This may be a dumb question, but is it easy to drill through iron?
I need to drill 2 x 3/16-inch holes through the cast iron cap of a 1- inch black pipe. I've never drilled through anything tougher than wood, so I don't know if that's a big deal or not. What kind of drill bits should I buy? What drill speed should I use? Should I use a lubricant? How many holes can I make with each bit? (I need a total of
8.) Since the surface isn't flat, do I have to worry about the bit bending away from my target spot? How long can I expect each hole to take?
Browsing this group, I've seen mention of laser and EDM. Should I consider finding a shop which can use one of those techniques for me?
Cast iron is probably easier to drill than almost any metal other than aluminum -- unless it happens to be chilled cast iron, in which case they would have had difficulty making the internal threads which allow you to screw the caps onto the pipe.
You don't mention whether you are using a hand-held electric drill or a drill press -- and whether you need to have the holes parallel to the pipe's axis, or whether they can be at a slight angle.
With a hand-held electric drill, you should be able to drill perpendicular to the surface of the crowned end at the point of drilling without problems -- especially if you use a center punch to mark where you want the drill bit to go. If you get a split point drill (you probably can't find those in the typical homeowner hardware store, but an industrial one should be able to provide what you want.
Things would be a little easier to control with the split point drills, but just about any quality drill bit should work. (Note that cheap import bits can be of a very poor steel and can give problems with even one hole.
For a 3/16" bit, for as few holes as you are considering, probably whatever a 1/4" electric drill motor produces will be close enough. However, going into _Machinery's Handbook_, for HSS (High Speed Steel) bits in cast iron, the *maximum* speed should be (Assuming ASTM class 30, 40, and 50 -- it is actually probably not as hard a cast iron), the SFM (Surface Feet per Minute) is 80, which calculates out to about 1630 RPM.
You can always run slower and get longer life from the bits.
Keep the speed down, and you probably don't need lubricant for as few holes as you mention below -- especially since cast iron tends to be self-lubricating anyway. But if you really feel like using lubricant, try the high sulfur oil used for pipe threading (Rigid is probably the brand you will find in your local hardware store.)
I would expect over 100 holes with one bit -- if you are careful. If you apply side stress, however, you can break the bit long before it gets dull, so it would not hurt to have a couple of spares. Watch the bit (and wear safety glasses). If the bit visibly bends, you are applying too much force -- and too far off center. You are better off applying the force to the handle directly behind the chuck. If you move down the typical handle, you are more likely to bend the bits as you drill.
As I mentioned above -- it is easier if you can drill perpendicular to the domed surface of the cap -- but if you have to drill parallel to the pipe axis, be sure to use a center punch to mark the center of the hole and to guide the bit.
Depending on speed and sharpness of the bit -- between fifteen seconds and one minute.
Those are totally overkill for this job. Get a couple of extra caps to experiment with and see how easy it is.
Yea. What the other guys said. Sometimes pipe caps have raised crud on the end or even an initial or something that sticks up. If so, you can flatten any humps off at a grinding wheel of almost any sort.
Walmart sells "bullet point" drill bits. I don't remember the name on the tag. These things are great for what you want to do. Still use the center punch.
Buy a spare cap and a 3/16 drill from the hardware store and have at.
Try around 500 rpm. More or less. Don't worry if you cannot get it exact, the cap won't tell. Center punch the start point, keep steady pressure. Hold the work in a vise if you can, vise-grips, if no vise.
Don't worry about lube. It's 8 holes, not 8000.
I am sure that there are several EDM and laser shops that would be GLAD to take your money. And they would laugh, and laugh, and laugh!
Any lubricant is better than none in my opinion. A little oil off the dip stick of you car would work if you don't have any oil on hand. If you are going to buy some oil the high sulfur stuff for threading pipe is really good. Automatic transmission fluid is another useful oil.
Use a file on the surface if it is really rough and use a center punch. If you have problems with the bit skating away from the spot where you want the hole, use a short small drill to drill a pilot hole. It will stay in the dent made by the center punch better than the larger drill. By small I mean about a 1/16th diameter drill.
Most would laugh, but at a shop like the one I'm at, as long as you don't demand it now or tight size or just being an ass aboutit, we'll likely just whip it out for you and if we charged anything, it'd be a couple bucks.
"Harold and Susan Vordos" wrote: (clip) It needs no lubrication, (clip) ^^^^^^^^^^^^^^^^ Right. What better lubricant is there than graphite? That's what characterizes cast iron.
That sure is true. Our cnc's machine cast iron, aluminum, and steel. My preference for repairing said machines is steel, aluminum, cast iron.
Cast iron with coolant is like carbon black mixed in water and honey. The only good thing I can say is the chips don't cut my skin.
Aluminum in our processes tends to look a lot like chaff. With the coolant it sticks to everything, gets through any gap and can give you a ton of small cuts.
Steel really isn't too bad. Most of it goes down the chip conveyor, doesn't seem to stick to the machine. Just have to be sure if you kneel down to look under the machine and rest your hand on the floor there are no curlies around or it can and will bite.
Cast iron cuts better with a bit that has had the hook taken off the edge. A drill bit can be modified by grinding the cutting edge's flute to a surface that's aligned with the bit's axis rather than having the slope created by the helix. Such an edge won't snag and break the bit, and cast iron (gray cast, anyway) cuts best when it's pushed a little rather than scooped out as a normal drill will do. And a modified bit has a thicker section through the cutting edge and doesn't heat so quickly. HSS lathe bits will cut cast well if there's a neutral rake on them.
We used to have people stop in (two-way radio shop) with simple little jobs that were smart/kind enough to bring along a dozen dough nuts give-or-take (grin, burp! aah!)
They usually got good service and little in any paper work, plus a cup of fresh coffee while they waited.
I just finished step-drilling a 3/8" hole through a 1/4" thick cast iron table of an old table saw. Centerpunch, started with a 3/16" good quality bit, finished with a 3/8" bit. All done with a cordless hand drill. (couldn't hold it up properly on the drill press).
Caveat: if the hard surface layer from casting is still present, use a file to knock it off. Drilling through that layer is likely to ruin the bit.
Hmm ... why *two* holes then? I guess that you *could* set up an electric fuse and run the two wires each through their own holes, but that is stretching it a point. :-)
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