Fly Cutter Questions...

[parkerbender]

I have been looking around for some fly cutter bits, and can't find anything, anywhere... The main thing I am looking to do is flatten out cylinder heads. I've seen a few videos around with guys using big fly cutters, and I have a 1/2" fly cutter holder, but I can't find any bits. I have been considering using lathe facing tools, but I can't find anything really there either, at least nothing longer than about 4" Does a guy just make this kind of stuff, and if so, what do you call tool blanks, so I can find and buy some? Ideally, i'd love to have a 6" long 1/2"x1/2" lathe facing tool, that accepts a carbide insert. I know that the best way to do this is with a big face mill, but money is super-short, and I am content spending an extra hour or so taking a couple thou at a time... also, i have only seen people knocking down heads using a tool big enough to cover the entire head, but I have a 2" face mill, and have knocked plate off flat, to see how flat I could make it, and it seems pretty darn smooth... does anyone face heads using multiple passes? I'm looking to throw together this fly cutter because i have never seen it done with multiple passes, but if i could, my problems would be solved already...

If I am missing anything, or there is a better way, please feel free to tell me that I don't know anything... because I'm already assuming that's the case...

-Parker Bender

[Shotout]

To get the 6in length you want in a lathe tool your looking at a 1" brazed tool bit. You could machine a step into it to so it would fit your fly cutter holder but I wouldn't be real comfortable loading it up. To buy blank carbide tips to braze on you'd probably have to find an importer, a quick google search showed several Chinese importers. If I remember right the Machinery Handbook has a section concerning this as well. If you have a saw repair company in driving distance you could probably get your blanks from them and just grind it in to suit. Machine your blanks, braze and grind. Facing cylinder heads is outside my experience so not knowing flatness and surface finish tolerances I'll let someone else address the face mill question.

[Fegenbush]

For a long reach application like this, you want the stiffness of a HSS/Cobalt tool bit. Tool bits, that's what they're called. Here are a couple links to a popular supply house and a less expensive one. I'll let you make the call as to what you would like to purchase. You will have to form either of them on your grinder to get the finish you want.

MSC:

http://www1.mscdirect.com/CGI/NNSRIT...MT4NO=80167773

Shars:

http://www.shars.com/products/view/2...quare_Tool_Bit

I hope this helps,

Fegenbush

[Mcgyver]

Originally Posted by Fegenbush For a long reach application like this, you want the stiffness of a HSS/Cobalt tool bit.

why do you think the hss is going to have stiffness? almost all steels have very similar young's modulus - in other words almost all steels will flex about the same amount under a force

Parker, what machine are you using? A 6 inch flycutter is pretty far out there for a regular old knee mill with an R8 spindle. Yes, it is something guys would just make. If I had to I'd make a balanced one with more than one cutter. I normally like hss because its cheap and easy to grind the right geometry but for 6" unless you have horizontal mill you probably won't be able to make it run slow enough for hss.

just make a fly cutter that holds a lathe knife brazed carbide bit in a vertical position and it will work. A lot guys slap a knife tool into those common flycutters and the geometry is all wrong....whatever style you make just think through how the tool bit is presented to the work, where the cutting edge is and where the rake and clearance should be. Here's one style Frank Ford presents on his web site

http://www.frets.com/HomeShopTech/Pr...flycutter.html

Here's a link to thread where i tried to explain the geometry for the common little fly cutters we use....and some notes (bad form i suppose to quote oneself lol) on why you should learn the fundamentals of tool bit geometry

the great part about it is that once you understand the cutting action, work and cutter materials, shear planes, speeds, angles etc, its universal. The metal doesn't know whether you're bringing a lathe tool, end mill, drill etc to bear, at simply responds to the forces and angles its presented with as its molecular structure commands it to....once you 'get it', that knowledge applies to any machine/cutting tool....you wont need a specific lesson on fly cutter geometry & speed because you'll know generally what rake and clearance angles and cutting speed a hss cutter in AL likes and can figure speed, feed and geometry out from there

oh the other thing is, don't get too hung up on tool bit angles.....if someone says us a 10 degree such and such angle, anything between say 8 and 12 will work fine. Shoot for the 10 it calls for, but don't hold off because you haven't some super precision angle grinding stuff. Eyeball and a protractor is more than enough for lathe bits/fly cutter bits

[BobWarfield]

Originally Posted by Mcgyver I normally like hss because its cheap and easy to grind the right geometry but for 6" unless you have horizontal mill you probably won't be able to make it run slow enough for hss.

