Thread: Chatter when using 50mm face cutter

Quote

Would I have been pushing the limits for a face cutter like this trying to take off 2mm? I am trying to work out if operator error was the cause for the racket or if the machine is in need of attention.[/QUOTE]


Brendan
Some good information on this page as to the application of milling cutters

http://www2.coromant.sandvik.com/cor...1/tech_d_1.pdf

Good info there, just in case people want to see or download the rest of these guides, here is the link where they can be found

The Metalcutting technical guide contains quick and adequate information for trouble-free and productive machining using Sandvik Coromant products.

Thanks for the tips fellas. Will read up on those links before I use the machine again.

Brendan

Originally Posted by Col2310

Quote

Would I have been pushing the limits for a face cutter like this trying to take off 2mm? I am trying to work out if operator error was the cause for the racket or if the machine is in need of attention.

2 mm is too much cut for a HM 40 . It lacks rigidity and HP . Also the spindle speeds being touted in this thread are too high for steel .
For soft steel at 100 SFPM a 50mm x 6 tooth face mill should only be spinning at 200 rpm . My machine is way more rigid than a HM40 and I only run mine at 240 RPM and I get grumbling at a 2mm cut . It will do it but it don't like it , Chinese machines are not very rigid.
You have to find the right Surface Feet per Minute of the metal you are cutting first then work out the correct spindle speed for the cutter .
Here is some common SFPM speeds .
300-800 for aluminium
200-400 for brass
100 mild steels
40-70 for high carbon steel
30-80 for stainless steel

I work out the spindle speed by SFPM x 4 -;- diameter of the cutter in inch.
Mild steel = 100 x 4 = 400 -;- 2 inch cutter = 200 Rpm.
There is more complicated ways but that is simple and works for me.
Adjust the depth of cut according to feed , rigidity and the HP you have available and the needs of the work being done .

Hi Retro,
I think you'll find that table is for HSS.

Stuart

Originally Posted by Stustoys

Hi Retro,
I think you'll find that table is for HSS.

Stuart

It does not matter it still works for indexable inserts even though you can speed it up in some cases . However for general hobby workwithout flood coolant it works ok for me and 200 to 250 RPM on a 2 inch face mill is about right for 100 SFPM .
The trouble is if you run the face mill too fast , it will cut but gets very hot and you burn your inserts early without flood coolant .
Run slower and you can do a lot of milling without coolant .

The iscar tips i buy have the recommended speeds on the box, MS is 80-150 Meters P/M, so i use my 50mm cuter at 760rpm, the next speed up on the HM50's is 1300 and it is too fast at 200 MPM 760 equates to 119 MPM, i find i get blue shavings, and when i have a full or close to full cut it feels almost buttery....
Brendan, if you want i can give you a demo of what it is like on my mill just so you know if the tafe's is in the ball park.
Retro, i was told not to use coolant with my tipped cutters, i have never had lifespan problems and i cut a lot of 5160 in less than 100% rigid situations.

Originally Posted by Ueee

The iscar tips i buy have the recommended speeds on the box, MS is 80-150 Meters P/M, so i use my 50mm cuter at 760rpm, the next speed up on the HM50's is 1300 and it is too fast at 200 MPM 760 equates to 119 MPM, i find i get blue shavings, and when i have a full or close to full cut it feels almost buttery....
Brendan, if you want i can give you a demo of what it is like on my mill just so you know if the tafe's is in the ball park.
Retro, i was told not to use coolant with my tipped cutters, i have never had lifespan problems and i cut a lot of 5160 in less than 100% rigid situations.

I agree 1300 is too fast for most hobby situations . I have run mine upto 700 rpm on K245 steel but it gets too hot without coolant . Now I just use 250 to 400 depending on the steel . If I use flood coolant the SFPM can increase quite a bit .
I don't know what kind of cutters you have but most coated carbide inserts are designed to run with flood coolant that is how the professional machine shops work .
Keep the heat down and they can run at much higher speeds and will last longer . Heat is the killer of coated inserts quicker than abrasion .
Some professionals forget that the average hobbiest will not be using flood coolant or a $50 000 machine or the top grade cutters . So they can't run at the max cutting speeds and feeds that the pros use .

I just put up some shields to stop getting burnt, and then let the chips fly.
Carbide likes speed and feed and up around that range I quoted (1300 rpm) for my mill (HM52) is just about right. I have tried lower speeds and found it just takes a lot longer and get no better results (actually worse at a lot lower speeds).
For a smaller mill I would just recommend a bit less depth of cut, Pipe Clay could tell you what a bench top mill is capable of, as he has one and has used it extensively.

These are the colour I get off the face mill.



PS
I chased up this thread on the same subject
Carbide question

Dave

I produce blue chips also but not as much as that. I feel you are just hardening up the steel as you cut . Carbide inserts will do it but the extra heat will reduce their life .
For the hobbiest time is not the big factor but expense is .
If you are getting paid for a job it's different as the tooling is factored in.
I have slowed down a bit and find my latest set of carbide inserts are lasting way longer than before . That makes it worthwhile for me . If I run coolant it's different .

I don't run coolant on carbide as the speed they run at just spray it around to much. Those chips where ones I took making the 40 odd tool post holders recently, and the feeds and speeds helped get through them a lot quicker. It would have taken an awful lot longer if the speed and feed where reduced.

With the heat in the steel, the chip carries the heat away from the job and I have not noticed any reduced life out of the inserts.

Have you done the top taper bearing mod to your machine. I not I would recommend it as it does seem to make a difference to the surface finish.

Dave

Originally Posted by Dave J

I don't run coolant on carbide as the speed they run at just spray it around to much. Those chips where ones I took making the 40 odd tool post holders recently, and the feeds and speeds helped get through them a lot quicker. It would have taken an awful lot longer if the speed and feed where reduced.

With the heat in the steel, the chip carries the heat away from the job and I have not noticed any reduced life out of the inserts.

Have you done the top taper bearing mod to your machine. I not I would recommend it as it does seem to make a difference to the surface finish.

Dave

No Dave I would not know how to do that mod . I am sure better bearings would help heaps . That is one of the reasons I run a bit slower to help control the coolant but if I put up coolant barriers then I can run much faster but most of the time I don't bother . Time is not a big issue .
I don't want to spend too much money on this mill as I want to sell it one day and buy a better quality one. If the bearings fag out then I might think about it.
I don't have big issues with surface finnish , infact I get good surface finish even when not using coolant . I make the last cuts to size very light . Your machine may be more cappable of taking a heavier cut than mine after all the mods you have done.
However the HM40 in question is a very light machine .

so its not just the HM52's and clones

Coolant can actually shorten carbide life by causing edge fracturing due to heat and quenching of the cutting edge.
I would try about 1000 rpm and reduce the depth of cut to about 1mm.
Seems your problem is mainly machine rigidity though.