I have seen conflicting information in my drill press manual (high speed) and here (low speed) when it comes to drilling aluminum.
So I would like to start this thread to discuss the pros and cons for optimum RPMs for drilling in aluminum and steel.
Does it vary with a hand drill as opposed to drill press? Type of bit? Oil or no oil? I assume it does, so can we get some answers from you experienced machinists out there?
thanks
So I would like to start this thread to discuss the pros and cons for optimum RPMs for drilling in aluminum and steel.
Does it vary with a hand drill as opposed to drill press? Type of bit? Oil or no oil? I assume it does, so can we get some answers from you experienced machinists out there?
thanks
I have always drilled steel at a low speed with plenty of oil to ensure that the bit does not heat up (if it does then it rapidly dulls). It needs to continuously remove large chunks of the metal. Aluminum I typically work around 3500 RPM using a vertical miller for drilling or shaping, again with plenty of oil. I have titanium nitride drill bits for either metal-even the cheap ones work pretty well.
I have been a machinist over the last 23 years and have drilled a lot of holes.
Here is a simple formula that will put you at the correct RPM.
For steel take 300/Diameter of drill. So 1/4" drill bit in steel = 1200RPM
For Aluminum (grade 6061) 600/Diameter of drill bit. So 1/4" drill in Alum. =2400 RPM.
For Stainless Steel (303,304) 180/diameter of drill. So 1/4" drill bit in stainless = 720RPM.
This is assuming yor using a 118 Dg. High Speed steel drill bit.
You always want to keep the drill bit and material cool. I use a water soluble coolant. It is mostly water but has some lubricity and keeps steel and your machine from rusting. You can buy this from mcMaster carr supply.
If you are drilling aluminum I just spray on some WD40 if I'm not doing a ton of holes. You can always use pipe threading oil on steel, Moly D on stainless and tapping fluid for the proper material but it is a lot messier to clean up than simply water.
Mark
Here is a simple formula that will put you at the correct RPM.
For steel take 300/Diameter of drill. So 1/4" drill bit in steel = 1200RPM
For Aluminum (grade 6061) 600/Diameter of drill bit. So 1/4" drill in Alum. =2400 RPM.
For Stainless Steel (303,304) 180/diameter of drill. So 1/4" drill bit in stainless = 720RPM.
This is assuming yor using a 118 Dg. High Speed steel drill bit.
You always want to keep the drill bit and material cool. I use a water soluble coolant. It is mostly water but has some lubricity and keeps steel and your machine from rusting. You can buy this from mcMaster carr supply.
If you are drilling aluminum I just spray on some WD40 if I'm not doing a ton of holes. You can always use pipe threading oil on steel, Moly D on stainless and tapping fluid for the proper material but it is a lot messier to clean up than simply water.
Mark
Amateur drilling
I agree with MTW above but use the following shortcuts as an amateur with a hand drill. For one thing, the drills available to you at the discount store and the hardware store have drifted away in shape and metallurgy from the ones available to corporations that buy from mill supplies. The discount store ones seem to have a thinner web, and are more likely to shatter as a result. The hardware store ones, specifically Irwin HS drills made in Brazil, have enough metal but are also prone to shatter. I use as reference the drills fished out of the dumpster from work and resharpened, from Lawson and Fastenal. These behave more like the ClevelandTwist and VermontAmerican US made drills of the past. I have taken to buying Irwin cobalt plated drills from the hardware store, not because I drill stainless (it is designed for that) but that the metalurgy is okay and it doesn't shatter so badly, and the price is less than the pro drills plus freight from Mcmaster. Wear safety glasses!.
A machinist told me once you have the speed and pressure right when little curls of chips are breaking off. Long twisted curls are too slow or too light, and can cut your hand besides. I use a vari-speed hand drill, as unless you center the work exactly and bolt the vise down on a drill press, I find the vise spinning around at the bottom of the hole too exciting for words. Drilling left handed allows the drill motor to snap out of your hand if it snags, which helps preserve your wrist against sprains.
