RANT/follow up re Query - fly cutter tool grinding geometry

I corrected the spelling of "tool" this time.....................
OK. I will admit it. I am a concrete thinker - I work with me hands,
solve problems by drawing diagrams, pondering a lot - trying things
out, when they stuff up, try another method. . If I don't have a
skill, and want one, I look around for a course to do. So I am doing
fitting and machining at trade level. Cant do it at the level I would
like, as I am too old to get an apprenticeship..
And my back is stuffed from a lifetime of lifting too many heavy
things, I look 20 years older than I am cause I spent most of that
time working outside, in the weather. I got the scars from flying bits
of metal and wire and concrete and collapsing ceilings and jumpy power
tools and car crashes. Hearing stuffed. Eyesight the same. If I was a
dog, someone would have shot me by now.
And I got no regrets - the "dignity of labor" I think its called.
Happy is I. Can argue with Gunner, and still think no less of him as a
person even thought hes a nutty winger.
I asked a question about fly cutter tool grinding geometry. Thanks to
all who answered. Your time, knowledge IS appreciated.
What I should have said was:-
Can someone post a diagram, in crayon if necessary, of what the bloody
thing looks like.
Cause from your answers, I don't have a clue. I NEEDS A PICTURE. With
the correct angles marked - then I can go and grind it. I CAN freehand
grind tools - it took me literally DAYS of standing in front of an 8
inch grinder, with a protractor, grinding down practice bits of 1/4
inch mild steel bar. When the instructor thought I was good enough, he
handed me a bit of tool steel to do a real one. I keep this in my
overhauls pocket, its MY lathe tool bit. And if it gets blunt, I hone
it. Or touch it up on the grinder. Cause I KNOW WHAT IT LOOKS
LIKE......... I got HEAPS of diagrams of tools in me textbook(s), but
still can only really grasp the idea when theres one sitting in me
hand.
Thinking about buying a set of HSS preground tools, local supplier has
em - keep them as a reference set. Then I can go make more of them. I
have a box of 1/4 tool steel I was given. Enough to last forever.
BUt I needs a PICTURE of a flycutter tool bit. ..........
Wish I had a Yartz degree like me wife, then I might understand the
esoteric explanations that are given. Havent. High school education
only. A spade is a spade, not a bloody manually operated excavation
implement...
Andrew VK3BFA.
Reply to
Andrew VK3BFA
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Take a right finish-cutter for the lathe. Hold it straight to the surface you want to cut. Voila!
Take a right hand rough-cutter for the lathe, round the vertical corner (when it is in the lathe) a bit. Take it to the mill, hold it vertical onto the surface. Une autre vois voila!
Compris?
Nick
Reply to
Nick Mueller
I'm a show me a picture guy too.
This was my machine shop 101 text 20 years ago. Lots a how to and pics on many things you'll want to do.
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Karl
Reply to
Karl Townsend
I thought someone posted about 4 links to pictures ?
Gunner
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Reply to
Gunner
====== click on
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Thomas Jefferson (1743-1826), U.S. president. Letter, 17 March 1814.
Reply to
F. George McDuffee
Actually you don't need a diagram. Just look at the tool and you can figure it all out by yourself.
I'll describe a lathe tool but the same thinking applies to any single point tool.
Put a tool blank in the tool holder and run it up against the end of the work piece (machine off!). You can see that it probably won't cut because the whole side of the tool is rubbing on the work. so - you need to grind some clearance below the cutting edge to stop that rubbing, grind an angle below the cutting edge.
Now you have some side clearance, you need some end clearance so run the end of the tool up against the work and grind enough angle so the end of the tool gets to the work.
Now you have a flat ended tool that will cut. It will also chatter like crazy so better make it pointed. Grind some off the back of the tool bit to make it pointed.
So far, so good.
Now then, just like a knife a tool bit will cut better with a thinner cutting edge so grind the top of the tool at an angle so the cutting edge is highest.
Congratulations, you have just ground a tool bit.
Notice I haven't mentioned angles so we'll talk about that now.
