This is my first post, hopefully I haven't done anything horrible.
I am a highschooler (junior) at the Harker School (San Jose, Bay area,
California), part of the robotics team there. We participate in FIRST
, every year we build a 120 lb robot out of
raw materials and compete against teams nationwide.
Up until now, we've relied upon generous machine time donations from
machinists in our area, but we would like to do machining in house (for
both learning and time purposes, we only have 6 weeks to make our
robot, and the lead-times for machinists are long).
we've had everything from 6x4 plates with less than a mil of tolerance
to 36 inch long tubing with about 10 mils of tolerance.
I'm here to ask you what you all think is a good mill for us to aquire.
Space is not a problem, but we only have one-phase power wired to 15
amps. Although perhaps we can get the breaker changed, its unlikely we
can get three-phase. Would we have to invest in a VFD?
Also, I'd highly appreciate it if anyone could help us with how to find
auctions .etc in the area.
Lastly, would a CNC retrofit be as accurate (if not more) than a simple
Tatsunori Hashimoto, Harker Robotics.
Not easy questions to answer, as there are many possibilities. Used
Bridgeport, but they're usually 3 phase, and converter, either solid state
or rotary would be required. New, lower cost, KBC tools # VM-22-R8,
(kbctools.com) would be a good choice, BUT 220V single phase. Motor could
be changed out to 110V, possibly 1 HP without any great loss. Mill drills
can do nice work, but depend more on the experience of the one using it
than anything else.
Quick answer, the repeatability of a machine, to make identical parts within
tolerances is dependent somewhat on the machine. How accurately a machine
can work is dependent on the man running it. I've done some incredibly
tight work on a mill drill, but that doesn't mean I want to do it again,
only that it can be done. A good CNC retrofit for a mill will include ball
screws to replace the lead screws, eliminating backlash. A DRO reads the
actual positions of the table, both will reduce the errors caused by not
considering backlash. (But so would a handful of simple dial indicators
with mag backs on them, it just depends on how much fiddling you want to do
before you start cutting.)
A machine that is poorly set up will do only poor work, and who made it,
it's condition, will mean nothing. Again, right back to the man that's in
front of it. Not having enough time to do it right the first time only
means you'll find time to do it over. Cutting corners to save time will
only mean doubling the time it takes. Cnc requires that you know the
diameter of the cutter as closely as possible, Dro means cut and measure,
then take the finish cut. In the end, the results are liable to be
identical with one or the other. Cnc can produce complex curved shapes more
easily, but that's something that's been done with other methods for over
100 years too. Cnc imposes it's own set of requirements, different from
other methods, Other methods have their own set, mostly measure, measure,
measure. Getting in a hurry is the mother and father of all screwups.
Did you do the work or did the machinists do it for you? When I think
back to some of the stuff I managed to do as a kid, nothing would
surprise me, but I didn't know what a mill was at that time.
The reason I ask is that machine tools can be extremely(!!!!) dangerous.
All readers of your post will want you to go through life with fully
functional limbs. You need supervision, and from people who really know
their way around machines. Further, I would greatly prefer that the
supervisor(s) have experience teaching people to run machines.
A deadline can be a good source of motivation, but it can also lead
people to take risks. Be CAREFUL.
On a 6x4 inch plate, I would try to hold 0.001 in tolerances regardless
of the requirements, if only for practice, and because keeping things on
size avoids a spiral of corrections for errors in corrections for other
errors. A part that is 36 in +/- 0.010 is going to pose an interesting
measurement problem - by interesting, I mean it will require some
relatively expensive measuring tools. I think I would make the parts
adjustable, and then either tweak until it fits/works, or calibrate the
machine after assembly.
CNC adds another level and type of skill: beyond knowing how to run the
mill, you will need to know how to program the mill to run itself.
Mistakes can lead to dangerous forces on tooling and the work, and the
fact that the machine is running itself, it is all the more difficult to
detect. Note that I have never used a CNC mill, but I have this from
good sources, and it makes sense.
A DRO simplifies some tasks. I have never actually used one. I started
on an old Bridgeport mill, disappeared for a while, and am now doing
quite a bit of machining in my garage on a mill-drill (a rebranded Rong
Fu 31). It has a power feed, but no DRO. The more I work, the less I
care to bother with a DRO. I will admit there are times when it would
help, but it is no substitute for skill and understanding of machining.
