DIY Valve Shims

fred · February 24, 2009, 06:09:23 PM

After my last experience getting valve shims from my local dealer, I've decided to make my own valve shims for my project bike. I just got a one foot length of A2 air hardening tool steel from McMaster for $30. My plan is to turn the rod to 29.5 mm and then use the EDM at work to slice it like bread into new valve shims, then harden them. With the EDM I can cut things to 2.5 micron accuracy, so not only can I make my own shims, I can make custom sizes to get my valve clearances to be exactly what I want them to be. Not counting the massive cost of shop time, which I get for free, I'm going to save money over the $16 per shim the dealer wants the first time I do valves. Also, since I can use the shop whenever I want, I can probably also beat the 3 days it takes the dealer to actually get shims. I plan to turn the blank some time this week, check the valves on the weekend and then make the actual shims some time next week. Has anyone ever tried this before? It seems like such a good solution if you've got access to the right tools. According to my calculations, my $30 bar of stock should make about 95 maximum thickness shims, even allowing for kerf, which should keep my pair of GSs happy for quite some time...

GeeP · February 24, 2009, 07:35:40 PM

Awful lot of trouble...

I swap my shims at the local Suzi dealer for free. If I need a little off, I tease 'em with the surface grinder then lap. Go light, or you get a concave pretzel. Your shims should always get thinner, not thicker, as the valve clearances tighten.

If you just need something to do on the off-time (dont' we all?) I'd be more inclined to use one of the Shock-resisting S-series tool steels or even 4140. In fact, check Machinery's Handbook under the alloy application guide or "The Internal Combustion Engine in Theory and Practice". Both books have guidance for tappet followers or similar.

It would be worthwhile to test the shim for hardness and case first. My guess is they're case hardened. You DO NOT want that shim shattering, which A series steels will be prone to do.

qwertydude · February 24, 2009, 07:40:46 PM

Why not just lap your existing shims flatter until you get the thickness right? Since they always get thinner as your valve seats wear and you only really need one side hardened it's perfectly ok to sand them. Common practice actually in the Ducati world.

gearman · February 24, 2009, 07:45:03 PM

I agree with GeeP, S-7 would be a better choice for through hardening. Even then I would avoid maximum hardness. Not being familiar with the process, what surface finish can be maintained? How about chamfers?

zeusrekning · February 25, 2009, 05:13:04 AM

Fred, I dont think you'll be able to get the required flatness or surface finish with just the EDM. And this is just based on the EDM work I have had done. Awesome process for sure but... I think you would need to , at least grind, preferably grind and lap flat. Last thing you want to do is start grinding away at your cam lobes.

ohgood · February 25, 2009, 05:39:25 AM

hmm, most of my stuff is a-2 or d-2. iirc (don't have the bible in front of me) s-7 would be more like what you want for shims with all that beating around.

+1 for the "I got the tools, might as well use em!" part.

+1 also for the "it's allot of trouble for a shim"

i'd be torn. sure, go on and part off some shims. i'd assume you're going to treat and draw it first ?

i'd love to have access to a wire/plunger edm. either one would be a blast to play with !

(subscribed to thread)

The Buddha · February 25, 2009, 08:27:08 AM

Yea awful lot of trouble but whatever floats your boat. BTW you never tried getting on the valve adjustment kit list ?
Also you can get thinner than the 220 or whatever is the thickest they have huh ...
Cool.
Buddha.

fred · February 25, 2009, 11:32:28 AM

Hey everyone. Thanks for your input. I went with A2 instead of S7 because A2 is a bit easier to work with and doesn't need to be oil quenched. Also, according to the hardness charts I saw, A2 and S7 overlap a lot, with A2 being the harder of the two, not that I plan on going for maximum hardness... I do need to test the hardness of some stock shims too. Quick tests show that I can't scratch them with the hardened points of my micrometers or a file, but there are more sophisticated tools for testing hardness floating around in the shop somewhere and I plan on using them. As for surface finish on the EDM, it will be a slight problem. With many finish passes, the EDM can create the surface finish required, but since I'm cutting the shim off a bar, I can only do many finish passes on one complete side and then 90% of the other side. I figure I can just grind and lap the surface on the second side a bit and then put that side down. I realize this is probably a huge amount more work than just getting the valve kit or buying shims, but I come primarily from a blacksmithing background when it comes to metal working and this gives me a chance to get the machinists around here to teach me how to use the EDM...

GeeP · February 25, 2009, 12:56:49 PM

Fred,

I just pulled out my copy of "The Internal Combustion Engine In Theory and Practice" Volume 2.

Table 9-1 says the following:

For camshafts AND cam followers:

Casehardened steel, SAE 4119 (Timken bearing steel) or 4317 650-700 BHN

Remark: Resistance to wear.

Toughness, obviously being the choice for the low carbon moly steels.

fred · February 25, 2009, 03:39:41 PM

Quote from: GeeP on February 25, 2009, 12:56:49 PM
Fred,

I just pulled out my copy of "The Internal Combustion Engine In Theory and Practice" Volume 2.

Table 9-1 says the following:

For camshafts AND cam followers:

Casehardened steel, SAE 4119 (Timken bearing steel) or 4317 650-700 BHN

Remark: Resistance to wear.

Toughness, obviously being the choice for the low carbon moly steels.

So it does, right on page 309 in my copy. I've seen A2 listed as good for cams elsewhere, and if I did my hardness conversions correctly, I should be able to get the A2 to be the same hardness. A2 is also listed as being resistant to wear, so everything should be OK. Hopefully when I check the valves on the bike, I'll be able to use one of the stock shims I have so I can then measure a stock shim and a homemade shim carefully with micrometers and pull them both after a thousand miles or so and see how much they have worn. I think everything will be fine, but that doesn't mean I don't plan on checking a bit more frequently to make sure...

ohgood · February 25, 2009, 04:47:03 PM

cool !

i was used to the rockwell "C" scale from years ago at a delco daughter plant. that's all we used.

now, at work all we talk is brinnel / brinell (i don't have the bible at home) and i had to convert to get an idea how hard/tough stuff was.....

last week did a 24 hour shift on the big boring mill with some 625-650 brinell stuff. took all night and 12-15 inserts (with coolant!) running around 4-5 rpm.

ANYWAY.......

case hardened really surprises me. i figured it would need to be hard through and through, but i guess with the shock of engine forces, millions of times, ya, case hardening makes sense. i've -never- gotten case hardening right, so i defaulted to a2/d2/01/s7 for stuff. ya, they all overlap in hardness, but a2 is wayyyyy easier to machine than d2, and you shouldn't have to worry about work hardening it. s7 is tough as heck, better shock resistance, blah.

d2 ? expensive, and good for sharp corner die parts. really neat when you get into grinding them with profiles to see which ones take a wheel better/easier.

neat thread, and learning a edm must be a (slow kinda!) blast.

keep us posted how it goes.

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DIY Valve Shims