I
am not a professional machinist or engineer. I'm not giving advice, just my
opinions. I'll endorse no use of this information, nor accept any liability
for its use or misuse.
You
NEED one of these machines. I didn't know how much I needed one until I got
one. I've made a lot of stuff over the years removing metal with files and a
bench grinder. I was pretty proud of some of the stuff I made. But this opens
up a whole new world. I can remove metal so much faster and so much more accurately
than I could before that it isn't even comparable. I can take on projects that
I wouldn't even have been considered before. I can easily make multiple parts
exactly the same. I can...I can...
And besides all that, it's a blast to run.
This
mill/drill is from Enco. It's a clone of the RF30 mill made in mainland China,
imported and sold by Enco.
I'm not a supporter of mainland China's politics, but I just couldn't pass up
the price. I've had great service from Enco and I'm really happy with the mill.
After initial disassembly, cleaning, lubricating, and reassembly, it has worked
great. The mill runs quiet and smooth. I like the belt drive (quiet and easy
to change). Really powerful (2hp motor). Very accurate. Most cuts, no matter
how long, are straight and square to within 0.001". I needed to tram the head
after the mill arrived. The front and left edges cut slightly deeper than the
other sides of a mill. This wasn't a serious problem. With a 1 1/2" diameter
mill there was a noticeable effect, but the inaccuracy was just a couple of
tenths (~.0002"). I didn't go through the whole process of checking the tramming
with a dial indicator. I loosened the bolts and added shims between the base
and the column mount while I was milling some non-critical surfaces until it
seemed like all edges of the mill were cutting equally. It finally only required
one shim 0.025" thick and it's as close as I need it to be.
Originally,
I thought I wanted a Bridgeport (doesn't everyone?), but I've been very pleased
with this mill. Certainly this machine is far more accurate than a worn-out
Bridgeport that I could have bought for the same amount of money. Besides, it
fits in my garage better. After using this mill for a couple of months, I think
I can comment on the differences between this machine and a bigger mill. I've
got all the power I could want or use, the machine is as rigid as you could
ask for, the accuracy is great. So what did I give up? The size of the workpiece.
I don't have as much table travel as you would get with a big knee mill.
Don't misunderstand. This is still a BIG machine. I really didn't understand
quite how big until it arrived and I unpacked it. You can't move one of these
by yourself unless you have a forklift or an overhead crane handy. That little
silver circle by the vise is a quarter. That should provide some indication
of the size of this beast.
I'm
really proud of the bench for the mill and the lathe
behind it. I built this bench from angle iron and plywood. The paint is a two-part
epoxy designed for garage floors and has been really durable. The benchtop is
sealed and has a drain in the middle so that I can use flood coolant on both
machines. The coolant pump and tank sit under the bench on a shelf and the nozzle
is on a magnetic base so it can be moved around and positioned where it needs
to be. The bench is really solid, is a comfortable height for work, and has
just generally worked out really well. There are drawers underneath for storage
(it turns out you need a LOT of stuff for machine work). The casters on jacks
underneath so that the bench can be moved can be seen on my shop
page.
You
need a good vise for successful milling. The work is going to have to be held
solidly (no flex, no vibration). The more accurately the vise is ground, the
easier it is to set up your work. The vise that came with the machine is basically
worthless. Not solid, not accurate. This vise is a Chinese-made clone of the
Kurt 6" vise. (I buy a lot of import tools. They're cheap and mostly the quality
is pretty good. Not great quality, but pretty good.) I bought the vise from
JTS machinery (they'd ship by UPS, Enco insisted on much more expensive truck
freight). This vise has been really great. It's a little big for the mill and
reduces y-axis movement slightly, but I can live with it.
You can't mill without milling
cutters. Open up a catalog from one of the big industrial suppliers (MSC,
KBC) and you'll find a
bewildering array. You need at least two of every size/style/material available.
Just kidding, but if you do want to work on different projects and materials
you will need several different sizes and styles of endmills. It works much
better if you match the mill to the job. Almost all the endmills I use are
imports. Some are Chinese, some Spanish, some Indian, a few Japanese. I can't
swing the difference in price for the American ones. At the top is a 1 1/2"
indexable face mill. I bought this one a couple of months ago when Enco was
closing them out. This was a great investment. Really moves a lot of metal
and leaves a nice finish. For $10.00 worth of new inserts you get four brand
new cutting edges. I'm going to get an indexable end mill that does the same
thing but with square shoulders. The end mills to the left are 4-flute mills.
Work best on harder materials. I have some carbide for very hard steels and
cobalt for steel and titanium. Even though the titanium is very hard the cobalt
resists welding of chips better. All the mills to the right are 2-flute for
milling aluminum. There's also a ball-end mill, a dovetail cutter and a keyseat
cutter. These specially shaped mills are necessary for some cuts.
addendum
(11 October 2001) I almost hate to say this because if too many people know
it will spoil the whole deal. I like American made cutting tools. Mostly I just
can't bring myself to pay the MUCH higher prices. Lately I've been buying a
fair number of endmills on Ebay. You can't get exactly the size/style you need
on demand, but if you're patient you can get some great deals. If the price
is comparable, the American made mills are definitely better.
