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Models for grinding HSS Lathe Tools

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mikey

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Hi Mike
Thanks again for taking the time and putting forth the effort to help all of us with this endeavor! I have a question regarding the grinding tool. I am currently stuck with a bench grinder to use for grinding my tools. Using the periphery of the wheel to grind, where do I need to set the angle in relation to the tool? Does the 15-degree tangent need to fall at the top, middle, or bottom of the tool? In other words, If I match your example to my grinder, would I set the table angle with the wheel actually touching the ground face on the top or what? I ask because the tangent location will change the apparent angle of the ground face as seen by the workpiece being cut in the lathe.
Thanks again for your guidance.
Randall

This is a difficult thing to answer because a lot depends on how the tool rest is situated. Some grinders allow the top of the rest to be at the centerline of the motor spindle; this is a true zero. Most don't do this so who knows where zero is, much less where 15 degrees is. This is one reason why many of us use an independent rest that is not attached to the grinder. Examples are like the one Jeff/ @Z2V made, or the Veritas rest or the Glendo Grind-R rest.

For grinding the model tools, I would just butt the face of the tool to the wheel and set the rest to duplicate the angle as close as you can. That's why I made a physical model. That angle should allow you to duplicate the three tools. Then, when you have time, you can sort out how you want to make your own rest or choose one to buy.

Sorry to be of no help, Randall. I ground tools on a bench grinder for 10 years and hated it the whole time. The rest was one of the reasons for hating it. A belt sander works better for me.
 

mikey

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Hey Mike, Thank you for all the great work you have done. Do you think this belt sander below would do the job, its on sale thru tonight.

https://www.zoro.com/dayton-beltdisc-sander-13-hp-120v-6y945/i/G2309045/

Thank you for your input
michael
Hey Mike. Its been a fun thread, hasn't it?

That belt sander is the same as the Craftsman belt sander. At 1/3hp, its pretty anemic. The basic design is great; its the same as my 1/2hp model and I know it works for tool grinding. The only issue is the weak motor. In a few hours, I will have some time to grind a tool using the exact same grinder you linked to but with a ceramic belt. If it grinds a cobalt tool adequately, I will report it here and you can make up your mind. So, check back here in a few hours, okay?
 

mikey

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Mike, and anyone else who is considering the 1/3hp Craftsman/Palmgren/Whoever 2 x 42 belt sander, I would like to report that a Red Label Abrasives 36 grit ceramic belt successfully and quickly ground a 3/8", 10% cobalt HSS tool bit with no problems.

I did not grind the whole tool but I ground the entire side cutting edge, which is the biggest chunk of material you have to grind, and it ground it in under 2 minutes without stalling or slowing down. And this was with a belt that had already ground 9 model tools from keystock and 3 other HSS/cobalt tools so it was well used. In contrast, I can completely stall this motor just grinding wood with an Aluminum Oxide belt so the belt is what makes the difference.

If you are willing to commit to using ceramic belts then this machine will work for grinding tool bits. You still have to make a good tool rest and epoxy on a ceramic glass platen liner on it but I think it will suffice. With that said, if you ever find the 1/2hp version of this machine, buy it! In the meantime, this one should be okay. I warn you that I have reservations about the power of the motor but it walked right through a 10% cobalt bit rather quickly so I suspect you'll do okay with it.

Here is a link to the mods I made to my own grinder: http://www.machinistblog.com/modify...inch-belt-sander-for-tool-grinding/#more-5349

Feel free to copy the tool rest and platen mods, guys. The tool rest is a very good one and I have found no fault in the design so far. I am now on my second platen liner but only because a belt broke and knocked the liner loose, not because the liner wore out.
 

q20v

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Hey again guys,

I was back at it tonight to try and touch up the RH turning tool based on Mike's feedback and I think I've made a bit of progress. I welcome the tips and hints at areas to improve so keep those coming.