Drilling fluid makes a big mess, the cooling is more important than the oil. I spit on the bit to keep it cool, makes much less of a mess in my garage and costs nothing. A squirt bottle would also be handy. No, I don't chew red man. The oil is important to pros to keep the expensive shop machinery from rusting from the water, but if you're drilling 1 or 2 holes you are unlikely to apply enough water to seriously damage your vise. Oil your vise first with non-detergeant oil to prevent rust, you should do that anyway. Air compressor oil or tractor hydraulic fluid (generic) or type F Auto Trans Fluid are non-detergeant oils. Type F ATF is $1.50 a quart at the discount store, I lubricate most anything with it anyway except engines.
Drills over 1/2" in sheetmetal are likely to snag and snap off, and are expensive. On big holes I've taken to drilling a lot of little holes in sheet metal and connecting the dots with a carbide tree bit (3/8") in an air die grinder. Diamond dust bits from harbor freight (their only good tool) is also useful for connecting the dots. You can also do square holes that way. Use safety glasses and ear plugs with the die grinder.
I have a friend that uses LPS spray tapping fluid on bigger holes, 3/8" up. It really does work better than water and allow faster cut. It is also about $8 a can. He is rich, I am not, and just use water and more electricity. The tapping fluid we had at work did not seem to provide the same advantage.
I agree with MTW above but use the following shortcuts as an amateur with a hand drill. For one thing, the drills available to you at the discount store and the hardware store have drifted away in shape and metallurgy from the ones available to corporations that buy from mill supplies. The discount store ones seem to have a thinner web, and are more likely to shatter as a result. The hardware store ones, specifically Irwin HS drills made in Brazil, have enough metal but are also prone to shatter. I use as reference the drills fished out of the dumpster from work and resharpened, from Lawson and Fastenal. These behave more like the ClevelandTwist and VermontAmerican US made drills of the past. I have taken to buying Irwin cobalt plated drills from the hardware store, not because I drill stainless (it is designed for that) but that the metalurgy is okay and it doesn't shatter so badly, and the price is less than the pro drills plus freight from Mcmaster. Wear safety glasses!.
A machinist told me once you have the speed and pressure right when little curls of chips are breaking off. Long twisted curls are too slow or too light, and can cut your hand besides. I use a vari-speed hand drill, as unless you center the work exactly and bolt the vise down on a drill press, I find the vise spinning around at the bottom of the hole too exciting for words. Drilling left handed allows the drill motor to snap out of your hand if it snags, which helps preserve your wrist against sprains.
Drilling fluid makes a big mess, the cooling is more important than the oil. I spit on the bit to keep it cool, makes much less of a mess in my garage and costs nothing. A squirt bottle would also be handy. No, I don't chew red man. The oil is important to pros to keep the expensive shop machinery from rusting from the water, but if you're drilling 1 or 2 holes you are unlikely to apply enough water to seriously damage your vise. Oil your vise first with non-detergeant oil to prevent rust, you should do that anyway. Air compressor oil or tractor hydraulic fluid (generic) or type F Auto Trans Fluid are non-detergeant oils. Type F ATF is $1.50 a quart at the discount store, I lubricate most anything with it anyway except engines.
Drills over 1/2" in sheetmetal are likely to snag and snap off, and are expensive. On big holes I've taken to drilling a lot of little holes in sheet metal and connecting the dots with a carbide tree bit (3/8") in an air die grinder. Diamond dust bits from harbor freight (their only good tool) is also useful for connecting the dots. You can also do square holes that way. Use safety glasses and ear plugs with the die grinder.
I have a friend that uses LPS spray tapping fluid on bigger holes, 3/8" up. It really does work better than water and allow faster cut. It is also about $8 a can. He is rich, I am not, and just use water and more electricity. The tapping fluid we had at work did not seem to provide the same advantage.
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Kool Mist Coolant
I use Kool Mist Formula 78 and buy it from McMaster Carr Supply Co.
It cost about $30.00 and will make 15 + gallons which will last a lifetime for some. I just use a standard $3.00 spray bottle and keep the bit and hole constantly wet.
