Models for grinding HSS Lathe Tools

[moorejl57]

I am new to this forum and I just went through this whole thread, quite a lot to take in, but very informative. I have a Sherline 4400 I bought back in 2004 and just now want to try grinding a general purpose square tool as you outline. I have been using the negative rake insert holder that is now obsolete. The finish is nowhere as good as a sharp hss tool. My question is about the side angle. In the instructions you mention marking the 3/8" blank at 1/8" at the top and 3/4" along the side to define the angle. Doing a little math, the tangent is sin/cos = 0.125/0.75 = 0.166667, and the angle is the arctan = ~9.5 degrees. Is this the angle I should set? I am going to grind a 1/4" blank since I have a handful of these and my tool holder is for 1/4" as well.

 

[brino]

@moorejl57,

Welcome to the group!

-brino

 

[Janderso]

Mikey,
Didn't you grind a bit for Ulma Doc's shaper back in 2018?
The beauty of HSS, you grind it right then just touch it up as needed.

 

[mikey]

I am new to this forum and I just went through this whole thread, quite a lot to take in, but very informative. I have a Sherline 4400 I bought back in 2004 and just now want to try grinding a general purpose square tool as you outline. I have been using the negative rake insert holder that is now obsolete. The finish is nowhere as good as a sharp hss tool. My question is about the side angle. In the instructions you mention marking the 3/8" blank at 1/8" at the top and 3/4" along the side to define the angle. Doing a little math, the tangent is sin/cos = 0.125/0.75 = 0.166667, and the angle is the arctan = ~9.5 degrees. Is this the angle I should set? I am going to grind a 1/4" blank since I have a handful of these and my tool holder is for 1/4" as well.

Welcome to HM!

Don't worry about precise angles for the side and end cutting edge angles. For a 1/4" square tool bit, mark about 2 times the thickness of the bit on the side, about 1/2". Then mark about 1/2 way across the top, roughly in the middle of the bit on top, then draw a line. Set the tool rest to whatever angle you wish (I suggest 15 degrees) to get your desired side relief angle and grind to the line. On the end, you want about an 80 degree included angle so draw that line and grind to it. Then do the rake angles as shown on page 4 of this thread and you're there.

I also have the 55 degree negative rake tool and while it works, a HSS tool will easily outperform it on your 4400.

Let me know if you have questions.

 

[mikey]

Mikey,
Didn't you grind a bit for Ulma Doc's shaper back in 2018?
The beauty of HSS, you grind it right then just touch it up as needed.

I actually ground two of them; one for steel and one for aluminum. We actually had a long and fun discussion about what he wanted and he sent me the rectangular blanks. They seemed to work out well.

 

[Janderso]

I actually ground two of them; one for steel and one for aluminum. We actually had a long and fun discussion about what he wanted and he sent me the rectangular blanks. They seemed to work out well.

I was down at his house picking up some equipment he donated to me after the fire. He showed me what he received from a fellow in Hawaii.
I put 2+2 together.
You know your stuff dood!

 

[mikey]

Thanks, Jeff. We took an unconventional approach to shaper tool geometry on those tools but it seemed to work well.

 

[moorejl57]

@moorejl57,

Welcome to the group!

-brino

Thanks!

Welcome to HM!

Don't worry about precise angles for the side and end cutting edge angles. For a 1/4" square tool bit, mark about 2 times the thickness of the bit on the side, about 1/2". Then mark about 1/2 way across the top, roughly in the middle of the bit on top, then draw a line. Set the tool rest to whatever angle you wish (I suggest 15 degrees) to get your desired side relief angle and grind to the line. On the end, you want about an 80 degree included angle so draw that line and grind to it. Then do the rake angles as shown on page 4 of this thread and you're there.

I also have the 55 degree negative rake tool and while it works, a HSS tool will easily outperform it on your 4400.

Let me know if you have questions.

OK, got it, don't over think the side angle. Thanks for the quick response. All I have right now is a 6" grinder, but I think I can make it work for this.

 

[mikey]

Yup, a 6" grinder will work. I used one for over a decade to grind tools with so I know it will do the job. Just take your time and get the tool angles the way you want them and you'll be fine.

 

[fcs]

What tool will work well with bronze, either alloy c642 (duronze?) or c544? I am learning to make small fishing rod ferrules on my little Sherline. A good finish is more important than hogging off material. Any additional advise about working with this stuff (drilling, reaming) is welcome. Both these alloys are used successfully by others for the purpose, but they are using bigger machines. What is the machinability index? Its 60 for 642 and 80 for 544 I think.
—
Frank