Turning Tool And Facing Tool Questions

[Joe Pitz]

Carlo, thanks for the quick response of the pics. I like the close ups. I like how you grind the large reliefs on the tool.
I have to keep on practicing.

Jim, Thanks for the tips, when I get more skills I will definitely look on craigslist for odd jobs.

Looks like you have a very diverse background.

If I was younger I would definitely want to get into machine design, micro-controller based or processor based.
I love to mix software and hardware.

Thanks

Joe

 

[mikey]

I think using mild steel keystock to learn how to grind tool bits is a great practice. New guys need to learn to how to move their hands and mild steel makes this simple to do. And that tool will cut, although the edge won't last long. The important thing is to learn how to shape the tool to its intended purpose. Tool geometry is important and when you understand it you can make that tool do pretty much whatever you want. You can use a bench grinder or a belt sander to grind tools but you need to know what you're grinding and why you're grinding it the way you are.

With enough power and rigidity you can make almost any HSS tool work. Will it work as well as a properly ground tool with the correct angles for that material? I submit that it will not.

Here is a roughing tool intended for use on steel, just off the belt sander and ready for honing:



This tool will work fine for steel and most harder materials but it won't work as well on, say, aluminum as a tool intended for aluminum - all the angles are wrong and the results will show this. Moreover, if you use this tool on a small lathe with limited rigidity and power you will run into the limits of the lathe much sooner than if you use this tool on a larger lathe. Cutting forces matter; accordingly, so does the tool's geometry. This tool would look different if I were to use it on a little 6X lathe or Sherline lathe because I need to account for the limited power and rigidity of those machines. And this is just a rougher; a finishing or facing tool would look very different since it would be ground to suit it's purpose. The relief, side rake and back rake angles would also differ from the roughing tool and they would be further adjusted to suit specific materials.

I'm not trying to be argumentative or insulting in any way. I just feel that there is a rhyme and reason to tool geometry and as I said before, getting it close is not as good as getting it right. The bottom line is that each tool is ground to suit its purpose and the material it is intended to cut. While you can also make general purpose tools that will work for most materials they do involve compromises that we need to understand and accept.

 

[JimDawson]

If I was younger I would definitely want to get into machine design, micro-controller based or processor based.
I love to mix software and hardware.

Younger? He!!, I'm older than you are. At our age, that just means more experience to draw on.

 

[Tozguy]

Joe, if you think grinding stuff is expensive wait until you need more measuring equipment, collets, etc.
I look at it this way; it is very inexpensive medication. So much the better if you can make some dough back.
Mikey mentionned Sherline, hope that you don't mind yet another article link but this one seems tailored for beginners.
http://www.sherline.com/grinding.pdf

 

[Joe Pitz]

Younger? He!!, I'm older than you are. At our age, that just means more experience to draw on.

LOL, You are correct Jim, My wife will not let me quit my day job to pursue a new job, but I sure can have a part time job.

Joe

 

[Joe Pitz]

Thanks Tozguy, I will check out the article, I hate to tell you but Sherline is about 30 minutes from where I live. I have called them but never went by there showroom,. There stuff is good quality, but way too small for what I want.

Yes, When I was growing up my neighbor was a machinist, when he retired he gave me a complete set of Starrett mics, depth gauges and telescope gauges.

When I was going to school I worked in a gas station and one night someone got into my tool box and stole my test equipment. I was heart broken. Still to this day I wish I had that measurement gear.

Joe

 

[Joe Pitz]

Thanks mikey, as usual great information to take to heart. I will work on my rake and relief angles when I can get good shape going.

Joe

 

[mikey]

Joe, keep in mind that you are grinding the relief angles at the same time as you are grinding the shape of the tool. That is, when you grind the side cutting edge angle you are also cutting the side relief angle at the same time. When you grind the end cutting edge angle you are cutting the end relief at the same time. The relief angles are set by the angle of your tool rest. If you choose to free hand the tool then your angles will be approximate at best. Your lathe has enough power for a general angle to work but for those guys with small lathes this is going to be a crap shoot. It is better to have a tool rest/table that can be set to a precise angle and locked down.

As I said, I agree with using mild steel keystock to learn to grind tools. You are trying to understand how all the angles on a tool are cut. Relief angles are cut as above, while rake angles simply involve a straight push into the wheel or belt; it is much easier and more accurate to do this when you have a tool rest that can be locked at accurate angles. Once you understand how the various angles are cut then you need to learn how those angles function and how they affect cutting forces so that you can alter them to suit your needs. For example, if you need a fine finisher then you can increase side relief to provide a sharper interface and better clearance at the cutting edge and increase back rake to focus the cutting forces at the tip of the tool. Then you can use a slightly larger nose radius to create a really fine finish. None of this is difficult to do but you must first learn how to do it, how to move your hands and how to set your table angles.

Stay with it, seek understanding about how the various angles work and you'll be way ahead. Carbide tools work great but when it comes to tailoring a tool to your specific needs you cannot beat HSS.

 

[Strtspdlx]

Joe, keep in mind that you are grinding the relief angles at the same time as you are grinding the shape of the tool. That is, when you grind the side cutting edge angle you are also cutting the side relief angle at the same time. When you grind the end cutting edge angle you are cutting the end relief at the same time. The relief angles are set by the angle of your tool rest. If you choose to free hand the tool then your angles will be approximate at best. Your lathe has enough power for a general angle to work but for those guys with small lathes this is going to be a crap shoot. It is better to have a tool rest/table that can be set to a precise angle and locked down.

As I said, I agree with using mild steel keystock to learn to grind tools. You are trying to understand how all the angles on a tool are cut. Relief angles are cut as above, while rake angles simply involve a straight push into the wheel or belt; it is much easier and more accurate to do this when you have a tool rest that can be locked at accurate angles. Once you understand how the various angles are cut then you need to learn how those angles function and how they affect cutting forces so that you can alter them to suit your needs. For example, if you need a fine finisher then you can increase side relief to provide a sharper interface and better clearance at the cutting edge and increase back rake to focus the cutting forces at the tip of the tool. Then you can use a slightly larger nose radius to create a really fine finish. None of this is difficult to do but you must first learn how to do it, how to move your hands and how to set your table angles.

Stay with it, seek understanding about how the various angles work and you'll be way ahead. Carbide tools work great but when it comes to tailoring a tool to your specific needs you cannot beat HSS.

Not to hi jack this thread and make it about grinding HSS tooling. But... You're making me feel like I need to learn a lot more about how tool geometry effects the loads on a machine. I have a little atlas 10". I work with what I have though which is a little ryobi bench grinder with an aluminum oxide wheel I believe it's 60. And then I just hone the cutter to death.


Regards-Carlo

 

[Charles Spencer]

I learned to grind lathe tools and drill bits free hand years ago. It works well, but I came up with something a bit simpler recently. I bought a Harbor Freight Mini Tool Grinder off a guy cheap ($10). I sanded off the tool rest, put Dykem on it, and laid out lines at 59 and 30 degrees from both sides. The beauty of this little thing is that you can position it exactly as you want and it's not intimidating at all. I plan on getting another wheel for the other side, cutting down a protractor, and affixing it to the base. You can buy one new for less than $25 if you use a 20% off coupon.