Learning the HSS ropes

[Batmanacw]

I've used HSS thousands of times on my lathes through the years and I've achieved "good enough" finishes and acceptable accuracy. I've never been wowed by the finishes but good enough is good enough.

Today I spent quality time with the Mulliner Enlund lathe. It's also a good time to practice with the Armstrong type tool holders in a lantern tool post. I've never ground tools for use in one of these tool.posts and holders and it is readily apparent I've got plenty to learn.

This was the tool that did the best today.



The lead edge took advantage of the tool holder angle, with back rake toward the tailstock. I ground enough clearance to work with the holder and not rub. I ground enough clearance that the tool can be used to turn and face. That turned out to be important later.

This is the beautiful old girl making chips.

Most of my test cuts showed some tearing in the cuts. I pretty much ran 340 rpm (top speed until tomorrow), at 0.003" to 0.005" feed with the point leading just a bit. My brain is thinking like a CCMT insert. 0.005" ipr was a bit nicer than 0.003" every time. Depths of cut ranged from 0.005" per side up to 0.020" per side.

This is an example of the slightly torn finish.



I tried a bunch of stuff including honing my cutting edges to a really high polish.

It wasn't until I set the leading edge more perpendicular to the direction of travel did I finally see a change.

This is my last pass tonight after changing the angle of the cutter. 0.005" and 0.005" per side.




It still isn't as smooth as I'd like so I'll increase the radius a bit more tomorrow and try again. I might grind another tool with a lead edge angle to give some more surface area and back pressure.

This piece is within 0.0001" at both ends but within 0.0003" over all. For a beautiful old machine of 106 years old I'm ecstatic.

 

[woodchucker]

does the cutting edge/CORNER have any radius? When I first started I played with geometries that were not in the book just to get an idea of how different changes affected things. I made a rounded edge on one tool. You won't see it in any book and it looked great. It told me that sharp corners will show every .001 of feed, while radiusing it will start erasing those lines.

I also played with my dremel cut off wheel after looking at pictures of carbide inserts, and thought I could just put a cut right near the edge to break chips.. As clumsy as my cut was, it worked well.

What I am trying to say is play, and learn. keep making A single change and cut, try different spindle speeds, different feeds. Forget the book, the goal is to learn when you change this, you are getting that in return. Then go back to the book. It was a few days or weeks of good education. I kept modifying one or two chunks of hss. so I wasn't destroying a lot. Sometimes I used the cut off wheel to start from scratch.

I'm no expert, but it sped up the education that I hadn't gotten from a mentor.

 

[Batmanacw]

does the cutting edge/CORNER have any radius? When I first started I played with geometries that were not in the book just to get an idea of how different changes affected things. I made a rounded edge on one tool. You won't see it in any book and it looked great. It told me that sharp corners will show every .001 of feed, while radiusing it will start erasing those lines.

I also played with my dremel cut off wheel after looking at pictures of carbide inserts, and thought I could just put a cut right near the edge to break chips.. As clumsy as my cut was, it worked well.

What I am trying to say is play, and learn. keep making A single change and cut, try different spindle speeds, different feeds. Forget the book, the goal is to learn when you change this, you are getting that in return. Then go back to the book. It was a few days or weeks of good education. I kept modifying one or two chunks of hss. so I wasn't destroying a lot. Sometimes I used the cut off wheel to start from scratch.

I'm no expert, but it sped up the education that I hadn't gotten from a mentor.

I totally agree.

The tool in the picture has around 0.010" to 0.015" of radius. I'm going to increase that a little tomorrow.

I'm looking forward to making a tool with a leading edge angle of like negative 10⁰ to 15⁰.

 

[T Bredehoft]

It's been quite a while since I worked HHS, but I'd have about two to three times the angle on top of the tool. And swing it around to that the "point" was behind the leading edge.

 

[Batmanacw]

It's been quite a while since I worked HHS, but I'd have about two to three times the angle on top of the tool. And swing it around to that the "point" was behind the leading edge.

Which angle on top? The back rake away from the chuck? The tool holder gives around 15⁰ from the part.

 

[mickri]

Have you read Mikey's thread on grinding HSS tool bits? As for nose radius the MOLO recommends a 1/32 radius. The MOLO also gives suggested angles for tool bits used in lantern tool posts and holders. That would be my starting point. Why reinvent the wheel.

 

[Batmanacw]

Have you read Mikey's thread on grinding HSS tool bits? As for nose radius the MOLO recommends a 1/32 radius. The MOLO also gives suggested angles for tool bits used in lantern tool posts and holders. That would be my starting point. Why reinvent the wheel.

What is a molo?

 

[Forty Niner]

It still isn't as smooth as I'd like so I'll increase the radius a bit more tomorrow and try again. I might grind another tool with a lead edge angle to give some more surface area and back pressure.

While you are searching for the tool that gives a great finish, try a "shear tool" grind. It is ONLY for a very light finish pass, but I have produced excellent finishes with it.

 

[benmychree]

Use of a cutting fluid would likely improve finishes.

 

[twhite]

It could also be your material. Cold rolled does tend to tear more than other materials. Depending on type of CRS you are using.


Cutting oil is my blood.