Keep breaking bits

[jmeineke]

I'm trying to drill 1/16" holes in 5/16" copper spheres and keep on breaking bits.

These are decent bits made of O2 steel. I've run them on the slowest setting I could (around 400 RPM) and was feeding very slow. I've had some successes but stopped trying after breaking 3.

What am I doing wrong? Shouldn't these be able to go through copper like butter?

[HWooldridge]

Faster is better on small drills and soft materials. Most likely, you are loading the flutes and twisting the drill in half...try increasing the spindle speed to the top of your drill motor's capability. Don't do the entire hole in one pass - "peck" at it by removing the drill every so often and letting the flutes unload. Spray a little WD40 on the work - you should have better success.

[pkrankow]

Copper also will suck the bit down by the chip pulling the bit deeper faster than intended.

I have gotten around this by deliberately dulling a bit, but I would be reluctant to do so on a very small bit.

Pecking and higher RPM is the best answer. You need to break that chip up. Even work hardened copper is pretty soft.

Phil

[arftist]

Yep, 400 rpm is way too slow for 1/16", even for drilling steel. Copper is tough, but soft. 2000 rpm, slow feed, as said above, light coolant.

[ianinsa]

Half the problem with drilling copper is it's fast heat absorbtion and resultant expantion. It is inclined to bind the bit, we add a dolop of non-abrasive hand cleaner at the hole spot this acts as a coolant and lubricant and it should solve the problem!
Ian

[Swamptroll]

I'm trying to drill 1/16" holes in 5/16" copper spheres and keep on breaking bits.

These are decent bits made of O2 steel. I've run them on the slowest setting I could (around 400 RPM) and was feeding very slow. I've had some successes but stopped trying after breaking 3.

What am I doing wrong? Shouldn't these be able to go through copper like butter?

Stone the flutes dull , I used to drill copper buss bars and we used special sharpened drill bits for this. The main thing is they were actually ground flat on the flute. This can be accomplished by stoning on a small drill bit

[jmeineke]

Very interesting.

Well, I tried the high RPM (can't remember exactly what it was, but it was over 2000) and the bits broke even easier - even with pecking - but I wasn't using a lubricant as suggested (I reasoned that if I only went a very small amount at a time, a half second "peck" or so, that it wouldn't matter. I was wrong...)

Last night I experimented at lower speeds using WD-40 as a lubricant. As long as I kept it wet, I didn't have any breaking (I was going pretty slow, but had some nice long threads coming out of the hole before I pulled back to clear the flutes and re-lube). If it got too dry, though, the long threads would disappear, the bit would not feed right and it would break every time.

I'll kick the speed back up to around 2000 and will keep it lubricated. I like the soap idea too - I may give that a try. I have some beeswax I was going to try too, but at this point I'll stick to what I know works (I'm running low on 1/16" bits!). If I still have breakage I'll experiment with dulling the bits a little.

Quick Question - would I have better results with carbide bits? I know they are even more brittle, but would they handle this better?

[fciron]

Part of the reason that you're breaking bits is that they are sharpened for steel: the edge digs into the soft copper and it self-feeds in until it jams and breaks. The trick with a stone is not to actually dull the stone but to change the flute angle, if the end of the flute is perpendicular to the surface it will scrape off a chip rather than digging in.

Typically the recipe is higher speeds and lighter feeds for softer materials. Usually higher speeds have lower torque, thus are less bit breaking. (Although it doesn't take much at 1/16".) The idea is to deliver the right amount of force to cut the smaller chip and to go faster so that there is less depth on each pass.

...and, as you seem to have noticed, LUBRICATE!

[Frosty]

Yeah, you need to blunt your bits slightly and hog the feed more so the heat is carried away in the cutting rather than building in the base metal work hardening it. It's still a matter of feel to get the right feed rate right but having the bit sharpened correctly is a must.

Copper alloys tend to tear under a sharp cutter be it drill bit, mill cutter, lathe tool, etc. The sharper the cutter the more likely it is to grab and tear so if the speed and feed rate are wrong the base will work harden and it'll either break the cutter or dismember the work.