As soon as you let the material your drilling get hot (like steel) it will work harden in seconds and take out the cutting edge of the drill almost instantly. If you use the proper RPM and keep the drill and material flooded with coolant the drill bit can last several hundred holes before resharpening. Using coolant is a very cheap investment and will save you a ton of money in drill bit replacements and give you better quality holes.
McMaster-Carr
Mark
I use Kool Mist Formula 78 and buy it from McMaster Carr Supply Co.
It cost about $30.00 and will make 15 + gallons which will last a lifetime for some. I just use a standard $3.00 spray bottle and keep the bit and hole constantly wet.
As soon as you let the material your drilling get hot (like steel) it will work harden in seconds and take out the cutting edge of the drill almost instantly. If you use the proper RPM and keep the drill and material flooded with coolant the drill bit can last several hundred holes before resharpening. Using coolant is a very cheap investment and will save you a ton of money in drill bit replacements and give you better quality holes.
McMaster-Carr
Mark
I never commit to a certain rpm. It depends on the material, condition, diameter & grade of the tools.
IMO the best way to drill in metals is to look and listen very carefully and adjust the rpm accordingly. You'll find the optimum speed soon enough: too slow or too fast will slow your progress. In some materials you'll find yourself constantly adjusting the speed as you hit harder or softer spots deep inside the material.
Do it right and your bit will require less lubricant, yet it remains cool and sharp. You can use even the cheapest HSS drills to go through RVS almost like it's butter.
IMO the best way to drill in metals is to look and listen very carefully and adjust the rpm accordingly. You'll find the optimum speed soon enough: too slow or too fast will slow your progress. In some materials you'll find yourself constantly adjusting the speed as you hit harder or softer spots deep inside the material.
Do it right and your bit will require less lubricant, yet it remains cool and sharp. You can use even the cheapest HSS drills to go through RVS almost like it's butter.
To me it sounds like you're trying to go too fast. As you noticed that can be dangerous, plus it can cost you lots of bits.
Hey All,
Thread cutting oil, ATF or even WD 40 work fine, as well as simple motor oil. Cobalt machine bits are best in my opinion. I have a set from Snap On That have lasted for years. If you're going to drill a lot of holes invest in a drill doctor sharpener. This sharpener is a must if you're going to be drilling a lot of stainless.
What is really important, much more important than RPM, is pressure. You want to put as much pressure on the bit as you can, Without distorting or bending the bit. Learn to feel when the bit is about to break through and then back off the pressure a bit. With enough pressure and a sharp bit the bit will CUT which is what you want. A dull bit, or too much RPM/too little pressure will mean a lot of friction, which creates heat. Heat makes the material harder and more importantly the bit softer, and duller at the tip. With a sharp bit and the right amount of pressure the metal will come out in two thin continuous ribbons. BE CAREFUL these ribbons are razor sharp and will cut accordingly.
Hand drills are meant to be portable. But unless you are moose, like me, you can't get much pressure with one. Invest a hundred bucks and buy a small Craftsman drill press from Sears or one Home Depot. Clamp the piece tightly to the table. If it moves the hole will be in the wrong place. Invest in a one hand spring loaded center punch. The ones you're meant to use with a hammer will always move when you strike them. With the punch you will have a tiny dimple in the metal. If you're trying to drill a large hole use a small bit to enlarge the dimple just a bit. Then use the full size bit. Small pilot holes for a large bit are a bad idea. You want the dimple to be large enough that the bit doesn't walk. But never use a large bit to "drill out" a smaller hole. When you do you dull the outer part of the bit cutting edge without affecting the tip. Then you'll have to sharpen the bit or it'll be worthless.
Thread cutting oil, ATF or even WD 40 work fine, as well as simple motor oil. Cobalt machine bits are best in my opinion. I have a set from Snap On That have lasted for years. If you're going to drill a lot of holes invest in a drill doctor sharpener. This sharpener is a must if you're going to be drilling a lot of stainless.
