Brazed Carbide Fail

foleda

foleda

Registered
Registered
Joined
Jun 8, 2014
Messages
99
After a case of sticker shock while shopping for an inserted carbide parting tool I cheaped out and bought a brazed carbide parting blade instead. Turned out to be a case of
"getting what you pay for." It worked fine cutting off a few aluminum and brass parts but when I used it to cut off a part turned from a grade 8 bolt it started out fine, with a nice chip curling out of the cut, then about 1/4 inch in stopped cutting. I backed it out of the cut and found:
carbide-01.jpg
carbide-02.jpg
Inspecting the other, unused end reveals that it comes pre-cracked for your parting pleasure:
carbide-03.jpg
 
lol, I have a Shars tool that looks almost exactly like that one, only mine is broken at both ends...

Get a cobalt HSS parting blade and never worry about the costs again. They are easy to sharpen, will cut anything, and last a lifetime.
 
Parting a Grade 8 fastener is going to be tricky. They're tough and hard. Not the best material to try and machine
and then if it's also an import bolt. Quite a bit of load on a parting tool.
IMO a Cut-off wheel and then clean up with a tool bit or heavy carbide insert tool would be best.
 
middle.road said:
Parting a Grade 8 fastener is going to be tricky. They're tough and hard. Not the best material to try and machine
and then if it's also an import bolt. Quite a bit of load on a parting tool.
IMO a Cut-off wheel and then clean up with a tool bit or heavy carbide insert tool would be best.
Click to expand...

The steel used in grade 8 fasteners is indeed tough stuff which makes if very nice for making parts that require high strength. I find that it machines nicely with carbide insert tools and leaves a beautiful finish. If I need to turn off the head of a bolt I use HSS because of the interrupted cut. The HSS tool dulls very quickly.

The part I was making (an alignment pin) could have easily be cut off external to the lathe but I had a (nearly) brand new
cut off blade that I wanted to try out to see how well it handled a tough job. With the pre-existing cracks it did not stand a chance.
 
brino said:
Hey Dave,

Great photos!
Horrible tool!

-brino
Click to expand...

Thanks, I used a $15 USB microscope for the microphotography. It was advertised as a 5 megapixel camera but I have only been able to get 640x480 images from it.
 
that does look crappy. Couple of things with brazed carbide. One, it needs sharpening out of the box. Look at the unbroken end - it's got a chip on the cutting edge. I use HF diamond cutting wheels in my dremel to sharpen mine and it makes a world of difference. Two, it's really unforgiving, especially in steel. The slightest bit of flex, chatter or a jam and BAM it's chipped or broken. I went through 3 brazed bits in quick succession on a recent project. Gave up, slowed down and used HSS. Now I tend to only use them for high speed finishing cuts in crappy steel.
 
foleda said:
Thanks, I used a $15 USB microscope for the microphotography. It was advertised as a 5 megapixel camera but I have only been able to get 640x480 images from it.
Click to expand...
You might still be able to get 5mp out of it. Has to do with the capture software.
Check the setting on the program that you're using. Needs to be in 'Still' Capture mode.
I was able to get 1600x1200 (2mp) out of mine.
I just went to fire up the laptop that I use it on to refresh my memory which program I used,
and of course the dang thing doesn't want to boot this afternoon.
 
You must log in or register to reply here.
Back
Top