Hard Metal

[Burgs]

Hi
Looking for help in turning 550 to 600 Brinell cast iron (27% chrome and nickle). The item is 580mm outter diameter, inner diameter of 476mm. It has to be faced off both sides. Just to keep us on our toes it has 12 mild steel inserts that have to be drilled and tapped after facing both sides, which give a very nice intermittant cut. We have tried all sorts of inserts except button at this stage, their next. Ceramics bust, CBN disappear at first intermittant cut, and hard inserts will do one pass at 0.4mm depth of cut, speed 45m/min and feed of .08mm/rev with lots of coolant. We do 2 cuts at .4mm and 1 at .1mm to take out the taper, turning the insert each pass. We are machining on a Mazac Slant Turn 30. At the moment it takes around 10 hours each item .
Best Regards
Burgs

[ImanCarrot]

Have you thought of lapping the flat faces? I've had a really good finish on all types of ferous metals using diamond lapping compond. Hyprez and Engis supply it in water or oil soluable form. Actualy I think on of those companies have gone bust, but cant remember which. Lapping also gives a really flat surface. I beleive they'll lap samples free of charge, but doubt they'd do both faces f a "sample"

[DareBee]

The mental image I have of the part would lend it to being blanshard ground quite quickly.
You didn't mention about turning ID and OD.
I realize you are looking to turn this but other options may be the way to go. Setup and grind on a blanshard should be under 2 hours.

[Burgs]

DareBee
We haven't looked at grinding yet, thought we would try turning first as we don't have a grinder. We have to remove 5mm one side and 2 mm the other no bore or od to be done. Blanish grinding I not sure I have come a cross this method, is it similar to a segmented grinder? If the blanish grinder could remove that much material in the time I certainly would have to look at one so long as cost is ok, or maybe farm out the job.
ImanCarrot
Not sure about the lapping as for time I have only seen lapping machines working in the hydraulic industry and they do a great job but seem slow.
Best Regards
Burgs

[One of Many]

Darebee meant to say Blanchard grinding. It is what you see on large plate and flywheel resurfacing. Not sure if the different hardness of materials would work in that regard. It would be reasonable to farm it out. Rough at least one side to give the grinder a good flat surface to reference on for grinding the opposite side. Then they can flip it over to finish the other side.

I have had a plate 2.25"x32"x40" ground .25 total to get it flat and parallel for $245USD. That was cheap. Your ring should not pose that much of a problem in terms of material removal.

DC

[HuFlungDung]

I would try Greenleaf WG300 whisker reinforced ceramic 1/2" round inserts.

Coolant is a no-no with ceramics. Theoretically, you want enough SFM to get the chip coming off hot, and for the metal to be hot enough when it comes around again that it will be slightly softer on the next rotation past the insert. I think the speed you mentioned is too slow to accomplish this. I would try 150 to 250meters/min. Maybe a tool rep would recommend even higher speeds.

The depth of cut per pass would be about what you said, but the feedrate with the round insert could be fairly aggressive, maybe .5mm/rev. Granted that it is not going to last a long time no matter what, but the WG300 is a great insert, and since you are only using a wee bit of the edge at a time, you can index it maybe 1/8 of a turn, and then flip it over and get 8 more cuts out of it. If the edge flake fractures while cutting, let it, this will typically expose a very sharp edge which will cut for a little ways further.

You did not mention the thickness, but the part should be well supported by the chuck so that it is rigid for the cutting.

[DareBee]

Here is some pictures if this helps any.
http://www.machinetools.com/MT/Machi...65882814301479
http://www.fpmiller.com/WebsitePhotos/15813aw.jpg

[Burgs]

Cannot find Greenleaf here in Australia. But have tried several different Ceramics including wisker, The trouble with ceramics is at the start of the cut, the rough casting and the finish of the cut again the rough casting, they usually bust.
To try and over come this we hand grind a bevel with an angle grinder to relieve the rough edges. If we get past the start then the next problem is the mild steel inserts. I have tried all sorts of speeds, feeds and depth of cuts. We have found the best results using ceramics is to take light cuts around 0.1mm and around 120m/min, after cutting the face flat using up old carbide inserts. When there is a constant cut the ceramics are ok but when trying high speeds they loose their edge quickly but as you say when they break a new sharp edge is present and nice red hot shavings come off. I have an idea thaat the material is actually work hardening.
Checked out the Grinders and now know which ones they are, Blanchard actually being a brand name. Liked the 1926 model I wish it was in Australia it might be in my price range. I am waiting on some information on performance of grinding from the abrasive suppliers. We have supplied 6 units so far and have another 14 to go, but have a little reprieve for the moment as the next 14 are for stores.
Best Regards
Burgs

[Equinox]

Hi

IMHO, busting out the interrupted cut with buttons is one way. Only cut where the interrupted cut is with the button with fast feeds and light DOC. Get it close to finish dimension with the largest button in the shop. this gives your insert a gradual relief for your inserts to enter and exit the cut.

Eq

^-----First time I noticed what novice to the forums is called here "chip sweeper" LMFAO------^

[Burgs]

Equinox
will try your method when new castings come in. May save grinding.
Best Regards
Burgs

[little bubba]

Burgs, I'm sticking with HuFlung on this one, ceramics. If you are busting them, your not going fast enough, if your running an interupted cut, you need to go even faster, need to keep the heat up during the interuption. A constant depth of cut with a ceramic is also a big NoNo. I would ramp into the face with as small of an initial contact as possible, and then ramp in and out. You want to keep your cut depth varying since the insert will crater at the top of the cut where it is cooler. Also you want to stay in the cut, wear on a ceramic insert doesn't seem to be determined by time, but by how many times you start a new cut.

As a possibility, maybe run this job on a mill with an iserted cutter where you can keep the surface speed up and program a toolpath that will ramp and vary your depths of cut.

Here is a really good article that helped me out a lot, its a good read if your interested in this sort of thing.

http://www.mmsonline.com/articles/049903.html

[Burgs]

Little bubba
Checked out the link and found some good information as you mentioned. A couple of things stand out, looking at what we have done and experienced so far it would appear we are in the correct speed range except for the interupted cuts we usually slow down which is the wrong thing to do, and the other is the constant depth of cut we use, which naturally wears the insert in the same area each cut. We don't have a round ceramic tool holder but will order one ready for the next go.
Best Regards
Burgs