I would be particularly interested in the knife for facing and a threading tool in addition to general turning. Could you possibly show the difference between a roughing and finishing tool also.
Would also like to see your tool rest if you would care to share a pic or two. I'm looking for ideas for my own belt grinder.
Again, thank you
You can see my grinder and tool rest here:
http://www.machinistblog.com/modifying-a-craftsman-2-x-42-inch-belt-sander-for-tool-grinding/#more-5349.
You should also look at the thread by
@Alan H on his tool rest:
http://www.hobby-machinist.com/thre...and-work-table-upgrades-lots-of-photos.61968/
@ddickey also has a 2x72 grinder he is setting up for tool grinding; you can PM him.
As for roughing and finishing tools, if you intend to use separate tools for all three common lathe operations (roughing, finishing and facing) then we can do that. Having separate tools was popular before we had quick change tool posts and all three types were used with the tool shanks perpendicular to the work. The advent of the quick change post changed that and now most guys prefer to use a general purpose tool to rough and finish.
The relief and rake angles are different on a general purpose tool vs the older style tools and you have to understand how they differ because general purpose tools are a compromise. In order for a single tool to handle heavy cutting loads and then turn around and take fine sizing cuts with a fine finish is a tall order. And yet, we can come pretty close if we add a little more side and end relief, add in a bit more back rake and increase our nose radius just a little bit. These changes are subtle but make a huge difference in how the tool performs.
You also have to bear in mind that no tool cuts all materials equally well. A general purpose tool is really a shape, not a designated tool with specific angles. You can use the same shape but have relief and rake angles that are optimized for a given material class and that tool will work better for that material class.
Rather than grind a tool for every material class, I'll grind a Square Tool. This is a general purpose tool that will work pretty well with most materials commonly used in a hobby shop. If you work with a particular kind of material a lot then it will be better to change the angles on the tool to better suit that material. For example, a general purpose tool for aluminum will have larger relief angles, more side rake and way more back rake than a Square Tool will have but the overall shape of the tool will be the same. The aluminum tool will typically have a slightly larger nose radius than one for say, steel; this gives us a mirror finish that a smaller nose radius would not do as well.
As you can see, there is a lot to grinding a good tool. The thing is, once you see how the table angle is set to grind a relief angle on my model then it is a simple step to know that increasing that angle a degree or two more will reduce cutting forces further and allow the tool to cut with greater ease. Similarly, once you have a solid idea of how the side rake is ground then that really opens the door to changing how your tool can cut with lower cutting forces and cutting temperatures. I can tell you how to do it but if you also see the model so you can set the actual table angle then that makes it simpler to understand. I think that's been the missing link for a lot of guys and is the key reason for doing this model tool thing.
What I intend is to write an article that goes with the model tools. I will show how each is ground and why each angle is chosen. I will also tell you when to change the angles, how to change them and why. Once you are clear on this stuff it is a simple step to deciding how to grind a tool that will do exactly what you want it to do.
I don't know how much you know about tool geometry or tool grinding, Jeff, so pardon me if I'm insulting you by referring you to an article that I wrote that might make all of this clearer. You can see it here:
http://www.machinistblog.com/?s=belt+sander&submit=Search. Its in three parts but all the articles are on that page. Look it over and we can go further if you need to.
