Steel for a tommy bar

I am making some rear wheel spindles for a motorcycle that have a 1/4" diameter tommy bar fitted about 2.5" long. The spindles are EN16T, I need a recommendation for something that will not easily bend and do not want to use silver steel as they will be brazed in situ.

Re-purpose a decent quality screwdriver blade

MichaelG.

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Edit: is brazing essential ?

... Loctite 638 is very effective.

Edited By Michael Gilligan on 14/01/2017 17:34:31

The carbon equivalent of EN16 is well above the 0.4% above which you've got to think carefully before doing any hight temperature processes. I'd stick with Michael's suggestion of loctite, or even a press fit (make one end of tommy bar a few thou small so you don't have to press it all the way)

You could use EN16t and put a straight knurl in the middle.

Thanks for the responses. I do not want to use Loctite due to the item being nickle plated after finishing. What I did not mention is the tommy bar only sticks out one side by the two and a half inches, hence the concern about it bending. I can drill and tap the hole and bottom the thread to make secure and not braze. With six to make the screwdriver idea does not stack up but a good choice of steel.

Have you thought of using a 5/16 dia bar and turning the location down to suit the hole in the spindle. With a small chamfer in the hole you can peen the end of the pin and making it permanent and stronger. You can do with out any heating and Brazing.

David

Something does not sound right here. This Tommy bar is in the spindle or nut that holds the rear wheel in place?

It could be described as being safety related.

If its a full size roadgoing bike then the EN16T is going to be (say) 12mm diameter and you are looking to tighten the thread with a thin rod 'spanner' with minimal leverage. Even if you extend the Tommy bar with a length of tube I imagine the bar would bend when the correct torque is applied.

I dont know how fine the thread pitch is, or I may have I misunderstood the requirements?

Ian P

EN8?...n" case harden if need be?

Edited By Michael-w on 14/01/2017 21:23:10

Just reread the OPs posts and see that the spindle is going to be Nickel plated.

I thought plating (or electroplating anyway) was not used nowadays on highly stressed vehicle components because of Hydrogen embrittlement. I know for certain that some vehicle manufacturers will not use plated bolts at all.

Ian P

Yeah, I thought they mainly used blacking rather than plated material.

I was involved in frame manufacture for racing motorcycles and saw a frame that had been nickel plated fracture at the headstock, but all other frames which were plated with cadmium had no problems. And all the wheel spindles engine plates etc were cad plated similarly as there is no noticeable change in dimension where as the thickness to nickel has to be taken into account.

David

Edited By David George 1 on 14/01/2017 21:47:35

Could use threaded cap head screws. You can get these in 14.8 grade and with long plain shanks.

Chrome vanadium is an ideal steel for Tommy bars as used in socket sets etc. I used a surplus t bar from a socket set as the Tommy bar on the vice of my automatic hacksaw, it is not going to bend unless 3ft of scaffold pole is used on it. Might be difficult to adapt to you application though.

Mike

Very interesting note, David ... Thanks

It's a pity that Cadmium plating seems to be verboten these days.

MichaelG.

Presumably if the frames were Cadmium plated, it was quite a long time ago. Cadmium plating is now used only in very special (military?) purposes.

Ian P

Cadmium plating also causes titanium to develop titanium embrittlement which will cause failure.

The wheel nuts on Vincent motorcycles had/have captive tommy bars, never had one fall off.

Out of interest, which manufacturers use blacking.

Right it is time for some more info on the job. I am making these for a mid 1920s machines and all I want to do is copy the original design. The reason I asked about material is the desire to fit something that will not easily bend, the main securing nut is released from the opposite end and the tommy bar used to twist and pull the spindle clear. As for plating we can always use chrome on a lightly vapour blasted surface.

If you screw the bar in you could lock them using solder paste, this was the method before Loctite. Clean both threads, coat with solder paste, assemble and the heat to melt the solder. Soft solder will take chrome or nickel plating. The solder paste will much stronger than any loctite available.