Do I Need A Coolant System?

[Al-Hala]

I'm doing this in my basement. I guess I need to count on some kind of sump under the mill and a full enclosure so I won't end up spraying WD40 or whatever all over the place. Right?

Flood coolant is needed to make high performance machining possible; carbide "hates" shock cooling from weak/intermittent cooling, deep holes/pocketing need to have chips evacuated, re-cutting work hardened metals like stainless steel leads to short tooling life so the flood clears the chips, etc. It is not mandatory in a hobby level machine. A mister/atomizer setup will require a air source, which means in a home environment, shielding the compressor away for noise reduction, or getting one of the California Air variants (trade off is they have lower lifespans). Misting does not cure the need to evacuate chips and re-cutting, however, so it is not the end-all. A lot of professionals are using "Minimum Quantity Lubrication" systems.

Jim Dawson, as usual, is has hit the proverbial nail on the head. Here is a new term you should become familiar with: "Built Up Edge". I've referenced one YouTube link, there are others. As Jim mentioned, metal being machined welds itself to the tip, changing the cutting angle, rubbing, ripping parts of the edge away, all sorts of fun stuff. Aluminum is a "grabby" material, and lends itself to this very easily. there are coatings on tooling to help delay this, and there are some edge cases where people claim to have done without coolant/lubricant (usually high speeds and small bites), but in general, not recommended.

Check out some of the other machining videos on the 'tube; here are some excellent high speed camera shots that can show the cutting operations, note the differences in the different materials.

 

[grepper]

That's some amazing SEM photography! Very cool to actually see what's happening. It would be interesting to see the photographic equipment.

Really proves the case for coated cutters. I wonder what coating they mean, TiN? CrN?

 

[Al-Hala]

That's some amazing SEM photography! Very cool to actually see what's happening. It would be interesting to see the photographic equipment.

Really proves the case for coated cutters. I wonder what coating they mean, TiN? CrN?

Yes, I found it very illuminating. The high speed photography ones are not scanning electron, however.

As to the terms, all can be looked up without much difficulty, or as previously stated, the Handbook *grin*. Try a Google search on the tooling of your choice: end mills, lathe inserts.

TiN is Titanium Nitride, a very common one. Once the coating wears off, you are exposing the bare metal cutting edge. Diamond is another. Keep in mind the coatings "dull" the edge somewhat, which has its own series of trade-offs. It is worth noting at least one type coating requires high temperatures to work effectively, which would seem counter to high volume coolant *rolls eyes*

 

[grepper]

Will I ever actually make some chips?

 

[Al-Hala]

Will I ever actually make some chips?

"There is no try..." *bonks green muppet with a precision level*

 

[grepper]

Once the coating wears off, you are exposing the bare metal cutting edge.

That's exactly why I don't bother with it for with standard drill bits. When they get dull, I just sharpen them.

 

[Smithdoor]

You find on large machines it just not work with coolant
I have coolant and oil on some tools but found most work did not need coolant
Some time on cutting steel I will use mist only keep the temp of chips down
On threading and some milling I will brush on oil. Most of time today I just use a vacuum my wife is happy.

Dave

 

[Al-Hala]

Here is a brief discussion of some coatings used on tooling inserts: http://www.productionmachining.com/articles/a-guide-to-insert-coating-processes-and-materials

 

[mmprestine]

NO, Spray Bottles!

 

[TomS]

I'm doing this in my basement. I guess I need to count on some kind of sump under the mill and a full enclosure so I won't end up spraying WD40 or whatever all over the place. Right?

The problem I had was not containing the coolant (I have flood on my mill) as much as containing the chips. First couple of jobs I ran took about an hour each but I spent the better part of a day cleaning up. I had chips spread out in a 10 foot radius around my mill. My full enclosure now keeps my work area clean for several days of run time.

As Jim said you do need coolant of some sort. At first I used cutting oil and a squeeze bottle, gravitated to a no-fog mister system, then settled on flood coolant. Each method has it's advantages and disadvantages as others have pointed out. I prefer flood but that's my opinion. Whatever you choose it has to work for you.

Tom S.