"Alan Kamrowski II" wrote in message
...

I really only have one of these to do, so I am trying to do it the best
way I can without spending much on tools. I'm pretty lucky in that the
buttons have a bit of overhang that should hang over the cut can should
be a little forgiving.

How much is "a bit"? A hole saw was never designed to cut precise holes.
There are four problems with hole saws:

1) They are not perfectly sized (due to the offsets on the cutting teeth)
2) They are not perfectly round (again due to the offsets, as well as the
nature of the design)
3) They are not perfectly centered. Hole saws screw on to a mandrel and it
is the threads that locate the center (not precise).
4) On larger hole saws, there are driving pins on the mandrel that must
engage holes in the back of the saw. In order to line the holes up with the
pins, you can not screw the saw tightly onto the mandrel. That means there
will be some wobble in saw because the centering feature (the threaded part)
is loose. When cutting metal, that wobble will lead to chatter and a very
sloppy hole. I know, I've done it before. You can choose to not engage the
pins and just screw the saw on until it contacts the end of the threads, but
you risk jamming the saw on the mandrel and/or damaging the threads of the
mandrel and/or saw. Of course, this still won't solve the other problems
listed above.

That's not to say that hole saws do not have their place in metal cutting
operations; they can be used effectively for cutting large holes provided
you do not have any expectations that the holes will be exactly sized (or
precisely round).

Another problem you may encounter is that in cutting thin metal, the teeth
of the hole saw may catch the metal as the saw breaks through and could tear
the metal. When I used a hole saw for metal cutting operations, I was
cutting holes in 1/4" mild steel.

I found that hole saws typically cut up to 1/8" oversize for small
diameters. For your large 2-1/4" hole, I would expect the hole to be
anywhere from 1/8" to 1/4" oversize. Can you allow for that much error?

You said you don't want to spend too much on tools, yet that single-point
hole cutter by General is less than $11 and will cut perfect holes (and I've
seen them sold at local hardware stores, so you don't have to order it). You
can use it to cut your 1-1/8" holes too, although it will be more
time-consuming than using a step drill bit like I suggested previously.
Since you said you have more than 10 holes to cut, you may have to sharpen
the HSS bit once or more during the job.


If I do end up having to use a hole saw, do you have any other
recommendations on the best way to do it and still have the
panel look good?

I simply cannot recommend using a hole saw for your application, no matter
how you try it.


Should I cut from the top or bottom?

Top.


When you say a light feed, you mean low pressure when drilling?

Yes.


What kind of fluid should I use?

The best would be water-soluble oil, as that has the greatest cooling
properties (to protect your powdercoat finish). If you don't have that, then
a light cutting oil would be the next best choice, but you may end up with
some burning around the hole. It depends also on how careful you are when
cutting. Use low RPM, light (but steady) feed, and you may need to stop
several times (retracting the tool) to allow the part to cool between cuts.
Again, the single-point tool will be the best option because it's not
cutting along the entire circumference at once (i.e., the metal has a chance
to cool as the cutting edge turns 360 degrees).


Apply it once when beginning or more?

Flood cooling (continuous stream) is best. If not, apply a puddle at the
start and apply more while cutting if it starts to get too hot.


Should I take my time--drill a little bit, then let it cool,
then drill again, etc?

Yes, if necessary (as mentioned above). But when you are cutting, keep the
pressure light but firm. You don't want too much feed as you will overheat,
get chatter, and probably have the cutting tool dig it. But you don't want
the tool to drag either as that will just generate friction instead of
cutting.