I have a new little problem with the engine I'm rebuilding (Skoda 120L '70s, RWD, RME): after milling, adjusting and cleaning the crankshaft, camshaft and pulley I found out that their woodruff keys have a lot of play. I torqued the pulley 1/2 way and still feel a play when rotating it, so...I need to make new keys. I'm not scared about adjustment work, but the question is: which kind of steel should suffice?

I have no access to "named" or "numbered" steels, but just scraps I can get, which includes: suspension spring leaves, stainless steel bars, construction (structural) mild steel, broken/old drill bits, old engine valves, old wrenches. So please don't refer me to "use C-1035 or C-45" because I won't be able to find it that way...although I know what they are.

Any idea how hard or soft the keys should be? The sprockets are steel, driven by chain.

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  • The keys in engines are not the primary way of holding the pulley from turning. The keys are there only for the initial alignment and then something else holds it. The pulley could be press fit or held in place with a bolt. The key could be made out of almost any metal (even aluminum) as long as the primary method of holding the pulley is robust.
    – vini_i
    Mar 23, 2017 at 19:19
  • Excellent news :) yes, both sprockets in this engine are secured by big bolts, using 100 Nm torque setting (the only so-high torque in the whole engine...head nuts require only 50! Nm) Mar 23, 2017 at 19:24
  • Just saying, it's nearly impossible to properly answer this question. You're asking for the "proper" steel to use, but you don't know the grades of steel you have and you say you can't get graded steel (even online???). The best it seems you can do is just guess and see if it works. I'd start with drill bits (commonly O-1, or similar).
    – Hari
    Mar 23, 2017 at 22:12

2 Answers 2


Some pulleys, while they have a woodruff key, are fitted with a taper and that, with the high torque of the pulley bolt is sufficient to prevent movement. Others have a sliding fit and are just held with the compression of the pulley bolt.


Woodruff keys are generally made from Carbon steel or Stainless Steel with some being coated in zinc to help prevent corrosion. The following Key Steel is popularly used for woodruff keys... 080m40(En8), C45+c, 1.4571. A2 Grade 303/304 Stainless Steel A4 Grade 316 Stainless Steel

  • You'll need to be far more specific. "Carbon steel" can refer to any AISI XXXX series steel, though most commonly 10XX series. Those have exceptional variance in properties, as the carbon content depends on those last two digits. Many grades of stainless have similar numbering schemes, but 4XX series and 3XX series differ significantly. You can also get 17-4, PH, duplex, etc.
    – Hari
    Mar 23, 2017 at 22:09
  • The questioner requested that he/she didn't want specifics.
    – Orb
    Mar 23, 2017 at 22:12
  • I read that, but your answer applies to literally everything they mentioned they could use. My comment was to point out how the broad terminology reflects such a wide range of steels.
    – Hari
    Mar 23, 2017 at 22:13
  • I certainly appreciate the reference to specific grades, and will remove my downvote, but it might also help to provide examples of what scrap materials may contain those steels. I, unfortunately, don't have quite that much knowledge.
    – Hari
    Mar 23, 2017 at 22:33

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