Super Newbie Question - Cheap Machine for Drilling ONLY?

[Steve Garber]

Hey guys,

Sorry if this is super obvious - I operate a laser cutter and have gotten some great tips on here for that = ) but have no idea about other CNC machines!

I need to get a piece of equipment to drill an array of 0.44" diameter holes in a 12" x 12" x 1/2" piece of wood, and my tests with the laser (and from reading on here) have shown that it's just not the right piece of equipment for the job.

I don't need to do any horizontal cutting at all - I JUST want to be able to lock down my material, start the program, and end up with an array of holes in the material (which I would then remove and put on another, identical piece).

Just googling for CNC machines is extremely daunting, and I wanted to ask if any of you had a recommendation for something like this, with a 300mm square / 12" square workspace.

Thank you so much for any tips, recommendations, or links to such equipment!

Cheers,
Steve Garber

[Brian Lamb]

I don't know where you are located, but I would check Craig's List for a small CNC router. You could use a 3/8" router bit and do a helical spiral down through your 1/2" thick wood and then step out a few thousandths and make one final circle to establish your .44" diameter. Don't know how many holes you are talking, but with a fairly decent router spindle you should be under 10 seconds per hole.

Here is just an example from my local CL, don't know what price level you think you can do this with, but you will need something with at least a 2-3hp spindle it you want to do it with any speed.

http://phoenix.craigslist.org/evl/for/5524236076.html

[Gary Campbell]

Steve...
Make sure that you keep in mind that in many cases the Z pressure required for drilling is greater than that required for routing. You can find numerous posts where users tried drilling with poor results and ended up using a spiral machining strategy to machine their holes.

This will make your quest for a "cheap machine for drilling" even harder.

[Paul Lawrence]

Keep in mind that the only routing I'm doing right now (other than non-CNC) is with a Trial version of Vcarve Pro.

So, what you could be saying is I'm not going to be happy with "drilling" 25 flat bottom holes with a 1/2" diameter end mill?

I don't think I can even afford a 1/2" diameter end mill!

So, is drilling with a 1/2" diameter drill bit any easier on the CNC?

[Gary Campbell]

Paul...
I would much rather "spiral interpolate" those 1/2" holes with a 1/4" bit. Like Brian says above, but I like a smaller bit as it evacuates chips better.

Once done a few times toolpathing is not that difficult. Much easier on the machine, bits and saves on tooling costs too!

[Paul Lawrence]

Is it as easy as choosing "Spiral" in the Ramp tab in Vcarve Pro?

That's good tip for the OP to find any old CNC router to fix his problem.

[Gary Campbell]

Paul...
Yes it is. Bit will make one circular pass with a depth increase as the "pass depth" is set in the tool database.

[Gerry Grzadzinski]

So, is drilling with a 1/2" diameter drill bit any easier on the CNC?

At our old shop, we had a $150,000 Holz-Her CNC (1997), with a cantilevered gantry that probably weighed over 1000 lbs. We had a job that had hundreds of 1/2" holes. We put six 1/2" carbide tipped boring bits in the drill bank, and when it drilled the holes, six at a time, it would visibly lift the 1000lb gantry.
Drilling, or plunging, is VERY hard on machines.

[William Adams]

Drilling needs lower speeds than most CNC routers can do.

General guideline is an end mill is four times as efficient as side-to-side cutting as a drill. A drill is four times as efficient as an end mill at drilling.

The spiral in cutting paths work, but they take time.

You might find the shapeoko wiki of interest as an introduction to CNC.