Face Cutter Woes

[kelvin2164]

I bought a cheap 2", carbide tipped face cutter on Ebay from China. Most of my tools are Chinese and are fine, but this thing just does not cut. A light cut just squeals across the top without cutting, leaving a heavily scratched surface and quickly making the work piece too hot to touch. It seems to have plenty of back rake. I tried working the inserts with a diamond file but same result. Pic of cutter attached. I have a 3" cutter with 5 triangular inserts and it works beautifully

 

[V22]

What type of machine are you running and at what rpm and feed? I have that cutter (APKT) in multiple sizes. It's a mongrel without horsepower. In fact most indexable milling cutters are. You will do better with name band inserts over the Chinese supplied ones that come with the cutter. The best indexable cutters to run in low hp machines are the SEHT type. High positive rake and great finishes. Just don't push your luck on the DOC.

 

[Niels Abildgaard]

Is it the rigth inserts?To me they look made to turn anticlockwise.

 

[bazmak]

I too bought the same cutter for my sx2 mill and it works OK
I have just machined a piece of 50mm sq Mild Steel bar down to 40mm sq
taking .5mm cuts.Finish is ok but not the best.I think any problems
are down to lack of power with the smaller benchmills they don't have the grunt
or rigidity for this type of cut.Also the tips are not the best only adequate
I made a lathe tool usind one of the tips and it works well.However I have
reasoned that this cutter will only be used for rough milling and hss or carbide
flycutters I have found are better for a good finish.I too have touched up
the tips with a diamond file which seems to improve things.I paid $60
for mine with R8 spindle and 10 tips ,a good buy at the price.I also took off
the cutter head and made a collar to fit involute cutters with 20mm bore
2 tools for the price of 1

 

[BaronJ]

I think Niels has got a point, those inserts don't look right to me either.

 

[django]

You would be better off with a cutter that used triangular inserts, look to me that the bottom has to little or no clearance angle at all and will be causing either chatter or rubbing resulting in poor finish.

 

[kelvin2164]

Thanks for the replies. The machine is a HM 48, 2HP, which I bought recently and am very dissapointed with. Not very rigid. But my other cutter works ok. I would like to get it working as it as many applications. I was thinking of replacing the Chinese inserts with name brand ones. Which would cost more than the original whole cutter and inserts.
I have noticed that the inserts are all marked. At one end as a single centre pop mark and at the other end is 2 centre pop marks. All inserts the same. Does this mean anything.

 

[bazmak]

When you started this thread I was in the process of making an ER16 collet block using the same cutter.I found the cutter a good buy but soon found
it was better for rough milling.At the price of $65 with an
R8 holder and 10 tips + I made collars to fit the 20mm dia spigot and use it to hold my involute gear cutters.TO MY MIND A BARGAIN.Here is how I used in on my ER16 collet block

 

[BaronJ]

I have noticed that the inserts are all marked. At one end as a single centre pop mark and at the other end is 2 centre pop marks. All inserts the same. Does this mean anything.

The pop marks are so that you can identify which end of the insert is in use. ie all inserts with a single pop are fitted the same way round.

Can you post a good picture of an insert, side and face please.

If you compare the inserts in the picture that Baz posted, they don't appear to be the same.

 

[petertha]

I've got a 2" dia 4 insert face mill (Taiwan made I believe) that uses what I think are same inserts as yours - APKT I believe? I don't agree the inserts are backwards for typical milling direction (clockwise when looking down at work). Is that what you guys are talking about or do you mean how the inserts are positioned? Pics show 2 versions, long axis up-down vs long axis laterally across? Are you sure its fitting the arbor properly? Can you measure runout?

Anyways mine cuts like a dream. I take 0.050" passes off steel & looks as good or better than any flycutter I've owned. Aluminum comes out like a mirror. One slight nod to flycutter is it can look more uniform if cut swing diameter spans entire surface vs. multiple passes of smaller face mill. But that's minor, not enough for me to warrant chucking up a separate tool & re-dimennsioning. I have not touched the flycutters since.

