Kennametal can recommend a drill size that will leave an appropriate amount of material for the reamer to efficiently size the finished hole.

most people (particularly beginners) when they drill have the drill come through the piece of metal in a location completely different than where the hole was started on the front. This is due to the fact that it is very difficult to drill 100% perpendicular. The rotation of the piece compensates for this as well as slightly enlarging the hole as you are drilling which is a good thing, this helps the drill from binding in the hole as it goes deeper into the metal. Even if you don’t feel comfortable turning the piece, you should “wiggle” the drill to accomplish the same thing, enlarge the hole slightly as the drill passes into the metal. As far as rotating the piece, I am speaking of turning the piece aprox. a 1/4 turn every time the drill is removed for lubricating which should be every few seconds. The smaller the bit, the more frequently it will need to be lubricated. The piece is actually held stationary while the drill is being fed into the metal. I’m sure you have seen a band ring with stones set in it and looked inside to see the holes behind the stone all over the place creating a very un pleasant and amateurish appearance. You definitely want to make a punch mark in the piece to start your drill, once it is started the rotation will have no affect on the drill remaining centered only enlarge the hole slightly. I once won $5 from a young and hard headed co worker by betting him that I could have the drill come out centered on the inside of the ring while holding the drill at an almost 45 degrees to the piece. Small bites and lots of turning and his money was mine. Hope this helps, Tim

Any suggestions? Am I doing something obviously wrong, or is this just a skill I need to develop? Any good tutorials online?

cutting edges that run across the “front” end. Everything else is just there to either support those edges, or get the chips out of the hole. How those edges cut is a function of how fast they intersect the material they’re cutting. That speed is a function of diameter. For the same RPM, the outer edges of a 1/2" drill are moving at 1/2X and so on. For copper, a good conservative speed would be around 100 SFM (Surface feet/minute) At 1", that gives 382 RPM.

At 1/2" you get 764 RPM. At the.0135" diameter of a #80 drill, you need 28,294 RPM to get the drill running fast enough to cut properly.

– Use a pin vise with just enough drill showing to fully penetrate the work (minimizebending). – The smaller the top part of the pin vise, the better. (more twist = higher rpm)

What kills drillbits, especially small ones, is if they bend. Hand holding a bit that small is just about guaranteed to blow it up. You need a drill press, and a good one, for holes like that. Start with one of the foredom ones that holds a #30 handpiece, if you can find one, or one of the other little “Precision” drill presses. What you’re looking for is absolutely minimal chuck runout, and what will seem like insanely high speeds. You also need to make sure the copper is clamped down solidly, so it can’t move at all.

My experience, is the reverse, I drill as slow as possible, with minimal pressure, use a lot of ‘home made’ lubricate rio grande blue lubricant mixed with 3 in 1 oil and take every 10 seconds the drill bit out to clean it, have not broken a drill bit in ages, touch wood

So, yeah, you need coolant. LOTS of coolant. And get the drill press running as FAST as you possibly can. Then peck, very lightly at it. You’ll be under-turning the drill, no matter what you do, so it’ll want to jam with chips. The pecking brings the flutes out of the hole so they can clear themselves before they jam and blow up the drill. Also lets the drill cool before it fries. It doesn’t help that copper’s as gummy and nasty as it gets. The silver final piece will be easier, but not by a vast amount. Sterling’s still pretty gummy.

I feel that if I had a good quality Archimedes drill I might have luck with that, but I can’t find a good quality model that would (for instance) take watchmakers collets.

You’re asking a drillbit that’s about 0.35mm to drill about 6 times its depth in copper. A very gummy material. That’s asking a lot.