What is really important, much more important than RPM, is pressure. You want to put as much pressure on the bit as you can, Without distorting or bending the bit. Learn to feel when the bit is about to break through and then back off the pressure a bit. With enough pressure and a sharp bit the bit will CUT which is what you want. A dull bit, or too much RPM/too little pressure will mean a lot of friction, which creates heat. Heat makes the material harder and more importantly the bit softer, and duller at the tip. With a sharp bit and the right amount of pressure the metal will come out in two thin continuous ribbons. BE CAREFUL these ribbons are razor sharp and will cut accordingly.
Hand drills are meant to be portable. But unless you are moose, like me, you can't get much pressure with one. Invest a hundred bucks and buy a small Craftsman drill press from Sears or one Home Depot. Clamp the piece tightly to the table. If it moves the hole will be in the wrong place. Invest in a one hand spring loaded center punch. The ones you're meant to use with a hammer will always move when you strike them. With the punch you will have a tiny dimple in the metal. If you're trying to drill a large hole use a small bit to enlarge the dimple just a bit. Then use the full size bit. Small pilot holes for a large bit are a bad idea. You want the dimple to be large enough that the bit doesn't walk. But never use a large bit to "drill out" a smaller hole. When you do you dull the outer part of the bit cutting edge without affecting the tip. Then you'll have to sharpen the bit or it'll be worthless.
Yes, feed rate is as important as RPM.
Just like electronics there is a science behind proper machining. There are simple formulas you can use to calculate speeds and feeds and most hobbiest will have far better results if you are at least in the correct ballpark for both. If interested you can do a simple google search on calulating speeds and feeds for drilling.
Mark
Just like electronics there is a science behind proper machining. There are simple formulas you can use to calculate speeds and feeds and most hobbiest will have far better results if you are at least in the correct ballpark for both. If interested you can do a simple google search on calulating speeds and feeds for drilling.
Mark
Pressure is wonderful, if you are a big beefy (pick a race). I'm built to run down mastodons with a spear (Ie native am) and don't have enough chest muscle to use a 135 deg point effectively. When I resharpen bits, I resharpen them much pointier than 135 deg, which suits my body style. Try that with your drill sharpener tool. All you need to sharpen bits is a flat surface grinding wheel with one sharp corner, safety glasses, good light, and a water dip.
Perhaps the Netherlands doesn't have the same trouble with carrefour destroying the quality of everything they sell to make it cheaper. Discount store drills here are definitely inferior to hardware store ones, and real HS drills in my tool box are way better for not shattering than anything I can buy for cash except maybe the cobalt irwin ones. Fastenal has a local outlet with real drills but they really ****** the cash customer, besides being an 8 mile drive one way.
Lubricant is great, if you enjoy cleaning & cleaning. My neighbor spent longer cleaning up after his LPS tap fluid than we did drilling the hole. Now I keep a C clamp out in the country and drill stuff clamped to my trailer steps instead of dirtyiing up his shop. If I put a vise out there, someone would surely steal it.
Perhaps the Netherlands doesn't have the same trouble with carrefour destroying the quality of everything they sell to make it cheaper. Discount store drills here are definitely inferior to hardware store ones, and real HS drills in my tool box are way better for not shattering than anything I can buy for cash except maybe the cobalt irwin ones. Fastenal has a local outlet with real drills but they really ****** the cash customer, besides being an 8 mile drive one way.
Lubricant is great, if you enjoy cleaning & cleaning. My neighbor spent longer cleaning up after his LPS tap fluid than we did drilling the hole. Now I keep a C clamp out in the country and drill stuff clamped to my trailer steps instead of dirtyiing up his shop. If I put a vise out there, someone would surely steal it.
I don't find that speed makes a lot of difference other than how long the job takes, and it's short regardless. I drill most things (under 3/8") at about 1000 rpm or a bit higher. WD-40 makes a pretty good lube for aluminum- one of the very few things I use it for. For more serious work and for tapping I use Cool Tool II- never liked the tapping specific fluids. Always lube that gummy junk heat sinks are make from and back the chips out frequently. Can't imagine using anything other than decent USA made drills from a machine tool company- Travers Tool, Enco or MSC. Cheap drills end up way more expensive in terms wrecked stuff.
