Lathe Tool Sharpening?

I've had a HF mini-lathe for decades, but never used it much.
Picked up most of a Unimat DB-200.
Got the bug to make the DB-200 mill work.
Prices for Unimat parts are insane. Not gonna spend much
fixing up a $15 DB-200.
I'm at that awkward stage where it would be nice to have a mill
to make parts for a mill.
Couple that with the fact that I have no idea what I'm doing...
I'm an electrical engineer...all this mekanikl stuff is not my forte.
I expect to be working with aluminum and plastic, but steel seems
to be what I need to build the tools to do it.
With the lathe, I'm not so much cutting metal as I'm rubbing it off. ;-)
Been experimenting with sharpening bits by hand, but I no longer have the
manual dexterity to get it straight.
I bought the $4 HF set of carbide tools. Work pretty well
on straight cuts,
but the first thing I want to do is turn a square into a round.
Interrupted cut is not recommended, so I'd rather not break 'em.
I went googling for sharpening methods and found a bewildering
array of tutorials, all suggesting different angles.
I found this site particularly interesting.
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In particular, they downplay the importance of back rake. That
simplifies the sharpening process.
And the jig is something I can make with the tools I already have.
Recommendations for a newbie without a lot of machine tools or experience?
This is a hobby. Guiding principles are:
Cheap
Simple
Barely good enough is OK.
Build it from stuff you find on the floor in the garage.
Have fun learning stuff.
Did I mention CHEAP?
It's not logical, but I've spent $10 and a week to save a dollar...
and enjoyed every minute of it.
Thanks,
mike
Reply to
mike
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You don't really need any back or much side rake and the front and side relief angles can be as low as 5 degrees. The advantage of minimizing these angles is being able to cut brass, aluminum and steel, the disadvantage is less than optimal cutting rate.
When I grind form tools such as threading, gear and spline cutting bits in an angle vise on my surface grinder I use 5 degrees for the side rake and leave the top flat to make measuring the geometry easier. Since they do cut slowly I rough out the part with bits that have a more aggressive rake on top. -jsw
Reply to
Jim Wilkins
================= Tool rest specific response More Details - Uncle Dave Gingery's Shop Notebook
Written by Vincent R. Gingery
Published by David J. Gingery Publishing, LLC
ISBN 1-878087-25-8
5-1/2 x 8-1/2 Paper Back Booklet. Staple Bound. 59 Pages.
machine shop philosophy and how he has applied it to his
seemingly complex problems. Solutions that can teach those of us who are still learning valuable lessons.
grinding tool bits, a sturdy work bench with spacious drawers, a rack for storing round rod, a versatile miniature rotary table, and a hat full of tips and tricks from drilling and reaming to mounting odd shaped work and building valuable fixtures.
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also see
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Sadly Lindsey is out of business but see
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which stocks most of the Lindsey books. one of the best for the new machinist is
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Reply to
F. George McDuffee
This was my shop learning text 30 years ago. its been updated, one GREAT reference,buy it used
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Reply to
Karl Townsend
Mike - like on wood the square to round is nasty to do.
I'd hand grind the 'points' down so the round is almost there and then turn the final part on the lathe.
Saves lathe parts and uses a cheaper grinder part.
On wood I plane or file down the corners to get the job going.
Martin
Reply to
Martin Eastburn
When you say sharpening bits by hand, I am assuming you mean holding the bi t by hand and sharpen using a bench grinder. It really is not that hard t o do. I would recommend that you spend a little time practicing. Getting s o you can do it is worth the effort.
If you let us know where you are someone might take a little time and show you how they do it. I sharpen drill bit by hand but do not do it as most pe ople do it. I start at the heel and progress to the cutting edge.
Dan
Reply to
dcaster
Thanks for the input, but that ain't gonna happen. Knowing how is not my biggest problem. Manual dexterity has never been my strength. At 66, my hands don't always go where my brain tells 'em to go. Trying to cut a compound angle in three dimensions isn't working for me. I can't hold the bit still enough to grind a flat surface at any angle. I need to build some simple guides/fixtures to constrain movement relative to the grinding wheel. Of course, a better grinder would help...
Reply to
mike
Us old dogs need to stick together...
You need somebody to show you. But i know finding that guy ain't easy.
Barring that, you need something to make it easy. I'd suggest this:
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if you go this way, I'd go to using brazed carbide lathe bits and just sharpen the cutting edge.
Reply to
Karl Townsend
These young kids........... I am thirteen years older than you. But I still think you ought to try. You will not get worse.
I kind of roll the piece I am grinding into the wheel. I probably grind three sides and then look at what I have done and try grinding it closer to what I want.
Dan
Reply to
dcaster
I clamp new lathe bits in the bench vise and rough them out with an angle grinder. The bit can be tilted to the cutting edge angle you want so you hold the grinder level, then drop the handle down to the relief angle instead of trying to guess two angles at once. Whem I want back or side rake on the top I stand the bit upright and grind it with the edge of the wheel so I can better see what I'm doing and keep the cut depth fairly even.
Then I press the bit against the motor housing on the pedestal grinder as a proxy for the wheel to align the bit to the same angle to finish grind it. Setting the grinder tool rest to the front/side relief angle, somewhere between 5 and 10 degrees, helps a lot. -jsw
Reply to
Jim Wilkins

