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View Full Version : Carbide insert side milling.



Black_Moons
12-29-2009, 12:47 AM
Hi, I recently tryed side milling mild steel at 400sfm with my negative rake carbide insert endmill... Uh, the mill and steel really did'nt like it.. really horrable finish unless the depth of cut was only a few mils, but rather independant of the width of cut. Seemed to really hammer with high depth of cut too, even with minimal width of cut.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=230400838004
I was using the little triangular insert mill on the left

So im wondering, What kinda insert endmill does one use for getting that nice finish you get from side milling with a typical HSS endmill?

bobw53
12-29-2009, 01:11 AM
You're most likely not going to get that nice finish. Though you can get decent.

For what its worth, those TPG cutters seem economical, but they really are just a PIA. Nice straight edges that will hammer and hammer and hammer and no real "geometry" to the insert at all.

If you want to keep messing with the inserted cutters, the APKT's are pretty good. Exkenna sells the TMX brand, I think its south korean and brought in by the same folks that import bison products. They had a deal a while ago, they may still have it, buy 20 inserts and get a free cutter body, a small one, I ordered up 20 and got the surprise of a 7/8" 3/4 shank 2 fluter I wasn't expecting.

APKT's are not the latest and greatest, I wouldn't put them up against the Sandviks and Iscars, but they come pretty darn close and at $6-7 an insert vs $14-$18 and cutter bodies at a fraction of the price, they are pretty good. You can also get nice polished up sharps for AL.

Having said that, you may be better off sticking with solid endmills. Variable flute endmills can really make a smaller floppier machine seem like a superstar. Solid endmills are much free-er cutting than 99% of all inserted cutters. You don't need giant ones, a 1/4" variable helix/flute (carbide) can move a few cubic inches a minute in mild steel (a 2hp cut). Maritool has some double enders that are insanely cheap compared to anything else out there. A little short on the LOC, but a lot of bang for the buck.

Black Moons, whats the end goal? Figuring out your mill and tooling or is their a specific project in mind? or task that you are working on?

JoeFin
12-29-2009, 01:39 AM
What TPG cutter is good for Shoulder milling.

Most end mill style TPG mills are only good for .030" or until you reach 50% radius of the insert. If you want to shoulder mill some thing you'll need a insert and mill designed for it

Black_Moons
12-29-2009, 02:37 AM
what is Shoulder milling?

0.03"? haha thats exactly the depth I was cutting away at.. tryed 0.04" a couple times but it often left big burrs so I went back to 0.03"

Insert radius is something I realised when I noticed the large radius on my shoulder that I needed square.. ended up taking a light pass with a HSS endmill and then a few touchs with a file.. I suspect a very pointy insert is not gonna work well in this insert mill?

Mainly just trying to figure out my mill and tooling. I kinda don't like the idea of using my shiny HSS endmills to rough out mild steel, seems like its gonna take a long time and wear out the endmill fast. I don't mind them eating lots of aluminum however :)

So I guess stick to using it to remove mill scale and such... or well, just end milling.
How about the 45 degree and circular insert ones included in that kit? What are they good/bad for?

Hmmm, maybe I will stick to solid endmills for side milling. I'll look into APKT, I did'nt really like the look of them at first as they did'nt look like anything id ever be able to use in my lathe.. but I guess that doesnt really matter.

oldtiffie
12-29-2009, 04:52 AM
Those inserts:
http://i.ebayimg.com/11/!BfSgd4g!mk~$(KGrHqUH-DMEr)jg4zkyBL!sReVmf!~~_35.JPG

have no spiral cutting edges, zero top rake and seemingly no back rake or "hook" either.

Of course they will "pound" in steel as they are all to similar to a wood-worker's router bit which hasd no spiral but at least has a "hook angle".

Even those with straight edges and positive rake will not and cannot cut a true straight vertical face if used for "side-cutting".

They seem to be of more use for "end cutting".

I have one on which the the tool-holder was rubbing on the job instead of clearing it - so it got an appointment with the angle grinder - it worked much better after that.

beanbag
12-29-2009, 07:32 AM
I mean this in the nicest way possible, but stop using ****ty tooling and then asking why you are getting ****ty results. :o

For good side milling performance, I have found that you need a sharp cutting edge, high helix, and climb cut with minimal backlash. The high helix helps the bit stay engaged in the cut, but is hard to achieve with an insert cutter. Failing that, you go with more flutes.

I have here on my desk a 5 flute, high helix, carbide TiAlN end mill which I am sure would be great for side milling, except that I have decided that I would rather look at it than actually use it.

Black_Moons
12-29-2009, 07:35 AM
Ahh. just making sure it wasent something I was doing wrong and that the tooling itself is just not suitable for side milling.

JoeFin
12-29-2009, 09:33 AM
As in 1 of these

http://i198.photobucket.com/albums/aa83/Freakindj/Lathe/Jacobmotorcycle038.jpg

Carld
12-29-2009, 09:49 AM
Black_Moons, it's that square shoulder your mill is cutting that is causing the hammering. If the triangle tip were pointed straight down presenting the 30 deg angle to the advancing cut it would not hammer very much.

Think of it like a smaller flycutter. A flycutter with a straight side advancing into the work will hammer but if it has about 30 to 45 deg of angle as a leading edge it will hammer very little. Especially if run at 1000 rpm or so.

The slower you run a cutter the more it hammers, the faster it runs the less hammering you will have.

Evan
12-29-2009, 10:10 AM
I still haven't quite figured out what the problem is. I also haven't figured out exactly what is being attempted.

