Kryptonite Bushings

epanzella

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A friend of mine needed to get four bushings turned down in a hurry as a huge job paving an airport was held up waiting for the work to be done. The bushings were 9 inches long, 6 1/2 inches in diameter and had a 3 inch bore. The busing are used to mount a paving hammer on a 50,000 pound excavator. One excavator broke so they had to move the hammer to another machine and they were too wide by 3/8". I don't know what the hell they were made of but any faster than 200 rpm and .025 DOC and my carbide cutters were spewing flames like the 4th of July! HSS cutters would last about 5 seconds! It took me 9 hours to do the four of them. Anybody have a clue what those kinds of bushings are made of?
 
Unobtainium. Seriously, 'tho, just about any alloy steel can be heat treated to that level. Ceramic tools will triumph over such hard stuff.
 
Kryptonium. The fissionable isotope of Kryptonite.
R
 
I don't use mine often but these come in handy. Of course you can simply just use any file to get an idea of how hard something is & don't really need this set.


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I did a file test before accepting the job. It did score but seemed it took more effort than normal. Not having a lot of experience machining hard stuff I thought it was just my imagination but I guesss it wasn't.
 
Sounds like it was a job for a grinder.
 
Where I work we use a steel material called ETD 150. This is a prehardened grade with additives to make it machinable. We use it to make gears that do not require any heat treatment or other secondary processes yet wear almost forever at 7,000 rpm.
I took some drops home for my stock.
When I went to use it to make something, it literally vaporized the edge off of HSS tools. The HSS barely even left a scratch. The only way I found to cut it on the lathe was to use carbide tools and a fairly aggressive cut. No sneaking up on a dimension. Dig in and go right for size.

Your bushings might be something similar.
 
ETD 150 stands for "elevated temperature drawn"
It's a chrome moly steel with a fair percentage of silicon in it, no wonder it's hard to cut
 
Yeah those bushing were the nastiest stuff I ever machined. Because .375" had to be removed I tried at first to use a cutoff tool and just leave a facing cut. As I only have HSS cutoff tooling it dulled before it even made a groove. Even my normal insert tooling was having trouble because the inserts weren't thick enough and the tips were breaking. Finally I used a huge weded carbide cutter that I had to machine to fit my BXA holder. The carbide was about 3/16 thick and it lasted for the whole job but I had to sharpen it 2 or 3 times per bushing.
 
Where I work we use a steel material called ETD 150. This is a prehardened grade with additives to make it machinable. We use it to make gears that do not require any heat treatment or other secondary processes yet wear almost forever at 7,000 rpm.
I took some drops home for my stock.
When I went to use it to make something, it literally vaporized the edge off of HSS tools. The HSS barely even left a scratch. The only way I found to cut it on the lathe was to use carbide tools and a fairly aggressive cut. No sneaking up on a dimension. Dig in and go right for size.

Your bushings might be something similar.
I have used ETD150 for high stress parts, the "150" stands for the tensile strength, not a lot higher than 4140 HT, which I have machined a lot of, in my opinion, neither is particularly difficult to machine, but yes, skim cuts are not recommended. It is made by LaSalle Steel, also maker of "Stressproof".
 
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