– Prick and center, being very careful to create the smoothest "crater" possible without inverted mushroom sides, i. e. don’t hit it too hard. (my unproven theory is that they grab the drill) – Anneal just in case the prick andcenter process hardened the work. (why not remove that variable)

You can dissolve broken steel bits from gold with alum powder, which can be found in some old-fashioned drug stores as it was once used to stop the bleeding from a shaving nick, or order it on-line. I haven’t tried it on silver, but it might be OK since it’s probably attacking the iron alloy & will not effect non-ferrous metals. It’s been a while since I did it, but if memory serves me, put a high concentration of it in water, bring it to a boil, turn off heat, then soak your piece over night. Use a pyrex pot, not a stainless steel pot. What is a high concentration? I believe I used half of an 8 oz. container in a small pyrex saucepan, but I can’t be certain. But if you have 77 broken bits you can try a few experiments.

Thank you for all your excellent recommendations andthe math reminder. For one brief minute I was back at HSM, with ForrestAddy reminding me to “use your Handbook; if you can’t put the problem intonumbers it isn’t fully defined”!

Real, industrial drill presses that are actually intended for this sort of thing can be had, but they’re shockingly expensive. I ended up at the right estate sale at the right time, and came home with one, once upon a time. Its maximum diameter of drill is 1/4", and it weighs 150+ pounds. Mostly in the spindle mount. When I put a new chuck on it, I clocked the runout: 0.0002". And the max speed is about 8K RPM. (Not nearly the 28K you need for that little drill, but the best you’re going to get for anything half way sane.) (google “Hamilton Varimatic” or “Sigourney sensitive drill press” “Dumore sensitive drill press”) They’re called “sensitive” drill presses, because the spindles are designed to move very lightly, to give the operator some hope of feeling what’s going on with the bit. The big thing about them is that they’re fast, and the spindles are just about as close to perfectly concentric as you can get. When you’re working with drill bits that are only about thirteen thousandths of an inch thick, spinning at 10K RPM, a few thou of eccentricity in the chuck suddenly becomes a very big deal.

The smaller the drill bit the faster it should be turned, therefore get the speed up HIGH on this small of a bit. Use some form of bit lube, bees wax, oil of peppermint, something. Make a “set mark” a punch mark where you want to drill the hole to get the bit to stay in place and not wonder off the mark. The first thing that went thru my mind as I read your post was “the drill is being turned backwards" and that is still “dining in my head” as the problem but you have used different turning equipment so that is out. Are the drill bits "reverse twist”? Reverse twist drills are not common but are they ever handy to get a broken bolt/screw out of a hole!!! Check the twist direction of the drill bits to any of your other bits that work properly.

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Began with the Foredom handpiece then switched to Archimedes drill. With both tools the moment I put enough pressure to cut metal the drill bit would slip back into the holder or break. Switched to a heavyish pin vise, hoping to use the weight to sink the drill bit, same non-results. In each case, the drill was loaded correctlyin whatever I was using (centered in the bit), and I manipulated the drillby hand until it rotated without bowing. With the Foredom, I started slowly, worked the drill until it spun straight and seemed seated, and used different speeds to no success. Tried lubricated and non-lubricated.

We used to make our own small diameter spade drills using a needle which isalready hardened and tempered. The advantage is they don’t have a spiral cut in them which weakens the drill. The spade drill sort of scrapes its way through.

Make a divot with a centre punch first. You need to check the tip for a drilling angle of at least 90 degrees, but better is an angle around 115-150 so shallower to dig in without skating across the metal. Make sure you are using a twist drill bit for metals- in fact a diamond coated drills will work best. Don’t put pressure on the handpiece ; let the rotation at a slower speed than you are using do the work since you say it keeps breaking. also HSS bits aren’t as strong as a tungsten or carbide drill, and titanium or cobalt coatings over steel are acceptable as well. Keep the drill lubricated. A number 80 is the finest bit - why not try a # 60? #46-47 is closest to what is necessary for a 2mm sheet so using a #80 bit is like using less than a 3rd the size that will go through it most easily. even though you are using 8/0 saw blades to start the piercing it doesn’t matter what size the bit it- so use a reasonable sized bit and make your life easier- 20 is too many to have gone through already! Go larger. rer

