Drilling large diameter holes

[walker]

hmm, looks like I need to get to Harbor Freight.  The local electronics store wanted $70 for a step bit, and $22 i think for those gold ones.    I've never purchased from Harbor Freight because everyone says there stuff is so cheap (quality).  But I those step bits look sturdy. 

[Taylor]

For drilling steel or more demanding applications, they might be crap. But for thin aluminum boxes, they're excellent.

In general, for serious tools like real machine shops use, Harbor Freight is junk. But for things like heat guns, calipers, pliers, etc. their stuff is perfectly adequate and crazy inexpensive.

[tiges_ tendres]

The Step bits from harbor freight are excellent.  Not as good as the Irwin bits, but they are 1/3 of the price.

I have managed to break one.  However, it was my own stupid fault.  I put my box up on the table and got it ready to drill and hit the switch before I clamped the piece down.  The case went half way across the garage and the bit snapped in half. 

8 lives remaining!

[Mugshot]

the largest bit i use when drilling holes is 8mm. for the 3PDT switch and DC jack, i just use my trusty stainless scissors to ream the hole wider. easy, does the job, and very accurate (subjective). i mark my holes and the extent to where the holes would spread.

[served]

But what about Tube holes? 25mm is a huge hole. I have not seen a bit for this. How would you do that kind of hole?

[philbinator1]

The problem is not the speed but the type of bit you are using. A standard bits wants to dig in. You need a step drill.

http://search.harborfreight.com/cpisearch/web/search.do?keyword=step+drill&Submit=Go

I start by punching in my center with a punch. Then drill with a small bit, like 1/4". Then go with the step drill.

The step drill will not try to dig in.

Ha!  funny, i bought a step-drill bit (or Unibit, or whatever you wanna call it) AND a centre punch the other day!  and i
must say, it 100% easier and cleaner than a standard bit.  really easy, you just drill - try the part - drill again - fit the part
etc.  very neat holes.  easy!   

[jacobyjd]

But what about Tube holes? 25mm is a huge hole. I have not seen a bit for this. How would you do that kind of hole?

I've got a step bit that'll do that. A spade bit that size would also work for you, if you can find one.

[served]

Actually I didnt know that there is a Spade Bit for metal. In that case, I will get one. Thanks!

[jacobyjd]

Actually I didnt know that there is a Spade Bit for metal. In that case, I will get one. Thanks!

lol--there's not But--they're tough enough to handle aluminum--they dull fairly quickly this way, but they're pretty cheap. Someone above mentioned that they'll work on sheet steel, but I've never tried this.

They are a bit of a ride, though--takes a little getting used to.

[BlueFuzz]

 
 Once the tip breaks the bottom seal, cutting begins to accellerate very very quickly, there is a decrease in metal preventing penetration, and as the thin shearing strips between 1/2 way out from tip to the shoulder, the blades 'dig in' and get stuck trying to shear through a large depth cut in <1/4 turn, euyrrn.
 

I clamp a block of scrap wood under any thin material I'm drilling - gives the best result to prevent bending of thin materaials as you press down, and stops the drill bit snagging. It's a little more hassle with something like a box that you're drilling into, but a little setup time is always worth the end result

[jacobyjd]

 
 Once the tip breaks the bottom seal, cutting begins to accellerate very very quickly, there is a decrease in metal preventing penetration, and as the thin shearing strips between 1/2 way out from tip to the shoulder, the blades 'dig in' and get stuck trying to shear through a large depth cut in <1/4 turn, euyrrn.
 

I clamp a block of scrap wood under any thin material I'm drilling - gives the best result to prevent bending of thin materaials as you press down, and stops the drill bit snagging. It's a little more hassle with something like a box that you're drilling into, but a little setup time is always worth the end result

If you're pressing hard enough to bend an aluminum enclosure, you're pushing too hard!

[alparent]

But what about Tube holes? 25mm is a huge hole. I have not seen a bit for this. How would you do that kind of hole?

Step drill again!

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=96275

3/16" to 1 3/8" that's 4.7625mm to 35mm

Lot safer then a spade and you have all the sizes you could ever need!

[KazooMan]

Just back from Harbor Freight with my first step drill to try out.  I have a drill press and many bit sizes, but thought I would give the step drill a try anyway.

As for Taylor's question about clamping a PCB for drilling, you really do not need to do so.  The holes are so small that there is very little torque when drilling.  I use a scrap piece of wood as a backer board and just hold the PCB in place with my fingers.  Never had any problem.  If you want more control, you could attach the PCB to a piece of wood with double sided carpet tape.  If you are drilling larger holes for plastic standoffs you could drill them first and then attach the PCB to a piece of wood with screws.  Either way I adjust the table so that the tip of the bit is very close to the PCB (1/16 - 1/8").  That allows me to easily line up the bit with the mark on the board and then a small pull on the handle and the hole is done.  Very fast.

For drilling PCBs I like to use the drill bits from Small Bear that have a 3/32" shank.  That makes them much easier to chuck in the drill press.  They are more expensive than regular bits (3X the price), but they seem to last longer without breaking.  You can also grip them in the chuck of a Dremel tool.  That is really nice for drilling out the one hole you missed originally, or, more often the case, cleaning up a hole after desoldering a component for replacement. 

[tiges_ tendres]

Just back from Harbor Freight with my first step drill to try out.  I have a drill press and many bit sizes, but thought I would give the step drill a try anyway.

As for Taylor's question about clamping a PCB for drilling, you really do not need to do so.  The holes are so small that there is very little torque when drilling.  I use a scrap piece of wood as a backer board and just hold the PCB in place with my fingers.  Never had any problem.  If you want more control, you could attach the PCB to a piece of wood with double sided carpet tape.  If you are drilling larger holes for plastic standoffs you could drill them first and then attach the PCB to a piece of wood with screws.  Either way I adjust the table so that the tip of the bit is very close to the PCB (1/16 - 1/8").  That allows me to easily line up the bit with the mark on the board and then a small pull on the handle and the hole is done.  Very fast.

For drilling PCBs I like to use the drill bits from Small Bear that have a 3/32" shank.  That makes them much easier to chuck in the drill press.  They are more expensive than regular bits (3X the price), but they seem to last longer without breaking.  You can also grip them in the chuck of a Dremel tool.  That is really nice for drilling out the one hole you missed originally, or, more often the case, cleaning up a hole after desoldering a component for replacement. 

My fingers cramp up when I try and hold the board down and drill.  I prefer to clamp.

[KazooMan]

Cut your scrap of backer board to the width of the PCB.  You will have much more area to grip on and your fingers should hold up better.

[tiges_ tendres]

Cut your scrap of backer board to the width of the PCB.  You will have much more area to grip on and your fingers should hold up better.

Hmm, good idea.  I might give that a shot.

[walker]

I too, just returned from Harbor Freight.  At $10 for three step bits, I'll give 'em a shot and if they bust well, it's not a huge loss.

[SonicVI]

The Dremel drill press is the best for drilling pcb's in my experience, much easier than a big drill press.     As for stepbits I love the Unibit #1 cause it has the 15/32 step which is the perfect size for footswitch holes.