Welding a 2" pin

[F.J.]

One of my customers have a cherry picker and they need to replace the bushes where the boom pivots at the base of the machine. The pin is seized solid and this is where I come in. Rather than take it to the manufacturer as they have with other machines, they have invested in a hollow jack and have had a boss made that needs welding to the pin . The pin is 2" in diameter and about 18" long. The boss is also 2" in diameter but has been machined At the face to be welded so I have a 'v' when the boss is placed upto the pin. That way I can put enough welds on the boss to ensure it won't tear off when under tension from the jack.

Having never done anything like this before would anyone on here have any input on how to go about welding the boss to the pin, ie, would you pre heat the pin and/or boss due to them being 2" thick or just weld it on and build up the welds to ensure it not coming off?

It is a 35t hollow jack if that helps and once under tension I will be hitting the pin from the other side to assist with getting it out.

Cheers

 

[zzr1200]

Hi FJ, having had this problem many times before at work. I may be able to advise/help you, due to the designs of various machines it would help if can state the make/model of the MEWP, also a few pictures of the pins location will also help...

Mostly pins tend to be cut with a reciprocating saw, then the remaining stubs removed, there is another way depending on the access available using a mag drill...

 

[AndyStobbs]

Would say that penitration into the face of the seized pin will be the hardest bit. As you've said the puller boss is veed out but the other face is still flat. Depends how tight the seized pin is really, for how much strength you need the weld to attain . What will you be welding it with?

 

[F.J.]

Hi FJ, having had this problem many times before at work. I may be able to advise/help you, due to the designs of various machines it would help if can state the make/model of the MEWP, also a few pictures of the pins location will also help...

Mostly pins tend to be cut with a reciprocating saw, then the remaining stubs removed, there is another way depending on the access available using a mag drill...

It's a Houlotte HA16PX and if you look at the two pins (one above the other) on the image it is the lower pin. There is no room for a blade even though that how the other pins are removed and each arm that the pin goes through is 7" thick! A mag drill has been brought up but this was the preferred option for some reason

 

[F.J.]

Would say that penitration into the face of the seized pin will be the hardest bit. As you've said the puller boss is veed out but the other face is still flat. Depends how tight the seized pin is really, for how much strength you need the weld to attain . What will you be welding it with?

The pin has been smacked for pretty much a full day with a big sledge hammer with no joy whatsoever (not by me) and I will be using my Lincoln Electric Powertec 360 to weld it

 

[Paul99]

This may be of some use - came across it a while ago and found it interesting even if it was something I'd not try myself.

 

[AndyStobbs]

The pin has been smacked for pretty much a full day with a big sledge hammer with no joy whatsoever (not by me) and I will be using my Lincoln Electric Powertec 360 to weld it

Some jobs are just not suited to impact. Machinery just soaks up the impact or rocks away. It'll come out with the jack I'm sure. Is there no way to push it out though, always easier than pulling - or is it blind on the other side?

 

[zzr1200]

Usually the pins just seize in the bosses at each end of the pins (is the boom creaking when elevated/lowered), the pins are cut, box sections then pivoted out of the way and the remaining stubs removed. The remaining part of the pin in the box section tubes should just knock out.

If the pins have been mullered for a full day with a sledge, they are now belled in the bosses and even tighter.

Now you have two options:

1. Cut the pins each side of the box section (don't worry about the tubes welded in the box section to much) swing the section out of the way and porta power the stubs out (probably with a gas axe as well) or using a mag drill drill a 1 1/2 inch hole in the stub, almost completely through and then weld up the hole, thus shrinking the outer diameter of the pin then hammer inwards.

2. Using a mag drill, drill each end of the pin (as above but beyond the outer boss in to pin) then fully weld the hole up and hope the distorted pin will now punch out through the outer boss.

Personally I'd be using option 1

 

[dannyp]

a nice big mig will see to that no issue what so ever. once your spraying with 1mm+ wire for this sort of job you really don't need perfect even prep. if you can get the weld at it it'll stick.

