New Burrs, what shapes?

[LilRacr]

How often do you guys buy new burrs? Iron or alum cutting?

What is your favorite shape you typically use all the time?

I love the 1/2" eggshape burrs in alum cut and standard double cut.

What burrs is everyone using to remove large amounts is cast iron heads?
Shape and cut?

[bill jones]

-I run my carbides fairly slow (using air grinders only) and when I'm ripping cast iron heads I found that I like to have just a little controlled chatter in the tool to help get flutes into the metal good.
-So my favorite burrs for doing cast iron and these work well for me doing aluminum are 10 to 14 tooth on a 1/2 x 7/8" egg or oval, and I like the helix of the teeth to be 22 to 25 degrees with regular cut flutes (no diamond cut or crosscuts).
-I also like 3/8" x 5/8" long oval with same tooth counts and same helixes.
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-I actually strobe lighted my grinder speeds under load and found that I run'm at about 2400 to 2800 rpm when I'm excavating large amounts of metal.
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-My best cast iron carbide burrs are ugly after you use them a while because they chip the edges and that seems to make them cut even faster sort of like a roughing endmill.
-When the edges of the burrs chip off the edges the burr becomes more of what Joe Mondello calls a "flegg", a combination of an egg and a flame.
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-I recently bought a small variety of Joes' burrs and I bought one of the 7/16" 18 tooth reverse taper burrs that I like pretty good but that one popped the head off when I had to do a Dart castiron 215 that has a ton too much metal on the exhaust port floors.
-Apparently these reverse tapers aren't as strong because the tail of the flutes actually are cut into the 1/4 shank slightly so there is 18 edges at the weld joint to start a break away point and I'm pretty disappointed that it popped and that I didn't buy more than one the first time.
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-One thing I like about Joes' burrs is I can get the ovals in 7/16" diameter and since I'm doing a lot of aluminum Subarus' with smaller ports than typical large port domestic heads, these slightly smaller burrs are reall suited better than the 1/2"ers for getting down inside those smaller ports.
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-I bought a dozen of 1/2" x 7/8" diamond cut burrs for something like $2.50 each from some mail order industrial supply place that are short shank, then I made my own 5" and 6" shanks with a 3/8" end for the burr that I bored and I shortened the burr shanks real short and then installed the burrs into the shank using loctite and a very light press fit and one crossdrilled 1/16" roll pin.
-So I use these to smooth up the real rough surfaces of my cast iron ports and they seem to be pretty decent even on aluminum.
-These are way too smooth to be removing any serious metal but they have their place in my port work.
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-One other thing I did was to buy a diamond wheel with an edge and set it up on an electric motor so that I can hand sharpen the leading edges of the flutes.
-If you have real fine tooth count it's difficult to keep the diamond wheel edge sharp enough to get in there so the coarse flutes allow me to touch up those edges occasionally.

[Darin Morgan]

How often do you guys buy new burrs? Iron or alum cutting?

What is your favorite shape you typically use all the time?

I love the 1/2" eggshape burrs in alum cut and standard double cut.

What burrs is everyone using to remove large amounts is cast iron heads?
Shape and cut?

We usually go through about $1000.00 to $1500.00 worth of burs annually. We have about 20 or so being sharpened and try and rotate the sharpening with the sharp ones. I HATE DULL BURS! Its one of my pet peeves. Its a waste of time to use them in my opinion. I have specially dulled burs for blending seats but that's the only dull things in the house. I use Joes burs and have only had two out of about 50 or so snap the head off but I was getting really fricken mean with it bouncing the thing around and taking off .100 cuts trying to rough out a Pro Stock port. I only have about .550 per wall to rough out! Thank god I only have to do Prototypes and the CNC does the rest. I have only hand ported about five sets from scratch and I don't want to ever do it again.

[charlied]

it's a real hog in a grinder for shaping port openings and roughing