Dad was a metal spinner and we did a LOT of copper alloy jobs and everybody learned how to sharpen and blunt the trimmers and deburring cutters correctly.

Weird stuff copper but fun, especially to forge. Just be REALLY careful if you find copper buss, some is Beryllium alloy and a serious health risk breathing the dust.

Frosty the Lucky.

[BIGGUNDOCTOR]

I have worked with copper, and the shop I am the tool maker for now goes through literally tons of copper a month.


One thing no one asked is how well are they being held. It has to remain solid with no moving around, holding it by hand, or not snug in a vise will cause breakage.

Sharp vs dull or 0-rake. I have only flattened the edge when drilling brass, copper no. I have never had a drill grab in copper, but instead gall up with chips. For brass, and hand feeding, you grind the cutting edge vertically so that it is parallel with the shank. That way it scrapes instead of hooking.

I wouldn't use WD-40, use a motor oil/trans fluid, cutting oil,etc if you have it available. Being a thicker viscosity it will hang in the hole better.

The drills we run in the screw machines are razor sharp, and they get pulled at the slightest hint of dulling. We run solid in house ground carbide spade form drills, and HSS twist drills. Drills will last a lot longer cutting the berrylium alloys than copper. The copper will dull carbide faster than you would expect. For your application I would only use HSS drills, carbide will snap very easy if side loaded at all. Dulling them will also make you push harder causing breakage. Just peck the holes IE; drill till you see a small chip form than pull it out of the hole. Do not try for the long twisties, even if it seems to be going well. The other thing to watch is the breakout on the back-prime time to grab, and break. You may want to consider soldering them to a block, or make a sacrificial backer of some kind to eliminate the rounded breakout of the sphere. Each bead should use a new spot to breakout into.

Are you using a center drill/ pilot drill, or center punch? If you don't have a straight start you are doomed from the beginning. Drilling a sphere, or any round stock without a starter is not recommended.

Also use quality bits, not the cheapest ones at the big box store.

Speed- it depends on how well you can feed it, run-out of the spindle, and the drill bit. There is no set speed. Play with speed, and feed till it runs good, but 400 is way too slow, but 700 may run like a dream.1000 may gall up faster than you can clear the chips. But whatever you do keep the bit lubed at all times.

Feed-as mentioned before use a pecking cycle to get through these. If you are using a standard home drill press, do not use the handle in the the usual way. For small bits I will run the spindle down by gripping the center hub, not the long handles. By doing this I have less leverage, and less chance of bending a bit.

Keep us updated, and did I mention to keep the bit lubed?

[JNewman]

You mentioned drilling a sphere, a standard jobbers length bit will want to wander trying to start it on a face that is not flat. If the drill is off center that could be causing your breakage. I would try a screw machine length bit. Oh and a lubricant.

[jmeineke]

You mentioned drilling a sphere, a standard jobbers length bit will want to wander trying to start it on a face that is not flat. If the drill is off center that could be causing your breakage. I would try a screw machine length bit. Oh and a lubricant.

I use a punch to get the hole started / bit centered. Yeah, consistent use of lubricant is making a big difference. I still have to go pretty slow on the feed - maybe I'm just paranoid now. Running dangerously low on bits!

[BIGGUNDOCTOR]

It's OK, drill bits are like Doritos. Use all you want, they'll make more

Even with a center punch you can get off center on a sphere.

If you have a vise on the drill you can put a block in it, then take a 1/4" fender washer that has a 2-3 holes in it around the outer edge. Drill, and tap the lower block so that you can run a 10-32 screw through the washer and into the block. Then spot the block centered on the washer with a 1/4"-5/16" drill Once done it would clamp the ball between the washer, and the block in the same place under the drill chuck each time.

Then I would use a center drill to put a pilot dimple on the ball, before drilling.

When done loosen the 3 10-32's and pull the completed ball out. When you put the next one in it should still be aligned on center.

[jmeineke]

I have worked with copper, and the shop I am the tool maker for now goes through literally tons of copper a month.

One thing no one asked is how well are they being held. It has to remain solid with no moving around, holding it by hand, or not snug in a vise will cause breakage.

