Weld Repairing Cracked Bronze Castings

By MobeusI Date 04-04-2006 21:09

IN THIS DAY AND AGE......YOU WOULD HAVE THOUGHT IT WOULD BE EASY TO FIND ANSWERS TO ALMOST ANY QUESTION ON ANY TOPIC.......BUT ALMOST IS THE ACTUAL NORM.....
......DO YOU A) DRILL HOLES AT EITHER END OF THE CRACK......B) GRIND OR MACHINE THE CRACK OUT OR C) THROW THE BLOODY THING AWAY???..........CHEEPER IN THE LONG RUN!!.....OR DO I JUST TIG WELD THE CRACK IN FROM BOTH ENDS...OR RUN FROM THE BELL MOUTH TO THE HANDLE OR FROM THE HANDLE TO THE BELL MOUTH OR BACK STEP..??...THIS IS A BELL AND SO IT MAY AFFECT THE ACCOUSTIC PROPERTIES OR INDEED ,ALLOW THE ACCOUSTIC PROPERTIES TO RECRACK THE REPAIR....MY HEAD HURTS...I'M OFF TO BED!?!

By yorkiepap (***)

Date 04-04-2006 23:51

Hi MobeusI,
Over the years I have repaired many bronze castings, but never a bell. I silver-solder using oxy-acetylene. The silver solder I have was given to me many years ago by my father and it works extremely well. It is a wire that is .040 dia., has a tensile strength of 55K PSI, yet has a low melting point. My fathers' company used it for all their new and repaired thermostats for ovens. They were brass castings back then.

I repaired all my work by first beveling the crack the full length approx. 1/2 the width of the crack on each side. Then start at the thinnest point and solder towards the thickest. This way you are "pushing" the heat and kinda preheating the thicker portions as you go. You must have the entire cracked prepared with flux paste. I kinda make my flux past runny so I can brush it into the crack. After brushing it into the crack, run your flame over it quickly to make it harden a bit and dry. Then start at the thin end, dip the wire into the runny flux, and begin your heating on the crack and laying your silver-solder wire into the crack and allowing the flame to heat the bronze till the wire melts. It takes some practice, but once you get the hang of it, it is quite easy. I almost forgot to mention that a bell produces a harmonic vibration and this will affect the welded area. Silver solder is soft compared to other welding media, so it will "flex" a bit with expansion and contraction of metal.

Since I cannot tell you what the effect of the bell's sound will be, I can only wish you good luck. Hope I helped you a bit......Denny

By MobeusI Date 04-06-2006 18:32

Hi Denny...i have saved your post in my emails as i found it very interesting and may come in handy at a later date...:))
Today i had a few minutes to spare,..and 'had a go' ...i decided to Tig weld the crack with a tin bronze filler(QW432 F-No 33...92CuSn)...tacking the crack at both ends then working the plates and tacking them level...I didnt worry about the interpass temp and just welded in from both ends starting at the micro end of the crack.(gasp wheeze)...A small crack did develope off from the main but wasn't any prob.IT was just a simple case of grinding flush with a stone and re-applying the embellishments.....DING DONG job done!!!!!
If this repair fails..i shall give your method a try...this is a very old bell...years of abuse...a bit like myself!?!
many thanx....MobeusI.:)

By yorkiepap (***)

Date 04-07-2006 00:41

Hey MobeusI,
Glad to hear you had success. Someday I hope you try the oxy-acet. with silver-solder....it works quite well. And it does a marvelous job with iron & steel cast metals up to a thickness of 3/4".

BTW...."for whom does the bell toll? for thee?".......Denny