What do I do about this?

jeffk · Mar 24, 2016

I'm not sure where to post this (first time posting)

I have been noticing today on this batch of parts that there are these hard black spots in the castings. Also have been noticing I have the corners chipped on 2 end mills now.

This is what I keep finding.

And this is what happens

Is there anything I can do to stop this?

charlie gary · Mar 24, 2016

Your castings have inclusions. If the castings get big enough, the inclusions can be things like lathe tool bits.

hobbyman · Mar 24, 2016

When I was much younger and toured an ironworks the owner mentioned that when the machinists ran into a bad casting they would carry it back to the foundry and throw it at the nearest foundryman. I don't know what the number is but in the olden days having under 2% bad castings was acceptable. I would expect with automated sand packing and pattern removal it should be much less.

SIM · Mar 24, 2016

Your castings or supplied by customer?

If yours, I'd be bringing back to foundry unless you agreed to such a deal.

If customers I hope you entered a clause about bad castings effecting cost of machining.

In either case, before you machine I'd be certain the customer can still use the casting...inclusions, porosity can be a reason for rejection...you don't want to have a fight over whether they are willing to pay for your machining if you saw an issue with casting....who's right doesn't matter as the product is dead, someones out money and now you have a Rush to push out new parts.

Want to make tooling last longer...find a better grade tooling for hard interrupted cuts. A little land on cutting edge. I have had good luck with cermets...greenleaf had some good stuff.

jeffk · Mar 24, 2016

The casting are a customers part supplied. They don't care about the inclusions only want there bearings to fit in the bore loosely.

So there is a cutter that would hold up better to this?

MJR7 · Mar 24, 2016

looks like casting sand is in the casting itself.

Georgineer · Mar 24, 2016

You could always start by reading the guidance on meaningful thread titles. That way you are less likely to get your thread locked.

George

Heinz R. Putz · Mar 24, 2016

You obviously have bunch of bad castings, whoever supplied them is responsible.
It happen before and it will happen again.
Anchor Hocking in Lancaster, OH, sent castings to us in Chicago when I worked for Swedish machine Tool, to make samples before they committed to buying our Lathe.
I broke every tool I tried and I was very, very discouraged since this was the first job I ever tried to set up and run on this machine.
Then we tested hardness and it turned out that every casting was chilled and very, very hard.
They sent new castings, every thing went great and they bought the machine.
Good luck: Heinz, doccnc.

Perry Harrington · Mar 24, 2016

a) The finish on those parts indicates really cruddy metallurgy in the castings
b) Inclusions and cruddy metallurgy go hand in hand (lack of care)
c) "loose fit" on a bearing?

Sounds like customer does not have head screwed on straight.

Jashley73 · Mar 24, 2016

jeffk - Welcome to the forum. In the future, be sure to post a more descriptive title to your thread - vauge and non-descriptive titles will usually get locked, as that's kind of shunned around here...

Now, to your issue. I'm assuming that you're using a that particular endmill to machine the face that's shown, where the inclusion was pictured. (And a big "thank you" for posting pictures. It sure beats taking 3-pages to describe the issue... I'll take a vague thread title and pictures any day over the opposite...)

I can't offer any help on the casting side, but I'll say this about your tool - Unless you absolutely need a sharp, 90* corner in the part, I would strongly recommend using an endmill with a chamfer or radius on the corner. This is the weakest part of the tool, and it's the part that damages first. Getting a chamfered or corner-radius tool does wonders for protecting the corner of the tool. Even a .01" radius goes a long way. It's not a guarantee that a sand-inclusion won't cause a lost edge/corner, but it may prevent from all of the corners from chipping off...

Mr.Bronze · Mar 24, 2016

step 1 - don't machine other peoples castings.
step 2 - don't let other people machine your castings
step 3 - problem solved!

This is exactly why I try very hard to only sell finished parts, rather than castings. Nothing causes more headaches than buying/selling castings and shipping them back and forth.
Often I will quote a finished part at the same price as the rough casting.

That's a pretty bad inclusion, but switching to inserted carbide tooling will help lessen the pain. It stands up better to the abrasive and hard bits that you find in castings all the time, and you get more cutting edges per $. You won't really ever get away from inclusions in sand castings, especially in lower grade cast iron stuff.

Admin5 · Mar 24, 2016

Closed due to meaningless topic title

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What do I do about this?

jeffk

Plastic

charlie gary

Stainless

hobbyman

Hot Rolled

SIM

Titanium

jeffk

Plastic

MJR7

Plastic

Georgineer

Stainless

Heinz R. Putz

Stainless

Perry Harrington

Titanium

Jashley73

Titanium

Mr.Bronze

Cast Iron

Admin5

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