What Does The Swarf Tell Me ?

[brino]

I posted earlier that I still had some chips on the mill table, here's some photos......

I was cutting silicon-bronze using a 3/4" diameter roughing mill running at 375 rpm(max speed of my 1916 Cincinnati machine):


Both of the following piles of chips were made with a feed of 2-7/8in per min.
The bright ones were from a shallow cut:


These discoloured ones were from a deeper cut:


There's a bunch you can tell from the look of the chips.

Comments are very welcome!

-brino

 

[brino]

The attached pic is the swarf I got conturing my smokeless muzzle loader barrel

It looks like you sheared a robot sheep!

-brino

 

[GA Gyro]

Those bronze chips, are IMO good chips...

I have read chips that are kinda like a figure 9... and slightly discolored, yet not burnt... show a good cut. Enough DOC/speed, yet not too much DOC/speed.
If one added a little coolant (maybe just a squirt of WD-40 now and then, as opposed to a stream of soluble oil sling all over the shop), the color of the chip will lighten, which means one may be able to take a little more DOC and/or speed.

 

[brino]

If one added a little coolant (maybe just a squirt of WD-40 now and then, as opposed to a stream of soluble oil sling all over the shop), the color of the chip will lighten, which means one may be able to take a little more DOC and/or speed.

Thanks John,

I read before I started that job that bronze is often done dry.
Of course, I did have my wd40 bottle handy and did try it......all it seemed to add was smoke.
So I continued dry.

-brino

 

[jererp]

Most people when they grind a chip breaker make it too large. The ledge formed is supposed to hit the chip and turn it back on itself, causing it to work harden to the point of breaking. If you look at most ground chip breakers, the chips start to curl before they reach the chip breaker.

 

[brino]

If you look at most ground chip breakers, the chips start to curl before they reach the chip breaker.

Wouldn't that mean that either
1) the chip breaker is unneccesary, or
2) the chip breaker is simple too far from the cutting surface?

I have inherited some tooling with chip breakers, but seldom used them, I believe my personal need for them is low.
Also it seems to me they would limit the tool life in terms of the number of sharpenings before you had to do a full-scale reforming of the tool bit to grind off the chip beaker groove itself.....

-brino