FYI I also tried some knock-off Chinese/AliExpress inserts & they perform the same from what I can tell. The finish does vary by nose radius. Can you get a feeler gauges under the inserts or touch off to see if they are not contacting properly? Maybe you have a Monday morning defect. (How does that happen on CNC's?) Still - I've heard people remove an insert or 2 & run them that way in certain operations.

What is the significance of the pop marks now? I assumed it was ID to switch them for wear but are you saying they are dimensionally different relative to screw hole or something?

 

[kelvin2164]

Attached are closups of the inserts. I dont mind buying name brand inserts, but not if I'm only wasting my money. The inserts are APMT1694. The problem seems to my uneducated opinion to be a back rack problem, as it just scrapes across the surface without cutting.

 

[petertha]

I Googled a bunch of APMT face mills & they all seem generically like yours. At least from this distance. Mine happen to be APKT 16xx. You might have to get your full number out & correlate to insert geometry, but I think for starters:
A=parallelogram 85-deg
P = 11 deg relief
K & M are tolerance values in 3 different insert dimensions. I believe M has slightly wider tolerance than K (does it really matter I wonder?)
T = chip breaker & hole config
... the rest you will need to cross reference, they can be a bit weird by brand.
I can check mine in more detail but I'm thinking the tools should almost be documented since they cant stray very far from the formula in order to use a particular insert. I don't see anything obviously wrong. Unless they packaged a different insert in a mislabelled box? Not to be insulting but you didn't switch the red & black wire & rotating mill in opposite direction? (should be clockwise viewed from overhead).

 

[petertha]

Highly likely (and fingers crossed) this is a camera angle distortion effect. But if I squint, it almost looks like flat along the bottom. I'm just guessing here but I think the pocket long axis must be parallel to shank/spindle axis & the 85-deg parallelogram shape takes care of the rest with resultant slight (5-deg) relief so only the nose is touching work. So probably an optical illusion. Set it on something flat & see what contacts where. Does it wobble resting on inserts alone? Is the shank perpendicular?

 

[petertha]

Found a pic of my face mill.

 

[kelvin2164]

Hi Petertha
Thanks for your input and you may be onto something here. See attached pic. The sides of the insert are parallel with the spindle, but bottom looks funny. Looks like 85 deg angle, but due to the funny shape, the outside corner isn't the first point to touch.

 

[kelvin2164]

Here's a better shot, sitting on a mirror

 

[BaronJ]

It does look a little strange. Almost as if the corner of the insert has been rubbed off. That could explain the scraping rater than cutting, though you can push these inserts quite hard if the mill has enough power. 0.5 mm DOC at 1000 RPM, 6 inches a minute should be easy.

 

[petertha]

Hmm.. I'm learning things myself here I hadn't realized before. Ive attached some links explaining what the designations mean.

What I'm not clear on is dimension BS. Is that a flat section or does it just pertain to the chip breaker bump width or...? See how it varies by model number of same insert. On another insert type they refer to it as length of wiper section but slightly different code. We need someone qualified here!

https://www.mitsubishicarbide.com/mmus/catalog/pdf/catalog_en/c007a_j.pdf
http://www.sandvik.coromant.com/en-gb/products/Pages/productdetails.aspx?c=apmt+16+04+08-m+4240
http://www.carbidedepot.com/formulas-insert-d.htm

 

[petertha]

Meant to include the corresponding column header. Note BS is not same thing as nose radius

 

[ninefinger]

Peter,
The "BS" is the width of the wiper edge (look at page J003 of the mistsubishi carbide link you attached), probably not the concern here.
This does appear to be a case of the shape, maybe impacted by the chip breaker, or its dimension "RE" which I take to be the "Radius Edge" - looks like some inserts have quite the large radius (0.125")
Kelvin,
Its probably a roughing insert, would do well for material removal but not for taking a light cut / finishing. Have you tried a deeper cut?
By the way - are you sure they are 1694 and not 1604?
For not too much money (but a lot of time waiting ) you can try some different inserts that might be better:
http://www.banggood.com/10pcs-25R0_8-Carbide-Inserts-for-Mill-Cutter-CNC-Tool-p-1023234.html
That one has a corner radius of 0.8mm or 0.031" - looks ok in the pictures...no guarantees...
Mike