Type of bit?

[bob_reda]

What is the best type of bit to cut extira?

Thanks
Bob

[myxpykalix]

call Fred at www.centuriontools.com (http://www.centuriontools.com) he probably can tell you. They are one of the better mfg's around and reasonable in price too.

[andyb]

Bob,
Jack is correct on calling Fred at Centurion for your bits. They are great bits. You can't beat the price for the quality.

What are cutting out of the Extira? I just cut a small sign out of Extira using a 60 degree for the letters and a 1/2" up-shear to pocket it out. I used a 2 flute 3/8" straight to cut the sign out. These are the bits that worked for me. So it really depends on what you are cutting out to what bit to use. In my opinion, it cut like MDF. Others may say difference, but either way the dust is nasty.

Andy B.

[Brady Watson]

It is nasty to cut, and if you plan on cutting more than a sheet of it, buy some coated end mills. They are cheap, easy to get and available everywhere. End mills are the same grind as a 2-flute upcut spiral, they are center cutting - unlike most router bits & they are made of top quality microcarbide.

-B

[elcruisr]

Brady, have to disagree with you on the geometry of tooling! An end mill for metal usually has a different edge angle than a tool designed for cutting wood or plastics (which each have their own geometries). There are even slightly different geometries between aluminum and ferrous metal tooling.

They will work for materials like Extira, yes but the geometries are different.

When I cut Extira I use my usual Onsrud up spirals or compression spirals.

[Brady Watson]

Eric,
You are correct to a degree. Pull an Onsrud upcut spiral (like the one in SB's starter kit) and an OSG (or other good quality) endmill, and you will see that the helix and overall grind is EXACTLY the same. Buy an upcut spiral 'router bit' from another company, and the helix will be different or a high helix end mill for AL and it will be different still...

The 'upcut spiral' in my write-up 'A Tale of Three Bits' is in fact an end mill. I'd like to see the difference in cut quality in Extira between an 'upcut spiral' and a standard end mill...not sure anyone here can show me the difference, which is why I will continue to recommend an end mill...and keep on pushing the idea wherever an upcut spiral 'router bit' is specified since an upcut 'router bit' and a standard grind end mill are identical...except router bits are grossly overpriced. (Why pay more for the same grind?)

I'm sure that Onsrud can or has engineered a bit specifically for cutting Extria, but I thought my suggestion was better than promoting a specific brand for gratuitous endorsement...especially since both you and I have actually cut the stuff before.

-B

[elcruisr]

I agree that the helix angle is probably the same but the actual "angle of attack" at the cutting edge will be different due to secondary grinds or differences in the gullet in many tools. Plain ol' spirals though do run pretty close all over. For Extira, who cares! The stuff cuts easy but messy and there's nothing like the sight of all that fine dust the dust collector missed, oh boy!

In the world of materials though, carbide comes in many, many formulations and they are not all equal. One of the major tooling companies uses dozens of different carbide formulations for their tools depending on intended use of the tool to maximize stiffness and wear life. I've tested my cuts with many different brands on the stuff that runs through my shop. I make my choices on cost per part and long life. Not stumping one brand for everyone as the solutions for different people will yield different results. I have three different brands I use for different jobs.

Got to get back to making dust of my own now!