How To Grind A Hss Turning Tool

What kind of aluminum oxide belts are you using? I went shopping today. got a wax stick, different brand, meant for threads or grinding etc, but looks like the right stuff. got a new 40 grit belt and a couple discs. I can grind about half a face using about 1/3 of the 4" belt. I get half a face ground and the belt is dull.
I'm trying to grind a 3/8 hss tool bit, pictured below...
Is this bit super hard? even my grinder is having a hard time. I like these 3/8" bits. the 1/4" ones I have seem to grind nicer...
What am I doing wrong here...

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The name on the belt is "Deerfos XA617+". Not sure why your belt aren't lasting - maybe the platen? My grinding times are with a 24 grit belt. I am putting about half the force needed on a bench grinder but there is force. Be sure your platen is not flexing as you apply pressure.

3/8" bits are much harder to grind than 1/4" bits - takes about twice as long to grind. What you have there is a T15 cobalt bit, which is even harder to grind - takes about twice as long to grind as a 3/8" M2 HSS bit. That bit will hold an edge for a long time and will cut harder steels but for most stuff you will turn, M2 is sufficient and easier to work with.

I have two suggestions. First, buy some M2 bits. Second, buy some 3/8" mild steel square key stock from the hardware store and practice with that first. When your practice tools look the way you want and you're clear on how to move your hands, etc, then move to the M2 bits. When those come out good, then go to cobalt.

By the way, what kind of lathe are you using and what is the top speed you can get on it?
 
I was wondering if it was harder... that was a nice uncut piece I had in my tool box. So I wanted to try to make a nice new bit. Others that had been previously gerund do grind better. The pieces I have coming are just standered hss. I don't think I'm too concerned with the mild steel practice. I was just dwelling on that one piece. I'm other words, it was kicking my ass...
I have another piece of 3/8 that ground nicer when I tried it, but then I got yelled at cause the noise woke the kiddo. Haha.

I have an enterprise 10 lathe. Check out "crazy threads" in the questions forum. It pretty well dovers all aspects of my lathe but it has a posted top speed of 2000 rpm. But I do most of my work in the 500-1000 range. Actually. I don't think I've ever even ran it at 2000. It would probably scare me half to death.
 
Okay, yeah, the M2 will be easier to work with at this stage. Oh, by the way, I had a good laugh as I pictured your face grinding that cobalt tool ... WTF!!??

I wouldn't be too afraid of higher speeds. The softer the material (aluminum, brass) the faster you can go. I usually turn aluminum at around 2800 rpm with HSS. Harder stuff and deeper cuts require slower speeds.
 
ill try the higher speeds. Just get it over with and learn.

What's the proper way to grind those harder tools? Specific wheels? Belts? Diamond?
 
I think I'm comfortable the slower speeds because my lathe can handle it better. Last time I used the high belt positions the lathe hogged down a bit. 3/4 hp motor.
 
Hukshawn said:
ill try the higher speeds. Just get it over with and learn.

What's the proper way to grind those harder tools? Specific wheels? Belts? Diamond?
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Use whatever speed works. My tools allow me to go faster.

I use the same belt sander to grind cobalt. It just takes me a little longer.
 
Hukshawn said:
I think I'm comfortable the slower speeds because my lathe can handle it better. Last time I used the high belt positions the lathe hogged down a bit. 3/4 hp motor.
Click to expand...

Oh, yeah, a 3/4HP motor might be an issue. My lathe has a 2HP motor on it. This is all the more reason to learn to grind tools - they will enable you to do a lot more with the power you do have.

I truly hope this turns out to be a worthwhile endeavor for you, Hukshawn.
 
Since It's on topic I thought i'd share this, special thread relief tool I made last week from a 3/8" square blank. The short end is .030" wide, and the long one is 0.045". Each end took about 5 minutes on my grinder using a CBN wheel. You can't see it in the picture but the short end is actually at an angle to the blank so that I could get the clearance need to clear a large shoulder.

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Whoa, Dan, that is awesome! Super-clean grind done with skill! Did it work as good as it looks?

I've been wondering how good a CBN wheel grinds HSS lathe tools. They're expensive so I was waiting for someone like you to report on it. Can I ask which wheel you're using? Is the corner of the wheel sharp or radiused? What grit works best for shaping and/or finishing?

Have you ground any turning tools with this wheel? I'd sure like to see some pics if you have them. No pressure, Dan, really but I just have a good friend that prefers a bench grinder and I've told him to look into CBN wheels and I think he, and others, would like to see the results.
 
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