Help with metal drilling

patrick_g · Jan 11, 2007

Berniep said:
Contrary to another poster it is not idiot proof as this idiot (me) couldn't get a good edge on a bit at first.

You really should get down below 200 for larger bits, ie 1/2" or larger.

I have the drill doctor also and it took this idiot a while to get a good properly sharpened bit.

We have two drill presses, my HF 16 speed floor model that will go slow enough for 1 inch bits in steel and the one I am borrowing from my wife. Her's is a Delta with CVT but the slowest it will go is too fast for drilling large holes in steel. Even with light pressure it is a BAD choice for large holes in steel. You will not get pairs of long continuous (Christmas tree decoration) shavings with her's using large bits. That said it is really good for lots of other things and as she won it as a door prize and didn't know what a drill press was it was easy to con her out of its use.

Pat

Egon · Jan 11, 2007

Kinda curious what the real cost of the supposed con job was???

patrick_g · Jan 11, 2007

Egon said:
Kinda curious what the real cost of the supposed con job was???

Actually, she really didn't know what a drill press was but as it was very heavy and industrial looking and was clearly man stuff she wasn't super interested. She was just super pleased to have won the best prize of the day as she had never ever won a door prize or similar before in her life. I made her a standing offer to show her how to use it and promptly started treating it as if it were mine. She has never inquired about its well being other than a conversation we had when it self destructed. Delta sent me a slew of new parts re-engineered to avoid the problem and it has been fine ever since. Then Delta sent me another set of parts. Their "SYSTEM" got a little messed up when they merged with that OTHER tool company.

Pat.

Egon · Jan 12, 2007

Ahh - Then your still paying for it!

dfkrug · Jan 12, 2007

I have been drilling 1-in holes in 1/2" plate for a long time with my
16 y.o. Delta drill press. I never use it above its slowest speed,
250 RPM. And that is too fast. Turns out it will be tedious to
convert it to a slower speed, so I am considering a replacement.

I am strongly considering the HF 20" "production" drill press. It
has a coolant pump and 3/4" chuck, as well as an on-sale price
of $359. 150 RPM is its lowest speed, which is good.

Anyone have that unit, 39955? It seems well-built enough at the
store. I like the heavy construction and 1 3/4 hp 120V motor.

patrick_g · Jan 13, 2007

dfkrug, IF my experience with my HF press is typical then you will probably get a lot of good service from the HD unit. Mine is a 16 speed (you change two belts on three pulleys) that is only a 1/2 inch chuck so you have to use reduced shank bits for large bores. I feel underpowered when I drill substantially thick material for holes above about 3/4 inch diameter or so.

I sometimes wish I had more HP but then if I did I would probably just make bigger mistakes most likely with this unit. I think I have had it for about 20 years. Never replaced a belt or had any problem. It just works. I could stand to have a larger tilt table for it. I have the rather smallish circular one but it isn't a big problem as I can mount a larger table on top of the original when really needed.

With HF's innexpensive extended warranties you could get the whole thing replaced if you have a problem.

Pat

bamatoolmaker · Jan 13, 2007

Never heard of hardened bed rails.Speed is the front runner for dulling drill bits.Using force on a dull bit is going to break it.One thing I have not read yet is spraying WD40 on a red hot drill will cause combustion.I know I've seen it happen.On our machining centers we use synthetic coolants which I think mainly consists of parrifin.Water soluble oil is a good coolant/lubricant too.The only problem is degreasing the parts before you can get paint to stick.For just a couple holes on a manual milling machine we use chainsaw bar oil.The advice about multiple drilling to increase diameter is the correct way it is called step drilling.Here is something else to think about, did you all know that the end tip of a drill bit does not cut the absolute center doesn't even turn.

patrick_g · Jan 14, 2007

bamatoolmaker said:
Here is something else to think about, did you all know that the end tip of a drill bit does not cut the absolute center doesn't even turn.

OK, I thought about it and expect I'd have to have some things explained and defined before I could agree.

At first glance I'd expect that the center turns at the same angular velocity as the rest of the bit. If it didn't then the part of the bit next to the center would either be turnning slower than the rest(more outer portions) or would be shearing and tearing the metal. If all parts of the bit don't have the same angular velocity somewhere the metal is being sheared, twisted, or otherwise greately deformed and the bit would be disintegrating while getting really hot.

There is one way I can easily agree to the center having a zero value. The various parts of the bit and also of course the cutting edge have a linear (Circumferential) speed depending on angular velocity (RPM dependent) and the radius or distance fron the center of that particular part of the bit or cutting edge. The outer extent of the cutting edge is moving the fastest and as you move in toward the center (smaller radius) the speed falls off linearly until you reach the center where since the radius is ZERO the circumferential or "linear" speed is therefore also zero.

So, it isn't that the center isn't turning it is that the center is ONLY turning but not going anywhere so the distance covered by the center as it rotates is ZERO.

If the center is traveling at a zero speed then it does not cut! We certainly agree on that part!

I hope this is what was intended by "bama" and if so we are in total agreement. Otherwise I guess we'll just have to agree to disagree.

I hope I was clear enough so that if anyone disagrees they can point to a specific portion they believe to be in error.

Pat

dqdave1 · Jan 14, 2007

I never read on this thread but; since bed rails are soft steel, not hardened; I hope the drill was running the correct direction. Running in reverse makes a simple hole drilling project take a long time..
To slow down the presses; change pulleys; it is that easy; if you have the space. Smaller pulley on motor usally will do it.