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Old 05-05-2009, 08:37 AM   #1
Old Nubbins OP
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Valve shim OEM specs

Anyone know where I might find the OEM material and heat treat specifications on valve shims such as material type (8620, 4340, etc.) and heat treat requirements (normalizing, case hardening, etc.)?
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Old 05-05-2009, 02:38 PM   #2
fritzcoinc
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Valve shims are not heat treated. If they were they would look like potato chips as something that thin would warp all over the place when it is heat treated. Shim stock is hardened by cold working. The material itself is melted with high levels of chrome or nickel or manganese depending upon its finial application. All of these work harden. The process of manufacture that rolls the material to the desired thickness is the cold working I am describing. Razor blabes are made the same way ( sure some have lazer hardened cutting edges but most are just cold worked material). The shims are then cut out with dies, called blanking, in something like the way an electricians knock out cutter works. Except of course many shapes of shims ( rounds, washers, feelers, ect. ) per second are cut from a big sheet as it rolls out.

To get an idea of how cold work hardening happens, take a paper clip and straighten it out. Now bend it. You will notice that it bends in what was a straight area adjacent to the factory and your straightening cold bends. Or keep bending back and forth without forcing the bend in a certian area. The new bend will occur in the least bent area.

Bottom line is, just go buy shims or make a cutter and blank out your own from good quality purchased shim stock.
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fritzcoinc screwed with this post 05-05-2009 at 02:47 PM
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Old 05-05-2009, 03:10 PM   #3
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I have never made valve shims, but I have done lots of toolmaking, 95% of which is heat treated, none of this sounds right to me, it they are as hard as I think they are, they wouldn't be able to be stamped out of stock, hard equals brittle, the act of stamping would shatter the stock.
Another problem with this is the stock would do only one shim size, different stock for every shim size required, like I have said, doesn't sound right to me.

You are correct is saying that they would warp somewhat when heat treated, but only if heat treated roughly after final size is fixed.

Edge on quenching rather than flat on quenching would minimize warping.
Heat treatment after stamping but before final sizing sounds more like the logical order of process to me.
But a more likely process would be machining the shim blanks from bar stock, heat treatment, then final sizing.

I made a whole swag of BMW Boxer wheel bearing shims for my own consumption years ago, and the manufacturing process was this.
Machine silver steel (hardenable, what scribes are made of) to size, a shallow cylindrical ring, harden, then surface grind one side to cleanup on a magnetic chuck.
Turn over, and clean up other side, remove one shim, grind down another shim interval, 0.025mm in this case, remove another shim, repeat until all consumed.

Quote:
Originally Posted by fritzcoinc
Valve shims are not heat treated. If they were they would look like potato chips as something that thin would warp all over the place when it is heat treated. Shim stock is hardened by cold working. The material itself is melted with high levels of chrome or nickel or manganese depending upon its finial application. All of these work harden. The process of manufacture that rolls the material to the desired thickness is the cold working I am describing. Razor blabes are made the same way ( sure some have lazer hardened cutting edges but most are just cold worked material). The shims are then cut out with dies, called blanking, in something like the way an electricians knock out cutter works. Except of course many shapes of shims ( rounds, washers, feelers, ect. ) per second are cut from a big sheet as it rolls out.

To get an idea of how cold work hardening happens, take a paper clip and straighten it out. Now bend it. You will notice that it bends in what was a straight area adjacent to the factory and your straightening cold bends. Or keep bending back and forth without forcing the bend in a certian area. The new bend will occur in the least bent area.

Bottom line is, just go buy shims or make a cutter and blank out your own from good quality purchased shim stock.
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Old 05-06-2009, 06:12 AM   #4
fritzcoinc
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Quote:
Originally Posted by Old Nubbins
Anyone know where I might find the OEM material and heat treat specifications on valve shims such as material type (8620, 4340, etc.) and heat treat requirements (normalizing, case hardening, etc.)?
Here's some bedtime reading on work hardening.
http://en.wikipedia.org/wiki/Work_hardening
Some additional research finds valve shim material varies by manufacturer and probably engine type. The Japanese use a powder metal process or sintering to make some of thiers from an aluminum alloy. Super high performance engines use titanium. Obviously you want this component to be the lightest weight to minimize reciprocating weight of the engine. Since the shim is under the bucket it is not worn by the cam and since the valve spring weights in multi valve engines are pretty low the shim does not need super high strength (I.E. high hardness).
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Old 05-06-2009, 07:28 AM   #5
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Thanks for the information.

Mostly for the 'fun' factor of making my own, but now it seems it could be more trouble than its worth if they're not made right.
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