PB102, Colphos 90 or other?

[Robert Smith 24Participant @robertsmith24]

I recently had a 1/4 BSP steel banjo bolt fail which was fitted to my 4 inch Burrell steel boiler. Having had a hell of a job getting out the remnant from the steel boiler bush I now have to make another bolt. I intially thought of using Colphos 90 as it machines so well, but it has been suggested that PB102 would be more suitable. Others said the galvanic reaction with steel would cause problems but as many boiler fittings are bronze, I’m not too sure about that.

Anyhow I would be grateful for any advice as to the safest option. Thanks in advance.

[DiogenesParticipant @diogenes]

Is the actual banjo fitting bronze or steel?

[duncan webster 1Participant @duncanwebster1]

Pb102 is stronger, but drilling it is a right pig. It tightens up on the drill. If anyone knows how to overcome this, tell all and earn undying gratitude

[bernard towersParticipant @bernardtowers37738]

Is the real problem the amount of material between the bottom of the thread and the outer dia of the hole in the bolt?, Just a thought.

[Robert Smith 24Participant @robertsmith24]

Thanks for the replies. The banjo fitting is bronze. I have no experience of machining PB102 so it looks as if I may have fun drilling the centre.

The wall of the original steel bolt is ample but it had been waisted where the transfer holes are and it sheared through at that point.

[bernard towersParticipant @bernardtowers37738]

I always thought that the banjo should be wasted and the bolt plain.

[Robert Smith 24Participant @robertsmith24]

<p style=”text-align: center;”>I agree. The waisting on the bolt has made it weak. I didn’t build this engine so I plead not guilty. I will modify the replacements as there is plenty of room in the banjos for steam to pass.</p>
 

 

[noel shelleyParticipant @noelshelley55608]

1/4″ banjo bolts are readily available commercially, I would not try to make them. Annealed copper washers either side and DON’T over tighten. There is no need to waist the bolt, there should be ample way for the steam, or it should be 3/8″ Noel..

[Robert Smith 24Participant @robertsmith24]

Hi Noel. Thank you for your reply. I would rather use commercial bolts but the banjos are not standard and need longer bolts. I confess I could use the time taken to make them elsewhere.

[StevePParticipant @stevepye68246]

Hi Duncan

To help stop the material tightening on the heel of the drill, grind the lips  (cutting edges)  different lengths which makes the drill cut an oversized hole.

I hope this helps.

Steve p

[duncan webster 1Participant @duncanwebster1]

I’ll give that a go next time I’m unwise enough to use Pb102. Presumably I have to go from nothing to finished size in one hit, or at least to big enough the get a boring bar in.

[Robert Smith 24Participant @robertsmith24]

Bolts have been successfully made using PB102. I found that hss tooling soon lost its edge. Insert tools worked fine. Deep drilling the central holes 32mm deep was fun but new cobalt drills coped well.

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