Sharp vs dull or 0-rake. I have only flattened the edge when drilling brass, copper no. I have never had a drill grab in copper, but instead gall up with chips. For brass, and hand feeding, you grind the cutting edge vertically so that it is parallel with the shank. That way it scrapes instead of hooking.

I wouldn't use WD-40, use a motor oil/trans fluid, cutting oil,etc if you have it available. Being a thicker viscosity it will hang in the hole better.

The drills we run in the screw machines are razor sharp, and they get pulled at the slightest hint of dulling. We run solid in house ground carbide spade form drills, and HSS twist drills. Drills will last a lot longer cutting the berrylium alloys than copper. The copper will dull carbide faster than you would expect. For your application I would only use HSS drills, carbide will snap very easy if side loaded at all. Dulling them will also make you push harder causing breakage. Just peck the holes IE; drill till you see a small chip form than pull it out of the hole. Do not try for the long twisties, even if it seems to be going well. The other thing to watch is the breakout on the back-prime time to grab, and break. You may want to consider soldering them to a block, or make a sacrificial backer of some kind to eliminate the rounded breakout of the sphere. Each bead should use a new spot to breakout into.

Are you using a center drill/ pilot drill, or center punch? If you don't have a straight start you are doomed from the beginning. Drilling a sphere, or any round stock without a starter is not recommended.

Also use quality bits, not the cheapest ones at the big box store.

Speed- it depends on how well you can feed it, run-out of the spindle, and the drill bit. There is no set speed. Play with speed, and feed till it runs good, but 400 is way too slow, but 700 may run like a dream.1000 may gall up faster than you can clear the chips. But whatever you do keep the bit lubed at all times.

Feed-as mentioned before use a pecking cycle to get through these. If you are using a standard home drill press, do not use the handle in the the usual way. For small bits I will run the spindle down by gripping the center hub, not the long handles. By doing this I have less leverage, and less chance of bending a bit.

Keep us updated, and did I mention to keep the bit lubed?

The bits are split point, TiNi coated O2. Not sure if that's high quality or not or how it stacks up against HSS (what exactly is HSS made of, anyway? I know what it stands for, but what kind of steel is it?).

I'm using a center punch to put a dent in the surface. After I do that, I chuck the sphere in the x/y vise and visually line up the punch to be as vertical as I can looking from all sides. I then rough-adjust the x/y feeds to line up the bit with the punched area. Then I lower the bit onto the sphere, make any fine adjustments to the x/y position, examine the vertical alignment again. Once I'm satisfied that it looks ok, I lower the bit into the hole, apply light pressure and turn the press on to get the hole started. At that point I back off, apply lubricant and then keep going. This process seems to allow the bit to go right back into the hole every time raise and re-insert and as long as I keep it lubricated it seems to work.

I don't have any special mount for the spheres on my vise, but I probably should. Right now I'm just wedging the part in the smooth jaws (which mars the surface of the copper a bit, but I do some more shaping to get rid of those after I drill). It's not optimal, but careful alignment and reasonable clamping force seems to be working pretty good.

I know I need to come up with something better, but since this is just a small run I'm not going to spend a whole lot of time making mounts. If I decide to make some more of these, then I'll get serious about the setup.

I'm less concerned about the bits than I am about losing the copper spheres - those take me quite a while to make. Once the bits break off inside, it's about impossible to get them out. I was able to salvage one, but the rest I had to throw away. I need to go back and make some more spheres. I had a few extra but have already wasted those and then some.

I'll try to get some pics uploaded tonight.

[fciron]

I sometimes find it useful to make a holder for repetitive jobs so that the vise does not need to be repositioned each time. Once it's positioned for the first piece then all that is required is swapping out the parts, with an occasional accuracy check. A center drill or spotting drill works well to start the hole accurately.

Probably too late for this job and not apropos your bit breaking problem. Glad to hear it's going better.

[BIGGUNDOCTOR]

Don't trash the bad ones recycle them into something else, get all blacksmithy on them Try piercing them hot,and making rings, use them as clappers in sleigh bells, play around melting them, sell them to the local kids as high performance shot for their slingshots--ummm, you may want to scratch that idea, but you get the idea. If it don't work out sell them as scrap.

