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View Full Version : how do you sharpen you lathe tooling?



kjbllc
02-15-2008, 06:14 PM
do you have a sequence of operations? Such as do the side first to such and such degrees and then the top and then the rake? It would be helpful to have some guidelines like that for me as a beginner, I am having a bit of difficulty with the pictures in the SB book. thanks.

NickH
02-15-2008, 06:21 PM
I rotate my insert to present a fresh edge :D
No shimming for edge height, re-zeroing for the center zero etc. etc.
:D
Nick

lazlo
02-15-2008, 06:26 PM
Just about any intro machine shop text will have a set of photos showing the sequence of grinding operations on a pedestal grinder.

The South Bend "How To Run a Lathe" has a good section on grinding lathe tools, as does Moltrecht's Machine Shop Practice.

Oldbrock
02-15-2008, 06:45 PM
Have patience Keith, the books WILL arrive Peter

oldtiffie
02-15-2008, 07:38 PM
do you have a sequence of operations? Such as do the side first to such and such degrees and then the top and then the rake? It would be helpful to have some guidelines like that for me as a beginner, I am having a bit of difficulty with the pictures in the SB book. thanks.

Hi kjbllc

To the question and then to the point.

First of all, do keep water at hand for 2 reasons:
- to stop over-heating the tool as that may damage its cutting qualities: and
- it gets bloody hot and uncomfortable on your hands/fingers -as you've probably discovered for yourself.

Start off with a "fresh" wheel if possible. Not a new wheel but one that has been "dressed" so as to "true it up" and present/have a better/"sharper" cutting action.

The reality is that when you are roughing the shape of the tool out, whether the grinder is grinding away from the cutting edge is not important - at all.

The better the cutting edge, the better the cut - so finish off with a finer grinding wheel and then a diamond hand-lap "stick" (available for moderate cost from most better hard-ware stores). Again push/move the "stick" "away" from the cutting edge as before.

When finishing, the sequence doesn't matter either, but it is best to have the wheel grinding away from the cutting edge on each face - that is say have the cutting edge at the top facing you and the wheel grinding "down" - you will get a naturally sharper edge that way.

Needless to say, just about every metal has different optimum tool and cutting edge shapes/profiles.

I can post a basic list of diagrams and shapes etc. later if you wish.

kjbllc
02-15-2008, 07:44 PM
Just about any intro machine shop text will have a set of photos showing the sequence of grinding operations on a pedestal grinder.

The South Bend "How To Run a Lathe" has a good section on grinding lathe tools, as does Moltrecht's Machine Shop Practice.


books on the way, I am going by the south bend book and having a bit of difficulty transferring what I see to what to do I guess. It doesn't really give you the angle of the cut, just the picture. The top view and such. If I knew what the angle for mild steel would be I could set the wheel up that way to start. Do you guys just freehand the whole thing? Just from experience?

kjbllc
02-15-2008, 07:51 PM
Have patience Keith, the books WILL arrive Peter

you are right of course, when your in focus on something its hard sometimes.

kjbllc
02-15-2008, 07:57 PM
did a google and found this:

http://www.sherline.com/grinding.htm

Your Old Dog
02-15-2008, 08:16 PM
Just remember when you quench the tool in water to leave it in the water as long as you held it on the stone. I suggest no gloves so you can feel the bit starting to get warm and you won't get it too hot if using bare fingers.

I can help you with the thread cutting bit pretty quick. Set your tool rest at 10 degrees and then use your adjustable square set to 30 degrees for each side of the bit. Don't forget to take off the very tip of the cutter if you want your threads to look nicer.

