Shim for setting valve clearances (steel hardening question)

[masterx81]

Hi!
I've done some work on the seat of an engine head, and now i can't find any shim that can i use for setting the valve clearances.
The clearance is set by a 11.5mm in diameter diameter shim that is placed just under the bucket, between the bucket and the valve stem.
The minimum shim that i can find is 2.00mm. I'd suppose that it's difficult to find shim under this value because this shims seem case hardened, and under 2.00mm the core can be too brittle, and can split in two under the load of the valve stem (6mm stem loading something like 60/70kg at max rpm, spring load + inertia).
I need some 0.95 /1.00mm shims, so i must find a way to machine them by my own.
I know that the tip of the valve is hardened at least at 53 hrc.
I've think about grinding the shims and get them nitrided, so that the core will be untouched.
Someone have a suggestion for me?
Really thanks!!!

 

[masterx81]

I've tryied to buy a 4ch model helicopter, but it need much patience that what i have After it has crashed a couple of times on some walls, i've abandoned And that was after a lot of hour on the simulator! I'snt the right hobby for me, i'll prefer engine tuning I'm mading all by myself a 500bhp impreza, after years that i study on complicated car books, specialized forums, etc :|
In any case, for work i'm a computer programmer (.net laguages, mainly vb.net and asp.net, but also sql and js), but i know also a lot in networking (cisco ios programming, complicated server configurations, security, network configurations,etc) and computer in general (virus removal, assistance,etc). I work in a little office (as emplyee), and every day there is something new to do
I know also about electronics (it's what i've studied at school), and in the last years i've developed a passion for engines and mechanical stuff

I not know much in nuclear stations, but searching on wikipedia they say that the biggest steam generators made weighted about 800tons, might be are speaking about the one's that you have worked on
You work must be quite interesting, and higly specialized!

I go always late to bed, else i've not time for my passions. When i'm not at work, i'm in the garange, or on the pc searching something, or studying on books, or mading some small extra works for moneys, like repairing electronic stuff, pc assistance, mechanical works (mainly works for friends that made by a mechanic will costs too much, or that wasn't sloved by others).

But now it's time to go to bed, only 4 hour of sleep

 

[metman]

The following link is provided only to show that annealed S7 is apparently available:

http://southerntool.thomasnet.com/a...ys=1&type=order&prodids=3001038&oln=&PcValue=

If not available, you can buy it prehardened then anneal it or have it annealed.

Grinding the desired shape from prehardened S7 is not very practical although it can be done. Turn the desired shape on your friend's lathe using annealed S7 then quench and temper to HRC53 to match hardness of the valve stem. for the prototype, you can use S.S. foil to wrap the shim for protection against oxidation while you torch heat treat then temper in your kitchen oven. If this sounds like an approach you want to try, myself or another here will provide you with more detailed instrutions to accomplish the quench and temper.

If you intend to produce in quantity, you will want the shims heat treated in a vacuum furnace or protective atmosphere furnace for best results.

 

[masterx81]

Mmm, i have an infrared thermometer, and also a 1000°c type k temp reader, and i can buy a poldi hardness tester quite cheap...
I don't need to do a big quantity of shims, only a set (also for future regulations).
Surely isn't the best setup, but can be ok for made my own?
Until now i've excluded to do myself the heat treatment, for fear to made more damage than benefits...

 

[metman]

Another possible deterrent is that although the S.S. wrap is readily available at least here in the US from suppliers like McMaster-Carr or MSC it is not cheap. About $100 MSC order number 00049957 but this would probably be a lifetime supply for you.

I do not have heat treat info readily available as I thought for S7. Some of my info is at work and I am home for a week. If someone will provide the austenitizing temperature, quench medium, and approximate tempering temperature, we can walk him thru the process. If you obtain the hardness tester, you can measure the as-quenched hardness and then someone can give you an appropriate tempering temperature. Your oven might not be hot enough for the tempering operation but you can re-wrap the shims in the S.S. Foil and use the torch since you have the infrared thermometer.

You will want to make a few heat-treat test samples so as not to waste your precision made shims as you hone your heat treat skills. The test samples can be made by simply parting off the bar stock in the lathe to the approximate overall thickness of the shim say 1-1.5 mm to signify the mass in question. Practice the heat-treating process on the samples by wrap in foil, clamp a heavy piece of angle iron in a bench vice and lay the sample on the angle iron. Now heat the iron from underneath using your oxy-acetylene torch but of course measure the temperature of the foil. The mass is so little that I will guess 5 minutes at the austenitizing temperature will be adequate but let us see what some others might suggest or maybe agree.

