Models for grinding HSS Lathe Tools

[mickri]

The people who actually know something about this will chime in here. I would start by looking up the surface speed per minute for the type of steel that you are turning. Then look at feed rates and depth of cut. The MOLO has some of this stuff. The machinists handbook would probably be the best resource. Then move on to the shape of the tool bit. Wish I could offer more help.

 

[9t8z28]

Yup, already know sfm. Around 90 for roughing and as high as 250 for finishing. I was all over and in between plus the DOC was figured and was all over the place as well.
Now that I think about it, 1018 isnt the most notable for good finishes. I should retract my previous statement and worry about other things. These tools work exceptionally well on the majority of materials.

The people who actually know something about this will chime in here. I would start by looking up the surface speed per minute for the type of steel that you are turning. Then look at feed rates and depth of cut. The MOLO has some of this stuff. The machinists handbook would probably be the best resource. Then move on to the shape of the tool bit. Wish I could offer more help.

 

[mikey]

Sitting in the ER with my wife right now so I can't give much feedback at this time. Basically, 1018 doesn't finish well, regardless of the tool. Your best shot is to angle the tip towards the tailstock, increase speed and take light cuts.

 

[mikey]

Brandon, 1018 really sucks when you need a good finish. I know of no other material that is worse for that than 1018. About the best I've been able to do with it is to cut it with the side or end cutting edge just adjacent to the nose radius, taking very light cuts at the highest speed my lathe will go and manually feeding it. 1018 often has hard and softer spots so your bands are not surprising. I avoid this material unless I just need something made of steel. I haven't bought it for many years because it is so difficult to finish.

If you need an alternative material, try 1144 Stressproof - better steel for most uses and finishes really nicely.

 

[mikey]

Mikey and I exchanged a few emails regarding me doing some drawings of the common tool bits. He thought that I should post my drawings. I did the drawings in Google Sketchup. Then converted the drawings to a jpg image. I can't upload the sketchup files. If anybody would like a copy send me a pm. All of the angles are what Mikey set forth on page 4 of this thread. I did the drawings using 3/8 x 3/8 x 3." While the actual drawings are to scale I doubt that the jpg images are to any particular scale. I did not attempt to round the point. Sketchup won't do a 1/64 radius. Hope these are helpful.

Thank you for the drawings, Mickri. Some of us are visual learners who will find the drawings very useful.

 

[mickri]

Mikey, You mentioned being in the ER with your wife. I hope all is well.

 

[9t8z28]

Sorry to hear that. Hope everything is ok.

Sitting in the ER with my wife right now so I can't give much feedback at this time. Basically, 1018 doesn't finish well, regardless of the tool. Your best shot is to angle the tip towards the tailstock, increase speed and take light cuts.

 

[9t8z28]

mickri, I think the drawings look excellent. I studied them in comparison to how I thought that Mikey describe them and how I grinded them and they appear to be spot on. I think these are an excellent visual aid to go with Mikey’s specs.
Could you somehow match the colors with the degrees in some form of a little chart?
EDIT: If matching the colors with the degrees is to much to do then it would be nice to have a listing with the back rake degrees, side rake degress and so just to keep it all in one place.

 

[9t8z28]

Thanks Mike.
I have been wanting to make a 2x72 belt grinder but I am unsure on how to go about it. I haven’t really done to indepth research but I probably wil eventually. It would be a very useful tool and after its built I would probably not use the 6” grinder as much.
I agree with you that grinding is all about developing muscle memory. I can still remember working in shop class when the teacher had us all grind a turning and threading tool. We all stood in a circle behind the teacher watching him grind the tools. Not one of us had a good view of what he was actually doing. Out of the whole class I had the most experience grinding tool bits so I wound up teaching and coaching half the class on how to do it. Some toolbits were ground down to a stub! The teacher tried to tell a few students that they got their HSS toolbits too hot and ruined the hardness and had to start over with a new tool. I argued with him that if it was possible then a 1/4 of the class would have had 2nd to 3rd degree burns on their fingers!

I'll make some comments but let me preface them by making something clear to you and everyone else. Your work piece doesn't know or care what your tools look like, and your lathe only cares about what your tool angles are. Many of us are grinding on small bench grinders or belt sanders; not everyone has a cool 2 X 72 and this will impact on the quality of the tool - can't be helped. Add to that the fact that for many of you, this is a new endeavor and your brain is still learning how to move your hands to produce a working tool. Please do not compare your tools to anyone else's efforts, including mine, because it doesn't matter.

Okay, your square tool came out really, really nice. All the angles are there and you stopped the rake angle grind at exactly the right place so that the tip is at the same height as the shank - good job. Your nose radius is on the large side but not overly so. This tool will cut well, for you, Sir, and I think you did great! I honestly don't think I could have done that tool much better.

Your knife tools are a bit rough but again, the angles are there and those tools will work for you. I know they will because my early knife tools looked very much like them and they could shave off a few tenths on tool steel. I cannot see a nose radius on them but I can barely see one on mine; as long as it is there then it will work for you. In time, they will look nicer but I'm not sure they will work better.

This stuff takes practice. It took me a very long time to make tools that actually look like lathe tools. Not everyone has the talent to grind tools right off the bat like Jeff, Travis, DaveH, Brino, HBilly or Barry. If you ask me, those guys are mutants. For us regular guys, Brandon, I think you did great. More than that, I bet your tools will work just fine and your grinding efforts will only get better with time.

My suggestion is to work at understanding how the tool angles work and how you can adjust them to do what you want them to do. The shape of a tool only determines function; how well it works depends on the tool angles. The other thing to consider is making/buying a good belt sander if tool grinding is something you intend to stick with. If you go that route, consider a 2 X 72. It will be good for tool grinding but it will be even more useful for general shop use and fabrication.

 

[mickri]

I chose the colors to make the ground faces show up better. No other reason. Mikey did a table of the different angles. I'll see if I can copy it and add it to the post with the drawings. I thought about trying to include the angles on the drawings. I'll see what I can do.

I just tried to include the angles in the threading tool drawing and was not able to show the angles in a way that would be usable. Was able to add Mikeys table of angles to my previous post.