Order a hss bit and ground hss tap (msc has fast shipping.) Cast is usually like butter compared to most metals (generally speaking) so I'm not sure where the trouble is coming from.
Order a hss bit and ground hss tap (msc has fast shipping.) Cast is usually like butter compared to most metals (generally speaking) so I'm not sure where the trouble is coming from.
Is the drill turning in the right direction?
Happened to to me once...(insert red face here).
Cast iron has always drilled easy for me...
Too much to do...Not enough time...life is too short!
Appreciate all the inputs into this!
Here is a picture of what I am trying to do in case it highlights what I may be doing wrong. I'm going to try my drill press this evening....
There's your problem. Turn the bandsaw right side up so that gravity will help you.
"Anything seems possible when you don't know what you're doing."
I would guess 10-20 pounds force into the bit.
Bill D.
ok tried to drill a hole in a different section that is maybe 1/4" thick vs 1" thick where I've been trying to drill. Worked pretty well as everyone has said. I did change to a new bit halfway through as I assume I killed the other bit. I'll use a nut here instead of tapping it and that will work for my purposes.
IMG_0319.jpg
Maybe the 1" hole is in an area that was extra hardened...
<sorry for some reason the website keeps rotating my images...>
You drilling into or next to a rib?
You drill and tap cast iron dry.
Glad its my shop I am responsible for - I only have to make me happy.
That's pretty funny Van.
I just drilled and tapped four holes this morning in a tablesaw for a power feed. Dull bits, and used a cordless drill. Started with a 1/8" bit and went to 3/8" for a 7/16-14 bolt. I think I drilled each four times.
I drilled dry, tapped with cutting oil.
Anneal cast iron? Awesome. Please understand what what separates cast iron from steel. Cast iron is full of free graphite and is self lubricating. I've tapped dozens if not hundreds of threads in cast iron with a shop made guide and no lube.
Have you considered a mag-based drill? Great way to get good pressure and perpendicular holes
Watching Adam on his Abom79 YouTube channel (machinist) he sometimes runs into a hard spot on cast iron that defies a normal drill. Solution is a carbide or cobalt drill. In my limited experience, I found that cast iron was a dream to drill and tap dry with normal HSS tooling.
NOW you tell me...
I know this is an old thread, but since it might turn up in someone's search, I'll add my experience in drilling, and tapping cast iron. I had to upsize, and rethread some stopped depth holes in the engine block on one of my tractors, that held the front end loader on. 5/8" threaded holes had to be upsized to 3/4", and 3/4" threaded holes had to be upsized to 7/8".
In the past I had drilled and tapped holes in cast iron without much trouble. For this job, I tried hand drilling the holes up to the correct size with a handheld 3/4" drill, and that didn't work out too good. Bits were broken, and one 49/64" bit was bent. I ended up buying a magnetic based drill press, but shortening the story to get to the threading part.....
I read what I could find on threading cast iron, and a number of places recommended cutting oil, but not regular cutting oil. There is a "dark" cutting oil that has Sulphur in it. You can even find it in the plumbing section in Home Depot.
Those holes had bottoms in them, so I could not safely risk using the magnetic drill press to tap the holes, even though that is one function of that drill press. I found some large tap handles on ebay. They could be tapped by hand, but it was a bit scary in dry holes, because I could feel the tap flexing (edited to add: might not have really been flexing, but I could tell I was close to the limit on the dry tap). Once I found out about the dark cutting oil, and bought some, the tapping went like cutting butter.
From that experience, I'll recommend using the dark cutting oil when tapping cast iron. Those large holes exposed all the weaknesses.
Also, note that taps come in different types. The commonly seen type is used for starting the hole, and for through holes. With stopped depth holes, you need a set of three taps in that size. The regular one starts the hole, there is another one that cuts the threads a little deeper, and then finish with a bottoming tap. Be careful to note what depth you are going to, because taps are hardened, and pretty easy to break. It's an extra pain to break one off inside a hole.
Last edited by Tom M King; 09-15-2019 at 8:54 AM.
If that is the drill bit you are using, it is the wrong type of drill bit. That type is designed for wood. Try to find bits that look like this:
drill bits.jpg
Lee Schierer
USNA '71
Go Navy!
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Good eye Lee. That would surely cause the problem.