PDA

View Full Version : Indexable endmills vs. HSS type



S&S_ShovelHead
03-22-2011, 08:00 PM
I just got my mill in (RF-45 clone) and now need to get tooling. I will be working mostly in steel and some aluminum, stainless and brass. What would be recommended, indexable endmills or solid HSS endmills? I have a coolant system if that makes any difference.

PixMan
03-22-2011, 08:11 PM
Start with HSS end mills. They are cheap and you won't cry so much when you burn one up or chip it. If you've not done much milling yet, get HSS mills and see what works. Learn first the difference between climb milling and conventional milling. If you try climb milling on a machine with even good-condition Acme screws, you'll soon find out what ruined work and busted end mills look like.

Solid carbide has come down dramatically in price over the years, but resist the urge to buy "this week's special" set of 20 S/C end mills for $30. Wait, then buy quality.

Your machine probably doesn't have the power or speed to get much out of insert carbide tooling. I have some for dad's 1HP Bridgeport, but rarely use them. Also, those work best with climb milling, something I can't do on a 1961-vintage Bridgeport. Solid carbide I do use because I can get higher cutting speeds without wear, and/or cut harder materials.

The 2 on left are HSS, the next 9 solid carbide, the one 2-flute with the "bronze" look is HSS-Co, and 3 on the right for aluminum are high-performance Powdered Metal.

http://img.photobucket.com/albums/v466/kenm10759/Dads%20shop/IMG_0993-r.jpg

These are some indexable end mills, ball mills, bull nose mills, chamfer mills, etc.

http://img.photobucket.com/albums/v466/kenm10759/Dads%20shop/IMG_0740-r.jpg

And these are HSS corner rounding mills, end mills, a Woodruff key cutter, and brazed carbide boring bars (which suck.)

http://img.photobucket.com/albums/v466/kenm10759/Dads%20shop/IMG_0724-r.jpg

noah katz
03-22-2011, 08:44 PM
Your machine probably doesn't have the power or speed to get much out of insert carbide tooling. ...Also, those work best with climb milling,...

Why's that?

PixMan
03-22-2011, 08:56 PM
Because insert end mill cutters tend to be proprietary (read: expensive), and need climb milling with heavy feed per tooth to be effective and not wear too soon.

The ones I have rarely get used. I tend to go with the end mills for most stuff.

How much HP does an RF45 clone machine have, anyhow?

Black_Moons
03-22-2011, 09:17 PM
I would highly recommend HSS endmills for 99% of the work you wanna do.

When that 1% comes up, You'll know it and can buy a solid carbide or insert tool for about the same price as your first 10 or 20 set of chinese HSS endmills.

Some things solid carbide REALLY excells at, For example, really long tools. Carbide (IIRC) is 3x as rigid as steel. All steels being about as rigid as eachother, this is about the only way to actualy get more rigidity outta a long tool. Very long boring bars and very small endmills can greatly benifit from this. Or if you have to drill a very skinny but long hole without much drift.

However these jobs are very rare to come up, And you are likey better off buying a single $20~50 tool for them when they do come up, then buying a $200~500 set of tools just incase it comes up in the future sometime.

sansbury
03-22-2011, 09:30 PM
HSS tooling to start. You don't *need* carbide unless you're trying to move massive amounts of metal on a CNC machining center.

I would probably start with a couple each of 2- and 4-flute endmills in 1/4", 3/8", and 1/2", and a fly cutter. Beginners are one case where cheap Chinese tooling makes some sense, there's a good chance you'll bust some tooling and $3 endmills will break just as easily as $15 ones. Likewise, if you goof with the fly cutter, it's just a walk over to re-grind the toolbit, or $5 for a new one if you royally $#@! it up. A 2" or 3" APKT face mill would be great on an RF-45, but a screwup with that could cost you 4-6 inserts at $7 each.

Tooling in general is a discipline all its own, and insert tooling is very confusing to the newcomer. I am a fan of carbide and insert tooling on very small machines--I think the idea that you *need* tons of iron and horsepower to benefit from it is wrong, but at the same time, HSS is almost always cheaper, almost always more forgiving, and almost always capable of doing the job. For where you are now, a pile of cheap HSS is a great place to start.

Once you move on and start making more clever mistakes you can start to buy some better endmills and experiment with indexable tooling if you feel you might benefit from it.

sansbury
03-22-2011, 09:39 PM
Some things solid carbide REALLY excells at, For example, really long tools. Carbide (IIRC) is 3x as rigid as steel. All steels being about as rigid as eachother, this is about the only way to actualy get more rigidity outta a long tool. Very long boring bars and very small endmills can greatly benifit from this.

According to Bob Warfield, who has studied this more scientifically than anyone who doesn't work for Kennametal, "very small" might mean anything below 1/2" diameter.

http://cnccookbook.wordpress.com/2011/03/18/carbide-vs-hss-and-chatter-for-small-mills/

Bob has an RF-45 type machine so what he says is pretty relevant for the OP. I do agree with the advice to start with HSS for economy, but carbide definitely has benefits for the HSM even with small machinery. This is especially true with some of the newer high positive-rake inserts for milling and turning. I use them on my tiny 7x lathe for a 2-3x increase in material removal rates over HSS as I can usually maintain DOC while doubling or tripling the feed rate.