I certainly do not want to discourage you, but if you have the money to
get even a mill-drill and tooling, or the money required to get and ship
even a used knee mill, then you are obligated to spend it well. I had
to deal with lost mail, retailers recovering from two hurricanes, and a
less than interested salesman, but it took a few months to select and
receive a mill.
IMHO, it is not realisic for you to find, obtain, and learn to use a
mill with six weeks to delivery of your product. Once you have a mill,
keep in mind that the mill is useless without tooling. Some tooling
is very expensive and "permanent" (unless damaged by collision with a
cutting tool), other tooling is comsumable. You need an ongoing budget
for tooling and maintenance, but you also need to know how to care for
Most important, you must have skilled supervision. It sounds as though
you have engineers working with you. That's good, but many engineers
are not machinists. My experience is that most engineers would be
helpless in a machine shop. I know some glowing exceptions, and learned
a lot from them. BTW, I am an engineer, so I can speak.
What Bill said, and more.
The real value in the donated time you were getting was not the machine
but the machinist. The 'lead time' for learning machining is measured in
years. Presuming, of course, that you have a qualified instructor to
help you keep all your fingers, etc. while you are learning.
That said, it still might be worthwhile to buy or even borrow a benchtop
mill/drill for minor quick modifications. You will need a considerable
assortment of cutting, fixturing, and measurement tools that will cost
more than the mill/drill - the "borrow" option might provide all of
those if you are lucky. And you will still need the qualified instructor.
If any machinists local to Tatsunori are listening: you should consider
offering your time and equipment to help. I've done this and working
with bright, motivated high schoolers is an absolute boatload of fun.
The kids these days are awesome, incredibly more aware and sophisticated
than we were at their age. 'Public opinion' tends to be stilted by the
press' choice to publicize only the dysfunctional kids. (Imagine that!!
The press doing a bad job .... )
Silly question but there is likely a High School in your area that still
has a machine shop and a Machine shop teacher with the tools and
experience to help and get you guys started.
REGARDLESS of whether there are competing high schools in your school
board cross school assistance when it comes to equipment is done and is
reality because the school board owns the capital equipment. (Meaning
all the inter school competition really doesnt matter when another
school or team needs a hand)
Approaching the teacher to see if you could get some time or assistance
from a highschool with a full machine shop would likely get you good
results. or the VIce procipal or shop coordinators
Had i heard about FIRST earlier i'd have volunteered some of my time and
machines for the idea where i am from.
Thank you very much for your insightful opinions, I appreciate it.
so would you say it would be easier to do work on a bridgeport rather
than a cheap RF-31 milldrill because of the rigidity?
And is a DRO absolutely accurate? (ie reading on DRO always corresponds
to table distance..)
We definately understand the need for careful setup; RC, our main
machinist, always stressed the importance of setting up the work
Also, how would you cut complex shapes without CNC? with a rotary
Bill Schwab -
We've used bandsaw, lathe at RC's shop but not a mill. How much more
dangerous would a mill be? (fly cutters do look dangerous..). If we
have this at our school, we'll definately have machinist supervision
and instruction. I believe we have a few former machinists in faculty..
6x4 1 mil of tolerance is easily doable? or is it a fairly difficult
task? I'm trying to gauge the relative difficulty of the work we do.
And as a user of RF-31, do you wish you got a larger mill or one with
dovetail ways on the z axis? (we're looking at some benchtop mills..
from RF-31, Sieg X2 clones, X3 clones, and the mill at
And our build season is already over this year (we shipped our robot on
tuesday). I intend to learn how to use a mill (regardless of whether or
not we acquire one) over the next year. (any suggestions? I've been
thinking about volunteering at a machine shop..)
Thank you for your suggestion about having a machinist supervise us. We
have a few machinists on facutly (who arn't being utilized because our
school doesnt have a machine shop..)
I'd imagine that it takes many many years to be skilled at milling (our
machinist says he's worked for 50 years..)
As for tooling, a graduating member is willing to donate to us R8
collets , vises, indicators and end mills. Of course we'd still have to
buy alot of tooling, but I think we can get buy most jobs with end
mills and a boring head (of course I could be terribly mistaken..
please correct me if I underestimate this)..
Also, what mill-drill would you reccomend? if its a RF-31, I've always
wondered why one wouldn't get the sieg x3 (Grizzly carries it as g046)
it has dovetail ways which means you dont loose your position..
Also, what other good ways of learning (for highschoolers..) do you
Brent Philion -
We used to have a highschool next door, (a jewish school) with a
machine shop, but we bought the campus and our school sold off the
machines. Now I think there isnt a highschool close by with a machine
shop (most of the ones I know have closed theirs..)
