Are End Mills Tapered?

JPMacG

JPMacG

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I am reducing the size of a small 1/4 inch thick steel plate using an end mill. I got lazy and started cutting the full 1/4 inch thickness in one pass, rather than taking a number of smaller cuts.

I notice that when taking the full thickness cut I am getting a tapered surface. - maybe .010 over the .250 thickness. It is like the mill is larger in diameter at the end and it tapers down gradually toward the shank. It does not matter how aggressive the cut is. I can take a .003 inch cut and I still get the taper. I don't think anything in my set up is flexing.

Is this normal? I thought end mills were a constant diameter. This is a cheap 5/8 inch diameter 2-flute mill from Harbor Freight. It cuts well otherwise.
 
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Not normally tapered, but it is a HF end mill. I assume you are using your Atlas, so is the work piece square to the spindle? Does the table run true to the spindle? Is the table square to the spindle? Just a few things that need to be confirmed in the trouble shooting process. And as ronzo suggestes, mic the endmill.
 
They do make tapered end mills, they are for mold making where you need a taper so that the part will release from the mold.
 
They make tapered endmills with different tapers. I have a couple different tapered ones. They would be marked with the degrees instead of the diameter. I would make sure everything is square first. The endmill also may not have been sharpened properly causing a taper on it.
 
Also if the endmill is already dull it may be deflecting. You would be surprised how much a dull endmill can be deflected without it breaking.
 
coolidge said:
They do make tapered end mills, they are for mold making where you need a taper so that the part will release from the mold.
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I believe the OP said it is cutting as if it were tapered in the wrong direction, more like a dovetail cutter. Deflection of the endmill is possible with a heavy cut but it would also cut as if it tapered toward the end rather than the shank.

I would suggest checking runout of the endmill. If the endmill were bent, it would cut as if it were tapered as the OP describes.
 
JimDawson said:
Not normally tapered, but it is a HF end mill. I assume you are using your Atlas, so is the work piece square to the spindle? Does the table run true to the spindle? Is the table square to the spindle? Just a few things that need to be confirmed in the trouble shooting process. And as ronzo suggestes, mic the endmill.
Click to expand...

This is what I was wondering too.

kingmt01 said:
Take a spring pass to see if it goes away.
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Taking a spring pass (don't change any settings and run over the part again) gives amazing results sometimes.
 
Make a pass with another endmill, preferably a different brand.. It will tell you whether it is the endmill or the mill Have you tried cutting from both the left and the right side, front and back sides, with the same results? If it is a tram issue, the results will be different.
 
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