I would go in very hot, for the first run or two at least so it may need a few moments to cool inbetween.

there are Meany ways to get such pins out all depends on the weapons you can get in there tbh if it hasn't moved with with 5-6 good belts with the sledge hammer it's unlikely to do anything other than swell the pin and make it harder to remove.

the chosen solution sounds like a lot of hard work for what it's likely to achieve but by all means try it a worn chewed up manky pin can take a lot of tonnage to remove, quite a few times i'e had a pin refuse to acknowledge 70 tons of persuasion.

then you into cutting / drilling them out, if you cant cut the am out burowing a hole right the way through then get it red hot with gas and quench it then it should welt out.

if it doesn't you can always gas the bugger out if you've got a steady hand

 

[F.J.]

This may be of some use - came across it a while ago and found it interesting even if it was something I'd not try myself.

I hope I have the kind of luck he had. I have a boss to weld to the pin but he only welded the threaded bar to it, I thought the threaded bar would of come off for sure! His home made pump was impressive too!

 

[F.J.]

Some jobs are just not suited to impact. Machinery just soaks up the impact or rocks away. It'll come out with the jack I'm sure. Is there no way to push it out though, always easier than pulling - or is it blind on the other side?

The machine doesn't rock when hit, it is just that stuck its like hitting a solid block of steel. Ive got my fingers crossed it comes loose with the jack

 

[F.J.]

Usually the pins just seize in the bosses at each end of the pins (is the boom creaking when elevated/lowered), the pins are cut, box sections then pivoted out of the way and the remaining stubs removed.

If the pins have been mullered for a full day with a sledge, they are now belled in the bosses and even tighter.

Now you have two options:

1. Cut the pins each side of the box section (don't worry about the tubes welded in the box section to much) swing the section out of the way and porta power the stubs out (probably with a gas axe as well) or using a mag drill drill a 1 1/2 inch hole in the stub, almost completely through and then weld up the hole, thus shrinking the outer diameter of the pin then hammer inwards.

2. Using a mag drill, drill each end of the pin (as above but beyond the outer boss in to pin) then fully weld the hole up and hope the distorted pin will now punch out through the outer boss.

Personally I'd be using option 1

I will propose cutting if this doesn't work but would I then need to replace the tubes as the blade would eat into them or would the slight play between them and the boom not make that much difference?

 

[F.J.]

Usually the pins just seize in the bosses at each end of the pins (is the boom creaking when elevated/lowered), the pins are cut, box sections then pivoted out of the way and the remaining stubs removed.

If the pins have been mullered for a full day with a sledge, they are now belled in the bosses and even tighter.

The pin is seized in the bosses yeah but I don't know what the boom does as I haven't seen it in operation. One thing I do have in my favour is that the pin had 'walked' out to one side before seizing so I hoping that if it moved one way then there may be room for it to move the other way!!!

The ends of the pin had mushroomed but they have been cleaned up with a grinder now

 

[zzr1200]

I will propose cutting if this doesn't work but would I then need to replace the tubes as the blade would eat into them or would the slight play between them and the boom not make that much difference?

The blade is only about 2 or 3 mm wide cut one side of the pin then you can usually bar the box section over or use fox wedges to hold the box over. I've never replaced an arm because of cutting a pin out, (even cutting with a 9 inch angle grinders and cutting disc, but that can be very dodgy if it grabs).

Tip: Only buy top quality blades (Bosch, Dewalt or Makita are my favorites) and don't push the blade let it cut at its own rate.

A flap wheel to clean up the bosses, tubes and any bushes, plus a BIG POT OF COPPER SLIP to re-assemble it with....

 

[Shox Dr]

This may be of some use - came across it a while ago and found it interesting even if it was something I'd not try myself.

Good video (the bit I watched) Jesus that guy can waffle

 

[wyn]

What is the "boss" you are going to weld on.....is it threaded and you screw the threaded bar in?

 

[F.J.]

What is the "boss" you are going to weld on.....is it threaded and you screw the threaded bar in?

Ive just got on site now and here are some pics of the boss. Yes its threaded and the jack comes with a length of threaded bar which screws into the boss. After removing the access panel I can see that it would be possible to cut the pin but they want to try and get it out in one piece first!! The problem they face is not being able to get the bushes out as they dont want to move the boom out of the way. I have to wait till lunch time to start welding because thw firms H+S exec, the manufacturers main engineer and other managers are coming down to watch me do it!!!

 

[F.J.]

Oh and its not 18" long its 700mm long

 

[F.J.]

This is the jack and the threaded bar im using

 

[Robotstar5]

If the welded boss method doesn't work, at least you've got a few back-up options available.