For small [1/4 inch] HSS lathe tools a small belt sander can be better than a wheel grinder as this eliminates problems with dressing the wheel. Most have table/fence and you can rig a grinding jig. For example
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FWIW -- given your equipment and level of experience, the standard (cheap) M2 steel is more than adequate.
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for grind details see
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videos
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for an idea on a jig see
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and
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As you get deeper into sharpening lathe tools you will come across honing the sharp edges to improve life and finish. An easy way to do this is use an abrasive bristle brush in your drill press. Just a touch is all you need.
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Reply to
F. George McDuffee
Mike , I use the HF 3" grinder that has an orange grindstone on the right and the "buffing" pad on the left . My rest is set just above center-of-wheel , and I can hold the lathe bit flat on the rest and get a pretty decent angle on the sidesand front . It's a cheap unit , around 30 bucks IIRC , and works really well for lathe bits . If you'd like I can email you a sheet that has angles and all that for several common lathe cutters . Heh , I probably got it here !
Reply to
Terry Coombs
That's the kind of link I was looking for. How and WHY and proper sequence and some pictures to clear up the terminology. Thanks, mike
Reply to
mike
I have a 4.5" ShopSmith that I've been using for almost 50 years. Biggest problem with it is that the tool rest is worthless. I need to fabricate something more adjustable and stable.
I had a nice 6" grinder with much better tool rest. Never had anywhere to set it up, so I tripped over it on the garage floor for a decade or more. Last month, I cleaned up the garage and sold off some stuff I thought I'd never use...including the grinder. Same day, I found the box with the Unimat parts and decided to make it work. I try not to be a hoarder, but I've run out of space. I rarely need stuff until just after I got rid of it.
Reply to
mike
Perhaps jig up a cross-slide drill press vise and use it to steady your hands. Mount it (or the grinder itself?) to a board and use yet another screw to change Z.
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Reply to
Larry Jaques
That's a large club , to which I also belong . Toss it today , need it tomorrrow . This little grinder I use is really small , takes up about 4 by 7 inches of workbench space . I also have an 8" grinder , which I drag out from under the lathe occasionally to rough new bits . It carries a 3/4" gray general use stone on one side , and a 1" thick green stone on the other side for carbides . Check out the Veritas adjustable rests , adjustable in several directions and it has a slot you can slide a toolholder in .
Reply to
Terry Coombs
Several years back, I bought a small two wheel grinder at a yard sale for acouple dollars, fixed it up a bit, dressed and balanced the wheels and gave it to Junior. He claims that it is in-adequate for his needs but it does remove metal and doesn't take up much space in his limited work area. Meanwhile I have a pedestal grinder made from a double shaft, quarter horse, 1725 RPM motor that I have been using for 50+ years and have no plans to replace.
Reply to
geraldrmiller
When my 1/2 HP pedestal grinder isn't cutting fast enough I get out a hand-held 7" angle grinder, even for lathe bits. Yesterday I used it with a cutoff wheel to quickly and neatly slice off some heavily rusted 2" pipe couplers without damaging the threads on the pipe.
For some jobs holding the grinder gives better control than holding the work because you can see the cut.
BTW wasps will nest in pipes left outdoors. -jsw
Reply to
Jim Wilkins

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