Positioning bushes for welding

This topic has 14 replies, 9 voices, and was last updated 17 November 2019 at 20:53 by sparky mike.

Viewing 15 posts - 1 through 15 (of 15 total)

Author

Posts
17 November 2019 at 11:01 #437632
sparky mike
Participant
@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.
Advert

17 November 2019 at 11:01 #19532
sparky mike
Participant
@sparkymike
17 November 2019 at 11:08 #437636
pgk pgk
Participant
@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
17 November 2019 at 11:09 #437637
ega
Participant
@ega
I would tack them, check, adjust as necessary and then finish weld.
17 November 2019 at 12:09 #437647
Daniel
Participant
@daniel
+1 to ega's post.

Tack weld, adjust to final position, finish weld;

ATB,

Daniel
17 November 2019 at 13:17 #437649
sparky mike
Participant
@sparkymike
It has to very accurate so think this is the way I am going.

Thanks for replies anyway.

Mike.
17 November 2019 at 13:19 #437650
sparky mike
Participant
@sparkymike
Photo
17 November 2019 at 13:29 #437651
Martin Connelly
Participant
@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
17 November 2019 at 14:26 #437662
Dave Halford
Participant
@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.
17 November 2019 at 15:06 #437672
Nicholas Farr
Participant
@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.
17 November 2019 at 16:57 #437708
sparky mike
Participant
@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.
17 November 2019 at 17:33 #437717
Brian Oldford
Participant
@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.
17 November 2019 at 17:50 #437720
Dave Halford
Participant
@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
17 November 2019 at 18:19 #437724
John Reese
Participant
@johnreese12848
My preference would be a bush with a shoulder on the OD to set depth and squareness.
17 November 2019 at 20:53 #437750
sparky mike
Participant
@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.
Author

Posts