Turning Tool And Facing Tool Questions

JR49 said:
Will do, Mikey, but it may take a day or two (medical issues, old man stuff)
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Made me laugh. I just had major back surgery 5 days ago and I've been typing these responses while doped up on Hydrocodone. If I offended anyone I sincerely apologize.

I don't mean to put you in an uncomfortable position, JR. You don't need to make the tool but if you do I suspect you will be surprised that geometry well beyond what we normally use can work well. I would be very interested in what you think.
 
Strtspdlx said:
Not to stick my nose in although I do love to learn. My entire strategy behind grinding tools is to have the cutting edge present itself with the least amount of force necessary. I try to use smaller nose radi in hopes the heat will stay in the work vs being absorbed into the tool and I try to adjust for proper chip clearance but I haven't quite figure that one out yet. So far the only time I've damaged a tool is when I'm not paying attention and touch off way to hard. Or I think I touch off and I don't and run the tool way to deep. My whole outlook has been to present the cutting edge too the tool with enough clearance to keep heat in the work and not the tool.


Regards-Carlo
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Carlo, most of the heat in a cutting operation is carried off by the chips so chip clearance is very important. Chip clearance is enhanced by side rake - the more side rake you have the better the chip clearance will be. Back rake also plays a role here but not as much as side rake.

In your pictures of your tools you posted earlier in this thread it looks like you use very little side rake and almost no back rake. This will cause your tool to cut with very high cutting forces and poor chip clearance because you are basically presenting a square edge to the work. I would suggest you grind in both side rake and back rake in amounts appropriate for the materials you are cutting. This will give you a much sharper cutting edge that will not only cut cleaner but last longer. It will also clear chips much better and keep cutting temperatures down.

You also said you free hand your tools and never measure angles. That's fine - lots of guys do this. I can free hand a tool and come within a degree or two of what I want but I've been doing it for over 25 years. For best results or until you have a lot of experience I highly recommend you use a rest that you can set at known angles so you can control your geometry. Then take the time to learn to grind the proper relief angles, side and back rake and the tool shapes you require.

Please don't take this the wrong way as I'm not trying to criticize you in any way. I want you to succeed and I assure you that there is a great deal to be gained from learning to grind a good tool. Those three articles that Joe linked to above will give you a good start in understanding how all the angles work and how they can be ground into your tools.

Joe started this thread and it has evolved into a tool grinding thread. That's okay - so far, Jim hasn't put a stop to it and until he does we can all use it to help each other and share what we know about tool grinding. I, for one, value your input.
 
mikey said:
I don't mean to put you in an uncomfortable position, JR.
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Are you kidding? Threads like this one are my favorites. I hope Joe is OK with how his thread has evolved, cause there is definitely a lot to be learned here. As far as putting me on the spot, here is what I'm planning. Just the other day I ground a 3/8" tool with front and side clearance, a small nose radius, but almost no side or back rake. This tool seemed to cut pretty well on my 12" Logan, BUT, I don't really think that I have enough experience to know the difference between a good cutting tool or a poor cutter. So I'm going to grind another 3/8" tool with the angles that you listed in post #78. Then I will cut the same steel rod, half with each tool. This way even a beginner like me should see a difference, and if it is OK with you Joe, I'll report my findings here. One thing I need from you first Mikey is, please tell this beginner what you mean by a "square tool" Thanks, JR49
 
mikey said:
Joe started this thread and it has evolved into a tool grinding thread. That's okay - so far, Jim hasn't put a stop to it and until he does we can all use it to help each other and share what we know about tool grinding. I, for one, value your input.
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I think this thread has a lot of valuable information and even this old dog is learning :) The lack of learning how to hand grind tools is one of my pet peeves. I don't use insert tools and have always hand ground my own, be it carbide or HSS.
 
JR49 said:
Are you kidding? Threads like this one are my favorites. I hope Joe is OK with how his thread has evolved, cause there is definitely a lot to be learned here. As far as putting me on the spot, here is what I'm planning. Just the other day I ground a 3/8" tool with front and side clearance, a small nose radius, but almost no side or back rake. This tool seemed to cut pretty well on my 12" Logan, BUT, I don't really think that I have enough experience to know the difference between a good cutting tool or a poor cutter. So I'm going to grind another 3/8" tool with the angles that you listed in post #78. Then I will cut the same steel rod, half with each tool. This way even a beginner like me should see a difference, and if it is OK with you Joe, I'll report my findings here. One thing I need from you first Mikey is, please tell this beginner what you mean by a "square tool" Thanks, JR49
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I call it a square tool because all the angles are the same - side relief, end relief, back rake and side rake - all 15 degrees. I've ground hundreds of experimental tools and have found this particular combination to cut well in most materials. It is not optimized for any one metal but will do a decent job on most, from mild steel to stainless to 1144 and even aluminum. It is fast to cut because the table angle doesn't change. It is also easy to resharpen for the same reason. On my belt sander I can grind one from a blank in about 4 minutes and hone it for use in another minute.

