I'm re bushing a small machine (210 Hitachi) and now in pieces it is apparent that the main stick pin in groved quite severely where it passes through the bucket coupler. I will try to upload an image shortly... Due to time and supply restraints I cannot simply replace the pin. I will be building it up with wed and taking back to round. My question to the knowledgeable collective is what sort of rod should I use? As always, a big thank you in advance for all opinions and thoughts shared
I would think 7018 would work. Will you be turning back to round with a lathe?
Yep, 7018 will be fine but if you're not welding all the way around the pin, its possible you might bend the pin into a U shape. This happens as the weld cools, Another option is to heat the dickens out of the pin before welding, keep it hot while welding and then heat it up a bit more, uniformly before letting it cool. Heat bends everything.
Not sure if that worked...
It did... so maybe half the circumference of the pin both ends. Unfortunately I am limited to a straight edge and grinder...
Fun fun fun. I'd guess that welding your beads circumferencially is better than welding axially, for minimizing shrinkage/bending anyway. No idea what that will do to the strength. Get the end hot, keep it hot, but not all in one spot, let the welded area equalize with the unwelded side. The way to bend it most effectively is to add the weld all at once to the one side while the other side is still cold, just avoid that, right?
In my experience welding up pins is a last resort. Because you weld onto induction hardened alloy there is a broken pin waiting to happen. The weld is very soft compared to the pin and will wear out very quickly. And there is no way to weld it and keep the pin straight.
best would be to tig welding around the pin ,heating all sides, this way you can put no material on the side that isnt grooved and feed more in on the sides that are grooved, then polish up the non grooved side while grinding flat the built up side...what is the diameter of the pin?
I imagine that bushing is hammered to beans as well! You could just rotate the pin and grease the heck out of it. Then replace it with a piece of pin stock.
All the Japanese machines match the pin and bushing hardness together. Basically welding the pin will never match the surface hardness of the bushing so will just grind right back out almost as fast as you put it in. I've tried it several times using a few different types of rod. Low alloy (7018), stainless, hard face and high alloy (11018) all brought the same results. Quick failure. You might try finding some alloy line shafting and having it treated to get as close to the same properties as the bushing.
It's a design floor I think, the main stick bushings and wear area thereof were not too badly worn at all. The damage to the pin was from the bucket coupler bores not the stick. If the grease groove was sufficiently longer on the pin, the coupler would have been lubricated and likely not damaged the pin excessively... I'll be making some changes... Thanks for all the input... after having a chat with the customer it was decided that the wait for a replacement pin to be made was worth the time so it's now a waiting game... not that I'm waiting... duo cone time...
Thumb and coupler? Always an issue, almost never grease right. I used to drill the stick end for a zerk, then one zerk on every collar with a bushing, let the pin float with a welded cap on one end and some sort of retainer plate bolted on the other, or both bolted on the ends of the pin. YMMV
I have been making pins out of W1 steel, easy to machine, heat treat in propane forge, quench in water, draw in rod oven... www.mcmaster.com is my source for round stock, look under drill rod, but there are many sources out there. Howard