper spindles.

Benchtop machines that would be stouter than the Tormach although not much bigger are the old Dynamechtronics 2800/2900. They would be ideal for a newer retrofit. Travels would be about 10" x 7".

To go bigger, you either get something like a router table or a full size bed mill or VMC. The router table would have a lot of travel for the money, but little rigidity. A bed mill or VMC would be offer better rigidity and accuracy with only a small increase in travels over the benchtop mills. A router table with 48" x 48" travels is cheap compared to a VMC with that much travel in the Y axis. A small Haas or Fadal might have 20" x 16" travels.

Everything wears on mills. Wear is dependent mostly on the maintenence of the machine. Even the most expensive VMCs can be trashed in a short time if an oil lube line clogs or breaks and starves some portion of the machine of lubricant. Also, careless operators can repeatedly crash the spindle nose into the table throwing the machine out of square and beating up the spindle. Spindles can require rebuilding if they have been run near their max rpm for an extended time. Ballscrews and the end bearings that support them get contaminated with coolant that washes out the grease. Tool changers are assured of wear since a job shop may have the machine changing tools every 15 seconds all day long.

[Apples]

These are the machines I'm looking at.

http://www.machineryhouse.com.au/sample_2/home.php
and
http://www.machineryhouse.com.au/sample_2/home.php
and
http://www.machineryhouse.com.au/sample_2/home.php

You can click on the pdf icon to see better image.

Yes, out sourcing the odd longer job might be the go, at least you know it will be done properly.

I have 3 phase and a dedicated shed for the equipment so space is not really an issue.

I guess that I'd be needing to mill up to 3ft anyway, so a 4ft table would be the go.

Another question. Flood coolant, will that stuff the ways and ballscrews etc. There must be some kind of anti rust in the coolant I assume.

How do you enclose the bed of a mill for recycling coolant, woun't it go underneath the table and get the ballscrew etc.

Peter

[Caprirs]

Do you have more specific links? All those just show the home page.

Having three phase power and space is huge hurdle for a lot of hobbiest. You are ahead already.

Coolants vary with application. In typical use for general metal cutting, the coolant is about 90% water and 10% coolant. Like a leaner mixture of the anti-freeze in your car. The added coolant contains corrosion inhibitors so the machinery parts do not get damaged. Certain metals can stain from certain coolants but those are exceptions, not the norm.

I run a full synthetic coolant with 90/10 mix and change it once a year. A 5 gallon bucket of coolant costs me $100 and provides enough to mix up both my machines for that year. Because the coolant is low volatile, only the water will evaporate with use. Just keep topping off with water. Periodically, use a refractometer to check concentration and add a little more coolant to keep the mixture high enough to prevent corrosion. Disposal involves calling a waste oil company to come get the used stuff. That costs $100 but keeps things clean and enviro-friendly.

Enclosures are pretty standard on VMCs made in the past 20 years. For open knee and bed mills, there are pans that attach to the base to collect the run-off. For example, see http://www.americanmachinetools.com/...S_Bed_Mill.jpg

Once you have an enclosed machine with flood coolant, you will be unwilling to work with anything else. You get spoiled quickly.

[Apples]

Silly links...click on metalworking, then look for the "Mills turret 30 and 40"

You say I would be not wanting to work with anything else if I have an enclosure and flood cooling, Why? Is it simply the best?

Does the flood cooling give the best possible finish etc.

Peter

[Caprirs]

Flood coolant provides the ability to do everything better. The lubrication and chip flushing attributes are the main benefits. Soft metals don't stick to tools even in deep high rpm cuts. Tools last longer. Form/roll taps don't gall. And, yes, surface finish is often better.

The enclosure means you can run the spindle at max speed and the mess won't go far. Cleanup is easy.

I'm also spending your money pretty easily here. I just think used CNC VMCs and CNC bed mills can be a great deal if you do some homework and shopping. The hobby machines are neat but have a lot of compromises.

On the other hand, the hobby machines are a lot more travel for a lot less money. They are often easier to learn to use and much easier and less expensive to repair.