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grinding powdered metal

spock

Stainless
Joined
Dec 29, 2006
Location
Central Ky
machine: 12x24 okamoto wet grinder

Looking to grind parts about 6" square, about .01 per side. Need to hold .0003". I have heard it grinds "gummy" but no experience here. My grinder is in excellent shape and tolerance does not scare me. I have enough parts to make it worth a wheel purchase if needed. Question is, any of you guys ever grind this stuff? What works well/what to look out for? I can call Norton, but it is already after 6pm today....

Thanks in advance.
 
What metal powder? Iron? Bronze? Titanium? Magnesium? Dense or porous? Dry, graphite-filled or oil-filled?
 
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Just flat sides? Forms? Surface finish? Which PM in particular? How many pieces? Got a VFD on the grinder? You can probably use what you got for just one piece but if there's a couple I'd fold the cost into something other than AO.
 
Powdered metal parts are usually less than 100% dense. That means it is porus-- like a sponge. Gridning with coolant may allow your parts to soak up coolant.

One way to test is to put a drop of water or WD-40 on the part and see if it disappears, not evaporate.

One way around porosity issues is to have the part infiltrated by either something like an epoxie or infiltrated with a metal. Both processes can be done by who made the part.

Same thing with heat treating a steel PM part. If it is not 100% dense it will suck up the quenching oil.

Lost
 
I was told the material was very soft steel, told to compare to 1018. Just flat sides, some interruption. I was wondering about coolant soak: can this affect size? I know these parts were wet ground before by another shop and this issue did not come up. Surface finish called out: "1.6" No VFD. Hundreds of pieces. They are not heat treated, and will not be.
 
I wet grind cpm-10v and 9v on a daily basis. I would not worry about that.

either a good CBN wheel or say a 60 grit G, or H wheel to start and you should be good.

Norton has a couple stock wheel that will fit your machine.

Do you have a VFD? This helps out a ton.
 
Curious as to why someone would spend the money on a PM and NOT want it heat treated. Can you divulge the intended purpose of the component?
 
Curious as to why someone would spend the money on a PM and NOT want it heat treated. Can you divulge the intended purpose of the component?

I would "assume" they would be heat treating after grinding??

But this comment is crazy. I have questioned our tool steel supplier on the same topic. Sometimes when we do contract grinding for them we will have a spec to grind to say 1.000" x 2.000" x 10.000" long. I question does their customer not want some stock for grinding after heat treat?? They tell me not everybody realizes you have to heat treat this stuff. They try to explain but it falls on deaf ears.

Kind of like the old saying you can take a horse to water but you can't make them drink.........
 
Yeah, im doubting youd be work on a "green" PM part doing grinding. It would just crumble. It has to be sintered to have any mechanical properties. Heat treating is a different ball of wax.
If its normalized, it should be just fine.
Go to town.
But you still need to know what the material is that youre grinding.
I'm assuming that these are near net shape sintered PM parts, and youre just finishing them to thickness.
 
Good with .010 per side you have plenty of stock to play with.

My experience with cpm was almost as hard as carbide so don't know anything abut soft stuff..

still .0003 all around is close work.... good luck
 








 
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