Why does steel split like this? Very small parts.
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    Default Why does steel split like this? Very small parts.

    I am making some knobs and the steel keeps splitting...... I don't think I have ever had this problem before. I have been using stock from the same source for years. (bought a bunch)... I think it is 12L14 or some other leaded screw machine stock... all I know is it turns as easy as brass. The stock (you all would call it wire) is 3/32".... I am turning it down to .025", file a chamfer on the edge and run a 0.075 MM die down it...... and sometimes it just splits!!!! I have bent these a little so you see the separation. It seems maybe to split less if I take it from .093" to .025 in one pass than it does if I take lighter cuts.... could that have something to do with it? Or bad steel? There was a hole in the end from a earlier job but I faced it off well past that, but could that have something to do with it? I just want to know why.... gotta keep learning.

    Thanks




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    As I was taught;-

    Cold shut from rolling at too lower a temperature.

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    I have seen seamy steel like that before.. My old Pre WWII Prentiss vise screw had a visable seam its entire length.. Broke along it too...

    I know it happens pretty often. Sako stainless rifle barrels, were splitting lengthwise due to a bad lot of SS...

    As for exact cause, I bet a steel foundry worker will chime in...

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    who makes 25 thou" die?

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    Bill, it is .175 MM...... here is a chart but it leaves out the "half" sizes...

    miniature microminiature taps

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    Quote Originally Posted by rivett608 View Post
    Bill, it is .175 MM...... here is a chart but it leaves out the "half" sizes...

    miniature microminiature taps
    Well that's a whole new world to me

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    I can't help with your question, Rivett, but might I just say that I always love reading about your projects (and looking at the pics!), and you must be the most patient man on the planet to do this miniature stuff you're always at. Incredible work!

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    Bad steel is the short answer. Try another piece. But the flaw might have been very long, so it could affect many pieces that were cut from the same length of steel.

    I once found a big cap screw in our new fastener stock with a visible crack running the entire length, extending from the center of the bar out to the side. The head showed the crack, but the outside of the head had opened out a bit along the flaw when the hex was formed. Our metallurgist put it in his collection of classic failure modes and flawed material. Such cracks are known to happen during the rolling and drawing process.

    Larry

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    My bread and butter is parts in that size range, and I've never ever seen that. Sami's reason sounds as good as any, essentially it's a bad batch. Throw it out. Would suck to get a ways into a complex part and have that happen.

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    Quote Originally Posted by Limy Sami View Post
    As I was taught;-

    Cold shut from rolling at too lower a temperature.
    I have seen this a lot, most often with the lower priced (Lesser Quality) steel.

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    Save it for Cotter pins :>)

    Larry S
    Fort Wayne, IN

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    Rivett, it's due to the micro machining that you do, your starting to split atoms..................

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    Quote Originally Posted by Mr Bridgeport View Post
    Rivett, it's due to the micro machining that you do, your starting to split atoms..................
    Yeah...after seeing him with a .001 slitting saw, I would say its possible

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    Quote Originally Posted by jkruger View Post
    I have seen this a lot, most often with the lower priced (Lesser Quality) steel.
    I haven't seen it. But that is because we routinely made punch-press die pins for holes to pass wire down to #60 and brass rivets of 20 thou or less (hearing aids) ... but ALWAYS from ground tool steel (Timken, and 'Graph-Mo' stick in my mind - but it was 1963 and prior), ELSE 'drill blank' steel.

    Not as easy to turn, but it is unlikely to have such seams...

    And of course there is less NEED to turn it, as you can also buy it right on-size as drill blanks or even the lesser-grade and relatively dirt-cheap plain carbon 'clock steel'. Waste of time re-inventing THAT wheel...

    Bill

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    My experience in the area of smaller parts is somewhat limited. But it had been suggested to me not to make some critical small parts from leaded steel as there were occasional problems with the segregation of the lead. I didn't know any better, but I followed the advise.

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    rivett608 --

    Twenty-some years ago I read a piece in a magazine talking about a US-based hydraulic fitting-and-equipment maker being unable to win a contract to supply the US plant of a Japanese automaker. The reported reason for the two companies' inability to see eye-to-eye was, to me, fascinating: The fitting maker wanted to minimize cost by machining parts from leaded stock, while the automaker wanted (and was willing to pay a higher price for) parts machined from unleaded stock.

    The carmaker maintained that parts made from leaded stock were more likely to fail than those made from unleaded stock, because unevenly distributed lead in the ingot created lead seams in the rolled bar, and the lead seams promoted splitting of the fittings after after they had been in use for several years.

    The fitting maker's rebuttal was that the higher incidence of leaded-stock split hydraulic fittings did increase the carmaker's warranty costs, but that increase was substantially less than the price difference between the leaded-stock and unleaded-stock fittings.

    And that makes me wonder if your stock might have a seam of poorly-mixed lead that caused the splitting you've observed.

    John

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    Saw that crap off and keep a sample, take pictures and video.

    from there have it sent back to your steel truck man and they will go after it, they dont want to sell crap no more then you do its about reputation.

    If you let them know they will kick the steel mill in the butt, you might help them from hauling crap everywhere.

    I dont mind a shaft.0005"-.0015" undersize but .0015" oversize is not fun. cracked up stuff will send out a red flag.

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    Thank you..... so it is bad steel not something I did, Good, sort of. Now are we talking a few inches bad or a whole piece? or the whole batch? I bought these years ago so there is no going back to the supplier, they were 12 foot lengths, maybe a dozen, it was all they had.... I cut them up into 3 foot and mixed them up. Now nothing I do is critical but I don't want stuff to crack either...... is the finished part likely to crack even without any stress on it?

    I think this die was made by Favorite, others I have are Bergeon, both are Swiss companies. Nice stuff.... very expensive.

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    Quote Originally Posted by rivett608 View Post
    Thank you..... so it is bad steel not something I did, Good, sort of. Now are we talking a few inches bad or a whole piece? or the whole batch? I bought these years ago so there is no going back to the supplier, they were 12 foot lengths, maybe a dozen, it was all they had.... I cut them up into 3 foot and mixed them up. Now nothing I do is critical but I don't want stuff to crack either...... is the finished part likely to crack even without any stress on it?

    I think this die was made by Favorite, others I have are Bergeon, both are Swiss companies. Nice stuff.... very expensive.
    Just me - but leaded steel in general? Spacers. Bushings. Walk-behind lawn-mower axles maybe. 'Filler' IOW, where the dimensions HAVE to be way over the applied load just to get something large enough to fit common needs. Mate to nylon bearings and such, for example.

    But not something I've ever used for ANY 'critical' part. Nor plan to do.

    Better steels just aren't that hard to cut 'manually'. Leaded only makes sense for uber-high volume, low-production/tool cost where the applied loads are low and the machining and finishing time saved is actually significant. As it CAN be. But not for the sort of labour-intensive app you have in front of you.

    JM2CW

    Bill

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    I wonder if there's any kind of test you could do- dye penetrant, magnaflux, ringing it, crushing a short length in a vise, to determine if a given rod was going to have a problem?


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