PixMan
03-22-2011, 09:48 PM
I don't use the HSS end mills on dad's 1HP Bridgeport nearly as much as I do the solid carbide or insert face mills. That's not because the machine has lots of speed and/or HP, but because I'm impatient and want to get the job done before I retire. ;)

I haven't chipped or worn one out for a long time now, only because I know the limitations of an old machine. I'm much more apt to trash a HSS end mill because I forget just how slow and gentle you have to use them. :D

Mostly I have the tooling because:

1. It was bartered, cheap or free.
2. I expect to be getting a CNC mill with at least 7.5HP and 10,000rpm within the next 2 years, and I'll be ready when it shows up.

BTW, the end mills in the 1st photo are touching only for the photo, gently placed like that. Otherwise, their sharp flutes are protected in their original tubes/cartons.

jkilroy
03-22-2011, 10:17 PM
I use almost all solid carbide, except for things like face mills.

Black_Moons
03-22-2011, 10:23 PM
BTW, the end mills in the 1st photo are touching only for the photo, gently placed like that. Otherwise, their sharp flutes are protected in their original tubes/cartons.

Very good point, Endmills often have *razor* sharp edges, And a light ding can easily chip/dent the edge and cause some damage to its finishing abilitys. Don't leave em all in a drawer scattered like some people do with drills, As the sharpness of the flutes really matters with an endmill.

Bob Pastor
03-22-2011, 11:19 PM
I face a lot of aluminum plates and I wasn't happy with the finish of the carbide indexable inserts that came with my face mill. I called The Arthur Warner Co. and they supplied me with HSS indexable inserts. It's a good option if carbide doesn't give you the finish you want.

Bob Pastor

TClarke
03-23-2011, 12:10 AM
Use HSS for most manual operations, unless your setup requires the increased rigidity of carbide. Carbide excels at surface speeds of 250-1500 SFM in ferrous metals, while most manual operations will typically limit surface speed to around 150 SFM or less.

Small endmills 1/8" and smaller are an exception.

Terry

S&S_ShovelHead
03-23-2011, 12:53 AM
Thanks a ton for all the advise, looks like I will pick up a cheap set of chinese HSS endmills to get me started. Is there any benefit of TiN coated bits or are they more just for marketing purposes?

Also any recommendations for boring bars and boring heads? Indexable vs. carbide tipped vs. the type that take square hss bits.

Black_Moons
03-23-2011, 04:01 AM
Uhh.. TiN coating keeps em from rusting! thats one advantage... Uhhh.. Don't know any more :) other then it may help metal from sticking to the flutes/provide slightly better chip ejection.

As far as boring bars, you need em of all diffrent sizes and lengths.

I recommend a set of the ones that take HSS bits (Cheap, $20 for a set of 4), then you can grind bits as needed (threading bits, grooving bits, etc)

And a set of Brazed carbide boring bars.. they are good for general metal removal, come in a cheap set of all diffrent lengths and thicknesses for diffrent hole requirements, they are VERY cheap, and after 10~20 mins with some diamond hones to sharpen em, Can produce a decent finish.

Indexable boring bars on the other hand.. are like $50~150 each, and as I said you often need many diffrent sizes and lengths and styles. (Grooving, Threading and general metal removal for example)

(Note, Diffrent lengths only applys to those bars that are ground to have better chip clearance, Like brazed carbide bars, And *some* indexable bars. You would still need several diffrent sizes, And likey a few diffrent styles of insert however, So I would hold off on insert bars for now)

HSS insert bars are often.. just bars, So they can slide in and out of the boring bar holder to change length. This does provide poor clearance for the chips however.

Basicly, Im recommending brazed carbide for general metal removal and hole enlargement. And HSS insert bars for all the speciality jobs that brazed carbide can't do because its just too much of a pain to grind the proper form into carbide.
(By HSS insert bars, I mean the ones that take a standard square HSS toolbit that you grind yourself, Not an indexable insert bar)

Mcgyver
03-23-2011, 09:52 AM
On a small light mill like these 1 hp ones, the constraint on removal rate is hp and rigidity. There are times when you are taking a small amount off so spinning faster lets you increase feed and reduce time.....but so often the constrain you hit is cubic inches/ minute (because of hp and rigidity)....in which case being able to spin the cutter three times as fast doesn't accomplish anything is you have to take many smaller cuts.

Always the selection is striking the best balance - which of course depends on the machine but also whether you are trying to cover overheads or just to contain disbursements. Where it makes sense, I like slow rpms and big cuts and flood, it prolongs tool life. Time doesn't matter unless there's no (yet) power feed; get one machine going and start setting up or working another. Or take it all off in one pass on the horizontal mill:D

BobWarfield
03-23-2011, 10:30 AM
Another carbide vs hss post from CNCCookbook:

http://cnccookbook.wordpress.com/2010/05/25/is-carbide-always-faster/

HSS can actually take a higher chipload than carbide, and is more tolerant of flex (a good thing because it is 3x more likely to flex, all other things equal).

I like carbide for small cutters (anything under 1/2") and HSS for larger cutters in my shop.

Sometimes, if you're having great difficulty breaking small cutters, HSS will be happier. The runout of some inexpensive spindles is really harmful to carbide as are any jerky motions with the smaller cutters.

A really nice cutter to get hands on sooner than later is a 1/2" or so "corncob" rougher. Get it in HSS as it is cheaper and less brittle. They seem forgiving of a lot of abuse compared to a regular EM and can really move some material when roughing. You will have to plan on a finish pass, but you were anyway, right?

Cheers,

BW