What
sort of accessories will you need? That probably depends on whether you use
your definition of "need" or your wife's definition. When I was shopping for
machine tools I heard the opinion that you will spend as much on tooling as
you spend on machinery and I didn't believe it. Guess what... One of my favorite
activities (after I'm done in the shop) is reading tool catalogs. There's a
lot of stuff out there I need.
You
will have to have some means of holding the endmills. I didn't take a picture
of them but I'm using a set of collets from Enco. The choice between collets
and endmill holders is up to you. I like the collets. You will need a drill
chuck and arbor. These are the ones that came from enco with the mill. I'm not
real happy with the accuracy of the chuck and I've ordered another one from
JTS. Something else you will really need (anyone's definition) is a set of parallels.
This is one pair out of my set. Having a set of parallels makes setup so much
easier that they are really a necessity.
Then
there are accessories that you may need, but with somewhat lower priority. A
boring head and set of boring bars is nice if you need to bore large (or accurately
sized) holes. V-blocks are necessary for holding round work.
I
recently added a couple of bigger accessories to be able to complete more different
projects (generated a few projects too). Shortly after my birthday I added to
my shop a tilting table and a rotary table (had a good birthday, really looking
forward to Christmas, I've been very good). The tilting table is the 7x10" table
from Enco. It fits pretty well on the mill (although it's a bit tall) and seems
much more solid than the 5x7 tables I've looked at. The tilting table allows
one to mill angles. Of course, I needed some way to hold parts on the table.
None of the commercially available vises seemed to be just the right size, so
I spent several weeks building a vise to fit
on the tilting table.
I
also added a rotary table to be able to mill curves and to be able to make cuts
at precise angles from one another. This is a 6" horizontal/vertical rotary
table that I bought from JTS Machinery. An 8" table might fit on the mill, but
I think it would be pretty crowded (did I just decide on something smaller than
the absolute largest one that would fit?). I haven't used the rotary table a
lot, but it seems to work very nicely. I think I need to build a vise to fit
on it.
The only modification I've made to
the mill is to add a DRO to the Z-axis movement (although I have also recently
added a home-built powerfeed). The
original graduations on the Z-axis feed are fairly accurate, but the worm-gear
feed has a lot of backlash and makes accurate adjustments difficult. This is
especially a problem when you've made one cut and want to take another at a
different depth. For some things I used a dial indicator, but it was a pain
to keep setting. To overcome the problem I built this DRO. I started with a
cheap (<$30) digital caliper. I'm sure you could use a dial caliper as well,
but I like the digital readout (although I use dial calipers for general measuring).
Adding the caliper as a DRO required removal of the original depth stop from
the mill and some minor modifications of the plastic cover. The caliper was
modified by cutting off the jaws and drilling a couple of holes (danged hard
stuff) to mount the top end. It took a couple hour's machining to build the
blocks to mount the caliper. The top end (below left) is mounted to a large
block (this is overkill, but it's the size of stock I had handy) that fits into
the mill head and is held in place by a screw threaded into each end through
a hole drilled in the head. The tail of the caliper is clamped between two blocks,
with one attached to the front of the quill and the other attached to this first
block (below right). Altogether it looks a little crude. However, it was really
cheap and it works great. I've now got realiable accuracy and repeatability
to within 0.001"
OK,
So what can the mill do? There are more pictures of things I've done with the
mill on my projects page.
The mill is very accurate and very powerful. It will hog out a lot of metal
and leave a very accurately sized piece with a nice finish. At the right is
a piece of 6061 aluminum with a slot 0.525" wide by 1.010" deep. The slot is
within .001" of stated dimensions everywhere. I milled this slot in five passes
(with a high helix mill which works better for deep slots) including two finishing
passes for the sides. The key to successful milling is to match the speed, feed,
and type of endmill to the job you're doing. I highly recommend getting some
reference material. I'm using an inherited, antique copy of Kent's Mechanical
Engineering Handbook. There's also a lot of good reference material on the internet.
Discount Tools
has a nice summary reference on end mill selection, speeds, and feeds. There
are a few other references on my links
page but there are a lot more out there. The slot at right was milled at
1500rpm and at a pretty high feed. I get the impression that most home machinists
use feeds and speeds that are too slow when they would get better results if
they were a bit more aggressive. Coolant also makes a big difference and I highly
recommend it if at all possible.
I've
made quite a few things in the 3 or 4 months I've had the mill (and generated
a huge amount of swarf). Besides making parts to modify the lathe,
I've made a few burr puzzles (will probably make a bunch more for Christmas).
I got the design from the Burr
Puzzles Site. The noteworthy thing about the puzzles is that the silvery
piece in the disassembled puzzle is of 6-4 titanium. I really like working with
the titanium. There are several sites on the web with recommendations about
milling titanium. Use cobalt 4-flute cutters, low speed, high feed, and plenty
of coolant.
I've
also been building an adjustable
hanger to use with competition holsters for USPSA action pistol competition.
These are pieces for the holster hangers. The mill is accurate enough that I
can make several (10 in the last batch) and the parts are interchangeable. I've
also used the mill to build a bunch of jigs so that I can make repeated cuts
on parts like this without re-indexing the mill.