If you recall I recently built a face mill with three negative rake square inserts. I purposely left the corners sticking out on the diameter so I could use it on the side as well as the face. The inserts aren't well supported there so I wouldn't want to take more than maybe .020 DOC but I hadn't yet tried it. So, I went down to the shop a few minutes ago and clamped a piece of 1" sq key stock to the table and took a few passes up and down on the end using the side of the face mill.

No hammering, just that nice smooth peanut buttery purring sound. The finish looks ok too.

http://ixian.ca/pics7/sidemill.jpg

Oh yeah, I was running it real slow too, about 200 rpm.

Carld
12-29-2009, 10:19 AM
Evan, I think he is talking about taking a side cut not up and down as if drilling or reaming. I wouldn't expect it to hammer on a downward cut.

Try clamping that key stock down and taking a full face cut horizontally on the end of the key and see if it hammers at 200 rpm and let us know.

Evan
12-29-2009, 10:34 AM
I would have to tilt the head 90 to do that and right now I am in the middle of facing a sub table so I don't want to mess up the tram.

JTToner
12-29-2009, 11:01 AM
I've had good luck with TPG's in a 3" dia tool at about 1K rpm for facing in both harder steels and 6061, but I don't know the brand name or grade of the inserts. This was in school with their equipment.

Johnny

Carld
12-29-2009, 03:23 PM
I think what he is taking is similar to flycutting across a surface parallel to the surface of the mill table. like using an endmill to cut a slot in something.

Black_Moons
12-29-2009, 04:54 PM
Ah see evan, I wasent going up and down, I was feeding sideways, like trying to square the ends of a part by side milling. Also I was not using square inserts but triangular so the entire side of the insert was trying to cut. (note how they are held in the picture posted previously)

Apparently thats not what they are made for. I can realise why your result turned out well because with a square insert you where only using the corner to cut, not the side right?

Basicly im just learning about insert geometry and really what the diff is beween those thousands of diffrent shaped inserts and ways to hold them.
Thought it might work, Asked here if it 'should' work and If I was doing something wrong or if it was just the limits of the tool, I understand now its the limits of the tool. Im happy.

jkilroy
12-29-2009, 05:04 PM
Even with regular end mills I don't cut straight in with the X or Y axis but rather with the Z.

Black_Moons
12-29-2009, 05:18 PM
Im not saying cut 'straight' in but just a glanceing 0.03" pass, like to clean up a bandsaw cut.

Carld
12-29-2009, 05:24 PM
For doing what your doing I have the best results with a standard helix endmill. They cut fairly smooth and don't hammer. With the helix it's a progressive cut rather than flat cut on the face.

JMS6449
12-29-2009, 07:19 PM
Even with regular end mills I don't cut straight in with the X or Y axis but rather with the Z.

What do you mean? That works for roughing, by using a chopping method, but finishing requires side milling. Think pockets>

oldtiffie
12-29-2009, 07:22 PM
Im not saying cut 'straight' in but just a glanceing 0.03" pass, like to clean up a bandsaw cut.

BM - Carld has it pretty right.


For doing what your doing I have the best results with a standard helix endmill. They cut fairly smooth and don't hammer. With the helix it's a progressive cut rather than flat cut on the face.

Your straight (no helix) cutter with zero or negative top rake (aka "hook") is trying to bash its way through until it pushes a lump of metal forward until the "lump" separates and then the TC keeps it "lifted" so that the fracture remains ahead of instead of on or at the cutting edge.

That is why many TC "cutting edges" have a very small positive or a negative rake/"hook". That is the nature, intent and purpose of many - but not all - TC tools. Router TC tools have a very sharp edge but do have a big (~20 degrees) "hook" but no spiral. Same applies to wood-working planers, thicknessers and "buzzers".

The classic HSS spiral-toothed end-milling cutter has a positive rake/hook so that the cutting is done on or very close to the actual cutting edge. Because of the spiral the cutting action has a very high shear(ing) component in it.

A spiral cutter will progress accross a face to be cut - so it is a gradual and relatively easy shearing action.

To get a better appreciation of the value of shear and how it eases or facilitates the cutting action - try it on a bit of wood in your vise. Get a very sharp knife-edge (a pocket knife of a wood-worker hand plane or chisel will do fine).

Now - cutting "with" (ie not "against") the "grain" of the wood place the cutting edge square to the wood in your vise. The cutting edge will "push" until it "lifts" a chip then it gets easier.

Now off-set cutting edge by say 5, 10, 15, 20 and 30 degrees and try the effort required to make and maintain the cut and quality of finish.

There will be an optimum angular off-set up to which the value will increase and after which the efficiency of the cut will decrease.

The same applies for most material-cutter relationships - milling and lathe TC and HSS tools included.

It a matter of knowing what they are and how they will apply in the machining environment in which the variables of cutting speed and feed are introduced on one hand and the rigidity of the machine and set-up are introduced on the other.

Using that - or any other - cutter of yours is no different.

Evan
12-29-2009, 07:51 PM
Ah see evan, I wasent going up and down, I was feeding sideways, like trying to square the ends of a part by side milling. Also I was not using square inserts but triangular so the entire side of the insert was trying to cut. (note how they are held in the picture posted previously)


OK, now I understand where the problem lies. You are trying to whack an entire piece the width of one edge of the insert off the work. No wonder it was hammering. You can use the inserts for side milling but they should be angled so you are cutting at a changing point of contact instead of an entire line of contact at once.