I touched the side cutting face on the grinder to try and even it out. That definitely helped as seen by my honing picture below. I was able to hone the entire side cutting edge now.
DSCN0143.JPG

I then honed the end face again:
DSCN0145.JPG

Then the top of the tool:
DSCN0144.JPG

And increased the nose radius by hand, using the DMT plates (fine and then extra fine):
DSCN0146.JPG


This is the same steel bar as the previous post. The right hand band is after today's progress, the left hand band is from the other night. I think they look pretty similar but the right hand side feels a bit smoother.
DSCN0147.JPG

I increased the lead angle and made another pass. Smoother again.
DSCN0148.JPG

Here is the aluminum 6061T6 bar again.
Left band: same increased lead angle as the steel. Middle band: what I thought was amazing from the other night. Right band: chewed up surface from the bar sticking out too far from the other night, also with very little lead angle. So, looks like it's gotten better (left band).
DSCN0149.JPG


Another picture with a bushing I had made a long time ago, just to compare.
DSCN0150.JPG


Then for fun, I straightened the tool almost perpendicular with the bar and re-machined part of the end. Looks decent! Don't mind my fingerprints on the far left hand band.
DSCN0151.JPG

Mike, think I should try increasing the nose radius a bit more? Anything else I can do to improve at this point? Or just start using it and play around with the lead angle some more?
I also haven't tried taking any deep cuts. Might give that a go as well.

Thanks so much for everyone contributing to this thread. It's really become a fantastic resource.

Barry
 

mikey

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Now your tool looks like it should, Barry, including the nose radius. Great job! I would use it as is and see how it goes. You have a decent finish now; it will be better with more lead angle towards the tailstock but you can also enlarge the nose radius a tiny bit more if you like. By the way, if you mess with the nose radius and make it too big, just grind a bit on the end cutting flat and that will remove the radius; then stone a new one on.

I would spend some time making test cuts to see how your lead angle needs to be for roughing, sizing and finishing. This will not take long at all. Also take deep cuts and shallow finish cut and see how your tool behaves in different materials. In time, you will know how your tool cuts and you'll use it without even thinking about it.

Good work, Barry. You're on your way!!

Mike
 

mikey

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Barry, I meant to ask you what kind of lathe you're using. Do you have power longitudinal feed?
 

q20v

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Thanks Mike! I have a good chunk of time tomorrow that I can dedicate to working in the garage, so I'll try the things you've suggested. I'm also thinking about the next tool to make, and instead of the knife tool I may make a LH turning tool, since I'm really familiar with the geometry right now. Although if I get as much time tomorrow as I hope, I should be able to make both.

Here's a picture of my lathe from several years ago (~2012). It's a Busy Bee DF1224G and has power feed in the longitudinal and cross directions. I was using the slowest feed rate for all the cuts above. RPM was somewhere between 6-700 if I recall?

DSCN5259.jpg
 

mikey

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Okay, 12" lathe. You should be able to take pretty hefty cuts with that machine. I suggest you try some decent cuts to see how the tool performs. Adjust the feeds and speeds to suit the material. If you're not sure how to do that, say so and we'll discuss it; I assure you that you are not alone in this.
  • You should be able to take a 0.200" deep cut (0.400" off the diameter) in aluminum and mild steel. I don't think it is necessary to go deeper unless you're curious but this will show you what the tool can do. Try this with the tool maybe 5 degrees off perpendicular with the tip toward the chuck.
  • Once you make the cuts, measure the diameter and turn the shank of the tool just off perpendicular towards the tailstock and take an additional 0.010" cut to simulate a sizing cut.
  • Finally, turn the tool toward the tailstock another 5-10 degrees and take a 0.0005" finishing cut. This will show you the range of the square tool and what it can do.
Once you do these tests, try the same thing with your carbide tools and see what happens. You can also grind a general purpose tool with the angles found in an angle table to see how it compares to the square tool. You don't really need to do all of this but if you do, you will have a very clear idea of what your lathe can handle and the impact of a modified tip geometry.

A LH tool is a good idea. After that, maybe grind a tool specifically ground for aluminum or mild steel. We can discuss how to alter the angles if you like and this will get you on your way to learning how to modify tools for different material groups. You see, the real skill in tool grinding isn't in the grinding; its in knowing how to alter the tool angles to optimize its performance in the materials you work with.

No pressure here, Barry. You don't need to do any of this but if you choose to, I will help.

Finally, if you think you like working with HSS tools then consider buying a belt sander and make a good tool rest for it. It will make tool grinding much, much easier for you.
 

