If you have used a hand drill to drill some holes in metal, you have probably noticed the drill will want to "wander around" a bit before it takes a bite and starts drilling down. The next thing you do is grab a pointed punch to punch a divot at the location you want the hole, drill the hole to the desired size, only to find your hole is still off location a bit. Here is a way to make sure your hole will be on location when your drilling by hand. The rule is a drill or reamer will follow a hole. So lets get a small hole in there first (a pilot hole) to establish location, and larger drills will follow the hole (to a point, depending on the actual chisel web tip size of your final drill--no pun intended)

It is advantageous to make the prick punch divot on the big side IMO so you can use a bigger pilot drill, but punching on sheet metal, for example, may not allow you to do that if the metal surrounding the punch area is not supported, as you can see you can bend your whole part with each blow. Any size you can make the divot will dictate how big your pilot drill will have to be. I make sure the drill diameter is smaller than the divot I made, and if you have to use a really small drill to fit a tiny divot, it is worth it if you need location to be accurate. The small drill will not wander out of the divot, and your hole should be on location as good as your prick punch was. It is possible you may have to use a drill size in between your pilot drill and your final drill. At the tip of your drill bit, you will usually find what is called the "chisel tip" or "web tip". It is that straight line at the tip in the center, between the start of the cutting edges. That web tip has to be small enough to fit in your hole or it can wander a bit too. If your final drill tip is too large for a tiny pilot hole, you will need to use a drill in between the sizes. Don't think that more drill equals more location problems. As long as the web tip fits in the hole, the drill will follow the hole.

Follow these tips, and your hole should be on location with in a couple thousands of an inch. It is not good enough location for dowels, but your bolt will go through it every time if the punch is in the right location.

Feel free to add more if you know other tricks.

Doug @ ESP

Some very good info right there. I agree 110%... have been using that method since my dad showed me long time ago when accuracy is required. Just make sure you punch in the exact location to start with! ha ha!!!

And for God sake, never try to drill a large hole in thin material without having the material clamped down. If you don't clamp the material down, you just may end up with a whole bunch of stitches in your hands or fingers. AND, if you're drilling a hole in really thin material, ALWAYS have it backed up with a piece of wood or something for the center of your drill to cut as it goes through your thin material.

I have seen and gotten some bad cuts while trying to drill the thin stuff.

Any type drill that has a flat point similar to what is found on standard drill bits will walk without center drilling or center punching, even when the piece being drilled is secured & the drill bit itself is rigidly mounted. This is because the chisel point augers the metal out in the center creating high heat & a high drilling force. Drill points that cut at the center such as split point drills or faceted drills do not have this problem.

There is a drill designed to drill sheet metals that will not require backing or holding the piece securely. The point of the drill is shaped like the toroidal head shape Hugh was showing. The center of the drill is ground with a sharp faceted point while the remainder of the drill's cutting edge is ground in a concave arc to cut only at it's outer most edge. What happens when you have this ground properly is, the outside of the hole finishes it's cutting before the center. The scrap piece will look like a coin with a small sharp depression in the middle. This drill also needs no center drilling or center punching to start. It will not walk & if ground properly, there will be no burr to remove. If I can find some of the old pieces in the shop I'll post a photo.

JA

Sounds basically like a brad point bit... I use brad points a lot for drilling wood.

Almost the same principle except for the differences noted. Brad points also work well on plastics such as Delrin, Teflon, PVC, Nylon, etc.

JA

Yes, putting the punch in the right place is probably the hardest part. If your hands are jittery or your eye sight is not what it used to be, I have seen a tool that is a magnet bushing with cross hairs you look into to line up with scribe marks that you can use to spot the intersection of the lines. Once it is located almost perfectly (get with in + or - .001 for location easily), you remove the glass cross hair piece and slide a transfer punch through the bushing and make the prick punch. On thicker metal, you can actually move the punch prick a bit if you lean the punch opposite of the direction you need your first hit to move, and carefully punch it over, also making the punch divot larger.

Speaking of hole location, I hate hole templates made by a plotter. I just put on a 3-piece rear spoiler on my car, and used the provided template for the 7 of blind holes of the spoiler. One hole matched, and I had to slot the remaining 6. A template was also provided for the corner pieces with 2 holes each, but after the center piece template, I threw the corner template out. Instead, I made some "transfer punches" out of nails that would fit in the blind holes, with the point sticking above the surface no more than 1/32 of a inch. I then located the corner piece by hand to match alignment of the center piece, and simply pressed the tip of the nails into the paint. I did not have to slot any of the 4 holes for a good fit. From now on, if I ever get a template, I will try to directly transfer the center of the hole instead.

Was your dad a Machinist Marc?

"The only time I have pure negative karma, is when I thank a obama supporter (I hunt for the bumper sticker) for voting away my liberty and freedom as quickly as possible. That person might as well have a "kick me" sign on their back with me around."

They will kick you back.

www.modelgasboats.com/forum/13...709-drill-bits/

Yea Hugh. I deleted that part. I just wanted to leave it there for a day, and keep this thread about drilling holes as intended. I guess we need a political section, because I just have to reply to your comment.

They will kick me back (I assume you mean verbally)
Enforcing their right to vote away my Liberty,--of course. Right? Thank you master.

I would verbally tear them up in a political section, and expose their indoctrinated wisdom of the corn in my poop. (was that bad karma?--shoot!) I am ready.

This thread is to be about drilling holes, but only for metal. I can expose holes in the head of others in a political section---and I find it fun. But to quickly share the fun with others. If you see a obama bumper sticker, ask the owner to define communism---and watch the lights shut off in their head, no matter how "well read" they claim to be. No "confused American" obama supporter can define communism. I know why that is. think.

Man--a political section here would be a blast. Facts and results are stubborn things, and it is of the utmost importance that we discuss them IMO.

I don't know if Hugh and I will become good friends though. If he apologizes to me for voting away my freedom as quickly as possible, and promises never to do it again, we can have a real beer summit.

Goto cspan.com a political section here would SUCK! As an american you vote for who you want and deal with it for 4 to 8 years and move on.If drilling holes was "advanced" then weve been taught .

Thanks and here again someone else knocked your karma down again it was -1 coz I gave you a plus so someone went right back and knocked it down again. LOL. Id spend less time defining communism (websters does a great job ) and more time learning to be proficient in toolpath creation and 3d drawings - If you ever plan to tell the tormach to do anything special.

Youd still get kicked back irregardless of the soliloquy.