Models for grinding HSS Lathe Tools

[mikey]

Thanks for the kind words, guys. If you look at the pics in this thread and imagine my hands going left to right repeatedly, that is essentially how I grind a tool. Not a whole lot to the grinding thing. Page 4 of this thread will show you how to get the shapes you need for the three model tools discussed here, and you can PM @Z2V to get on the list to see and handle the model tools.

I do agree that a video would be nice to do one day, although as I said, it would just be me going back and forth.

As to the thought process behind the tool angles, that has been covered in this thread. Somewhere in this thread are some pdf files of all the stuff I've written on HSS tool geometry, too. I offered to do a group brainstorm thing where we would go through the thought process for grinding a tool for a specific material but it never took off; I figured the guys just weren't interested in it.

Guns, if you read this thread (yeah, I know its a monster), most of what is in my head is also in here. What is not here is how I think. That tool you referred to was something @Ulma Doctor and I brainstormed together to see if we could come up with a tool for his shaper. That was fun and it seems to work pretty okay but the thinking part is something we did in a PM. We can share that if the Doc chooses to do so.

Oh, and just to be clear, I'm no genius. All I did was not buy into the belief that the standard tool angles found in a tool table were gospel. Then I took the time to grind hundreds of test tools to see what worked and what didn't work. To be very honest, much of the motivation for learning this tool grinding stuff was so that I could make my live center. I needed to grind a tool that could reliably take a tenth of material off of 1144 steel and with control to make the arbor for that live center. You see, it isn't hard to rough stuff. Inserts and brazed carbide or even any old HSS tool can rough, but not every tool can take a micro cut with control. That takes an understanding of tool geometry so that is what I set out to do and it worked out pretty well.

Paul Thede, the owner of Race Tech Suspensions once said, "The best you've ridden is the best you know." If all you've ever used are inserted carbide tools then its natural to think that those tools are all you'll ever need. Little do you know that there is a whole lot more to precision turning than those tools will allow. I own carbide tools, too, but I don't use them often because HSS works better for me in most cases. The thing is, I have the option of choosing which tool to use; many do not.

I encourage you to give tool grinding a try. It isn't for everyone but if you own a smallish lathe or if you need to turn with great precision from time to time then it is a skill well worth learning. If I can help, I am here.

 

[WobblyHand]

 

[Ulma Doctor]

@mikey , you have my blessing to use any part of our communications to further the transfer of knowledge to the peanut gallery!!!

 

[ttabbal]

the peanut gallery!!!

Hey! I resemble that remark!!

Honestly all, I started from zero learning this stuff. If I can grind good tools, you can too. Get and read the Book of Mikey, and grind some cheap keystock to get a feel for it. I enjoy making my tools. I really enjoy dialing in a tiny cut and watching the metal dust just flake off.

 

[benmychree]

And a round nose tool! My machine shop teacher in high school showed us how to grind the various tools, gave each of us pieces of key stock and we went to work on our tools, when we could show him a properly ground tool, he gave us all brand new tool bits to grind, and all of us kept them for the school term.

 

[tmenyc]

Yes, I stalled at it partway through, after a few failed square tools, until Mikey got to me in a PM. Since then I've got it done, and actually like making them, it's fun, although a bit slow on my 6" Dewalt grinder. I now have LH and RH square tools, a RH square with a really small NR, and a 60 deg threading tool I use all the time. Absolutely worth doing, and creates a whole different perspective on turning, when you made the tool.
Tim

 

[WobblyHand]

Back to the inverted "el" tool. I tried it out, documented in the LED spindle light thread, and found it was rubbing more than it was cutting. Rarely made chips, more like grey dust. Sometimes when adding oil, it would start to cut. The tool needed a lot of pressure to work. It was a balancing act between applying pressure and stalling. It made the workpiece smoking hot, eventually boiling off oil! Even the chuck was hot! It seems that I didn't hone the cutting edge right up to the top of the tool.

Guessing that little flat edge up near the top of the triangle is the culprit, right? So I touched the belt sander to this face. (100 grit ceramic, about 14.3 degree.) I really couldn't even tell the sander was cutting, that's how light a touch. It removed just enough material on the triangle to remove the top facet. A lot more honing later, (325, 600, 1200 grit) I had this:

Is this good enough, or is more polishing is needed? There's a hint of a bright spot on the top right corner, but I'm having a difficult time removing it. I think it's a little less than 0.010". That face is about 0.100" wide. My patience is being tested, as honing seems to take forever. After thinking about it some, I took some of the tiny flat spot out by flattening the right hand side triangle edge, like one does on a single point threading tool. Still can see it at 8X.

My diamond cards are loading up with grey HSS dust and it's getting hard to get that nice polished face. (Get streaks, or tiny gouges.) I tried wiping the cards with an alcohol wipe, but the wipe fibers then catch on the stone. I then use a kimwipe to get some of the fibers off. There's still stuff on the cards. Is there an easier way to clean the diamond honing cards?

 

[WobblyHand]

An alternative is to use an internal grooving tool but its more fun to grind it.

Grinding is fun. You can see a tool taking shape. Honing by hand takes far too long to be fun (at least for me). It's hard to maintain the flat faces, especially if they are very small. Is there a poor man's diamond grinder that could be used for tool bit making? Would a Noga indicator holder be stiff enough to hold the tool and maintain a clean face? Or is something more robust needed?

 

[mikey]

... it was rubbing more than it was cutting. The tool needed a lot of pressure to work.

In order to cut, the edge must have adequate relief under the cutting edge. From the end of the tool, the profile must be shaped something like this. The arrow is pointing to where you have to have relief, a clearance angle. Only the cutting edge must touch the work piece.

Is there an easier way to clean the diamond honing cards?

Some scouring cleanser, like Comet or Ajax, works well. Scrub with cleanser and a brush and do this often.

 

[WobblyHand]

I can report that the new tool works! It has about a 14 degree relief. It cuts chips! Getting rid of the flat spot fixed it. Just touched the belt sander lightly and it cut the tool down enough to eliminate the flat spot. Lots of honing after that. The workpiece didn't get hot, and really didn't need much if any cutting oil.