Tough Steel?

Dynahoe Dave

Dynahoe Dave

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I made a couple of parts from a piece of 5/16" thick bar stock I've had for years. Never thought it was anything unusual. It has the black scale on it, like many pieces I have had. It cut ok on my bandsaw. I went to drill 2) 25/64" holes, and it was like not much else I've drilled. Center drill worked normally. Went back with the 25/64, and pretty much stopped cutting shortly after the full diameter was involved. Dulled as heck. Sharpened up, 2nd try killed it almost instantly. Sharpen again, drilled through with an old Sears 13/64" bit, as a pilot hole, figuring if it get wrecked, who cares. It went through, ok, not easily, but ok. Back to the 25/64, and instantly dulled again.... Hmmm... Went to get another bit, figuring maybe this one had been overheated or something. Found another 25/64, tried it, it worked ok, but wow, the force required was higher than normal, and the weird noises. Scratchy gritty sometimes. But it cut. Did all 3 holes with the pilot and this bit, both survived, but all were the same unusual to me tough cutting.

Any idea what this piece of bar stock could be? Why would it be so nasty to drill?
 
UNK, but running slower would have helped the burning up of tools in a big way.
 
I just grabbed a hunk of 304 from the scrap bound pile . 18" x 12" x 1 1/2" . One heavy pc of stainless . I have no immediate use for it but thought it would make a good tractor weight or something .
 
Dynahoe Dave said:
I made a couple of parts from a piece of 5/16" thick bar stock I've had for years. Never thought it was anything unusual. It has the black scale on it, like many pieces I have had. It cut ok on my bandsaw. I went to drill 2) 25/64" holes, and it was like not much else I've drilled. Center drill worked normally. Went back with the 25/64, and pretty much stopped cutting shortly after the full diameter was involved. Dulled as heck. Sharpened up, 2nd try killed it almost instantly. Sharpen again, drilled through with an old Sears 13/64" bit, as a pilot hole, figuring if it get wrecked, who cares. It went through, ok, not easily, but ok. Back to the 25/64, and instantly dulled again.... Hmmm... Went to get another bit, figuring maybe this one had been overheated or something. Found another 25/64, tried it, it worked ok, but wow, the force required was higher than normal, and the weird noises. Scratchy gritty sometimes. But it cut. Did all 3 holes with the pilot and this bit, both survived, but all were the same unusual to me tough cutting.

Any idea what this piece of bar stock could be? Why would it be so nasty to drill?
Click to expand...
You could try doing spark tests on the bar stock to get a rough idea of what you've got. First test is whether it is magnetic or not. There are some good videos on Youtube illustrate the spark patterns and colours.

BTW, it sounds like the first 25/64" drill is suspect. Sounds to me like it is made of tool steel and has lost its temper (if it was ever properly tempered).

Craig
 
the black scale indicates hot rolled steel
the scale can be quite hard and will wreck a drill bit in seconds
remove the scale with a grinder or through other means before drilling
hard feed and low speed are the names of the game when drilling tough materials

use of sulfur bearing cutting oils, bacon grease mixed with mineral oil, or anchor lube is how i do it
custom drill bit grinds can make metal peel off easily, reduce the rake to about 8° to 10°
i'll use cobalt bits if i know i'll be opening a can of corn when drilling into hard stuff
stepping holes up is another method that assures success too.
i'd start with a 1/8" and got to 1/4, form 1/4 go up to 3/8 then finish @ 25/65
 
Maybe an AR500 hot rolled? Sounds more like that 25/64" drill bit was suspect.
 
The 1st drill is part of a made in USA set, that have been pretty good in general. I can say the 2nd bit was likely a better grade. The second is likely a cobalt steel one, as I have been replacing any that get too messed up to fix with my Darex sharpener with cobalt. I have drilled a lot of holes in a lot of things, and short of stainless, this piece is the toughest I ran across. The sound was weirder and force was higher and than normal, even with the bits that worked..

Yes, I tend toward lower speeds anyway, but once I had this, I went down even lower. The dulling didn't happen until after I was through the scale - all of the tries after the initial were into the already started hole. Yes, I'll look at sparks, etc. The bar stock is magnetic, I have made some things with stainless, so I know it can be tricky. I don't cut stainless on the bandsaw. Killed a blade that had cut who knows how many feet of steel in a very short time. Sparks off the grinder make slightly finer and more branches than a regular random piece of bar that was handy.
 
I found a description of AR500. "Can be machined with carbide tools." If the piece I have isn't this, it is close.
 
I have found some scraptanium that I have yet to find a tool that will cut it effectively. One was a bolt that I dug out of a scrap bin. It was big enough to have something hiding inside of it so I grabbed it. First thing that came across as a possibility was to use it as a flycutter. So I chucked it up on the lathe and tried to cut it with HSS. It made a hideous noise and removed the edge from the tool. So I switched to carbide and tried. The carbide burnished the surface but wouldn't cut it.

I figured it must be hardened so I heated that puppy up cherry red and let it cool off in my makeshift forge. A bit of scale formed on it so I wire brushed it off and went after it with the carbide again. All it would do is squeal and polish. So I took it to the grinder and found it makes a decent wheel dresser. The wheel does wear on it some but it wears the wheel more. Still not sure what it is though.
 
Found a pile of laser cut diamond shapes at the metal supply scrap area.
1/4” thick with drilled holes in the center.
I’m Making a chain saw sharpening tool stand for a coworker.
Same thing, center punc ok, I only have good drill bits, I started out ok then it quit drilling.
Sharpened the bit, slow and hard second time, got almost through and the bit broke.
Broke two bits.
I assume it’s some kind of structural steel?
Tough steel!
 
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