Thank you very much for your kind assistance
Tatsunori Hashimoto, Harker Robotics
I just realized that I've never mentioned what material we work with..
We use 6061 aluminum for everything. The only steel on our robot is the
gears and shafts. So the only real machining of steel we'll do is
Does that change any of your advice? (esp concerning accuracy.. im
guessing alu is easier to machine..)
Tatsunori Hashimoto. Harker Robotics
Be sure the school has sufficient personal injury liability insurance,
that it has or can obtain competent instructors, that the parents all
sign permissions slips, and that your entire class and the instructor
follow all the other advice from all these other gentlemen responding
That beI'm window shopping for my own machine, and inexpensive but idiot
proof (BUT NOT CHILD SAFE !!!!) choices seem to be offered by MAX NC
. If you have a couple thousand to spend, I
would recommend that the school buy the MAXNC 10 CL-B.
Essentially, the CNC has already been done for you in a hassle-free
manner, and the owner evidently stands by his product. The only
problem might be shipping expense, this place is in Chandler, AZ (about
5 miles drive from where I live).
I can afford to talk like a naive idiot (at least in the eyes of some
of the people in this group and a lot of others) because not only do I
have no pride left, I'm also not afraid to speak up and ask lots of
questions just to learn... I've also found a friend who was a CNC
mechanic but was laid off, he is willing to be my tutor until he judges
me competent. Could be a while (he he).
The Eternal Squire
I think, judging by comments some of the skilled machinists here, that
there is no end to learning the finer points. Even learning to make
acceptable parts and fix mistakes takes a long time. The fact that you
*have* a 50-year machinist to talk to is a gift you should not take for
That is Wonderful! It certainly means whatever you get must use R8
tooling. As for how much you need, it seems to me that I am forever
buying yet another kind of cutter for milling jobs. One of the reasons I
got a shaper was so I could do small strange jobs using hand-ground tool
bits. 15 minutes grinding a tool blank from the bin-full on hand and
another 30 minutes setting up and cutting. Way better than spending $60
and waiting a day or more.
In short, More = Better. Roughing and finishing, shorter and longer,
various diameters. It does really help that you have somewhat
standardized on 6061 Al since it is tractable to machine and you can
focus on getting the cutter geometries appropriate for it. Delrin is
another material you might want to have on hand; it cuts well with the
same tools as aluminum and is great for sliding or rotating bearings
against either Al or steel.
Another reason to reserve a budget for tooling: remember that cutting
tools are consumables. Slowly when used correctly, very quickly if you
Speaking of ways, square ways do just as good a job as dovetails, they
just need two adjustments instead of one.
I really think your best value would be to find a carefully used
mill-drill. It will have the manufacturing leftovers (like the notorious
sand in the headstock) already corrected and may come with more tooling.
Try craigslist.org It is very active in your area.
a Smithy combination machine that was listed Saturday and is sold
a small lathe that would be handy for you as well.
Talking to and watching machinists is the best. Second-best is watching
videotapes and then CAREFULLY trying it yourself. After that you try to
stop the bleeding and figure out what went wrong. Then try it again.
Repeat until crispy and golden.
Have a great time!
With respect, the worst advice I have yet read in this thread.
MaxNC machines are too small and flimbsy to put up with ameteur machinists.
CNC is *not* required or recommended(!). A good manual machinist is required
to make a good CNC machinist, period.
I would recommend a Bridgeport or knockoff. You'll spend the least amount of
time messing around with the machine, they are the most tolerant of
mistakes, and they are the most rigid of the mentioned machines (desktop,
Personally I like a heavier machine with a more powerful motor and faster
spindle for manual aluminum work, but the BPT will be a good match for the
type of work being described.
It is always benificial to have the largest, most powerful machine that will
fit in your space, is within your budget, and will hold the part you're
A bridgeport is ideal for your work. A mill/drill is a compromise (less
rigidity and smaller capability in exchange for less money and smaller
As far as the work you're doing is concerened, yes.
What kind of "complex" shapes are you producing? Can you specify examples?
It's not a matter of degree. A bandsaw will cut your finger off while a mill
may pull your finger off. Neither are ever acceptable. Both machines require
respect and proper training.
Truly +/-.001" on a bridgeport is pretty tight, but certainly attainable.
What kind of work are you doing that requires such a tolerance?
