Drills & drill bits

[md21722]

you will continue to dull bits.

unless you pony up for really high end stuff, and even then, with the inconsitency of a hand drill, you'll probably ruin those as well.

How about you add some details to make this more than finger pointing & saying don't even try.

 

[rockclimber]

How about you add some details to make this more than finger pointing & saying don't even try.

seriously? don't be an asshat.

I (and pretty much everyone else in this thread) already told you what you need to know.

you are drilling too fast.

 

[md21722]

seriously? don't be an asshat.

I (and pretty much everyone else in this thread) already told you what you need to know.

you are drilling too fast.

Rough weekend? Look who started the name calling.

I'd ask what you consider to be "really high end stuff" but at this point I really don't care what you have to say about it. Other folks here have said to decrease pressure and increase speed at the end.

 

[rockclimber]

Rough weekend? Look who started the name calling.

I'd ask what you consider to be "really high end stuff" but at this point I really don't care what you have to say about it. Other folks here have said to decrease pressure and increase speed at the end.

seriously?

Get yourself a gear-reduction 1/2" drill. They're great for drilling though steel. I have one that's ancient but works great.

As for actual drilling go slow and use lots of lube (teehehe). If you see tiny chunks of steel flying off the bit you're going too fast. If you see nice long stringers coming off the bit you're just right.

Drill press with low speed attachment. Those Norseman bits are the bomb. I've got that set. You can save a bit by purchasing them from Harry Epstien

http://www.harryepstein.com/index.php/hi-molybdenum-29-pc-drill-bit-set-jobber.html

The speed in rpm's needs to be a function of a bunch of things. First off, machinists talk about cutter speed. That means how fast the cutting edge is going through the metal. As the bit gets larger you have to slow down. With a small bit, you need to speed up. Secondly, you need to know how hard the metal you are trying to drill through. If it is soft, you can handle a faster speed. If it is hard, you may need to slow way down.

The single biggest problem I find with drilling problems is turning the bit too fast. It causes it to heat up and in just a couple of seconds you can dull a bit.

The second biggest problem is keeping the bit lubricated. The same lubricant isn't for every type of metal. For instance, on cast or forged steel, you want to use a thick Sulphur based lube. With aluminum, you can get by with a much thinner lube. Some machinists will use WD40.

The third biggest problem is the type of bit you are using. There are a ton of variations here. Don't use the TIN (gold) drill bits in aluminum. The aluminum tends to stick to the drill and gum up everything. In iron and steel, the angle of the bit can impact the quality of the hole. Some bits are not designed to drill a blind hole where there was no predrilling.

My favorite all around bits are sometimes called step bits, not the ones that look like Christmas trees. There is another name for them but I can't remember it at the moment. DeWalt has them and they tend to drill a ton faster and cleaner. They look like a normal drill but if you are drilling a .5" hole, when you look at the bit, it has what appears to be a smaller diameter bit at the end, then it jumps up to the .5" diameter.

:dunno:

More times than I can count, I have been in the field with a Lawson Split-Point bit and a "Good grade of 30 Wt Oil" (per AAR S-486 and MSRP Section H-Lubrication Manual), and bored a half-inch hole through some 3/8" A-36, at the lowest speed the drill motor could turn.

Was it machine shop perfect? Probably not. Was it within industry tolerance? Absolutely!

That Lawson bit has been in my kit for awhile now, making steel curls, every time I need to make that bracket...

nominated.

 

[Hypoid]

Other folks here have said to decrease pressure and increase speed at the end.

I have said that. I think that was in reference to the bit grabbing as it breaks through the work piece. If I have the luxury of using a drill press, and can back up the material behind the hole, I see no need to lighten the pressure.

 

[dan1977p]

It hasn't been asked by the OP, but it's pretty relevant to this conversation so I'll ask here vs a new thread. What parameters should one look for when buying a drill press? It's on my short list of tools and though I know the theory or go slow, I need to know what slow really means and make sure I can adjust the speed of the press to match the common materials used in fabrication.

 

[old_man]

It hasn't been asked by the OP, but it's pretty relevant to this conversation so I'll ask here vs a new thread. What parameters should one look for when buying a drill press? It's on my short list of tools and though I know the theory or go slow, I need to know what slow really means and make sure I can adjust the speed of the press to match the common materials used in fabrication.

This is like asking what kind of car should I get. It all depends......What are you going to be drilling?

The biggest variables are the (1) depth of throat (2) size of bits you are going to be using (3) type of material (4) rigidity of the column (5) amount of slop in the quill (6) type of chuck.

 

[md21722]

I have said that. I think that was in reference to the bit grabbing as it breaks through the work piece. If I have the luxury of using a drill press, and can back up the material behind the hole, I see no need to lighten the pressure.

Right, I'm dealing with hand drills, not a drill press. I can't exactly put an axle in the drill press. Nor can I put an air tank top plate that's welded to the tank in the drill press. A hand drill is not the same as a drill press. The object being drilled is typically more fixed than the hand drill. Although with my gear reduction low speed drills that max out at 450 RPM, when they catch at the end they can spin an entire axle off jack stands and turn it. I have found that for large holes, drilling multiple small holes and stepping up works well. The split point has dulled on some invariably because of some error on my part, probably from higher speed, but on the larger drills I've seen the edges chip off likely because of the binding at the end. If I was drilling flat stock in a drill press I probably wouldn't be asking these questions.

