[SCzEngrgGroup]

Today got off to a bad start - I guess I should've had a second cup of coffee, before wandering out to the shop. The first job I setup, I didn't correctly setup one of the fixture offsets, so on the first plunge, my poor endmill exploded. I grabbed another one out of the drawer, corrected the fixture offset and the tool length offset, and started over. Much to my surprise, I was getting pretty horrendous chatter, using the exact same G-code that worked perfectly most of yesterday. The only difference was the new endmill was a different brand from the ones I'd been using. I stopped the program, replaced the new endmill with the same kind that I exploded, and the chatter was gone!

Looking at the two endmills, I can't see any difference that would explains such a dramatic difference in performance. Very surprising.... Both endmills are 1/2" HSS 2-flutes with 1-1/4" length of cut. The "good" one is a Hertel, which is TiN coated. The "bad" one is an Interstate, which is not coated. Both are designed for cutting aluminum, have the same helix angle, and basically the same shape overall. I can't believe the coating alone could make so much difference. I used to use exclusively Putnam endmills, and really liked them, but I can no longer find them anywhere. They probably got bought by some other company.

Here are the two endmills:



Regards,
Ray L.

[neilw20]

First image doesn't work. Second looks OK until enlarged. I know you wouldn't take a blurry picture Ray.
I see they have clamping flats. Do you actually put them in collets?

[LeeWay]

The only other differences I can see is that the grind on the cutting edges is shorter on the coated one.
I haven't been in the habit of checking my diameters either until recently.
I have been using Onsrud carbide 2 straight flute cutters in my router for polycarbonate. I order 3/16" and that is usually what I get. That is until recently. It was marked 3/16", but the diameter was actually .1765". That makes a difference. Fortunately I was able to redo the parts with the correct size bit, but I now check the diameters on every single cutting tool I install. Takes only seconds and could potentially save hundreds.

[MRM RCModels]

Both are designed for cutting aluminum, have the same helix angle...

Regards,
Ray L.

Oh! All of the stated feeds as speeds you've quoted are using HSS "for Aluminum" endmills? Now it makes sense.

[waltpermenter]

there are many small differences in the way an endmill is ground so compare gash angle, dish angle, helix angle, primary land width, rake angle, primary angle, secondary angle, tooth height, tooth width etc. it's obvious in the pictures that at least some of these parameters are different between the 2 not just the coating.

[forrey]

I have found that the coating will indeed make a large difference, the coating is not only harder but on the tools for aluminum a lot slicker so the metal flows up the flute just a bit faster and this makes a difference with cutter pressure. My cutters of choice at work (large VNC's) are coated solid carbide you sure notice the difference if someone puts in an un-coated cutter.
Forrey.

[SCzEngrgGroup]

First image doesn't work. Second looks OK until enlarged. I know you wouldn't take a blurry picture Ray.
I see they have clamping flats. Do you actually put them in collets?

Neil,

Both work fine here. Yes, the second one is blurry - cellphone pictures, and no macro mode. I'm using a set-screw holder at present. I have used collets at times - never seen any difference.

Regards,
Ray L.

[SCzEngrgGroup]

The only other differences I can see is that the grind on the cutting edges is shorter on the coated one.
I haven't been in the habit of checking my diameters either until recently.
I have been using Onsrud carbide 2 straight flute cutters in my router for polycarbonate. I order 3/16" and that is usually what I get. That is until recently. It was marked 3/16", but the diameter was actually .1765". That makes a difference. Fortunately I was able to redo the parts with the correct size bit, but I now check the diameters on every single cutting tool I install. Takes only seconds and could potentially save hundreds.

Lee,

Yes, the only difference I see is the "flat" behind/under the cutting edge is shorter on the coated one. Hard to see how that would make a difference, since that area never c contacts the material. And the chatter was still present when doing a peripheral cut, where the end of the tool was not even in contact with the work.

I would've sent those Onsrud tools back to properly made one. That had to be a QA failure!

Regards,
Ray L.

