Ti-N coatings on mills -- worth the extra cost?

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mneblett

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Title says it all. I'm about to purchase my first milling machine, so I'm researching mills.

Seems that cobalt-alloyed mills make a lot of sense, but I'm not sure how durable are the Ti-N coatings, or whether the coatings perform significantly better that cobalt-only mills.

Your suggestions, pls.?
 
Start out with cheap, smallish end mills (1/4”). You did not say what size mill, so I’m not too sure what size smallish would be. My rationale for going cheap is that when abused, expensive end mills break the same as the cheap ones.

Once you have the speeds, feeds, material selection, tool geometry, metal removal etc sorted out, then top end, top price end mills are worth it.

Don’t bother with coated EMS - unless the price is the same.
 
Thanks. PM28VT milling machine. I was thinking cry once, buy once, but there's some merit to what you suggest.
 
As mentioned earlier I would start out with less expensive end mills. In fact I would search Craigslist and eBay for some good used ones. Before purchasing any be sure to compare prices of those to prices of new ones from reputable vendors. Often times those being sold on Bay and Craigslist are done as part of estate sales, or by those that have no idea of the value of used tooling. On the other hand there are some real values to be found. On occasion I have been able to purchase new, or nearly new end mills for 10% or less of the cost of new. I recently bought a lot of 50 new end mills from an estate for about $2.00 each. The owner just wanted to get rid of them and put them on the market at a price that would assure they wouldn't hang around.

I would suggest you stick with known name brands rather than the Chineesium cheapies. Several years ago I purchased some of the cheapies and paid the price. They looked good to the eye, but had trouble cutting warm butter. They were so flexible it was like trying to use a piece of rubber to cut a diamond. I ended up returning them and purchasing Niagara and FastCut mills to replace them. Since that experience I have shied away from the cheapies. They may or may not work. If they don't you have to figure out if the problem is with the speed, feed, material, or the end mill itself.

Over the years I have purchased hundreds of both new and used end mills from used equipment dealers and places like eBay. I have never paid over 30% of the cost of a new one of the same size and brand.

As for coatings I would start with plain HSS with no coating whatsoever. They will work fine on anything from aluminum to 4140, and just about everything in between. Coatings are more important when tooling is used hard as in a production situation, or when doing multiples of the same operation. Until you become proficient at speeds and feeds I doubt you'll notice the difference. Of the 1,000 or so end mills in my cabinets I doubt that more than 20% have any coatings. Those were purchased for specific jobs, and worked fine. However I tend to stick with the uncoated varieties for the price and the fact that they aren't in a production situation.

Here's a link to a primer on coatings:

Harvey Tool - Tool Coatings For Ferrous and Non-Ferrous Materials

Wondering which coating or substrate is best for your cutting tool application? Use Harvey Tool's Coatings Guide to help you!
www.harveytool.com www.harveytool.com
 
Coatings shouldn't matter much to a home shop manual machinist. I certainly accept coated end mills, but as soon as they need sharpening they are no different from base HSS that they are made from. As for carbide, it has it's place, but I am far easier to get along with when using HSS in unhardened material, since I do only non-aerospace, non-production work at the cutting edge of 1940's technology.
 
Just starting out you will be breaking end mills, so plain HSS is the ticket (the feeling in your gut when you snap a $50 carbide end mill is not a good one). Once you have them figured out, then move on to carbide. In the home shop where you are not necessarily worried about production rates the only coating I would be interested in is the one that keeps aluminum from sticking to it (I don't remember the coating, it is specific for machining aluminum). The other reason you might want some carbide tools is larger diameter tools where your machine either won't go slow enough or doesn't have the torque to cut at the speed that HSS needs to run. You can use carbide in those applications to swing a larger insert face mill or end mill. I have that issue with my Tormach, for anything above about a 2" cutter you need carbide otherwise it doesn't have the torque to get any decent metal removal (in steel, this isn't as much a problem in aluminum).
 
cjtoombs said:
Just starting out you will be breaking end mills, so plain HSS is the ticket (the feeling in your gut when you snap a $50 carbide end mill is not a good one). Once you have them figured out, then move on to carbide. In the home shop where you are not necessarily worried about production rates the only coating I would be interested in is the one that keeps aluminum from sticking to it (I don't remember the coating, it is specific for machining aluminum). The other reason you might want some carbide tools is larger diameter tools where your machine either won't go slow enough or doesn't have the torque to cut at the speed that HSS needs to run. You can use carbide in those applications to swing a larger insert face mill or end mill. I have that issue with my Tormach, for anything above about a 2" cutter you need carbide otherwise it doesn't have the torque to get any decent metal removal (in steel, this isn't as much a problem in aluminum).
Click to expand...
Ain't that the truth? :cry: :grin:
 
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