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.
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Andrew VK3BFA wrote:

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
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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.
(Amazon.com product link shortened)
Karl
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On Thu, 12 Jul 2007 06:11:43 -0700, Andrew VK3BFA

I thought someone posted about 4 links to pictures ?
Gunner
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On Thu, 12 Jul 2007 06:11:43 -0700, Andrew VK3BFA

=====click on http://www.practicalmachinist.com/cgi-bin/ubbcgi/ultimatebb.cgi?ubb=get_topic;f0;t5675;p=0 http://www.practicalmachinist.com/cgi-bin/ubbcgi/ultimatebb.cgi?ubb=get_topic;f=1;t3627;p=0 http://www.practicalmachinist.com/cgi-bin/ubbcgi/ultimatebb.cgi?ubb=get_topic;f=1;t7238;p=0 http://www.google.com/custom?domains=cnczone.com&q=fly+cutter&sa=Search&sitesearch=cnczone.com&client=pub-8957509077914564&forid=1&ie=ISO-8859-1&oe=ISO-8859-1&cof=GALT%3A%23008000%3BGL%3A1%3BDIV%3A%23336699%3BVLC%3A663399%3BAH%3Acenter%3BBGC%3AFFFFFF%3BLBGC%3AFFFFFF%3BALC%3A0000FF%3BLC%3A0000FF%3BT%3A000000%3BGFNT%3A0000FF%3BGIMP%3A0000FF%3BLH%3A50%3BLW%3A152%3BL%3Ahttp%3A%2F%2Fwww.cnczone.com%2Fforums%2Fimages%2Fcnclogo2.jpg%3BS%3Ahttp%3A%2F%2Fcnczone.com%3BFORID%3A1&hl=en http://www.green-trust.org/junkyardprojects/FreeHomeWorkshopPlans/DIYFlyCutter.pdf http://books.google.com/books?id=wO0JAAAAIAAJ&pg=RA9-PA9&lpg=RA9-PA9&dq=%22fly+cutter%22 +(geometery%7Cgrinding)&source=web&ots=PdyHIiZyuv&sig=qBEj-9DRHOYbcjgEGe_gerT0NGE#PRA9-PA40,M1
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On Thu, 12 Jul 2007 06:11:43 -0700, Andrew VK3BFA

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)
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What Bruce said !!!
Read his post carefully. It contains all you ever need to know about the shape of tool bits.
Bob Swinney
wrote:>I corrected the spelling of "tool" this time.....................

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)
--
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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.
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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.
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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
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    [ ... ]

    [ ... ]

    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.
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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
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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.
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Andrew VK3BFA wrote:

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
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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.
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Andrew VK3BFA wrote:

**NO** pictures, please! :-)
Nick
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No worries Nick - I DO have some standards.......when I post , it will be something I am happy to put me name to...
Andrew VK3BFA.
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Try googling " Dressing grinding wheel ". I just did it and found lots of good information. A star wheel dresser will revive the wheel on your bench grinder. Even if the grinding wheel on your bench grinder is not a good wheel, you still need to get a dressing tool. You will need it with even the best grinding wheel. So why not get one now and try it out on your current wheel?
So much to learn, so little time. While you are learning machining, I am learning about Analog Devices DDS's. Have fun.
Dan
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Thats on the list too - but a flat diamond dresser like I learned to use at school. Funny, machining started as a sideline to homebrew electronics stuff - its taken on a life of its own!....the fly cutter is to machine some plastic I am making into spacers for 450R ladder line from a HF doublet antenna - the wife has now got her ham license and wants a station inside the house, so am putting one together for her....the metalworking skills are coming in useful, the new mast outside her craft room window is mostly built (with removable couplings turned from steel, with drain holes, and water barriers, and nicely turned pins to hold them together....got a bit carried away, but hey, I can now do it, so why not...all good practice) and reasonable welds to hold the tubing together - the spacers are to keep the ladder line clear of the pole.....so it doesnt whip against the pole and create disturbance in the cosmic flow of Domestic Harmony....
(Honey, I know its 3am, its pissing down with rain, but I can hear something banging around outside - will you go and have a look?)
Bought some 8mm steel rod today at the hardware, will practice on that to get geometry right - and even it will machine soft plastic of the kitchen cutting board variety. The "real" fly cutter can wait till I have a need for it on hard materials. (and learn to machine a bit better as well...)
Having fun, stuffing around, in between all the other stuff that gets in the way - ie, wife, kids, dog, house, job, etc etc....

Dan, I suspect the AD devices are like machining - wade through the stuff written by guys in long robes wearing pointy hats covered in stars, and it devolves down to what does the job you need it to do. And its a new language which doesn't help either - but sheer determination and doggedness will get there in the end. It doesn't matter you can go and BUY one - thats not the point...
And thanks everyone for the comments - some not necessarily making much sense now, but in time they will .....
Andrew VK3BFA.
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Read some of the info available on the internet when you have some time. There are times to use a flat diamond dresser, times to use a single point diamond, but I suspect the best dresser for your bench grinder would be a star dresser. The star dresser will put a surface on your wheel that will cut better than the surface gotten from using a diamond dresser. Here are some words from Harold.
"The heating is a sign of nothing. It is impossible to grind without generating heat. What is important is how the wheel is dressed, and how long you grind before quenching. Star type dressers do the best job of preparing a wheel for grinding, but they are difficult to use if you expect a wheel that runs true. They waste a lot of the wheel as you keep trying to improve the wheel condition. Diamond dressing is a poor method for offhand grinding because diamonds leave a wheel surface too smooth, necessitating greater pressure on the item in order to get it to grind. The wheel, in a sense, behaves as a bearing surface. A diamond, however, will true up a wheel with no problems, and by wasting almost none of the wheel in the process. The best of all worlds is a wheel that has been diamond dressed to flatten it and get it running dead true, then slightly roughed up with a dressing stick, but not one of the solid boron carbide variety. They leave a wheel in worse condition than a diamond does. If a boron carbide stick is rounded at all, it tends to dull the grain of a wheel, making it abrade rather than cut. That leads to very poor grinding, and considerably more heating. The dressing stick in question is usually a 1" square block that is 6" long when new, and has the appearance of a very coarse stone, shiny black in color."
Dan
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