Doubleeboy

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That is one heck of a crankshaft in photo above. You should be proud. Is there a write somewhere about its construction?

michael
 

Metal

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  • You should be able to take a 0.200" deep cut (0.400" off the diameter) in aluminum and mild steel. I don't think it is necessary to go deeper unless you're curious but this will show you what the tool can do. Try this with the tool maybe 5 degrees off perpendicular with the tip toward the chuck.
I'm working on restoring my new lathe, but I just wanted to say that is a bonkers cut, I cant wait until I can do them myself, lol.
 

mikey

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I'm working on restoring my new lathe, but I just wanted to say that is a bonkers cut, I cant wait until I can do them myself, lol.
My Emco 11" lathe manual says that if I want to go deeper than 0.200" I need to step down the speed one notch and then go for it. This is with a conventional tool so I figured a square tool would handle it and it did with no problem. It is a big cut, though, and we won't be doing this very often because its a waste of material but its fun to try it.
 

q20v

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Well I wish I could take credit for doing something to that crankshaft, but I had only mounted it up for fun! It's from my old Audi 5 cylinder.. a quattro, with 20 valve head... some would say, quattro 20 valve, or q20v... :p

Mike, the biggest cut I've taken is about .075" DoC on heat treated 4140, bar was about 5/8" dia. using a carbide insert. It went pretty smooth and I had no real reason to go deeper at the time. But I'm anxious to give this HSS bit a try tomorrow. I will follow your guidance and report back. I'll even try taking a video.

To be honest I typically don't use feeds/speeds formulas but I suppose now is as good a time as any to learn.

Using 550 SFM for Aluminum (https://littlemachineshop.com/reference/cuttingspeeds.php) I'd be looking at 1400 RPM:
http://www.custompartnet.com/calculator/turning-speed-and-feed
That about right?

And for feed rate, the slowest my machine will go is 0.0025 IPR, should I try that or is there a more scientific approach I should be taking? I suppose it depends on what my machine can do?
 

mikey

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Cutting speeds matter but I try to keep it simple. Instead of a calculator, I use the formula: RPM = SFM X 3.82 / D, where SFM is your cutting speed, 3.82 is a constant and D is diameter of the work. This works for both carbide and HSS tooling; the SFM will differ, with carbide being roughly twice the speed of HSS. Keep it simple.

The rpm derived from the formula is just an estimate of speed. Most folks go with the calculated value or the closest lower speed but with your modified tool, I would go with the next higher speed instead.

Feed is something you need to work out. It will vary with the gearing on your lathe and I would start with the lowest feed and work up until you get the result you want. When I evaluate a new tool, I don't power feed. I feed manually. I want to know what the cut sounds like, looks and feels like when I can feel a slight positive resistance to the feed. This tells me what to expect when things are right for that material, tool and lead angle.

Big depths of cut is an ego thing for the most part. We should be starting with stock close to our final diameter to reduce waste. However, its fun to see what a tool can do. If you like, try a 0.100" deep cut in aluminum and work up from there. I think you will be surprised how big a cut your square tool can handle in aluminum; I've gone up to 0.25" without even slowing down the lathe and I'm sure it can go deeper.

Do the same with mild steel; start low and go up. You will find that when the lathe slows or chatters, you need to drop down a speed but the lathe will make the cut. Play with it and see. Your square tool is capable of much more than you think.

Keep in mind that when a tool chatters you should first reduce your lead angle a bit. If that fails, reduce speed and increase feed and that will handle it.

Let me know if this is at all unclear.
 

q20v

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No, Mike, that is perfectly clear and is great guidance to follow. I'll play with it tomorrow and let you know how it goes. Many thanks for taking the time to explain everything in the detail that you do. I've been using the lathe for about 5 years now (intermittently) and although I feel like this is somewhat back to basics, it's obviously something I never had a good grasp on. I've been getting by for my non-critical parts, but now that I have a better grasp on what the lathe can do, I'm starting to think of more complex projects, and getting these basics locked down, I think, is vital.
 

mikey

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No, Mike, that is perfectly clear and is great guidance to follow. I'll play with it tomorrow and let you know how it goes. Many thanks for taking the time to explain everything in the detail that you do. I've been using the lathe for about 5 years now (intermittently) and although I feel like this is somewhat back to basics, it's obviously something I never had a good grasp on. I've been getting by for my non-critical parts, but now that I have a better grasp on what the lathe can do, I'm starting to think of more complex projects, and getting these basics locked down, I think, is vital.
When I'm looking for an answer, the worst thing that happens is when someone tells me what but doesn't tell me why or how or when. I hate that. That's why most of my answers will be fairly complete so as to not leave you in a lurch. I mean no offense.