I have found that I need to use a wax lub on my #80 bits. i first mark whereI want to drill with a center punch then I use my flex shaft and start out slow and work up the speed cutting a little at a time with very light pressure then I stop and clean off the bit and drill a little more. A slow process but works for me great very few broken bits. if you are doing fine piercing work the work is going to be slow anyway. I also only hold my saw with 3 fingers. reduced the amount of pressure I can put on the saw blade and makes me slow down and concentrate on the feel of the saw cutting. It is all about touch and feel. Hope this helps.

Another thought, is the silver work hardened? A decent bit should still have little trouble drilling hardened silver, just a thought. Wish I could see what you were doing in person, this should not be such a problem.

Wow Brian, what a great explanation! It allowed us to see very small things for the time necessary to comprehend the problem. Thanks Thomas III

Think about it, if your using a drill that thin sticking out say 15 mm, the thickness to length ration is way too much for the drill material strength.

– Use the thumb and forefinger to “twist” the pin vise while lightly holding it upright and bracing the work with the other hand. – The key: Use a counter cutting motion to break chips. I twist clockwise twice to cut, then spin back counterclockwise in the non-cutting way at least once to break the chip.

My experience is the same as that of Peter. I drill very slowly, stoppingoften to lubricate the drill. If I am drilling through a thick piece of metal–14gauge or more I slow the action way down. This way the drill never grabs, binds, or develops that screeching sound. Alma

I can also add that drill should be as long as possible. Long drills can absorb some misalignment which is unavoidable while drilling by hand.

Not included in my original post was that I also tried my Servo Drill. Better cutting at 20K rpm, but no control over drill breaks. By that, I mean the tip of the drill would twist off in the hole during rotation, essentially ruining the work because the broken piece is flush and cannot be removed. I have a dim recollection of a etchant used to remove steel bits from silver/copper, but I’m thinking that any etchant that will help take out a drill bit would probably ruinthe work.

The plan was to drill silver with #80 bits for piercing. I started by practicing on a similarly sized copper piece. The metal is 2mm thick, but I’m forced to use a 8/0 sawblade because of the difficulty of the design to be pierced. Final score: Broken drill bits, 20; Completedholes, 0; Frustrated artisan - 1. Fact of the matter is, I didn’t’ comeclose to completing a hole.

Drilling with small drills requires tools that will properly hold the bits and run true. The main thing is to take very small bites and use LOTS of lubewhich needs to be reapplied very frequently: drill for a second, lube, repeat. One tip that I will pass on is to rotate your work. This will compensatefor the slight angle that your drill will be entering the piece and your hole will come out centered. I have been at this for thirty plus years and I can come very close to drilling straight centered holes holding the piece in one position but by rotating I know it will come out centered. Remember, slow and lots of lube. Best of luck.

Couple of suggestions: Rio’s ‘good’ bits are good, but probably not good enough for this. If it’s any hint, I went to my normal supplier of industrial drills, and the smallest they had was #76. For $23 each. So, step one would be to look around for what are called “screw machine” drills. They’re shorter, and thus stiffer. And thus less likely to deflect and shatter. Get high speed steel, not carbide. HSS is more flexible. At this size, that matters a lot.

I did, however, come up with a solution that works (sort of). By that, I mean that drills still break, but won’t break in a manner that ruins the work or as often. Last night I got through 2mm of copper for almost 20 holes before anything broke. To your point, I am up to the#77 drill; anything less than that I can’t get to cut. My alleged ‘solution’:

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A common misconception is to leave too little material for the reamer to remove. The reamer needs enough material to make its cut. Too little material will cause the reamer to rub or burnish and results in accelerated wear and poor surface finish.

Cutting speeds should be about two-thirds that of drilling SFM for similar material and feeds should be two to three times higher.