You want the minimum side and end clearance, enough to get the cutting edge to the work but still enough to give good support to the cutting edge. You want enough top relief to make a good cutting edge but still support the cutting edge.
When you are an apprentice boy you spend a lot of time measuring angles of side clearance, top rake, etc, I even had a little gauge to measure the angles I made when I was a youngster in the shop, but after a while you realize that almost everybody grinds their tools a little different. They all have side and end clearance and side rake but that is about all that is the same.
For example, say you are cutting aluminum at a high speed and high feed rate then you want a bit more side clearance because your really ramming that bit into the work. If you were turning hard material you want the minimum clearance because you need all the cutting edge support you can get and you will probably be using slower feeds.
But that is all for later. For now hold the tool blank up to the work and envision the cutting action. For a lathe the tool is stationary and the work turns, for a fly cutter the tool moves and the work is stationary (yes I know the work actually moves but the tool doesn't know it).
Now, if you screw up and grind a little too much angle it will still cut but the edge will dull quicker. If you didn't grind enough angle things will drag and probably get hotter then normal and probably leave a lousy finish, either way you can correct it the next time you grind the tool.
Yes there is more to it then this, threading tools, chip breakers, and ,and, and, but that is for later.
That is about all there is to it. Enough clearance to get the cutting edge to the metal and not so little support that the edge breaks down too fast.
Tool bits are cheap, go for it!
Bruce in Bangkok (brucepaigeatgmaildotcom)
Reply to
Bruce
What Bruce said !!!
Read his post carefully. It contains all you ever need to know about the shape of tool bits.
Bob Swinney
Actually you don't need a diagram. Just look at the tool and you can figure it all out by yourself.
I'll describe a lathe tool but the same thinking applies to any single point tool.
Put a tool blank in the tool holder and run it up against the end of the work piece (machine off!). You can see that it probably won't cut because the whole side of the tool is rubbing on the work. so - you need to grind some clearance below the cutting edge to stop that rubbing, grind an angle below the cutting edge.
Now you have some side clearance, you need some end clearance so run the end of the tool up against the work and grind enough angle so the end of the tool gets to the work.
Now you have a flat ended tool that will cut. It will also chatter like crazy so better make it pointed. Grind some off the back of the tool bit to make it pointed.
So far, so good.
Now then, just like a knife a tool bit will cut better with a thinner cutting edge so grind the top of the tool at an angle so the cutting edge is highest.
Congratulations, you have just ground a tool bit.
Notice I haven't mentioned angles so we'll talk about that now.
You want the minimum side and end clearance, enough to get the cutting edge to the work but still enough to give good support to the cutting edge. You want enough top relief to make a good cutting edge but still support the cutting edge.
When you are an apprentice boy you spend a lot of time measuring angles of side clearance, top rake, etc, I even had a little gauge to measure the angles I made when I was a youngster in the shop, but after a while you realize that almost everybody grinds their tools a little different. They all have side and end clearance and side rake but that is about all that is the same.
For example, say you are cutting aluminum at a high speed and high feed rate then you want a bit more side clearance because your really ramming that bit into the work. If you were turning hard material you want the minimum clearance because you need all the cutting edge support you can get and you will probably be using slower feeds.
But that is all for later. For now hold the tool blank up to the work and envision the cutting action. For a lathe the tool is stationary and the work turns, for a fly cutter the tool moves and the work is stationary (yes I know the work actually moves but the tool doesn't know it).
Now, if you screw up and grind a little too much angle it will still cut but the edge will dull quicker. If you didn't grind enough angle things will drag and probably get hotter then normal and probably leave a lousy finish, either way you can correct it the next time you grind the tool.
Yes there is more to it then this, threading tools, chip breakers, and ,and, and, but that is for later.
That is about all there is to it. Enough clearance to get the cutting edge to the metal and not so little support that the edge breaks down too fast.
Tool bits are cheap, go for it!