[SCzEngrgGroup]

I have found that the coating will indeed make a large difference, the coating is not only harder but on the tools for aluminum a lot slicker so the metal flows up the flute just a bit faster and this makes a difference with cutter pressure. My cutters of choice at work (large VNC's) are coated solid carbide you sure notice the difference if someone puts in an un-coated cutter.
Forrey.

I've used coated and un-coated versions of identical endmills interchangeably in the past, and never seen any difference whatsoever. My impression is the coating is mostly for increased tool life. In any case, it's hard for me to imagine the coating making the huge difference in the tools performance as I'm seeing here. Only thing I can figure is the Interstate tools are considerably less stiff than the Hertel. Perhaps just an inferior grade of HSS.

Regards,
Ray L.

[SCzEngrgGroup]

Oh! All of the stated feeds as speeds you've quoted are using HSS "for Aluminum" endmills? Now it makes sense.

I'm not really sure how much difference that makes. I've used generic HSS tools, and never seen much difference in performance. Certainly nothing like what I'm seeing here. I've always found the "name brand" tools to be pretty much identical in performance. Avoid the cheap Chinese stuff. Good US made (well, at least US branded) tooling is available at very reasonable prices if you shop around, and wait for sales. I think the "aluminum cutting" endmills have a higher helix angle, to help evacuate chips better, but I've never seen a difference in how they cut compared to a generic endmill.

Regards,
Ray L.

[TiagoSantos]

I was under the impression that Interstate is an "imported" brand, isn't it?

[neilw20]

I am subscribed to this thread, and have not had the update emails.
1. the frequency at every 10 minutes was NBG, now when do they update??????(nuts)

[LeeWay]

I haven't received any email for subs for a couple days now. Last time I mentioned that, Paul said it was because of the weekly newsletter. I have also never received one of those, ut it must be a humdinger of read.

[SCzEngrgGroup]

I was under the impression that Interstate is an "imported" brand, isn't it?

Tiago,

You are correct! Don't know how I ended up with those!

Regards,
Ray L.

[GJeff]

My guess would be the metal itself. HSS is such a blanket term and you get end mills that vary in the actual type of metal so drastically that it's hard to believe.

I agree with virtually everything you do and say on these forums with the exception of your fascination with HSS. I'm not a fan of conventional wisdom, but in this case I think the recent conventional wisdom that carbide end mills end up being more bang for your buck even for aluminum is worth at least testing. I'm a huge fan of YG carbide end mills available on amazonsupply. They're a bit spendy, but they make aluminum cut like butter that doesn't melt and I think they'll last way longer. I don't even have to use coolant.

My guess would be that you came to prefer high quality HSS from doing lathe work where you can get a slightly better surface finish than with carbide. I'm not sure if that holds up with end mills, certainly not if you can't get good quality ones. There are simply too many crap HSS end mills out there and the first batch I got were absolute junk.

Edit: Considering it's HSS I'm sure the coating actually does make a big difference as well. With carbide it should not and I'm still trying to figure out if they're better off bright or not like the aerospace article I linked before stated.

[SCzEngrgGroup]

I have used carbide MANY times, and my conclusion is still that HSS is better for these machines, and they cost 1/3 as much, and are much less easily damaged. With limited spindle speed, limited power, and very limited rigidity, the MRR you can achieve with carbide is no higher that what you can achieve with HSS. I've seen no significant difference in life - I can use the same HSS tool for days at a time. You've seen the pictures in my other thread of all the parts I made with a single $10 HSS endmill. As I also said, I've used coated and uncoated HSS tools for years, and never seen any difference whatsoever in performance.

So, what kinds of feeds and speeds do you use with carbide? What MRR do you achieve?

Regards,
Ray L.

