Positioning bushes for welding

[sparky mikeParticipant @sparkymike]

I have to weld two 1" diameter steel bushes into two holes in a steel 3mm plate. How can I jig these up to be spot on square to the plate? They are not flush with the plate but protrude around 3/8" on the back side.

Mike.

[sparky mikeParticipant @sparkymike]

[pgk pgkParticipant @pgkpgk17461]

The obvious answer would be a 3/8ths cup on the back and 3/8th supports or tack from the back if flush at the front. But I guess there's a reason why you can't do that. Won't the bushes get distorted anyway? Can you not weld some plugs and machine them out afterwards? Or rely on locktite?

pgk

[egaParticipant @ega]

I would tack them, check, adjust as necessary and then finish weld.

[DanielParticipant @daniel]

+1 to ega's post.

Tack weld, adjust to final position, finish weld;

ATB,

Daniel

[sparky mikeParticipant @sparkymike]

It has to very accurate so think this is the way I am going.

Thanks for replies anyway.

Mike.

[sparky mikeParticipant @sparkymike]

Photo

[Martin ConnellyParticipant @martinconnelly55370]

Welding and accuracy are somewhat mutually incompatible. The weld pool freezes at a high temperature and all the way from freezing to room temperature it is contracting and creating stresses. These stresses will distort the fabrication to some extent. Fabrications for tools and jigs have to be stress relieved after welding and before machining as a result. No matter how accurately you position them for welding expect some movement away from the ideal position.

Martin C

[Dave HalfordParticipant @davehalford22513]

treat each bush as a compass.

Scribe the bush with the position of the plate

tack north, then south, then east, then west, like torqueing up a cylinder head.

Check the scribed line after each weld and adjust as required.

Your bridge is quite flexible so still expect some movement.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Mike, can you not turn a the end of the outside of the bush the required length and put in a smaller hole?

You will not stop distortion, no matter what you do, but it can be controlled by slight bowing of the plate before welding, but of course you will need some experience before you are able to do this satisfactory.

Regards Nick.

[sparky mikeParticipant @sparkymike]

I made the simple jig, but instead of two welded legs to the bridge, I tapped the top plate and now have two 3/8" unf long threaded bolts in. I had thought about having each end of the bushes with turned spigots, but plate holes were in before I got to thinking on a bit.

Mike.

[Brian OldfordParticipant @brianoldford70365]

Weld in pieces of rod that have only been centre drilled. Weld into the plate getting them as square as possible the drill through with a mag drill.

[Dave HalfordParticipant @davehalford22513]

Posted by sparky mike on 17/11/2019 16:57:16:

I made the simple jig, but instead of two welded legs to the bridge, I tapped the top plate and now have two 3/8" unf long threaded bolts in. I had thought about having each end of the bushes with turned spigots, but plate holes were in before I got to thinking on a bit.

Mike.

You could weld a ring around each bush then turn that down to form a shoulder

[John ReeseParticipant @johnreese12848]

My preference would be a bush with a shoulder on the OD to set depth and squareness.

[sparky mikeParticipant @sparkymike]

Hi John,

A solid round piece of bar , counter bored to the depth of the bush overhang and a good fit on the o/d of the bush, in conjunction with my jig on the other end should work well. Hope for a warmish day in the workshop tomorrow !!

Mike.

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