If I were you I wouldn't be trying to learn how to sharpen all the basic shapes at once. Just start with the left or right and work with it till you got it down pat and then move onto the other. If you don't have enough blanks then buy more. I got 20 HSS 5/16" blanks from ENCO for something like 1 dollar apiece.

kjbllc
02-15-2008, 08:25 PM
good point YOD, I have some to start with, I have been doing some cutting and they are working, but the finish is very rough. I thought It might be the way the blade was sharpened. That is what got me to start this thread. I actually have something to make but it has to be smooth, Its a shaft for an old craftsman band saw, the guide part. thanks for the advice

Mike Burdick
02-15-2008, 08:26 PM
kjbllc,

Did you download the video "Action, use and care of single point cutting tools"?

http://www.shinyobjectdesign.com/staff/paul/sbvideo/

If you can't download it from that site then email me an email address and I will send it to you.

Mike

kjbllc
02-15-2008, 08:28 PM
kjbllc,

Did you download the video "Action, use and care of single point cutting tools"?

http://www.shinyobjectdesign.com/staff/paul/sbvideo/

If you can't download it from this site then email me an email address that I can send it to you.

Mike

mike I wish I could, but my connection is only 25kbps, I get timed out on videos. I will try to get a friend to download it to a disc. thanks

kjbllc
02-15-2008, 08:40 PM
ha, I just looked at the page 89 meg! It took me 6 hours to download a 8 meg file once.

kjbllc
02-15-2008, 08:42 PM
kjbllc,

Did you download the video "Action, use and care of single point cutting tools"?

http://www.shinyobjectdesign.com/staff/paul/sbvideo/

If you can't download it from that site then email me an email address and I will send it to you.

Mike

Thanks for the offer of mailing to me that is a kind gesture. I think my friend with the cable internet can do it for me. thanks so much for the thought.

Mike Burdick
02-15-2008, 08:51 PM
kjbllc,

What size bits are you using? I would think the best thing to start out with is a post and rocker tool holder and 1/4-inch bits. They grind fast and are inexpensive. Then...remember one thing: The cutting edge of the bit MUST be the only edge that hits the metal! Anything else will rub. Don't be concerned with an "exact" angle. So start grinding and testing...you'll learn fast! No fooling!:)

Furnace
02-15-2008, 08:53 PM
I have tried downloading these videos but get an error saying the site cant be opened. And clicking on them to play the video causes an error. Id love to see these videos...any suggestions. Im on fiber internet 5 meg connection.

Mike Burdick
02-15-2008, 08:58 PM
Furnace,

Hmm, you're right! Guess Paul took them off again. I have them and I will see if I can find someone that can host them. To start off I'll see if Steve Wells will do it.

kjbllc
02-15-2008, 09:00 PM
kjbllc,

What size bits are you using? I would think the best thing to start out with is a post and rocker tool holder and 1/4-inch bits. They grind fast and are inexpensive. Then...remember one thing: The cutting edge of the bit MUST be the only edge that hits the metal! Anything else will rub. Don't be concerned with an "exact" angle. So start grinding and testing...you'll learn fast! No fooling!:)

That is one of my questions, how much of it is the cutting edge, right now it seems that it is only a nearly a point, thus it leaves the scratch behind as it moves. They are 1/4 inch bits. can you use a whole 1/8" of the side, or is it more like a 64th? that can be used as the cutting edge. Its funny I use a big tool holder, and carbide bit for my wood lathe and it cuts like silk, have not had to sharpen it and have used it for probably an hour, my HSS tools get sharpened about every 3 minutes or so. I was thinking of getting carbide holder and bits for this, because of the great results with wood. But I realize the they are two different things. I guess that is where my brain is having a hard time figuring out the concept of how the steel goes.
I think I have the right speed, I have it on pulley #3 with no back gears (SB 10k) and the travel speed is the slowest that it will go. I did a fine cut, and the swag? came off in very fine spring like form. I think I am the type that if I see it or someone do it my brain can grasp it better than with words. thanks for the help though, it is all kind of sinkin in!! I emailed the friend about the video, but his wife is due today so hard to tell what he is thinking about!!