Here's a rule of thumb: 1st and 2nd year apprentices are considered losses
(pay and overhead versus output). 3rd year apprentices might break even. 4th
year apprentices should make the company money.
If you happen to find someone willing to let you work in their shop (costing
them money! even if they never give you a dime), ask as many questions as
they'll allow, do your best always, and always be respectful of that
person's sacrifice as well as their experience and capability compared to
yours. *Important advice below*
Make a point of designing parts around the tooling you have. Cutters get
expensive *very* quickly and you will inevitably run out of time. If you
want to keep the price and complexity of your parts low, Keep It Sweet and
You're in a rough position.
In high school, I entered two Canada-Wide Science Fairs with projects I had
built in machine shops. I was lucky because of the people and facilities to
which I had access. I'm sure you've seen that there are many skills that you
have to master to be successful in large projects like a robotics
competition. Time management is huge. Conceptualization, design, fabrication
and assembly of the project. Perhaps a write up. Computer programming. The
list is endless. Adding machining is a big jump, but if you can pull it off
you'll be far ahead.
Good luck with everything. Enjoy this time, as you are working towards your
own goals. Once you start making parts for other people, it'll never be the
(Go for the Bridgeport, if you can)
With respect, the subtext of the original request is not fully
understood by my distinguished colleage somewhere else out there on the
No matter how well motivated or cautious or intelligent or bright a
high school student is, legally and morally that student is still a
minor. Special considerations apply.
The intended operators are not amateurs, they are children.
Bridgeports and related machines will almost certainly exercise lethal
forces in the event of an accident. While smaller mills can generate
lethal forces, due to physics the amount of total momentum applied
against any part of a child's anatomy will certainly be less. That
increases the chances that the ER team can save the child in time.
These children do *not* have the time, let alone the attention span, to
become good machinists. They best they can do is a 13 week semester
(never mind the 6 week deadline) is to develop an appreciation of the
basics. A good manual machinst,
however, should be required as an instructor, simply for safety
Probably for legal and liability reasons, the students should not even
touch the machine.
(Sorry!). A hands off approach would then mandate the use of CNC.
The students can develop an understanding of the parts of the milling
machine, draft CAD diagrams, download, and run in the presence of the
Can you image how high the school board would go ballistic when they
hear that you want to reintroduce the machine shop? Selling the idea
as a computer controlled demonstration that could fit on a desktop,
with live demo at the board meeting, would go a LOT easier with them.
Save that for college or vocational school.
I bought a MAXNC-10 for my electronics business
thinking it would be useful for making test fixtures.
The small working area, tiny spindle and steppers
and slow speed have caused it to be nearly useless
to me. I've had a couple chumps wanting to buy it,
but I'd feel guilty if I sold it.
A bridgeport or equivilent would be good. Next on
the list would be the cheapest knee mill you could
find with an R-8 spindle.
Explain your reservations to the chumps before the sale, if that be the
case - but they may have different needs/expectations, and if they go in
with eyes wide open, you have no need for guilt, some money, and less
space being taken up by nearly useless objects.
Perhaps "special considerations apply" but the size or power of the machine
has nothing to do with it.
Uh, they are amateurs. Call them children to their faces.
Absolutley wrong. *This* is what's wrong with the internet.
I've run a Taig milling machine (essentially a MaxNC without CNC),
Bridgeports, 3 ton horizontals and 30hp CNC machines. My Taig will cut your
finger off just as fast as the 50hp CNC machines at work will.
Tell me your experience with milling machines. I'm guessing you haven't run
a mill for more than a dozen hours. I've got 5,000 hrs of my tool and die
apprenticeship done. I've about 1,000 hrs on bridgeport machines and about
150 hrs manually programming and using CAM software to program CNC mills.
Then they *certainly* don't have time to become decent CNC machinists. As I
said, you have to be good on a manual machinist to perform on a CNC machine,
period. Ask me how I know.
They shouldn't be allowed to walk on the sidewalk or ride in a car either.
Very dangerous activities (bridgeport is 1hp, smallest common care engine is
Bullshit. Will the teacher saw off the stock for them? Put it in the vice
and set up the mill? Perhaps program the machine because there's not time to
teach the *children* how to do it? I guess we'll just let the students press
the green button.
Great learning experience. Indeed you've entirely missed the point of
They can setup their manual mill and crank the handles as well. It's not
rocket science and it isn't dangerous when the student has proper training.
Many Europeans start their apprenticeships well below 18 years old.