It's funny but whenever I have a machining issue, its usually something basic that I didn't attend to. So yeah, basics, I like basics.
 

tweinke

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When I'm looking for an answer, the worst thing that happens is when someone tells me what but doesn't tell me why or how or when. I hate that. That's why most of my answers will be fairly complete so as to not leave you in a lurch. I mean no offense.

It's funny but whenever I have a machining issue, its usually something basic that I didn't attend to. So yeah, basics, I like basics.
And that's why this has been a very good thread with lots of good learning. This has been one of those learning experiences where the teaching vs doing it for someone has really paid off. ( Teach a man to fish...........)
 

mikey

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And that's why this has been a very good thread with lots of good learning. This has been one of those learning experiences where the teaching vs doing it for someone has really paid off. ( Teach a man to fish...........)
Thank you, Todd. I'm waiting for someone to modify a tool for specific material so we can go through the thought process. I mentioned it when I discussed the tools I made for @Bamban; he has a short video he can post if he feels it appropriate that shows how the chips come off (vs his carbide tool) and where the chips come off at the tip. The tool does what we wanted it to do and the video shows it. I will leave it to him.
 

Z2V

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I'm looking forward to getting in on some of this fun. I've got some work in front of me but shouldn't take too long.
If you care to take a peek and confirm my dummy of the day,
http://www.hobby-machinist.com/threads/my-pm-1236-precision-arrived-today.63106/#post-519965

Q20V
I looked at the pic of your crankshaft chucked in your lathe and thought my eyes were playing tricks on me. I looked and counted and looked and counted but all I could come up with was five!!!
 

HBilly1022

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Mikey, I just discovered this thread and read through the whole thing. I want to thank you for your generosity in putting this together and providing on line instruction classes for us novices. This thread is extremely informative and easy to follow. Your pictorial sequence of how to grind tools is priceless and the information of how the lead angles affect the finish is great. I have hit and miss success with getting decent finishes (mostly miss) but I can now understand some of the issues I have been missing. I believe your tutorial will put me on the right path to producing better finishes.

Thanks again for all your effort and sharing your knowledge with us.

pm sent to Z2V to be in the Canadian loop for the sample tools.

I have one question if you don't mind. Do you think a 2" x 28" belt sander would suffice. The only 42" sander I can find anywhere near me is $775 and I'm not willing to spend that. There is a 1/2 hp 2" x 28" sander on sale at Busy Bee for $130 and I'm hoping the shorter belt would be ok or do you think it would heat up too much. I've been toying with the idea of building a 2" x 42" or even a 2" x 72" sander but would prefer to just get the 2" x 28" if it would be adequate. I have a 1" x 30" sander and use that for some sharpening tasks.
 
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mikey

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Mikey, I just discovered this thread and read through the whole thing. I want to thank you for your generosity in putting this together and providing on line instruction classes for us novices. This thread is extremely informative and easy to follow. Your pictorial sequence of how to grind tools is priceless and the information of how the lead angles affect the finish is great. I have hit and miss success with getting decent finishes (mostly miss) but I can now understand some of the issues I have been missing. I believe your tutorial will put me on the right path to producing better finishes.

Thanks again for all your effort and sharing your knowledge with us.

pm sent to Z2V to be in the Canadian loop for the sample tools.

I have one question if you don't mind. Do you think a 2" x 28" belt sander would suffice. The only 42" sander I can find anywhere near me is $775 and I'm not willing to spend that. There is a 1/2 hp 2" x 28" sander on sale at Busy Bee for $130 and I'm hoping the shorter belt would be ok or do you think it would heat up too much. I've been toying with the idea of building a 2" x 42" or even a 2" x 72" sander but would prefer to just get the 2" x 28" if it would be adequate. I have a 1" x 30" sander and use that for some sharpening tasks.
Thank you for your kind words, HBilly, and you're welcome. I'm sure Jeff can get a set of tools in your hands and I hope they help you. When you get them, share your efforts and results. If I can see what you're doing, I can help you fine tune things so they work as they should.

I think a 2x28 belt sander will work just fine. As long as you can access the right side of the platen, build a good tool rest and hopefully fit a ceramic glass platen in there then the thing will grind tools. You must be sure the entire right side of the platen is open - no housing or covers or anything that interferes with getting the tool bit right up on the right side of the platen.