Furnace
02-15-2008, 09:01 PM
Thanks Mike.

airsmith282
02-15-2008, 09:06 PM
i have been at this about 2 years now and i usually use the 5 inch disc in my sander for left right facing L and R and threading bits when i make them from blanks it works really slick and i get great cutting results as well, iam still trying to learn on hte bench grinder to do it but i get better results usuing 120 grit sander dics on my sander ,, what ever works best for you i think is the way to go..

kjbllc
02-15-2008, 09:08 PM
i have been at this about 2 years now and i usually use the 5 inch disc in my sander for left right facing L and R and threading bits when i make them from blanks it works really slick and i get great cutting results as well, iam still trying to learn on hte bench grinder to do it but i get better results usuing 120 grit sander dics on my sander ,, what ever works best for you i think is the way to go..

thanks I will give that a try also.

Mike Burdick
02-15-2008, 09:24 PM
kjbllc,

First off, what material are you testing with? Some mild steel cuts "gummy" and is hard to get a nice finish on it.

But let's assume it's not too bad of material. If the bit is cutting nicely but leaves a line try just lightly tapping the point against the grinding wheel thereby knocking off a little (very, very, little). I suggest using the grinding wheel instead of a stone because sometimes one can "round" the point such that it's NOT the first thing to hit the metal and thereby cause rubbing. Keep going, you'll get it!!!!:):)

Oh...get a loupe or something of at least 3X power and look at the bit you just ground. That'll tell you a lot!

Rusty Marlin
02-15-2008, 09:29 PM
Do you guys just freehand the whole thing? Just from experience?

Yup. You'll get there. I had a head start, Dad has a shaper I use to grind tools for as a kid.

For a right hand tool I start with the side relief. This is the left side of the tool and is what is under the cutting edge. When I get the side relief cut, then I do the end relief, and finally the top rake, if it needs it. I generally don't bother with chip breaker grooves. Then I use a large India stone flat on the bench and push the tool over the stone being careful not to round the cutting edge. And the last step is to take a hard white Arkansas stone and knock the dead sharp razor corner off where the side relief and the front relief meet. Just a .005 or so radius is all it takes to make a tool last MUCH longer than one that doesn't have the edge break.

When you get to more intricate tools, internal groovers, funky little form tools, tiney little boring bars and the like a Dremel with a glass re-enforced cut off wheel is the nuts...
just for furture referance.

kjbllc
02-16-2008, 05:42 AM
I am using some shafting from a large centrifugal fan, about 1.15" dia. I think its has some carbon in it but i am not sure if it has some other alloys too.

thanks for all the encouragement and support, I have a much better idea on what to do now and will give it a go today and see how I make out. I will also order some more bits to work with.

oldtiffie
02-16-2008, 05:51 AM
I am using some shafting from a large centrifugal fan, about 1.15" dia. I think its has some carbon in it but i am not sure if it has some other alloys too.

thanks for all the encouragement and support, I have a much better idea on what to do now and will give it a go today and see how I make out. I will also order some more bits to work with.

You are making good progress kjbllc.

Here are some of the lathe tool (HSS) profiles as a guide.

Just develop yopur own prefernces to suit yourself as you go along as I expect most of us have done.

http://i200.photobucket.com/albums/aa294/oldtiffie/Turn_tool_profile1-1.jpg

kjbllc
02-16-2008, 08:04 AM
thanks oldtiffie, that is a good diagram, its good getting ideas from different view points, it is helping me get the mental picture that I need.

SGW
02-16-2008, 08:23 AM
Get yourself one of those swing-arm protractors (like this: http://www1.mscdirect.com/CGI/NNSRIT?PMPXNO=4760002&PMT4NO=37954697 )
so you can accurately measure the angles you're grinding. It's notoriously difficult to estimate them accurately. Leo St.Clair, in his book "The Design and Use of Cutting Tools," which is 350+ page about lathe toolbits!, surveyed a number of professional machinists, and the best of them could estimate only to within a couple of degrees; I think the worst estimates were off by 10 degrees or more.

