# Milling strategy for longevity of endmills?



## MrCrankyface (Aug 3, 2021)

Hello everybody!

Looking for ideas and thoughts on how to make endmills last longer and work faster.

As an example, 12mm endmill in steel, 4 flutes.
Higher than maybe 22m/min it quickly starts sending blue chips and dulling itself so I stay at 20m/min(530rpm).
Recommended chip load is 0.024 to 0.073 per tooth so a middle ground is 0.049mm giving me a feed of 103mm/min.
Not much flex there since I don't want to take a bigger load per tooth(risk of chipping) or raising the rpm(burning up the hss).

So what's left to play with is width of cut(WoC) and depth of cut(DoC).
I try to take as deep of a cut as I can to utilize the maximum length of flute length, this should in theory even out the wear on the endmill rather than doing 100% of the work on the bottom 5% of the endmill.

But when it comes to WoC I'ma bit more divided.
If I take a small WoC each tooth gets smaller and easier chips to manage but I also have to do more passes to remove the same amount.
If I take a bigger WoC each tooth gets a tougher job(I think?) but to counter it needs less passes..

The question has been on my mind for a while since I find that my endmills quite quickly go from real sharp to leaving a burr everywhere.
As far as I can tell I don't have a chatter issue and I always have a strong airblast to keep chips out of the way.
I mostly use HSS or HSS-TiN coated endmills.

Would love some more peoples input on this.

Edit: fixed typos/brain farts


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## jwmay (Aug 3, 2021)

I'd love to know too! I'm afraid the answer is more scientific than my little brain can deal with.


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## talvare (Aug 3, 2021)

Probably the most effective way to increase longevity is by using flood coolant. Even one of the mist coolant systems probably helps a lot.

Ted


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## projectnut (Aug 3, 2021)

Here's a speed and feed calculator from the Little machine shop.








						Speeds & Feeds
					

The premier source of tooling, parts, and accessories for bench top machinists.




					littlemachineshop.com
				




Here's a speed and feed table for carbide mills




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						Speeds And Feeds For Milling With End Mills
					

Speeds and feeds charts for end mills from The Carbide End Mill Store.




					www.the-carbide-end-mill-store.com
				




There are also a number of wall charts that give the same information.




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						Milling speeds and feeds chart - Google Search
					





					www.google.com
				




Almost all speed and feed tables/calculators are intended for production work.  Essentially that means the fastest speeds and feeds that can be maintained to be profitable without prematurely wearing out the tooling.  In a hobby situation where tool life is more important than speed I generally run 60% to 80% of the recommended speeds and feeds with the proper lubricant.


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## markba633csi (Aug 3, 2021)

Have you tried carbide?
-M


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## MrCrankyface (Aug 3, 2021)

projectnut said:


> Here's a speed and feed calculator from the Little machine shop.
> 
> 
> 
> ...


That's the calculator I've been using, but as you say I've throttled back a lot from the machines and toolings feedback.

Markba633csi: I've tried carbide insert tooling but not carbide endmills as they're generally too expensive for my taste.
I usually use carbide insert for roughing but often I find that I need a "regular" endmill to get the best results.

talvare: I agree completely but the width of cut thing would still apply I think.


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## rabler (Aug 3, 2021)

My neophyte understanding is that width of cut has a significant effect on the temperature of the tool cutting edge.  Essentially it sets a "duty cycle" for the cutting edge, from 0% to 50%  (0-180degrees in contact cutting).  That duty cycle effects heat dissipation in the tool.  The use of coolant increases the dissipation while not in the cut, lubricating effect limits the heat buildup while the edge is cutting and rubbing.

Depth of cut for an endmill is mostly a rigidity issue.  Both from and chatter perspective and also the total amount of force being applied to the tool and workpiece, causing deflection.

This doesn't really give you any idea of what width and depth of cut to use, but does give you some idea of what to consider.  If your endmills are dulling quickly, maybe try less width per pass?


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## machPete99 (Aug 3, 2021)

A note on carbide end mills... Your workpiece needs to be secure and not have deflection, or you are likely to chip off your edges.


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## martik777 (Aug 3, 2021)

I use  a few indexable mills but nothing beats a good carbide or HSS end mill. I learned how to resharpen HSS (just the ends) a few years ago so that makes them last 'forever' . Sometimes I used the lathe with power xfeed for facing off a piece.  Lathe tooling  seems to last 100x as long as an end mill.


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## benmychree (Aug 3, 2021)

Coolant!


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## Suzuki4evr (Aug 4, 2021)

martik777 said:


> I learned how to resharpen HSS (just the ends) a few years ago so that makes them last 'forever' .


Would you care to share your method of sharpening or do you have a tool & cutter grinder?


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## benmychree (Aug 4, 2021)

End mills can be sharpened by hand on the ends with an ordinary bench grinder and a fine wheel that will hold a sharp corner, you just need to take care to grind the center a bit hollow and re split the center.  Granted that it may not cut on all the corners, but it will work well enough for most work.  My machine shop teacher in high school shared this with me.


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## mattthemuppet2 (Aug 4, 2021)

Roughing end mills are your answer 

If you're getting blue chips then you're probably running it too fast. Slow it down and adjust feed until you're getting nice chips.


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## AGCB97 (Aug 5, 2021)

I haven't ruined an endmill or drill since I added spray coolant to ALL my machines. Started out with a single one on a mag base that was brought from machine to machine but soon got one for each. Use Kool mist and still on the same bottle. Goes a LOOONG way! Not affected by any of the 'so called issues' everyone mentions against such things.
 My 2 cents.
Aaron


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## springer (Aug 5, 2021)

Get on eBay and get some new carbide end mills.  There are a few vendors that sell decent stuff at a good price.  I run all of my end mills with full axial engagement if possible and anywhere from 10-25% radial engagement.  In steel, I'll aim for 400 SFM for a starting point and adjust from there.  Don't run coolant on steel with carbide, but clearing chips is vital as recutting the chips will ruin an end mill faster than anything else you do to it.  Air blast is all you need.  I have a few steel end mills that have lasted for hours of actual cut time and are still cutting great.


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