Great. Buy a machine that DOESN'T have the capacity the students need,
requires programming and setup skills they DON'T have and probably costs
more than a used knockoff bpt.
Great idea. We need more great ideas like that in industry too.
There are those who say, and then there are those who go and do (as the
sayers watch). The student asked what kind of mill was required for the type
of work he is doing. A MaxNC WILL NOT DO THE WORK REQUIRED. That's the
of the floor models..they rank pretty low on the rigid scale.
If he were in California..I could probably get a company to donate a
Shizuka CNC knee mill with a Dynapath 10 control. Runs pretty well,
but the spindle bearings are likely to need replacement. Located in
Cross posted into alt.machines.cnc. Mostly pros there..may have some
"A prudent man foresees the difficulties ahead and prepares for them;
the simpleton goes blindly on and suffers the consequences."
- Proverbs 22:3
Are you talking about the open loop, or the closed loop MaxNC 10?
It is true, the open loop is only good for PC boards because of the
lack of torque.
I just got off the phone with MaxNC closed loop machine today. I asked
a fair number of questions very carefully:
1) How precise?
2) How accurate?
3) How tough?
4) Can I mill PC boards with it?
5) Can I mill aluminum boxes with it?
6) Can I mill small steel parts with it?
With qualifications, all the answers are yes for the NC10 closed loop.
The technician told me that with the closed loop the precision and
accuracy are both approximately the same, zero dot 2 thousanths of an
inch. The closed loop
can exercise about 8 times the force as the open loop, and one of the
is milling mini turbine blades from hardened specialty steel for a
model jet engine.
And from the way he talks he is hardly a jumped up Walmart hardware
Those who do are called artisans Those who say are called researchers.
One can't exist without the other.
The Eternal Squire
Thank you very much for your all's time.
As for MaxNC, that's out of the question for us since we'll end up
frequently manufacturing parts greater than the 12 inch travel.
For the safety question, we've gotten a ok for a manual mill as long as
there is a machinist watching over, and there is restricted access (to
ensure some of the more careless members dont play with it like a toy).
We've also been fairly careful with our handeling with machine tools
and even though it is a risk, we think its one worth taking (for the
Truly +/-.001" on a bridgeport is pretty tight, but certainly
What kind of work are you doing that requires such a tolerance? "
We manufacture our own high-speed gearboxes whose mounting plates
require about 1/1000th tolerance. we've previously found that even
1/1000th off can cause the motor to bind and start flipping the
breakers, or cause unacceptable current draw.
As for the mill, we are in fact located in California (bay area,
however.) , so we are highly interested in Gunner's offer of a Shizuka
CNC mill. If that is not possible, we can of course, go for a
bridgeport, or we've also been looking for something like
the square column mill. The work
envelope is more than adequate, it seems to have a strong enough motor
for our work, and the spindle speed seems okay for aluminum work. the
Free shipping also makes it very attractive for us.
As this was Tatsu's first, this is also my first post. Who knows, I
might get this right.
Anyway, I am student mentor for Tatsu's team at the Harker School. I
have had a good bit of machine tool use, and could say I am decently
proficient with manual and cnc mills. The robotics team is looking to
get about a bridgeport sized mill, but not a full knee mill. The one
that Tatsu posted a link to, from industrial hobbies, is a chinese
import mill with a decently sized travel (12x30x 24 vertical) and R8
taper, with a 2 hp single phase motor. This mill basically fits into
all of our requirements, and is what we are seriously considering
Gunner, thank you for your offer. We will have to see with the school
if it is at all possible to house something like a full-size knee mill
(I am guessing it is the size of a normal bridgeport).
I agree with all of you who say that a student that doesnt know how to
manually mill doesnt know how to CNC. I learned the hard way first, on
a 1967 bridgeport with no DRO. I have gradually worked up from then...
but I do believe that a high school junior or senior could be taught to
mill decently in three months. The kids at Harker are bright, I have
seen several outstanding examples. Of course, not everyone would be
even allowed to touch a mill, as Tatsu said.
We plan on having a mill, 3 axis DRO, milling vice, clamp set with
t-nuts and studs, rotary table, boring head, indicators and
edgefinders, end mills, full tap die and drill sets, mill vice parallel
bars, a nice keyless chuck, center drills, calipers and mics, carbide
insert face cutter, some reamers, and I am probably forgetting
something. Anything else we might want to get?
Currently my main concern is getting a DRO without selling an arm and a
leg. Would anyone have suggestions on DROs and where to get them?