Lathe Bits Again
Lathe Bits Again
I'm practicing grinding lathe bits for the first time. Seems to be pretty straightforward, although I have couple of questions...
- I have a Viking stone grinder that's been sitting on my shelf for years. I have ground a bit with it, but it seems to take a long time. The grinding stone grit seems pretty fine to me. I've seen youtubes where standard grinding wheels with much courser grits are being used, which I expect would be much faster. Should I ditch this Viking and just go with a standard grinder?
- Does a fine stone wheel such as is on the Viking grinder require dressing?
- What's a good source for grinding patterns/specs on lathe bits for different purposes. For instance, I'd like to grind a facing bit.
thanks, rex
- I have a Viking stone grinder that's been sitting on my shelf for years. I have ground a bit with it, but it seems to take a long time. The grinding stone grit seems pretty fine to me. I've seen youtubes where standard grinding wheels with much courser grits are being used, which I expect would be much faster. Should I ditch this Viking and just go with a standard grinder?
- Does a fine stone wheel such as is on the Viking grinder require dressing?
- What's a good source for grinding patterns/specs on lathe bits for different purposes. For instance, I'd like to grind a facing bit.
thanks, rex
Re: Lathe Bits Again
Hi Rex,
I googled Viking grinder since I didn't know what that was. It looks like you have a slow speed grinder like one would use for sharpening wood-working chisels and plane blades. While that might be good for putting a fresh edge on a bit that is already ground, you really need a high speed grinder with a pair of wheels, both coarse and other (either medium or fine).
Here's a link to one I have and really like:
http://www.deltamachinery.com/products/ ... gory_id=50
Do keep a little cup of water nearby to dunk the bit and keep it cool. Be safe and have fun!
Bill C.
I googled Viking grinder since I didn't know what that was. It looks like you have a slow speed grinder like one would use for sharpening wood-working chisels and plane blades. While that might be good for putting a fresh edge on a bit that is already ground, you really need a high speed grinder with a pair of wheels, both coarse and other (either medium or fine).
Here's a link to one I have and really like:
http://www.deltamachinery.com/products/ ... gory_id=50
Do keep a little cup of water nearby to dunk the bit and keep it cool. Be safe and have fun!
Bill C.
Last edited by Bill C on Sun Sep 06, 2015 9:40 am, edited 1 time in total.
Re: Lathe Bits Again
I bought a standard bench grinder and fitted it with a white aluminum oxide wheel for high speed steel tools and a diamond wheel for brazed carbide tools. It has served me well for many years and didn't cost much at all to put together.
Re: Lathe Bits Again
Harold had a great treatise on grinding lathe tools and the proper wheel to use. I followed his advice and while I'm still learning, my success rate has improved immeasurably.
Check it out here:
http://www.chaski.org/homemachinist/vie ... 85&start=0
HJ
Check it out here:
http://www.chaski.org/homemachinist/vie ... 85&start=0
HJ
Re: Lathe Bits Again
Actually, that Viking grinder has the big slow wheel and a fast smaller wheel sticking off to the left side. I think the idea is to do the rough grinding on the small fast wheel, and the finish grinding on the big slow wheel. As I understand, the big wheel is also for sharpening knives. I'm still thinking I could move much faster with a normal grinder with a couple of wheels of different grits. rex
Re: Lathe Bits Again
Hi Rex,
In addition to all of the good advice above, you can see a nice demonstration of lathe tool but grinding here:
http://youtu.be/rZbr7Sh8jQw
If you search YouTube for that subject, you will get many worthwhile choices to view.
Bill C.
In addition to all of the good advice above, you can see a nice demonstration of lathe tool but grinding here:
http://youtu.be/rZbr7Sh8jQw
If you search YouTube for that subject, you will get many worthwhile choices to view.
Bill C.
Re: Lathe Bits Again
I use a side grinder to rough out a tool shape quickly. Hold the tool with vicegrips and dip it in water often to cool. Then use a fine stone to do the finish work. I can make a tool in 5 minutes or less. I rough out a radius tool with a side grinder cut off wheel and finish it using the corner of the bench grinder wheel.
Fred V
Pensacola, Fl.
Pensacola, Fl.
Re: Lathe Bits Again
Lathe Bit grinding for the masses.
These are by Mr. Pete. He is a retired shop teacher if I understand and all his videos are great. There is something close to 300 of which half are on shop practices.
https://www.youtube.com/watch?v=hrDr4rYLiAk
https://www.youtube.com/watch?v=dRyqIm5JR5s
https://www.youtube.com/watch?v=HTQ46NMMc88
These are by Mr. Pete. He is a retired shop teacher if I understand and all his videos are great. There is something close to 300 of which half are on shop practices.