Bruce in Bangkok (brucepaigeatgmaildotcom)
Reply to
Robert Swinney
1.30 am. Had a big think, threw original design out....too bloody complicated. Finished making the tool holder. Looks good, even with finish from cemented carbide tools....Cleaned lathe, oiled ways. .
Will grind toolbit tomorrow and post results in dropbox.
Andrew VK3BFA.
Reply to
Andrew VK3BFA
Still stuffing around - it will cut, but badly. Still having problems with cutter geometry, and discovered I need to get the right wheels for my bench grinder - it wouldnt touch the drill rod I had, so had to use the angle grinder...not very precise...
Need to get some more 1/4 inch round tool steel.....anyway, school tomorrow after a 2 week break, will ask instructors.
Andrew VK3BFA.
Reply to
Andrew VK3BFA
A couple of thoughts. One is that you might need to put a better finish on your tool if you used your angle grinder. Using a fine grit stone is recommended by some after grinding a tool on a bench grinder. The idea is to have a polished surface that has less friction.
The second thought is that the geometry of your flycutter might not be correct. The cutting edge of the tool ought to be in line with a line from the axis of rotation or slightly behind that line. The same idea as a tool in the lathe ought to be on center or slightly below center. Otherwise when the tool has some force on it from cutting it deflects so that it makes a deeper cut.
Dan
Reply to
dcaster
I gotta ask why are you fooling with a fly cutter when an insertable carbide em is inexpensive if you shop around?
I'm going to take my stab at describing what you need to grind though.
I'm assuming you have a lantern type tool holder for your lathe. Orient it so that it is at the same angle to work piece as your fly cutter would be to work piece on your mill.
Grind your bit. The only thing you got to worry about is where the tip is relative to center.
HTH,
Wes
Reply to
Wes
[ ... ]
[ ... ]
You're using *drill rod*? I haven't seen that you've mentioned heat treating it, and the default condition for drill rod is annealed, to allow you to machine it. It then needs to be hardened *after* any machining, and after that, it needs to be finish ground.
The wheels on your bench grinder are likely reasonable for hardened drill rod, but way too soft to be used for annealed drill rod. (Assuming that they are not diamond wheels, which would be killed by the drill rod in any state, not just annealed.
I think that everyone was assuming that you were working with HSS lathe bits, which are square not round, and which can be ground rather hot without losing their hardness. Grind drill rod enough to discolor it, and you will have annealed it again -- so it would not be hard enough to hold an edge.
Good luck, DoN.
Reply to
DoN. Nichols
Because I want to do it meself. Could go and buy a face mill, but wanna do it meself. Wanna learn how to make things rather than buy them... Sick of being a consumer...
Andrew VK3BFA.
Reply to
Andrew VK3BFA
That's absolutely OK. But many of us are puzzled why your bench grinder didn't grind the bits and you had to use an angle grinder instead (HUH!).
So get a white disk (grit 60 or 80) for your grinder and post a picture somewhere what you have ground now.
Can't imagine that you are way off with what you have now. The rest is experimenting, trying and understanding.
Nick
Reply to
Nick Mueller
Stop shaving, stop using soap, and get used to the itch, then.
:-)
You already are a consumer.
Why do you not just draw out the fly cutter and it's bit to get a handle on it's geometry?
A grade school drawing set has all the tools you need to do an "accurate" drawing, but a napkin and a crayon would serve well enough.
Cheers Trevor Jones
Reply to
Trevor Jones
Here at Chaos Central the bench grinder has been hanging around for years, grinding shovels, axes, plastic, aluminium - anything and everything. Obviously, I had it BEFORE I did tool grinding at school and learnt that it shouldn't be used for such things...will get a decent wheel as soon as I can organise myself to find one....
And I will keep experimenting - just need to get some more steel to grind......
Andrew VK3BFA.
Reply to
Andrew VK3BFA
Yep. But not of fly cutters - and why do any of us try to make things that can be store bought? -
Why do you not just draw out the fly cutter and it's bit to get a
Run out of crayons......besides, drawing is a 2nd year subject....
Andrew VK3BFA.
Reply to
Andrew VK3BFA

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