TiAln end mill... superb, but what did I do wrong?

[TroyO]

I had some QCTP toolholder blocks I wanted to knock about 1/4 inch off. They are alloy steel, and hardened at least to some extent.

I tried with a regular HSS end mill (4 flute... first a 3/4 then a 3/8 if I recall.) but they both kind of melted. (They were cheap.)

So, it gives me an excuse to try something new, and they had (Still do I think) TiAln coated roughers on sale in the clearance section of Enco. A 3/8" one was around $15. So, I gave it a whirl.

http://www.use-enco.com/CGI/INSRIT?...PMKANO=274&PMKBNO=2335&PMPAGE=5&PARTPG=INLMPI

Turns out, the speeds and such were kind of out of reach on my Mini mill (According to G-Wizard) I was looking at about 1800 RPM with a 17 IPM feed rate. The RPM was achievable, but 17 IPM? LOL... lets see... 16 turns an inch x 17 IPM, 272 RPM, or about 4.5 cranks per second. LOL.... maybe when I was younger.

So, what the heck... I drop the RPM a little (1500-ish) and just crank the hell out of it. It cut like a DREAM.... 1/4" DOC, about the same in at full on crank-it speeds... no major freakout by the mill. Had the whole QCTP cut in less than a minute. Sweet! (It also "proofed" my column upgrades... BIG improvement.) No coolant used either, dry cut.

So far so good.... I was ready to mortgage my house to get a bigger collection of magic TiAln bits, or invest in a ore mine or whatever, LOL.

Drop the next QCTP in to be milled... right off the bat it's taking a lot more pressure to crank and not cutting nearly as well. By the end of the 3 inch or so straight run it's glowing red hot and just not cutting well at all. I checked the bit after the first run and it seemed fine. After that it looked like a melty ball nose end mill. Gummed up with metal BUE and rounded over.

Do you figure it was too fast, or not fast enough? Or is the Mini mill just not bad-arsed enough keep that kind of bit in it's comfort zone? Another thing I can note... the second QCTP was a different brand. Maybe the steel was gummier?

Anyway..... the first run was so awesome I want to be able to do that all the time... just not with a bit that self destructs, LOL. Any ideas what I was doing wrong?

 

[kvom]

I think it's better to use the side flutes with roughers. It sounds as if you were using the end flutes. As Bogs says, carbide handles heat better, but for quick material removal a rougher is hard to beat.

 

[hammers-n-nails]

even 1500 seems pretty fast to me i wouldnt run it over 1000 for sure. that tialn coating is good stuff if you ask me, i have a 3/4 in that ive used to take the hard skin off a plasma cut plate with no damage.

 

[steamer]

I agree....1500 rpm with HSS of any coating seems far too fast...Maybe with flood coolant to keep the tool cool and lubricated....maybe.

As Bogs said, I would opt for carbide here....and I still think 1500 is too much....maybe half that.

I cut hardened steel on my Van Norman mill fairly routinely...with carbide...but not that fast....maybe it's just me....

Carbide will cut it....

Dave

 

[TroyO]

Opps, I must have said something unclearly. I think the TiAln bit I used was carbide with a TiAln coating.... or maybe that's what I did wrong in the first place?

Material type listed was "Powdered metal" which I figured was carbide?

The first bits I "threw at it" were the HSS ones which were hopless and melted. (They were cheapies anyway). Thats' why I bought the TiAlN coated bit in the first place since the stuff I read about it was that it was right choice for hardened steels.

Anyway... for this particular project it's kind of moot. LOL, I decided it was easier to lower the compound than to trim the holders. (If the dog won't wag it's tail, wag the dog.)

But, the way it cut that first one has me hooked... I'll have to get a few more to try out on some less troublesome material. Although I'm thinking it's really the "Carbide rougher" part of it that made the most difference.

I'm definitley experimenting, Bogs.... I've used the lathe a lot more than the mill so I'm still on the uphill climb of the learning curve there. Those bits you linked are still decent-enough-for-home-use quality? The prices seem very reasonable. (Actually... the prices seem too cheap to be true, LOL.)

 

[jonesie]

why not look into buying a small 1 in or 1/2 in cutter with carbide replacable inserts. i also agree that the spindle speed is to high.i have a cheep 1 1/4 dia. with replacable inserts that wk. good for things like you are doing. jonesie

 

[TroyO]

Jonesie, definitley on my wish list. Would be on my X-Mas list but I don't think I could describe to my wife what I want, LOL.

I think I will be getting a nice pile of those end mills... I feel a lot better experimenting at those prices, LOL!

 

[TroyO]

I've actually been eyeballing that very set. They have them at CDCO Tools for less. 3/4 Shank is fine... up to whatever the max on an R8 collet is.

http://www.cdcotools.com/item.php?itemid=130

It's on the purchase list, but my wife already has my gift setting by the tree. (And it's driving me batty.... it's a "Kit", it's "Kind of a tool... in a way" and there are forums and sites about it where people talk about using it..and it can be upgraded/tweaked... LOL. GIMMEEE!!! ;-)

I'm a newb so there's a LOT on the list still.... I periodically get a bit here and a piece there. Most recently I got a coolant mister which blew my budget for the moment... I will review it when it shows up. Price and size seemed right.

http://cgi.ebay.com/Spray-Mist-Unit...896?pt=LH_DefaultDomain_0&hash=item20ae156fa8

No more WD-40... LOL

 

[mu38&Bg#]

Powdered metal may not be carbide. I was just looking at the OSG catalog and they list powder metal HSS cutting tools.

I think part of the problem is the unknown hardness of the material being cut. I cut a nut plate for a QCTP in my little mill earlier this year. Some parts of it were extremely hard and others cut just fine. I think you got lucky with the first block and the endmill was sharp enough to cut through the case. That cutter was done after that, and just couldn't cut through the hard outer case of the second one or the second block was much harder than the first. The Chinese aren't known for their quality heat treating and one part might be OK while another will be through hardened with no temper.

As far as carbide tooling the cheap stuff is just that. I don't use it anymore at all. Name brand only, it gets the job done. If you need a tool for a specific task you can get it with proper coatings, relief angles, etc. The manufacturer often provides specific feed speed for the cutter and material being cut.

 

[peatoluser]

Bogs,
Thanks for posting the links for cheap endmills. My set off small cutters are slowly getting dull, and for somebody without the facilities to sharpen them, i'm always looking out for a bargain.
yours
peter

 

[mu38&Bg#]

Everyone can make their own choices, such is freedom. I found that I didn't learn much with cheap cutters. My machine didn't cut well until I had real cutters. The frustration of scrapping a part because the cutter isn't up to snuff just isn't worth it, but half the time I'm working on a paying project.

 

[mu38&Bg#]

Like, I said we all make choices. If choosing to make metal toys over eating, one may need to reconsider priorities.

 

[bob ward]

I've bought cheap cutters here http://shop.ebay.com/iceyang09/m.html Delivery is cheap but slow, usually 2 or 3 weeks. Usual disclaimers.

 

[TroyO]

Posting the link again.... useful bit of info, IMHO.
It took me a while to locate it agaim since I didn't link it.

http://richontools.com/

 

[Layne]

You were running way too fast. I would run about 350 rpm on a bridgeport (not sure if your mill has the torque at that speed). Very few metals actually require carbide or coatings, they just allow faster speeds and longer life. If you can't cut it with a plain uncaoted endmill, you're doing something wrong. All the reccomended speeds are for CNC machines running flood coolant and trying to maximize production. When you don't have coolant and are more interested in tool life than production, speeds are much slower.