Death of a tool bit

[Robin Hewitt]

I thought this looked interesting so I pointed a camera at it..

Pic 1: Same program, two different metals. HE20 cuts nicely, pure aluminium creates an enormous burr. Proving the cutter can handle a bit of extrusion.

Pic 2: HE20 aluminium, 6mm HSS cutter, 1250 rpm, 0.1mm off final size, feed 2.5 mm/s, 2mm DOC, good flow of suds.

It enters the picture top right and you can see it already in trouble because it is only cutting on the leading edge. It has picked up metal on it's flutes, it's bending in to the cut and has gone past depth.

It slows up at the corner and things get worse, it is now barely cutting. It passes a hole and veers towards it, it is now bent in two directions, it tries to recover but everything gets too much for it.

I haven't got a clue why it suddenly decided to pick up metal, I dropped the DOC to 1.5mm and finished the job without losing another. A bit of a fudge, I hate not understanding.

Unrelated but I popped three 6mm cutters one ofter the other last week. Didn't make it an inch in to the slot. Problem was a new draw bar which bottomed out on it's thread. The collet chuck felt firm but it obviously wasn't. That had me scratching my head until I thought, what has changed?

[Jonathan]

Is HE20 just 6061? I've only once cut 6061 but the finish was amazing...

I notice you're not using carbide cutters, is this due to lack of spindle speed making it not worthwhile or some other reason?

[Robin Hewitt]

No idea what 6061 is, HE20 is the best seller for extrusions.

I heard that HSS takes a better edge than carbide, could be a myth.

I think my spindle speed is about right. Increasing the rpm means increasing the feed rate, which increases the power going through the tool which increases the bending. As soom as I drop below 8mm tooling I find bending to be a factor.

I just measured an outline on this part, the drawing says 28.25mm, Mitutoyo calipers say 28.26mm. The error is 0.0004", could be the mill, could be the calipers, works for me :beer:

[m_c]

HE20 is pretty much 6061, just that certain industries can't quite drag themselves to use international standards.

[irving2008]

HE20 is pretty much 6061, just that certain industries can't quite drag themselves to use international standards.

Yep,





NOTE : All Dimensions are in mm except weight










Sr.
No.



Standard



Composition



Remarks





USA



IS



UK



DIN



Cu



Mg



Si



Fe



Mn



Zn



Ti



Cr





1



1050



19500



E 1B



Al 99.5



0.05



-



0.3



0.4



0.05



-



-



-



Aluminum 99.5% Min.





2



1100



19000



E 1C



Al 99.0



0.1



-



0.5



0.6



0.1



-



-



-



Aluminum
99% Min.





3



3003



31000



NE 3



AlMn



0.1



0.1



0.6



0.7



0.8 - 1.5



0.2



0.2



0.2



-





4



3103



-



-



AlMn1



0.10



0.30



0.5 - 0



0.7



0.9 - 1.05



0.20



0.10



0.10



-





5



5051A



-



-



AlMg1.8



0.05



1.4 - 2.1



0.3 - 0



0.45



0.50 - 1.1



0.20



0.10



0.30



-





6



5052



52000



NE 4



AlMg2



0.1



1.7 - 2.6



0.6



0.5



0.5



0.2



0.2



0.25



-





7



6005A



-



-



AlMg Si 0.7



0.30



0.40 - 0.70



0.50 - 0.90



0.35



0.50



0.20



0.10



0.30



-





8



6061



65032



HE -20



AlMg SiCu



0.15-0.4



0.7 - 1.2



0.4 - 0.8



0.7



0.2 - 0.8



0.2



0.2



0.15



-





9



6063



63400



HE-9



AlMg Si 0.5



0.1



0.4 - 0.9



0.3 - 0.7



0.6



0.3



0.2



0.2



0.1max



-





10



6351



64430



HE -30



AlMg Si 1



0.1



0.4 - 1.2



0.6 - 1.3



0.6



0.4 - 1.0



0.1



0.2



0.25max


-







From: Chemical Composition of Aluminium Alloy (http://www.siddhiindia.com/chemical%20composition%20of%20aluminium%20alloy.ht ml)