 

[GSequoia]

One of the best tools I have is my ancient Thor 1/2" reduction gear drill (it's older than Tom!). It runs at about 500 rpm and has serious power behind it. I use it for all of my offhand thick jobs.

 

[AIbandit]

Some great info in here thanks.

 

[md21722]

After many more holes and a few more drill bits, I have found that the published drill speed charts aren't necessarily applicable to pistol grip hand drills. I don't have a drill press at this time to check against. The difference is that with a drill press you have a lot more ability to set the feed rate. With a hand drill its almost impossible to apply enough force for the proper feed with larger bits, so the drill bit more or less vibrates and bounces around. This creates heat and friction rather than cutting. Using a pistol grip drill, at super slow speed, with firm hand pressure, you can actually feel it cut the metal.

As Mike (Hypoid) alluded to drilling "as slow as the drill will turn" I have successfully drilled 1/2" - 9/16" holes with nothing more than a 1/8" pilot hole and my 450 rpm and 700 rpm air drills turning as slow as they will go and without stalling and applying firm pressure. They have a sensitive trigger and will turn slow enough that I can see the chuck key holes turn one at a time but I go faster than that. With these super slow speeds, the drill is more likely to stall than spin around and try to break your wrist at the end.

Everyone I see using a press tends to drill faster, maybe around 700 rpm which is the lowest speed many of the drill presses go.

So, in summary, as best I can tell, for hand drilling, ignore the drill speed charts. Save the drill speed charts for a drill press with hand or automatic feed.

 

[rockclimber]

most full size drill presses will go well below 700rpm. mine will do 250 at its slowest. I'd like to go even slower sometimes.

 

[md21722]

A bunch of the folks I ran into were saying their presses didn't go slower than 700. Maybe they don't know or they have cheaper ones. I know HF sells one that doesn't go below 760. The better ones are after 15-16 speed and will go down as low as yours.

 

[TRCM]

If their drill press doesn't go slower than 700 rpm, it ain't worth a crap, or it's a table top or bench version.

Mine is a harbor freight special, and it goes down to 180 rpm.

If you have a bench drill press. like this, then you are right...760 is min
http://www.harborfreight.com/8-in-5-speed-bench-drill-press-60238.html

If you have a real drill press like this, well.......
http://www.harborfreight.com/12-speed-floor-production-drill-press-39955.html

 

[md21722]

If their drill press doesn't go slower than 700 rpm, it ain't worth a crap, or it's a table top or bench version.

Mine is a harbor freight special, and it goes down to 180 rpm.

If you have a bench drill press. like this, then you are right...760 is min
http://www.harborfreight.com/8-in-5-speed-bench-drill-press-60238.html

If you have a real drill press like this, well.......
http://www.harborfreight.com/12-speed-floor-production-drill-press-39955.html

I agree, I think a good many are real cheap drill presses. One guy I talked to is using a $129 Ryobi from Home Depot and others are in a similar boat.

The missing link to all of this for me was that feed and speed are directly related. When using a hand drill you cannot provide the necessary feed so the drill speed charts go out the window and you just go much slower than suggested. The best part of all of this is that the bits don't bind up anymore and so they don't chip edges off and aren't rendered useless.

Bottom line, using a hand drill is way different than using a press.

I've seen some comments that say past 1/2" you cannot even set feed with a manual feed drill press so you'd need to use an auto feed or slow down.

 

[md21722]

To the other poster who asked about drill presses, the key points are buy one with a powerful motor that go down real slow, less than 500 RPM. These good ones are often 15-16 speed. You will probably pay at least $600-700 for a new one and a lot more if its an auto feed.

 

[dan1977p]

To the other poster who asked about drill presses, the key points are buy one with a powerful motor that go down real slow, less than 500 RPM. These good ones are often 15-16 speed. You will probably pay at least $600-700 for a new one and a lot more if its an auto feed.

Thanks.

 

[md21722]

I discovered something else I need to figure out. Drilling through weld.

A good example is filling in some holes in plate that needed to be redrilled.

I can drill hundreds of 1/8" pilot holes in mild steel at 3200 RPM with a simple HSS black oxide bit without issue. But if I do that in weld, I can't drill even a 1/3" of ONE hole. If I grab a new bit and drill it REAL slow I still can't drill one hole. Next I tried a NEW Norseman which is made out of harder metal, and at 3200 RPM I could not drill one hole either. So then I tried drilling it REAL slow. And I could drill about 2-3 holes before it stopped working.

Googling around, drilling through weld is basically drilling through very hardened metal and may require a solid carbide or carbide tipped drill bit ? The prices of carbide tipped drill bits are staggering, and if they are solid carbide, its even more staggering. I'm seeing 7 piece sets that cost over $200. And 20-29 piece sets cost $500-700.

Any suggestions?

 

[md21722]

Doing a little more digging, it seems like carbide is too brittle for hand drilling. Cobalt is probably the way to go?

 

[rockclimber]

I've never had any problems drilling through weld on mild steel.