This may help some. Take a tap with a sharp point on the tip, put it into the chuck, and line up on where you want to drill the bead. Lock the vise down, and bring the tap down hard enough to center punch the bead. Replace with drill, and it will be lined up from the start.

One thing I have seen is cheap bits with Titanium lipstick. The main thing I would look for is Made in USA. When you put a cheap bit next to a good quality one you will see the difference. My shop teacher showed us some bits from a big box store, then proceeded to bend them in half with some pliers. I wouldn't be too concerned with any coatings for this job.

HSS is an alloy(s) used for drill bits, lathe tools, milling cutters, etc. It can get extremely hard with heat treating, and holds its hardness even when extremely hot. I don't have my Machinery handbook handy, but it probably has chrome, vanadium, etc to take the heat.

[ianinsa]

Just a thought, to try on one of your 'scrap' spheres, drywall screws have a good 'drill point'' try chopping off the head of one and using the front in the drill chuck as a drill bit to do the initial peirce. Possibly worth a try as they wont break the same way a bit will.
Ian

[John B]

I assume these are your forged spheres, if so an annealing/normalising cycle may assist before drilling them

[jmeineke]

I assume these are your forged spheres, if so an annealing/normalising cycle may assist before drilling them

Yeah, they were cold worked so they are work-hardened. I had thought about annealing but figured they wouldn't be as resistant to any impact (accidental drops, bumping into each other, stuff like that). I don't know how big a difference it would make, though. They dent pretty easy as is.

[jmeineke]

I sometimes find it useful to make a holder for repetitive jobs so that the vise does not need to be repositioned each time. Once it's positioned for the first piece then all that is required is swapping out the parts, with an occasional accuracy check. A center drill or spotting drill works well to start the hole accurately.

Probably too late for this job and not apropos your bit breaking problem. Glad to hear it's going better.

Since I'll most likely do this again, my plan is to make all new tooling. The guillotine dies I made are about shot and the design needs improved. I'll be making a holder too.

Here are some related threads in case anyone is wondering what I'm up to:

http://www.iforgeiron.com/topic/18067-14-brass-beads/page__p__183805__fromsearch__1#entry183805

http://www.iforgeiron.com/topic/18658-die-material/page__p__191032__fromsearch__1#entry191032

[pkrankow]

OK, here is a thought: punch them cold or hot with a piece of piano wire, then heat and remove.

Feel free to call me nuts, I haven't tried this, however the coefficient of thermal expansion is greater for copper than steel.

http://en.wikipedia.org/wiki/Thermal_expansion

Phil

[jmeineke]

OK, here is a thought: punch them cold or hot with a piece of piano wire, then heat and remove.

Feel free to call me nuts, I haven't tried this, however the coefficient of thermal expansion is greater for copper than steel.

http://en.wikipedia....ermal_expansion

Phil

is 1/16" Piano wire that tough that you could hammer it into a 5/16" piece of copper? Seems like that would be pretty tough to do. I like the idea of encasing the sphere in a mold and then just punching a hole, but what kind of setup would you need to do that? Is it even possible?

[jmeineke]

I got all the beads drilled last night and am in the process of putting it all together. The crucifix is somewhat small and I don't have a centerpiece yet, but I'm thinking about making both from scratch.

I thought it might be kindof cool to incorporate some copper in a metal cross using a process like the vikings used to do - cut out a groove in the metal and then hammer the copper into it to make patterns (at least I think it was the vikings). Don't know if I'd be able to do something like that or not, but it would look cool.

[jmeineke]

All drilled and put together. Thanks to everyone who responded - I really appreciate all the help. Ended up using a crucifix I had on hand for now.

Another member was kind enough to send me some bits that I'll be using for my next one and I'll be making some jigs and better tooling to make it go easier.

[Swamptroll]

All drilled and put together. Thanks to everyone who responded - I really appreciate all the help. Ended up using a crucifix I had on hand for now.

Another member was kind enough to send me some bits that I'll be using for my next one and I'll be making some jigs and better tooling to make it go easier.

you can always check fly tying supplies to see if they sell what you need for small quantities