 

[masterx81]

I've access to some wood/carbon stove, that must reach quite high temperatures... I can pack them in the steel foils with the type k sensor inside, and mading a sort of support for choosing the best height inside the stove for finding the right temperature, can this work?
So i need a bar of s7 annealed steel, the hardness tester and the ss foil?
I've done a fast search for the foils and i haven't found nothing... Maybe i need to do a more deeper search...

Quite interesting that this things can be used to harden any type of steel, in case i need this in the future...

 

[metman]

I will get you a link for the MSC company order number 00049957. This part number I found in my hard copy catalog.

Quote: ...can this work?

Yes if the k sensor is what I think. It's a thermocouple?

 

[metman]

Here is the link:

http://www1.mscdirect.com/CGI/GSDRVSM?PACACHE=000000121109343

Item #: 00049957 Mfr: Select
Non Catalog Item See Available Substitutes (I don’t know what is meant by this but you can call the number below or try to oder online)


24"X50'X.002" STAINLESS TOOL WRAP
Please call Customer Service 1-800-645-7270 for help

Price: $174.95 ea (My catalog is 12 yrs old so the price has jumped)

 

[masterx81]

Hmm... but it's in america, and i must add custom duties...
Else, this will be fine?

http://www.stephensgaskets.co.uk/StainlessSteelShim.html

they are in uk, so no custom...
0.002", 6" x 60"
304 steel would be good?
And is also quite cheap...

And, yes, they type k is a thermocouple Can handle up to 1000°c, but i'd suppose that i need to stay a little bit lower than this, something like 940/950, right?
Plus i need to buy the poldi hardness tester:

http://cgi.ebay.co.uk/poldi-hardnes...UK_Measuring_Tools_Levels?hash=item2eaa0bad59

Isn't that nice, but i hope to get at least a bit accurate reading...

Plus the bar itself (that with a bar i can made LOADS of shims)...

But... How i can get a 940°/950° temperature???
I't sufficient on a stove, might be loaded with bbq carbon? I've never tought how many °C can be inside on a stove!

 

[masterx81]

I've found this:

http://www.precisionshims.com.au

They have quoted me 6.00AU$ per shim (in any measure that i want)...
Plus 20$ of shipping!!
Seem quite cheap...
Are the only one that i've found that made shims on order...
For a set of 16 i spend 96+20+some custom duties (say 25%), and i pay near 150AU$, 93 euro. Near the price of the hardness tester. But if after 30'000 miles i need to redo the shims (for wear in the valvetrin components), i need to spend other 93 euros, and i'm quite in pair with the costs of the whole setup for mading my own shims...
What do you think about???
I'm quite excited to do this work (and learn how to do it) Might be my friend with lathes and mills isn't that enthusiast... lol

 

[metman]

Duuhh -- I did not think to look for "shim" stock and here we are talking about SHIMS of all things.

Probably the spendy stuff I linked for you is 304 S.S.

So yes the .002" SS shim should work fine for foil wrap.

I have never actually used this method but I suggest you will want to fold it over the part twice -- the second fold at 90 degrees from the first -- to result in only two edges for the foil to be sealed by then folding each one of those edges close to itself like about 5mm while pressing down on the package to remove as much air as possible. Then with a roller or hammer flatten the sealed edges firmly to make a tight seal.

Yes your type k will allow for proper temp range. Someone on this forum will answer the correct austenitizing temperature etc. Are you familiar with the Iron-Iron Carbide phase diagram? If not you will want to do so because it is a beautiful thing and you will see the Austenite phase range displayed and begin to understand what you are doing and why.

Quote: But... How i can get a 940°/950° temperature???
I't sufficient on a stove, might be loaded with bbq carbon? I've never tought how many °C can be inside on a stove!

How do you suppose a Blacksmith does it? You might NOT even need a little bellows but maybe yes or could be a hair dryer. The valve shim will be protected from the air atmosphere and will be isolated from the BBQ carbon because of the SS foil barrier. Otherwise your valve shim
if exposed to the carbon would become surface carburized and brittle.

You seem pretty sure of yourself to win a low bid on the hardness tester. Good luck!

 

[Metalguy]

I think you are on the right track in buying the shims from Australia. When you order them get some extras, a bit thinner than the ones you use in the engine. Then, as the valves slowly (you hope) sink into the seats a little deeper, you'll have thinner shims ready to use.

In a high HP engine I like to set the clearance on the exhaust valves a little more than what a stock (unmodified) engine is set for, because your exhaust valve temperatures may run a somewhat higher.