If you want accuracy, get a center punch and some center drills to start the holes. With nothing more than a magic marker (or layout dye), a steel rule and a sharp scribe, you should be able to put a hole within about .005" of where you want it.
To paraphrase from the movie Ronin- If there's any doubt than there is no doubt. If you have even the slightest doubt about whether you need to clamp something, you always clamp it. That would include all sheet metal parts of any type. I find the half Vise-Grip plier that fastens to the table very handy.
If you want accuracy, get a center punch and some center drills to start the holes. With nothing more than a magic marker (or layout dye), a steel rule and a sharp scribe, you should be able to put a hole within about .005" of where you want it.
To paraphrase from the movie Ronin- If there's any doubt than there is no doubt. If you have even the slightest doubt about whether you need to clamp something, you always clamp it. That would include all sheet metal parts of any type. I find the half Vise-Grip plier that fastens to the table very handy.
Hats off to mtj,
Speed
Rate
Heat
In my last life (still as hobby) I was a Pipe Fitter Welder. I have (still teach trade classes) drilled cut threaded and welded all of the above. Mark is the machinist, trust him.
Heat is not your friend. If it gets too hot you are not doing something correctly. Most aluminum we work with is pretty light. Drilling and tapping heat sinks is a little more complicate. Most 1/8 thick and less I do not use any lube. It your tool is sharp and the feed rate produces a good curl or spiral of removed material you are finished before heat is an issue.
For neat and precise work a table top drill press moves the quality a big step ahead. Amazon.com: Rockwell RK7032 10-Inch Drill press: Home Improvement
Consider a quality square, center punch and 4 oz ball peen hammer. Spring loaded punches are not jus for breaking auto glass.
Stainless steel drill lub trick. Use regular fat content milk. Milk does a good job and there is not too much trouble washing the work piece in the kitchen sink. No kidding, try it.
DT
All just for fun!
Speed
Rate
Heat
In my last life (still as hobby) I was a Pipe Fitter Welder. I have (still teach trade classes) drilled cut threaded and welded all of the above. Mark is the machinist, trust him.
Heat is not your friend. If it gets too hot you are not doing something correctly. Most aluminum we work with is pretty light. Drilling and tapping heat sinks is a little more complicate. Most 1/8 thick and less I do not use any lube. It your tool is sharp and the feed rate produces a good curl or spiral of removed material you are finished before heat is an issue.
For neat and precise work a table top drill press moves the quality a big step ahead. Amazon.com: Rockwell RK7032 10-Inch Drill press: Home Improvement
Consider a quality square, center punch and 4 oz ball peen hammer. Spring loaded punches are not jus for breaking auto glass.
Stainless steel drill lub trick. Use regular fat content milk. Milk does a good job and there is not too much trouble washing the work piece in the kitchen sink. No kidding, try it.
DT
All just for fun!
Hi,
drill bit r.p.m. must be related to material and diameter.
MTJ gives good advice. read it all and follow his instructions.
I specially bought a high power (1.5HP) low speed portable (Bosch) specifically for drilling. It offers 400rpm and 1100rpm with enormous torque. Wonderful!
Keep the feed rate high enough that the bit actually cuts pulling out the swarf in ribbons.
Break the ribbons regularly by stopping the feed rate (when hand fed).
Both edges should cut, with a properly sharpened drill bit.
If one ribbon is missing, or smaller, or breaks up, then the drill needs reshaping, accurately.
drill bit r.p.m. must be related to material and diameter.
MTJ gives good advice. read it all and follow his instructions.
I specially bought a high power (1.5HP) low speed portable (Bosch) specifically for drilling. It offers 400rpm and 1100rpm with enormous torque. Wonderful!
Keep the feed rate high enough that the bit actually cuts pulling out the swarf in ribbons.
Break the ribbons regularly by stopping the feed rate (when hand fed).
Both edges should cut, with a properly sharpened drill bit.
If one ribbon is missing, or smaller, or breaks up, then the drill needs reshaping, accurately.
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