https://www.youtube.com/watch?v=hrDr4rYLiAk
https://www.youtube.com/watch?v=dRyqIm5JR5s
https://www.youtube.com/watch?v=HTQ46NMMc88
Charlie Pipes
Mid-South Live Steamers
Current Projects:
Scratch Built 3 3/4 scale 0-4-4 Forney
Little Engines American
20 Ton Shay (Castings and Plans Purchased for future)
Mid-South Live Steamers
Current Projects:
Scratch Built 3 3/4 scale 0-4-4 Forney
Little Engines American
20 Ton Shay (Castings and Plans Purchased for future)
- Greg_Lewis
- Posts: 3014
- Joined: Wed Jan 15, 2003 2:44 pm
- Location: Fresno, CA
Re: Lathe Bits Again
There is an interesting book out there titled Design And Use of Cutting Tools by Leo J. St. Clair. Published in 1952, this is a whole book on single point, HSS cutting tools, with a chapter each on side relief angle, front clearance angle, side rake angle, and so on. He also discusses grinding wheel types and speeds in more depth than you can imagine. How someone could find that much to write about this I don't know, but it's amazing what's in there. St. Clair was an expert on cutting tools and consulted with many users in designing the best tools for given uses. His work is the result of careful research, not shop lore or customary practice. He does not advocate cooling HSS bits by dunking in water. He says this will result in microscopic cracks that will make a difference. He says if you grind the toolbit properly overheating won't be a problem.
You'll pay through the nose for a copy of this book but they can be borrowed from your library. If they don't have it, ask for the inter-library loan librarian, who can get it for you from some other library.
You'll pay through the nose for a copy of this book but they can be borrowed from your library. If they don't have it, ask for the inter-library loan librarian, who can get it for you from some other library.
Greg Lewis, Prop.
Eyeball Engineering — Home of the dull toolbit.
Our motto: "That looks about right."
Celebrating 35 years of turning perfectly good metal into bits of useless scrap.
Eyeball Engineering — Home of the dull toolbit.
Our motto: "That looks about right."
Celebrating 35 years of turning perfectly good metal into bits of useless scrap.
Re: Lathe Bits Again
And he's correct in his claim. Quenching HSS in water when it has been overheated is the source of micro-fractures that tend to limit the useful life of the cutting edge. The fractures are unlikely to be visible to the naked eye.Greg_Lewis wrote:He says this will result in microscopic cracks that will make a difference. He says if you grind the toolbit properly overheating won't be a problem.
Quenching of HSS cutting tools is, more or less, a carryover of the need to keep carbon steel below the annealing temperature. HSS is not annealed by heating--only by proper heating and SLOW (like 50° per hour heat loss) cooling. It is typically cooled in the furnace.
HSS can be successfully silver soldered to a shank without fear of losing its hardness. It likely goes without saying that it must be allowed to air cool, so one does not fracture the tool. If it can endure that degree of heat without injury, it certainly can tolerate the degree of heating that comes from grinding. One quenches only to keep the tool cool enough to handle with comfort. Based on that idea, it should be quenched regularly, long before it gets over-heated. If, in the process of grinding, the shank becomes too hot to hold comfortably, it is my policy to place the tool on a cool surface (like the table on my belt sander, which is near my tool grinder), until the intense heat has somewhat dissipated. I then quench the entire tool, cooling the shank so it can be handled.
Harold
Wise people talk because they have something to say. Fools talk because they have to say something.
Re: Lathe Bits Again
hi,
Harold has the experience, so it always pays to listen to him.
Cold water is a violent quench, hot water is more forgiving. What also works is to take the tool bit and clamp it lightly in a vise with smooth jaws. The mass of the vise will pull the heat out of the bit. Faster than air cooling but not nearly as violent as a water quench.
Just what I often do if the tool gets too hot.
Richard Trounce.
Harold has the experience, so it always pays to listen to him.
Cold water is a violent quench, hot water is more forgiving. What also works is to take the tool bit and clamp it lightly in a vise with smooth jaws. The mass of the vise will pull the heat out of the bit. Faster than air cooling but not nearly as violent as a water quench.
Just what I often do if the tool gets too hot.
Richard Trounce.
Re: Lathe Bits Again
I had always heard that you can safely quench HSS as long as it has not approached red hot, but if it has started to get red hot anywhere on the edge you should let it air cool. I usually hold the tools in hand when grinding, so I tend to quench fairly often, and the edges never get past a blue color. Should I be avoiding quenching completely? I know HSS keeps its hardness up into red hot so there's no need to quench to avoid ruining the temper, I just do it so I can continue holding onto the tool.Harold_V wrote:And he's correct in his claim. Quenching HSS in water when it has been overheated is the source of micro-fractures that tend to limit the useful life of the cutting edge. The fractures are unlikely to be visible to the naked eye.Greg_Lewis wrote:He says this will result in microscopic cracks that will make a difference. He says if you grind the toolbit properly overheating won't be a problem.
Quenching of HSS cutting tools is, more or less, a carryover of the need to keep carbon steel below the annealing temperature. HSS is not annealed by heating--only by proper heating and SLOW (like 50° per hour heat loss) cooling. It is typically cooled in the furnace.
HSS can be successfully silver soldered to a shank without fear of losing its hardness. It likely goes without saying that it must be allowed to air cool, so one does not fracture the tool. If it can endure that degree of heat without injury, it certainly can tolerate the degree of heating that comes from grinding. One quenches only to keep the tool cool enough to handle with comfort. Based on that idea, it should be quenched regularly, long before it gets over-heated. If, in the process of grinding, the shank becomes too hot to hold comfortably, it is my policy to place the tool on a cool surface (like the table on my belt sander, which is near my tool grinder), until the intense heat has somewhat dissipated. I then quench the entire tool, cooling the shank so it can be handled.
Harold
I have a microscope, and now I'm curious to see if I can spot any of these micro-cracks in the tools I've ground.