As for attempting to heat treat S7, you may find it requires a lot of care to do it correctly. S7 has a lot of carbon, and C will be lost from the surface if oxygen is present. That will cause a softer surface which you do not want.

Yes, the use of SS foils can work, but you may need practice to get it correct. The first temperature you must reach, and hold for ~45 minutes, is ~950 deg C. Then you must cool the parts in air, while still in the foil, of course. When they get down to ~60 C, you must reheat them to at least ~250 C for 1 hour, followed by air cooling. Then put them in your freezer for a few hours, followed by reheating back to 250 deg for another hour, at least.

Then you need to accurately measure the hardness, which will leave a tiny hole--unless you do it on extra pieces.

Finally, use some very fine silicon carbide sandpaper (~280 grit or finer)and using a flat glass plate, rub them on each surface to be sure they are still flat. Good luck with your fingertips trying to hold a 1 mm shim!

Here is a link to some S7 HT info:

http://buffaloprecision.com/data_sheets/DSS7TSbpp.pdf

"You see, wire telegraph is like a very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? Radio operates the same way: You send signals here, they receive them there. The only difference is there is no cat." A. Einstein

 

[masterx81]

Mmm, buying shims befor have actually measured the right clearance not seem to me a right approach, as on an engine with age the valves can settle deeper on the seats, but also the cams/buckets will wear out... Who knows what of the 2 will win? Acually isn't rare to find some with less and some with more lash than reccomended... Too many variables...

Surely you know that setting more valve clearance you are wasting cam timig, only 0.05mm of more lash is like wasting something 5° of cam opening time (depending on the cam profile)... I'll prefer to widen a bit the exhaust seat for better cooling the head of the valve, and maybe imstalling bronze valve guides (that helps to remove heat from the stem of the valve).
I've tryied to remove 0.05mm of lash on a fiat fire engine (that have HUGE clearances, something like 0.40mm on intake and 0.50mm on exhaust) and the difference was noticeable.

So you discourage me to try to get my own shims made and heat threat them?

What do you tink about that poldi hardness tester?
I'm always ethusiast when i can try to do something new, and learno to made things, but sometimes i'll admit that for made a good job the equipment will cost too much for an hobbist

 

[Metalguy]

From a Poldi website:

"Poldi type Impact Hardness Tester is not designed to replace the tensile strength testing machine or standard hardness tester. The accuracy of this hardness tester may very sometimes to the extent
+/- 10% as against the more accurate table type standard Hardness testers. However, the Poldi Impact Hardness Tester has the advantage of easy handling and greater flexibility. This is very important, especially for testing heavy specimens who cannot be taken to table type hardness are extremely costly eompared to Poldi tester and require greater skill to operated properly."

I think I'd spend more time getting your engine running well than trying to HT your own shims. If you're at 500 HP you must be turbocharged, and turbo'd engines like lots of good tuning. I have a 250 HP turbo'd engine, but it's not in a car. It's a Hayabusa motorcycle that weighs ~230 kg without me on it.

"You see, wire telegraph is like a very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? Radio operates the same way: You send signals here, they receive them there. The only difference is there is no cat." A. Einstein

 

[masterx81]

Thanks.

 

[metman]

I was hoping the Poldi was NOT an impact tester.

Maybe you have a friend who works someplace where they have a hardness tester?

If you find that making your own shims is your only viable option which sounds like it might be the case then Metalguy's comments trigger some other thoughts:

Quote:
"Then you need to accurately measure the hardness, which will leave a tiny hole--unless you do it on extra pieces."

Yes you should have some extra pieces as you would make some anyway for practicing the heat treat process.

I do not think you will have a problem with decarb. There simply will not be enough air (O2 molecules) to accomplish this if you do a reasonable job of collapsing the foil package around the part(s) in the sealing process.

Quote:
"Finally, use some very fine silicon carbide sandpaper (~280 grit or finer)and using a flat glass plate, rub them on each surface to be sure they are still flat. Good luck with your fingertips trying to hold a 1 mm shim!""

Good point Mguy. Might need to make an eeny-weeny holding device to accomplish this. Which brings up another point. These magnified pictures or 3D computer models that we deal with, often fool us when it comes to working with the real article. When machining these shims on the lathe, you will need to make the boss, then part off the shim with slight excess axial material length at the larger diameter. Then you will need a fixture to hold the part by the boss while facing off the excess material on the face opposite the boss. The boss is too small to provide sufficient torque resistance while facing the opposite surface. Therefore you will need to also clamp axially against the shim with a live center in the tail stock. This will leave a small tit at the center of the shim to be removed with a convex needle file.