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I was going to leave bodywork on the 5 to those that know far more than I, but with lockdown sending me slowly mad(madder) I've decided to have a go at sorting out the bonnet on VPK. I'm thinking that I'm going to have to separate the front inner frame of the bonnet from the bonnet skin to deal with some rust. Now I have the spot weld removing thingy and in my head at least fairly clear on what needs doing. My question relates to putting it all back together so do I repair all of the holes and grind off all of the weld 'stubs' and basically put every thing back to how it was in the factory before it was all welded up in the first place spray with weld though primer and then put my newly acquired spot welder to use or do I leave the holes and weld 'stubs' in place and Mig it back together ? I do have some large copper heat sink to reduce warpage. I think it should be the former process but your advice would be much appreciated. 

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Graham

yes take the front and rear frame out using the spot weld drill ,if you are careful the frame comes out with no holes , I normally separate the inner frame into front and rear where the cross brace meets the front section,  I normally clean everything up treat as necessary use weld through primer on the joints and bondarust  elsewhere, I the clamp frame back in and plug weld the drills , it is a good idea to put the 2 strengthening strips each side at the top where you lift the bonnet from when opening, I am sure Stewart will have some pictures.

graham

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Hi Graham,

I did this in the early 90's. it is the only way to get into all the rust and to sort it out. 

I don't think you will have a problem with warping as the welds are all along flanges..

Remove the weld bead in contact areas but leave the remaining weld bead as is.  If you are spot welding then there shouldn't be that much dressing needed.

I wish I knew back then what I know now.  Remove as much rust as possible. Do not rely on the rust converters. Remove as much surface rust then apply (or dip) something like DeOxC

This pickles down into the metal structure. Then go for the BondAprimer.  Then a decent gloss top coat to allow water/moisture to run off. 

These are my rear side supports from Stuarts template. I made mine in 1mm steel.  I had to shape the SP electrodes to get into the sides and then MIG plug weld the flat section.

Place a thin piece of wood between the bonnet skin and the inner rib to stop heat transfer.

 

Roger 

P1040667a.jpg

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Whilst on the subject I have 2 types of spot weld cutters one type looks like a mini hole saw the other like a flat faced twist drill with a centre point any recommendations for which is the better tool ?

 

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As said the Mini hole saw is good I tend to centre punch and drill with a 1.5mm drill then use the cutter as otherwise sometimes the pin will skate off. I also use a bit or cutting oil in a pot and dip the bit into it that way they last a lot longer.

The drill with the point I tend to use once when plug welding to remove any paint from the panel I'm plug welding to as I found I get better penetration.

Andy 

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I found that the cobalt ones which are the 8mm flat faced bit with a centre point worked best.  The mini hole saw didn't last very long.  And you can resharpen the cobalt ones.

Rgds Ian

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8mm Cobalt ones are the best. identity and mark each spot weld and then carefully drill through one layer only (you can always tell when youve gone deep enough as you`ll get a flurry of rust as soon as you break through the first layer) Then when you replace the inner you use the 8mm hole to plug weld through. The re-enforcing plates are easy to make and if you want I can send you my templates. I  make them out of 18Gauge as they need to be strong and spot weld them in and plug weld to the top inner frame again using 8mm holes.

These drills are good Spot weld drill 8mm

Plates pictured below

Stuart.

 

Marks TR5 510.jpg

Marks TR5 511.jpg

Marks TR5 512.jpg

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16 minutes ago, signalredshaker said:

Something that might be simpler and seems just as effective over several years- a strip of steel spot-welded as shown. No buckling yet and really inexpensive and discrete.

James

bonnet bit.jpg

I did that with my bonnet 26 yrs ago, it lasted about 15 yrs before it split again ;)

Stuart.

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The simple single plate flange stiffener looks attractive due t its' simplicity but Stuarts triangular gusset plate is a belt and braces.

And looks good at the usual club meet bonnet up situation.

 

Roger

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11 hours ago, stuart said:

8mm Cobalt ones are the best. identity and mark each spot weld and then carefully drill through one layer only (you can always tell when youve gone deep enough as you`ll get a flurry of rust as soon as you break through the first layer) Then when you replace the inner you use the 8mm hole to plug weld through. The re-enforcing plates are easy to make and if you want I can send you my templates. I  make them out of 18Gauge as they need to be strong and spot weld them in and plug weld to the top inner frame again using 8mm holes.

These drills are good Spot weld drill 8mm

Plates pictured below

Stuart.

 

Marks TR5 510.jpg

Marks TR5 511.jpg

Marks TR5 512.jpg

Hi Stuart yes if I could have a copy of your template that would be great 

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11 hours ago, Graham said:

Hi Stuart yes if I could have a copy of your template that would be great 

PM me your address and I will send them up.

Stuart.

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