Welcome to the thread, HBilly. If you have questions, ask them, please. I honestly tried to put it all in this thread but I may have missed something. No, I'm sure I missed something, so if you are not sure about something, ask. I guarantee you that some silent guy out there has the same question but won't ask it.

Mike
 

Z2V

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HBilly
I have you on the list. I'll give you a PM when they ship to you with info on who to forward to.
Welcome aboard

Jeff
 
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mikey

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Here is a link to the 2" belt sander I'm looking at. https://www.busybeetools.com/products/grinder-and-sander-8in-x-2in-combo-craftex-ct169n.html It doesnlt look like the right side is entirely open and the platen looks kind of wide which would likely interfere with grinding at the edges of the belt.
It looks like there is a cover on the right side; that can come off so you can access the right side of the platen. However, the platen looks like just a flat plate that screws in place. If you can figure out how to get a reliable platen with a liner in there, it might work. Is this thing somewhere you can go look at it and maybe take better pics?
 

HBilly1022

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It looks like there is a cover on the right side; that can come off so you can access the right side of the platen. However, the platen looks like just a flat plate that screws in place. If you can figure out how to get a reliable platen with a liner in there, it might work. Is this thing somewhere you can go look at it and maybe take better pics?
Busy Bee is about 5 to 6 hrs drive but there is a similar looking one at Princess Auto which is closer and I will take a close look at it on Monday when I go to the big City. Not sure 28" is a good size to get now. I read some comments on the Busy Bee site that the belts are very hard to find. I did some searching and only came up with 2 suppliers, Busy Bee and Princess Auto. Pretty limited selection too. Might have to consider using my 1" x 30" for now and building a 2" x 42" so I can get a better selection of belts. Great another project to put on the list, lol.
 

mikey

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Busy Bee is about 5 to 6 hrs drive but there is a similar looking one at Princess Auto which is closer and I will take a close look at it on Monday when I go to the big City. Not sure 28" is a good size to get now. I read some comments on the Busy Bee site that the belts are very hard to find. I did some searching and only came up with 2 suppliers, Busy Bee and Princess Auto. Pretty limited selection too. Might have to consider using my 1" x 30" for now and building a 2" x 42" so I can get a better selection of belts. Great another project to put on the list, lol.
Is there any way to make the platen on the 1x30 more solid so it cannot flex? Can you epoxy on a glass platen liner to it? If so, that may suffice for now.

Here you go:http://usaknifemaker.com/ceramic-glass-platen-liner-flat-platen-1-x5-x-0-192.html
 

HBilly1022

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Is there any way to make the platen on the 1x30 more solid so it cannot flex? Can you epoxy on a glass platen liner to it? If so, that may suffice for now.

Here you go:http://usaknifemaker.com/ceramic-glass-platen-liner-flat-platen-1-x5-x-0-192.html
Thanks for the link Mike. I'll check to see if I can find a Canadian supplier (the border thing can be a hassle and expensive too .... that's another story).

As for stiffening the 1" x 30" platen, I'm sure there's a way if the will is strong enough. I also have 2 grinders and 6" x 48" sander that I can use. The 6" sander backing plate is solid steel (no flex) but I couldn't use it for the top rake. Probably use a grinder for that until I get a better setup.

John
 

brino

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Here's a manual for the Busy Bee 2x28" CT169N
https://www.busybeetools.com/content/product_manuals/CT169N.pdf

Page 12 of that manual shows this:
1508081122267.png

and this:
1508081162451.png

So it appears that even with that cover removed you will not have a piece of sanding belt with a support platten behind it but with access to the edge of the belt.

Not sure 28" is a good size to get now.
Yeah, I think you're right.....I searched on the Lee Valley tools site (my "goto" site for sanding belts) and they have NONE that size.

-brino
 

Ken from ontario

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Busy Bee is about 5 to 6 hrs drive but there is a similar looking one at Princess Auto which is closer and I will take a close look at it on Monday when I go to the big City. Not sure 28" is a good size to get now. I read some comments on the Busy Bee site that the belts are very hard to find. I did some searching and only came up with 2 suppliers, Busy Bee and Princess Auto. Pretty limited selection too. Might have to consider using my 1" x 30" for now and building a 2" x 42" so I can get a better selection of belts. Great another project to put on the list, lol.
I would try "sandpaper.ca and see if there's a minimum order for 2"x 28" belt size, they might cut them to size for you as special order .

http://www.sandpaper.ca/product-category/sanding-belts
 
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