It'll be fine. Speeds and feeds are the same as turning a 6" diameter workpiece in a lathe.

For aluminum heads, it'd be about 300 rpm. For cast iron, use 50 rpm, but you could go a little higher without too much trouble, or you could use a brazed or inserted carbide cutter.

There are a zillion different flycutter styles, but for one this large, you probably will have to make it.

Cheers,

BW

[Mcgyver]

Originally Posted by BobWarfield It'll be fine. Speeds and feeds are the same as turning a 6" diameter workpiece in a lathe.

It'll be fine? so says the voice of experience lol....and you've made and run how many 6" flycutters?

Not a lot of knee mills will go down to 50, as I said, if you have a mill that will run slow enough you can use hss.

[BobWarfield]

I've run a 5" fly cutter quite a lot, McGyver. And I've turned 6" on many occasions.

Haven't you?

BW

[parkerbender]

I'm on a 15 Hp vmc that only goes down to 100... I think it can swing a 6-8"er but, do you think that a guy can get away with that speed, with coolant, maybe? I ordered a bunch of A2 stock, and am just going to make one, maybe a double-sided jobbie, that's steel on one side, insertable on the other! also, then it would be better balnced... anyway, can a guy get away with 100 rpm on something like that? also, with the A2, does a guy just go .002 at a time, or something? lastly, am I going to run into problems with that cutter going dull in the middle of a head? I'm assuming what I'll be doing is about 50/50 cast/Al...

[BobWarfield]

The A2 should make a nice one. Take a look at Widgitmaster's threads, he uses a big one to get real nice finishes. It looks like this:



Mine is similar, but half that size. Bought it somewhere, but can't remember now where, sorry.

The plans for Widgit's can be found here:

http://www.cnccookbook.com/CCBlogMar2007.htm

I don't know whether 100 rpm will work for you or not with HSS tools. I would've split the difference on an 80 rpm knee mill, but 100 is now 2x recommended. Might not be fine!

Be sure to make your cutter so you could install a brazed carbide if you have problems.

Cheers,

BW

[Mcgyver]

dude, you're on a serious machine, you gotta learn how to calculate cutting speed, grab a sr high machining text....i don't mean that to be rude, it'll really help you

it'll over tax hss, at that surface speed tool life will be shortened in steel and cast iron. AL is easy, you won't have a problem.

i would not bother making it from A2; to what advantage? its more expensive, just used mild steel

That machine cries out for a big diameter insert facing tool not fly cutters imo...you will have lots of horsepower to take a serious dept of cut...way more than .002

[parkerbender]

I was meaning to make it from A2, to use it as a cutting surface, as that I don't really want to take such a small bite with carbide, and tool steel would leave a smother finish anyway. I want to have the ability to take a little bit, because many times you only want to take enough off a head to clean it up, not to actually remove noticable material. I completely agree that a facemill would be way better, but I'm just getting this shop off the ground, and have basically no money for one that would be big enough, (at least 8, but probably 10") whereas A2 is comparatively way cheaper. If any of my logic is flawed, feel free to tell me... I'm an engineer, and not a machinist...

Thanks again for all of the replies, I had seen the CNC cookbook page before, but havn't read through the whole thing... yet.

-Parker Bender

[Mcgyver]

Originally Posted by parkerbender I was meaning to make it from A2, to use it as a cutting surface, as that I don't really want to take such a small bite with carbide,

you'd be better off using a hss bit or brazed carbide held in the fly cutter than A2 as your cutting tool...HSS will tolerate much higher temps.

. I'm an engineer, and not a machinist...

hey, we're all constantly learning, I figured since you didn't know how to calculate a cutting speed you were a newb with a benchtop machine, you took me back with a 15hp VMC must be nice.

I had seen the CNC cookbook page before, but haven't read through the whole thing... yet.

no need, most of content was pinched from guys here and home shop machinist bbs site