Mill/Drill Tips
- Tip number one is don't buy a mill/drill! Save your pennies, scour the used market, but try like heck to
buy a mill with a knee. There are some inexpensive imports, or you can look for a used Bridgeport. There are
also some other quality mills that are lesser known like Tree and Hardinge (usually known for lathes). If you
can get a mill with a knee, most of the other mill/drill tips here will prove unnecessary. If you have to get
a mill/drill, try to get the heavier model. It's often known as a #30, like my Grizzly G1006. It's probably
best to avoid the power feed options unless you really need them- less to go wrong.
- Disassemble the table section of your mill/drill and break all the sharp edges. Be sure all sand and debris
is removed, and that lubrication holes are free. Stone the table surface to remove the inevitable dings and
dents. Get some real way lube from a tool supply company and lube everything liberally during reassemble.
Don't try to get by with a regular oil.
- Acquire the minimum necessary accessories to do good quality work. Many problems that the beginner blames on
the tool are the result of improper setup and tooling. I'd suggest a good mill vise, full set of collets, a mounted
Jacobs chuck, an adjustable stop, a center finder, and some parallels, as a minimum. Naturally you'll need an
assortment of end mills, center drills, and drill bits. Some clamps and supports will also prove handy. Sooner or
later you'll also want a boring head. Buy a 2" model as the larger ones will shake the head too much. Take whatever
junk vise came free with the mill and put in on the drill press where it belongs.
- The biggest problem with the mill/drill is setting depth of cut. The feed dial is reasonably accurate, but the
travel is limited. There often isn't a good surface to reference to. This is where an almost forgotten technique
becomes valuable again. Back in the days of surface planers machinists used a planer gage to set the cutting
depth. This is nothing more than a steel ramp with an adjustable piece that moves up and down, usually 2" or so.
They are still available, but tend to be expensive new. They can often be obtained used for a few tens of
dollars. Try to get the extension plugs that normally come with it. The gage is set on the surface plate and
the movable piece is set to the desired height with a vernier height gage. You can also just use a
micrometer. The gage is then placed in the mill/drill and the (non-running) end mill is brought down to just
touch. This sets the cutter height above the vise. Lock the cutter. The part is now put in the vise and cut
to height. With care the result will be within plus or minus one to two thousandths of an inch.
- Being less rigid than a "real" mill, vibration is always a problem. In general, slower speeds and slower feeds
are the rule. Light cuts help, though if everything is right substantial metal can be removed quickly. Follow the
advice of the end mill manufacturer and the tables in Machinery's Handbook. An important part of this is very
sharp tooling. If you're using used end mills from some friendly machinist, try some new ones. Experiment with
coolant. I use an imported water soluble oil for most things, and the higher tech "Cool Tool II" for steels
and tougher materials. A spray mist lubricator works well, but avoid breathing the stuff. I keep a big spray can
of WD-40 around for aluminum. When a light cutting operation is running correctly, there should be little sound of
cutting, other than the motor running. If the mill/drill frame is vibrating or you hear a knocking sound, back off
and troubleshoot the problem! Heavy cuts will be noisy but it shouldn't sound like you're abusing the machine.
- I haven't tried this on the mill/drill, but changing the belts to Fenner link belts has done wonders to reduce
vibration on my other equipment. Just be sure to buy the right width belts, as the mill/drills often use a wider
series of belt.
- Get the mill/drill at the right working height. Build a sturdy support so you can see what you're doing and
don't have to bend over too far for every setup.
- Wear your safety glasses! Just one errant chip can result in disaster.
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