drilling harden steel -success

Southern Ray

Well-known Member
Did it with a carbide drill bit and antifreeze for lubricant.
My drill chart says 5/16" for a 3/8" pipe tap. I made the first hole. It was too small for the tap.
I measured my pipe tap in a 3/8" gauge hole and decided to go for 3/8".
I went back and bought a 3/8" bit and drilled it out and tapped it.
I can now breathe new life into the old disk.
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Glad it worked for you--carbide isn't for every application, but it sure does work well for those where nothing else will!
 
Wow time for a new tap drill chart, a 3/8 pipe tap takes a 37/64 drill, which is just over 9/16. Myself I would simply tap them 1/8 pipe for a standard grease fitting. Much smaller and easier to drill and tap
 
Yes sir, you are correct.
1/8" pipe tap is what I use.
Blame it on excitement and not paying attention to what I am typing.
 
Ah ok, then 11/32 would be the drill to use assuming you don't have a pipe thread tapered reamer
 
When drilling hard steel cast, machined or stainless, try a cobalt bit. They go through that stuff like butter. Thats all I own. Cost a few cents more but do better and last longer. Henry
 
I love cobalt drills - bought the 115 piece set from Harbor Freight, fractional, lettered, and numbered. Handles just about anything that comes up at or below 1/2".
 
Judging from the chips, it was, in fact cast iron. If steel, even with a carbide bit I would expect to see some "curls".
 
I replaced the cutting edge on a 992 Cat loader one time. Not the bolt on replacement, but the weld in spade nose edge that all of the wear plates bolt to. It was around 3 or 4 inches thick and probably 18ish feet long. After we welded it in, we had to drill all of the holes for the wear plates, which was probably around 40 or 50 holes. The Hougen magnetic drill with the carbide rotary cutters wouldn't hardly scratch it. We had to heat the area around each hole with a rosebud to a certain temp to take the hardness out. Worked much better, not fast, but at least it would cut.
 

Looks like cast iron chips to me. You can tell what you have for ferrous metal by grinding it a little and observing what the sparks look like. Google Spark testing.
 

Is that a clam shell and spool bearing?? I have worn out many many many of them... They dont seam to hold up very well.
 
(quoted from post at 09:19:42 09/22/16) When drilling hard steel cast, machined or stainless, try a cobalt bit. They go through that stuff like butter. Thats all I own. Cost a few cents more but do better and last longer. Henry

Check the thermal coefficient of water vs ethylene glycol .
 

Yup that is why some machines overheat when the mechanic thinks some is good and more is better . 1/3 propylene glycol and 2/3 distilled water sure beats 2/3 ethylene glycol and 1/3 tap water .
 

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