Broken yoke

[NC Rick]

I really had good luck Tig brazing cast iron with aluminum bronze on AC. I most recently used that process on the cracked Walker Turner base. BBQ preheat for me as well along with after heating and slow cool down. On a small part I just use a propane torch for preheat and slow cool.

 

[NC Rick]

Hello all,
While milling the ring for my head stabilizer I noticed that the Z-axis DRO numbers were a bit erratic.
I found the problem tonight. Seems the yoke around the spindle that holds the depth stop has cracked at the rear where it get pinched together.
I never use the depth stop but I do need a place to mount the Z-axis DRO scale.
View attachment 342920
I think I have a couple of choices here:
a) TIG braze the part back together
b) make a new yoke out of steel or aluminum
Any other thoughts oh wise members?

I would add a dowel pin and "v" out the crack before Tig brazing. Likely stronger than stock.

 

[DavidR8]

I would add a dowel pin and "v" out the crack before Tig brazing. Likely stronger than stock.

How would you see setting it up to drill for the dowel pin?

 

[NC Rick]

How would you see setting it up to drill for the dowel pin?

Not being a smarty pants, just funnin you, but carefully
I think if you X-Y from the side and bottom and centralize the pin it would work. Drill and ream for 1/8 or 3/16" pin. Even If your alignment is off a smige, the grinder will "fix it back".

 

[NC Rick]

you can practice with the silicon bronze (edit: aluminum bronze) filler using AC Tig on plain old steel too. I think you will find that stuff to be quite useful in the old bag-o-tricks.

 

[Skierdude]

I too would TIG braze with aluminium bronze. I had to repair a cracked casting on my old bandsaw. As NC Rick mentions, grind a V to let you get the filler into the join and of course very clean surfaces before welding. The pin idea might be worth a try too. I hadn’t brazed cast iron before this so I did run a practice first on some old scrap. I was not nearly as difficult as I was expecting. Check out Adam’s video

for plenty of sensible guidance.

 

[DavidR8]

I too would TIG braze with aluminium bronze. I had to repair a cracked casting on my old bandsaw. As NC Rick mentions, grind a V to let you get the filler into the join and of course very clean surfaces before welding. The pin idea might be worth a try too. I hadn’t brazed cast iron before this so I did run a practice first on some old scrap. I was not nearly as difficult as I was expecting. Check out Adam’s video

for plenty of sensible guidance.

I just started watching that

 

[Dabbler]

FWIW, brazing won't do you any harm, and when it breaks again you can replace it with a fabricated steel one.

On my 12X37 lathe I had a yoke for the change gears that broke. It was brazed by a welder well versed in cast iron repair, it lasted a week. I made a new one in soft steel, and it has worked for almost 40 years. If you do braze it, remember it has to be heated to at least 300F.

 

[Lo-Fi]

Are the oxyacetylene rods different from TIG rods?

Yes, very much so. The 'standard' rods contain some zinc, which explodes in a puffy little ball of crazy when heated with the TIG arc. Silicon bronze rods specifically marked for TIG are what you want for this application.

 

[addertooth]

It cracked for a reason. You might ask what stresses were applied that caused it to fail. It is always wise to address the underlying cause before a repair is done on a crack. Otherwise, the repaired item will face the same forces.