What exactly is Cylindrical Margin and what does it impact?

HawaiianMike · Feb 23, 2018

I understand it by definition;
Cylindrical Margin: Portion of the “uncleared” area on the peripheral area of the tool, allowing for a small area of contact with the work piece.

But why would someone opt to have an end mill have a greater cylindrical margin as opposed to the average end mill.

Wouldn't a larger cylindrical margin cause rubbing? Does it locate/stabilize the drill? Just increase the strength of the drill?

Any input would be greatly appreciated.

Thanks,
Michael

edwin dirnbeck · Feb 23, 2018

HawaiianMike said:
I understand it by definition;
Cylindrical Margin: Portion of the “uncleared” area on the peripheral area of the tool, allowing for a small area of contact with the work piece.

But why would someone opt to have an end mill have a greater cylindrical margin as opposed to the average end mill.

Wouldn't a larger cylindrical margin cause rubbing? Does it locate/stabilize the drill? Just increase the strength of the drill?

Any input would be greatly appreciated.

Thanks,
Michael

Drills have cylindrical margin ,end mills don't. Edwin Dirnbeck on edit what are you talking about ,end mills or drills.

HawaiianMike · Feb 23, 2018

edwin dirnbeck said:
Drills have cylindrical margin ,end mills don't. Edwin Dirnbeck

Don't ever? Or usually don't? Because I know there are end mills with margins on them, but no clear reason why.

Milland · Feb 23, 2018

HawaiianMike said:
Don't ever? Or usually don't? Because I know there are end mills with margins on them, but no clear reason why.

What I have read is they're used in some endmills for softer materials (i.e. aluminum) as a way of getting a smoother finish and damping vibration. Sort of like a wiper on a turning insert.

edwin dirnbeck · Feb 23, 2018

Milland said:
What I have read is they're used in some endmills for softer materials (i.e. aluminum) as a way of getting a smoother finish and damping vibration. Sort of like a wiper on a turning insert.

It is "MY OPINION" that cylindrical margin if it exists on and end mill at all,is there so that when you measure an end mill with a micrometer ,it measures the nominal size. If the fluting operation on an end mill is poorly done , the outside diameter will be reduced from nominal diameter.This is especialy true when cnc grinding the cutting clearance. Notice whenever you feel a resharpened end mill where they are not trying to hold a specific size,the cut edge is razor sharp.So yes I stand corrected ,a new end mill MIGHT have some of that stuf. Edwin Dirnbeck

Milland · Feb 23, 2018

About half-way down in the box chart: http://www.helicaltool.com/secure/Content/Documents/Tech_EndMillConstruction.pdf

CarbideBob · Feb 24, 2018

There are differing types of cylindrical margins.
One refers to a straight OD grind grind like a drill or reamer. These don't work on endmills and why your drill won't cut sideways like an endmill..
The other is a cylindrical ground relief grind which is a cylinder ground form but not on centerline with the tool itself but instead falls away to provide clearance. It's C/L is shifted.
Bob

Milland · Feb 24, 2018

Hi Bob,
The link in #6 looks and is described pretty much like a straight cylinder, they don't mention an offset. I'll try contacting Helical on Monday to see if I can get a clarification of how they do it.

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What exactly is Cylindrical Margin and what does it impact?

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