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  1. #1
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    Default What steel are king pins made from ?

    Automotive king pins: I need new king pins but with my vintage truck , they are nigh on impossible to find . From the info I have read online, king pins are machined from low carbon steel, case hardened and ground to final size . The inner core remains tough but is not brittle, similar to some automotive gears . Is this a reasonable method ?

  2. #2
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    Jun 2005
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    Helensburgh
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    Some of the ones I have seen and replaced were made from licorice. If it was a renovation and not going to do a lot of miles I would not get too fussed on using anything super special. It gives me nightmares thinking about this stuff now, doing this sort of work for a living. I think the McPherson strut was the single biggest improvement in car front ends. I can't give any material recommendations, I just felt like venting about kingpins and cars. I will get off my soapbox before I really say what I think about the junk they foisted on us as automotive technical brilliance.
    CHRIS

  3. #3
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    Sep 2008
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    Riddells Creek, Vic.
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    Default

    EN36A would be ideal. It is readily available from Bohler.

  4. #4
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    Mar 2014
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    South of Adelaide
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    Default

    Quote Originally Posted by Techo1 View Post
    EN36A would be ideal. It is readily available from Bohler.
    +1

  5. #5
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    May 2011
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    Murray Bridge S Aust.
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    Default

    Hi MM, found this on Google, which led me to the PM website.
    The material should be machined steel AISI 8630H hardened to 302-363 BHN
    I've made kingpins from EN 36b, which is sae 3310 iirc. Case hardened and ground.
    4340 52 RC Critical that tooling marks are polished out to eliminate stress risers.
    Is there a manufactured kingpin that is close that could be used, either bushes made to suit or ground down to fit???
    Hope this helps,
    Kryn
    To grow old is mandatory, growing up is optional.

  6. #6
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    Jul 2008
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    near Warragul, Victoria
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    Default pins

    The problem with grinding down a larger diameter pin is: there is a machined flat on each king pin , this flat is for the locking tapered pin . In my case the machined flat is not half way , it is off centre . There are also machined grooves for grease . EN36, sounds like it will do the job thanks .

  7. #7
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    Laidley, SE Qld
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    Default

    If you are making vintage vehicle kingpins from EN36A do they still need to be hardened and ground? If so, how much oversize should they be when they go to the heat treater? I'm thinking 3/4" diameter pins.

  8. #8
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    Quote Originally Posted by bob ward View Post
    If you are making vintage vehicle kingpins from EN36A do they still need to be hardened and ground? If so, how much oversize should they be when they go to the heat treater? I'm thinking 3/4" diameter pins.
    If the EN36 was not hardened and ground they would not last very long , they would be too soft I would think and wearing scoring marks would appear . The bushes are normally bronze . Not sure about the oversize allowance for the grinding . My pins are just over .9" Maybe .010" oversize ?

  9. #9
    Join Date
    Mar 2014
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    South of Adelaide
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    10 thou over is good. More than that takes too long to grind off. I would get them case hardened 20 thou deep.

  10. #10
    Join Date
    Oct 2011
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    Norwood-ish, Adelaide
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    Quote Originally Posted by bob ward View Post
    If you are making vintage vehicle kingpins from EN36A do they still need to be hardened and ground?...
    It's individual preference of course, but when looking at using/ making a replacement part that is used in a situation that is safety (or even function) critical I always try to make it so that the part does not become an unknown weakness. As an example, when I set up my grinders, even though they are 3 phase from a VFD, I set pulley ratios so that if the VFD was removed by a future owner in say in 50 years time the wheels will not run over speed.

    In this case while it may be tempting to not harden and grind the pins (or even use a less suitable material), it has potential safety impacts. While Morrisman may know that the pins were soft and needed to be checked every say 500 km, or know not to get airborne in the vehicle because the landing shock is too much, a future owner or even someone else driving the vehicle on loan may not. Any replacement part needs to be reliable enough that the vehicle can be used in the usual situations with confidence.

    Michael

  11. #11
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    Feb 2013
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    Laidley, SE Qld
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    Default

    Quote Originally Posted by bob ward View Post
    If you are making vintage vehicle kingpins from EN36A do they still need to be hardened and ground? If so, how much oversize should they be when they go to the heat treater? I'm thinking 3/4" diameter pins.
    Just to clarify, I asked this question because I know nothing about the properties of EN36A, not because I want to do a half-arsed job. It seems kingpins made from EN36A do need to be hardened and ground, so hardened and ground they shall be.

  12. #12
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    If the truck was designed and made in the 1940's then they would not have had the alloys we have today thus the truck would have been designed and built with only what was available at the time and to a price. I think 4140 was cutting edge back in that era.
    Gold, the colour of choice for the discerning person.

  13. #13
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    Mar 2014
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    Quote Originally Posted by .RC. View Post
    If the truck was designed and made in the 1940's then they would not have had the alloys we have today thus the truck would have been designed and built with only what was available at the time and to a price. I think 4140 was cutting edge back in that era.
    yeah that's a good point. from what i have read there were no standards prior to world war2, every steel mill had there own blends. To make mass production of war equipment easier the Emergency Number or EN standard was devised.

  14. #14
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    Apr 2008
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    NSW
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    Quote Originally Posted by Techo1 View Post
    EN36A would be ideal. It is readily available from Bohler.
    I agree EN36A is case hardening steel . It makes a wear resistant pin that is also softer in the middle so it bends but does not shatter . Also ideal for making gears .
    Case hardening needs to be done professionally though to get it right .
    The volume of a pizza of thickness 'a' and radius 'z' is given by pi z z a.

  15. #15
    Join Date
    Jul 2014
    Location
    melbourne
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    Default

    hi morrisman
    you could try aa bearings nunawading 98741660
    they sell hardened shafting for king pins and gearbox lay-shafts in various sizes for vintage vehicles.
    ask for Adrian say damien gave you the number cheers

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