[AUSTINMACHINING]

I'm curious to see how well carbide would work on the Torus pro. I've been using a cheaper round column mill the last few years, and I have used carbide, but I think as Ray said it was too floppy and would chip the carbide. I did have some success using a 3/8" Destiny diamond back rougher($$$). If I hit the sweet spot (high chip load), it would get smooth and quiet and just plow it's way through aluminum. Very impressive, but at the cost, one screw up and it's done. I also ordered a 1/4" end mill supposedly made for aluminum that had a blackish coating that was fairly expensive ($28.00) that was horrible. The squeal and chatter was so unbearable, I was glad when it hit a clamp and broke. I switched to my El cheapo Harbor Freight mill, used the exact same program, and it cut way better. End mills and coatings are still a bit of a mystery to me. I bought a set of super cheap end mills to get started with when my Torus arrives. I'll work my way up from there.

[SCzEngrgGroup]

I would NOT recommend using "super cheap" endmills, even for learning on. Quality does matter, and decent tools are not expensive. For example, my "workhorse" tool is a 1/2" HSS 2-flute, that I typically pay $10-13 for from Enco. Currently using Hertel brand, since my former favorite, Putnam, is no longer available. These do a fine job, and last a looooong time - most die through operator error, rather than being worn out. The "cheap" endmills I've used were absolute cr@p - right out of the box, they didn't cut worth a d@mn, and I wasted a lot of time trying to figure out why I couldn't get a decent result. I've got quite a few cheap, brand-new 3/4" endmills that I won't even use for roughing because they're so bad. Using good tooling, a good result is easy to achieve, and I'll get my work done much faster.

I have tried carbide on the Pro, and found, once again, no benefit. The Pro is somewhat less rigid than my knee mill (hardly surprising, given it weighs >1000# less), and has a slower spindle (my knee mill goes to 8200 RPM). Even on the knee mill, I could get the same maximum MRR with HSS I got with carbide, with far less drama, and at 1/3 the cost.

What I often see on these forums is people equating high feedrate to productivity, thinking they're doing "High-Speed Machining". So, they'll use a carbide tool, run max RPM (which is well below recommended SFPM for the tool), crank the feedrate, but then have to back way off on DOC and/or WOC, due to the limited spindle power and/or rigidity of the machine. They then feel like they're getting a lot of work done, because the machine is moving really fast (which IS great fun to watch). But, I still maintain, if you take the time, as I havem to optimize performance for each tool based on MRR, which is what really matters, there is little or no advantage to carbide in most applications, and I will get any job done just as well, and much faster and cheaper, using HSS. Power and rigidity of the machine itself will inherently limit MRR, and on machines in this size/price class, that limit is well below the level at which carbide has any real advantage, except for the advantage in stiffness on smaller tools (1/4" and below).

Regards,
Ray L.

[ihavenofish]

i generally dont even consider buying HSS end mills. i mostly use YG carbide which is cheap and decent quality. i find that for the price difference, HSS is a waste of money. HSS is just so flexible that it chatters away like mad. i use alot of extended flute cutters too, which makes it much worse. i also find the tool life is very limited with hss. i do have some cobalt sowa stubby 3 flute cutters though, which are decent but cost near as much as the YG carbide. the exception would be a very large tool like 1" diam, 4" flute. however, these i primarily use for super light edge cutting.

likewise, cheap cutters - be it carbide or hss - are not worth the money. had a chinese carbide end mill once. exploded the second it touched the aluminium on a cut that the YG end mills lasted 100's of runs. when my new machine is running ill switch to walter carbide, purely because their software will tell you what tool to buy, HOW to use it, and how long it will last in that use, recomending the most economical tool, even if its actually the most expensive to buy. no guessing is worth the extra cash, especially in stainless and copper. breaking 1 or 2 tools on a small job can turn it into a loss instantly.

[LeeWay]

I use mostly HSS on my mill unless it is the larger size ones. I have quite a few 1/2" carbide and like them. Smaller than that though, I use HSS. I have actually burnt up a few small carbide end mills running the same parameters as the same size HSS end mills. They were obviously the wrong type of end mill for those settings. That was all about the chip load. Ever seen a carbide end mill turn red hot under a stream of coolant? It looks pretty cool if it was a waste of money.
It pays to consult the charts when using a different type of end mill on the same old job, even if it is the same size and flute count.