# What Does The Swarf Tell Me ?



## BillWood (May 4, 2015)

What are the things that I can deduce from the shape of the swarf ?

ie Long tight curly corkscrewed pigtails vs smaller 1/8' short broken chips

I guess it will be different for every material ie Cast Iron will cut different to ALumium and then different again to free cutting steel to drill rod to black bar

Bill


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## Franko (May 4, 2015)

I've wondered that, too. What is good swarf supposed to look like? When I'm cutting aluminum, I kinda prefer long tight spiraled swarf, just because it is easier to clean up.


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## randyc (May 4, 2015)

That's an interesting thought.  Cast iron and brass will produce discrete chips, cast iron because of it's grain structure and brass mainly due to the fact that proper cutting tool geometry for brass requires zero or negative rake.

Tool geometry that produces long spiral strings of chips can be dangerous, right ?  On a lathe it's possible for the spinning workpiece to suddenly pick up the collection of stringy chips and whip them around violently.  If your hands happen to be nearby .... well, the results are obvious   (It is also possible for the entire mess of chips to be propelled toward the operator's face.)

Although it is definitely easier to collect those long, stringy chips, they can be a PITA.  If they tend to curl under the cutting edge, they will rub against the freshly cut edge, degrading the surface finish.  This can usually be prevented by grinding what is referred to as a "chip breaker" near the cutting edge of the tool.  The purpose is to force the chip to bend abruptly, breaking it from the curl being produced by the cutter.

FYI, most insert tools are sintered with an approximation of a chip breaker.  Chip breakers are often ground into parting tools by grinding a small, sharp "vee" groove across the center of the cutting edge.  A very sharp, fine-edge grinding wheel is required - often a cut-off wheel is used.

Here's a photo of a HSS cutting tool with a chip breaker groove ground near the cutting edge.  To the right is a common carbide insert - note the shallow chip breaker groove located near the cutting edge.  This is usually not very effective and often a separate chip breaking device is attached to the top of the insert in it's holder.




The color of the chips - mainly for the various steel alloys - can be very useful for optimizing speeds and feeds but that's another topic


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## T Bredehoft (May 4, 2015)

The shape of the chip will also  vary by the shape of your cutting tool. An angle leading ahead of the cut will roll a pigtail, whereas a tool with a leading point will break it, or allow it to curl on itself until it breaks. 

Cast iron will always crumble (with very minor exceptions) aluminum will always string (with exceptions) Steel will always vary.


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## brino (May 4, 2015)

BillWood said:


> What are the things that I can deduce from the shape of the swarf ?



Bill, great question! I hope this thread generates a pile of feedback from experienced members. I'd like to learn too.



randyc said:


> Tool geometry that produces long spiral strings of chips can be dangerous, right ? On a lathe it's possible for the spinning workpiece to suddenly pick up the collection of stringy chips and whip them around violently. If your hands happen to be nearby .... well, the results are obvious  (It is also possible for the entire mess of chips to be propelled toward the operator's face.) Although it is definitely easier to collect those long, stringy chips, they can be a PITA.



I even seen some you tube videos where long curly strings got wrapped around the leadscrew....yikes!

As for colour of chips, I saw that well this past weekend, helping a friend to clean up some silicon-bronze castings he poured. Most of the chips were like bright little "shells", but when we pushed the feed/depth of cut a bit they were either dark or red. I should get some shots of those, they are still on the mill table.

I look forward to more discussion.

-brino


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## Strtspdlx (May 5, 2015)

I'm not very experienced buy so far I've come to realize if I get long stringy tight coils in steel my machine is tight enough and I have correct angles height and feeds are correct. I haven't ground chip breakers yet as in using that to judge my setup as I'm so new to this. However this is for light cuts usually less then .030. If I'm over .050 I usually get tight winding coils of a gunmetal or brownish color about 3/4" to 1-1/2". If I get tiny little bits that fly in all directions I'm either off on speeds or my tool is dull or setup wrong as far as height or angle. Generally I can always get the swarf to go where I want it unless something as stated above comes into play. I haven't done any aluminum so I cannot comment on that. Brass I usually get nice solid looking chips with the correct setup I may get strings every once in awhile but it's usually if I'm using the wrong tool for the procedure. But take this with a grain of salt as I'm by no means a professional. 


Regards-Carlo


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## Ripthorn (May 5, 2015)

thatlazymachinist on youtube has a video about this.  I think it is called something like "feeds, speeds, and chips" or something.  He describes how the swarf reacts to tool height, cutting angles, feed rate, tool speeds, etc. and which you want to look for.  It was a good video.  Ah, here we go: linky


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## tomw (May 5, 2015)

Very helpful video. Thanks for the link!


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## Bill C. (May 5, 2015)

The shape sometimes depends on the shop you are in.  Short chips are easier to clean up and recycle.  They can get imbedded in the bottom of your shoes.  Causing scratched and slippery floors.

Long strings or ribbons are razor sharp.  Most of us have made or used long hooks to grab those ribbons.  They take a lot of space in the recycling barrels.  I pass a railroad siding close to one of my roads, there will be a rail car full of long shavings of steel. So someone still prefers cutting them.  Either way be careful handling them.


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## epanzella (May 5, 2015)

Brass and cast iron give me little individual chips. Plastics make spaghetti. Apparently my chipbreakers don't work too well on aluminum and steel because sometimes I get chips 8 feet long. Steel comes out long blue when I use carbide. The attached pic is the swarf I got conturing my smokeless muzzle loader barrel from 1.250" to .900"


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## brino (May 5, 2015)

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


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## brino (May 5, 2015)

epanzella said:


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



It looks like you sheared a robot sheep! 

-brino


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## GA Gyro (May 5, 2015)

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.


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## brino (May 6, 2015)

GA Gyro said:


> 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


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## jererp (May 6, 2015)

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.


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## brino (May 6, 2015)

jererp said:


> 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


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