Typically, I will shape this tool halfway between a rougher and facing tool so it is a general purpose tool that will turn and face by changing the lead angle. I made one just like this in the third article in the series Joe linked to. Your tool should look very much like that one. I think you will find it cuts well for you and wanted you to see that even on a lathe larger than a little Sherline such a tool can be useful.

Oh, just so you know, I chose you to do this because you said you were an excellent tool grinder and I have no doubt that you are. Once you add this to your collection it will give you a basis to experiment more with angle changes. It usually only takes a few degrees more added to a standard angle to produce a significant impact, especially side rake angles. Anyway, you're the guy right now. When Joe catches up we'll put him on the spot!

We await your report!
 
JimDawson said:
I think this thread has a lot of valuable information and even this old dog is learning :) The lack of learning how to hand grind tools is one of my pet peeves. I don't use insert tools and have always hand ground my own, be it carbide or HSS.
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Thank you, Jim, for your support. I know there are a lot of new guys out there reading this stuff and not saying a single thing. There are also a lot of experienced tool grinders who are just as silent. Jump in, guys!
 
mikey said:
Carlo, most of the heat in a cutting operation is carried off by the chips so chip clearance is very important. Chip clearance is enhanced by side rake - the more side rake you have the better the chip clearance will be. Back rake also plays a role here but not as much as side rake.

In your pictures of your tools you posted earlier in this thread it looks like you use very little side rake and almost no back rake. This will cause your tool to cut with very high cutting forces and poor chip clearance because you are basically presenting a square edge to the work. I would suggest you grind in both side rake and back rake in amounts appropriate for the materials you are cutting. This will give you a much sharper cutting edge that will not only cut cleaner but last longer. It will also clear chips much better and keep cutting temperatures down.

You also said you free hand your tools and never measure angles. That's fine - lots of guys do this. I can free hand a tool and come within a degree or two of what I want but I've been doing it for over 25 years. For best results or until you have a lot of experience I highly recommend you use a rest that you can set at known angles so you can control your geometry. Then take the time to learn to grind the proper relief angles, side and back rake and the tool shapes you require.

Please don't take this the wrong way as I'm not trying to criticize you in any way. I want you to succeed and I assure you that there is a great deal to be gained from learning to grind a good tool. Those three articles that Joe linked to above will give you a good start in understanding how all the angles work and how they can be ground into your tools.

Joe started this thread and it has evolved into a tool grinding thread. That's okay - so far, Jim hasn't put a stop to it and until he does we can all use it to help each other and share what we know about tool grinding. I, for one, value your input.
Click to expand...

I'm going to try as you suggested next time I can get out to my shop. I read the linked articles but I have memory issues and it just didn't seem to sink in. Maybe I'll read them several times over and see if any of it soaks in.
I had never thought of the chips being the place to direct the heat. I'm lad you mentioned it however as it makes more sense then my way.
Hopefully adjust the angles will achieve better results I use those two tools for just about everything mainly because I'm too lazy to reset everything for a new tool.


Regards-Carlo
 
Strtspdlx said:
I'm going to try as you suggested next time I can get out to my shop. I read the linked articles but I have memory issues and it just didn't seem to sink in. Maybe I'll read them several times over and see if any of it soaks in.
I had never thought of the chips being the place to direct the heat. I'm lad you mentioned it however as it makes more sense then my way.
Hopefully adjust the angles will achieve better results I use those two tools for just about everything mainly because I'm too lazy to reset everything for a new tool.


Regards-Carlo
Click to expand...

I know you feel otherwise but I really think practicing with mild steel keystock is the best way to learn to grind a tool bit. It cuts easily and allows you to understand how to hold and angle the bit to get the results you need. Once you are comfortable with the procedure then switch to HSS. Grinding tools isn't hard to do but it takes practice to wrap your head around the process. Stick with it, Carlo - it will come.
 
Ok, jumping in....

For starters I'm not especially new to the mechanics of tool grinding, but I am less versed with the performance aspects of various grinds so I've been following this discussion quite closely. I think for me, the most salient take-away has been that while the textbook numbers may be tried and true based on much research, those numbers may not be the best option for smaller machines that typically don't take huge cuts or do long production runs. It's a basic factor for me, a smaller lathe user to consider, and I'm almost embarrased I hadn't taken it to my tool grinding as well.

With that said, and the coincidental arrival of five fresh tool blanks last week, I ground one of mikey's "square tools" last night. I ground it as more of a roughing shape though, and in keeping with the theme made the lead angle 15-degrees as well. Then I honed it as I always do, stuck it in my little Atlas, and fed it some 6061.

Very nice, I'm liking it! Easy-breezy cutting, nice finish, decent chip direction. I can't give a percentage-point advantage compared to what I was using before, but it just *felt* better. Where I may have backed off my DOC before, that threshold has moved further out with the new tool. And to my mind, that's improvement.

So, I can't wait to try another one. I do use my grinder though instead of the belt machine. It works for me and I made an adjustable rest that is easy to adjust and holds the angles well so I'm sticking with it.

Great discussion, guys. Very useful indeed and some really good banter.

-frank
 
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