And have patience. There is a LOT to learn, and I can well remember, first starting out, that it can feel totally overwhelming. But it gets better as you get a few basics down so you have a least a little bit of a foundation to stand on.

You might also want to refer to an article I wrote for HSM back in June of 2003: Sharpening HSS Lathe Toolbits. It describes a simple tool rest setup for a bench grinder so you can get repeatable angles.

Al Messer
02-16-2008, 09:33 AM
Freehand all the way. Visit some older machinists and look at the weird shapes you will find in their tool kits! I presume that you are asking about HSS tool bits, not the Carbide CNC production ones.

lazlo
02-16-2008, 09:51 AM
Leo St.Clair, in his book "The Design and Use of Cutting Tools," which is 350+ page about lathe toolbits!, surveyed a number of professional machinists, and the best of them could estimate only to within a couple of degrees; I think the worst estimates were off by 10 degrees or more.

That was a great article you wrote in HSM.

I'm an anal retentive protractor user myself, and I've always been morbidly curious what the old timers would say if they read Leo St. Clair's data on how badly even professional machinists estimate the rake angles when they're free-handing a cutting tool.

boaterri
02-16-2008, 11:15 AM
Harold V on the Home Machinist BBS did a very complete discusion that was condensed by another member some time ago. It is downloadable, you might try an archive search to find it.

Rick

kjbllc
02-16-2008, 01:05 PM
thanks I will check that out.

38_Cal
02-16-2008, 01:56 PM
I was taught over thirty years ago in gunsmithing school to freehand cut HSS lathe bits with a grinder. Now, I use a grinder to rough shape them and switch to a 1"x42" belt sander with a 400 grit belt for final shaping/sharpening against the platen. I use a fine diamond stick at the lathe if they need touching up in use.

David
Montezuma, IA

Norman Atkinson
02-16-2008, 03:17 PM
Sharpen or hone? Which!

clutch
02-16-2008, 03:58 PM
I bumped into this on the web a while back. Maybe this will help.

http://smg.photobucket.com/albums/v30/jglass/?action=view&current=toolbitb.jpg

Clutch

Oldbrock
02-16-2008, 04:36 PM
It's me back. I seem to remember that you have toolholders meant for hss tools so the printout you had showed how to grind a tool that is horizontal holder not the positive holders. The SB book should give you a better idea of what the tool should look like. I, personally don't like the lantern style toolpost and have a student made quick change (copy of the Armstrong) Grinding tools that sit horizontal are less of a challenge for most neophytes. Something else, after the tool is set up and you're ready to take a cut, hone a small flat (maintaining clearance) on the point of the tool IN LINE WITH THE BED. then you don't have a series of vees but a series of overlapping flats. Slow down, use coolant for the final few cuts and you will be surprised. Use soluble oil and water in about 20% mix. Good luck. Peter

kjbllc
02-16-2008, 06:02 PM
It's me back. I seem to remember that you have toolholders meant for hss tools so the printout you had showed how to grind a tool that is horizontal holder not the positive holders. The SB book should give you a better idea of what the tool should look like. I, personally don't like the lantern style toolpost and have a student made quick change (copy of the Armstrong) Grinding tools that sit horizontal are less of a challenge for most neophytes. Something else, after the tool is set up and you're ready to take a cut, hone a small flat (maintaining clearance) on the point of the tool IN LINE WITH THE BED. then you don't have a series of vees but a series of overlapping flats. Slow down, use coolant for the final few cuts and you will be surprised. Use soluble oil and water in about 20% mix. Good luck. Peter

thanks I will give those ideas a whirl tomorrow. How wide is the flat, 1/32" , 1/64th? thanks.

Norman Atkinson
02-16-2008, 06:32 PM
It was a very serious question that was posed.

Hmmmm? Never mind.