Material choice

[MyLilMule]

I am a hobbyist, new to machining, and I would like to make a fly cutter. Seems to be a typical choice for the budding hobbyist, and I don't have one.

I have some scrap pieces on the shelf. Two of which I could use to make it from a single piece (3/4" integrated arbor). One is 4140HT and the other is 12L. My lathe is a South Bend 13". I mostly use carbide insert tooling, but occasionally some HSS tools (I am not the greatest at grinding them yet, but I manage to get lucky every now and again.

Which piece should I use, the 4140HT or the 12L?

 

[ErichKeane]

I'd use 12L14, its cheaper, and the additional strength of 4140 HT isn't really needed/useful in a fly cutter.

 

[twhite]

I second the 12L14 for a fly cutter.


Cutting oil is my blood.

 

[erikmannie]

If I were making a tool, I would use the hardest of the two materials.

 

[KyleG]

My vote is for 4140. I used it for a collet chuck and it machined well. I think the added durability and wear resistance is worth it for a tool.

My other go to is 1144.

 

[rabler]

No expert, but if you're going for an integrated arbor, how the tool interacts with the spindle (R8?) would be my consideration. I think lead in 12L14 may actually make it slippery? I wouldn't be looking for something extremely hard as the softer one is going to take the wear, and I'd rather wear out a tool than the spindle. I'd probably be thinking 1045, 1144. But if you have 4140 on hand ...