Streetneat on oxy hammerwelding

[streetneat]

 This is to answer  a PM and I thought I may as well post it here as well:
hi streetneat,
                   great stuff,could you explain oxy hammerwelding to the forum oneday.

cheers geoff.....
Once again if you go to http://streetneat.com/ and go to current jobs in the shop album all this and more is answered... Basically oxy hammer welding is the forging of the red hot weld by hammer and dolly work .. this forces all the steel into itself for a very strong weld that requires little if any clean up.. floors are the best area for this and it requires some poor bugger on the other side ready with a dolly and their own panel hammer so between the two of you you can get a seemingly straight welded join. Given a light stipple coat of sprayable tar or stone guard this becomes nearly undectable ... Cheers streetneat...

[nicko]

ok i was going to ask what body filing without bog was, so i assume its filing smooth the buildup from the hammerwelding is it?.
reguards Nicko

[streetneat]

Body filing without using bog is just another way to panel beat the lows up and make them into highs then using a dreadnaught STEEL file (not a wider tooth bog file) you simply stand there and file away and keep tapping up the lows until you have something that only requires the thinnest of wipes of two pack blade filler  (not bog) to finish it of prior to paint... I use Dolphin glaze and still have the same tin of bog I have owned in the panelshop for two years... Dont be fooled into think that lead wiping means that no small skim of final glaze filler is not needed.. the lead and steel MUST be coated with an epoxy primer first as nothing will stick to it otherwise.... The factory used red lead or oxide primer to build up a thick coat that meant the minor imperfections could be filled..and they never worried about the finish too much... too many cars to build..... cheers streetneat

[Glenn 'Stinky' Stankevicius]

I have heard that it is better to use a bit more bog than "over-work" a panel or file-finish it. I have also heard of file finish panel jobs that left the panel too thin then they buckle under road use.
What's your take on this, Streetneat?

[streetneat]

Over filing a panel will do some of what  you mentioned... However it takes an awful lot of filing to render a panel useles... A early Holden panel anyways.... The problem with the use of bog is that it tends to be over - used and unless applied over an epoxy primer when its more than just a skim, its going to have a limited life span. Epoxy primer acts as an adhesion promoter as well as a excellent means of sealing up the bare steel and existing paintwork. The filing of a body is used as a guide really to determine where the panel needs to be worked. In order to file a panel too thin  in a large enough area that it will destroy the over all integrity of the panel , you need to be filing for a very ,very long time.....So you are sort of right  but its a bit of an urban myth....

[Ed]

Hi Streetneat,

When hammerwelding, is this usually a two man job?  one to hold the torch

[Ed]

oops, dunno what happened there..

isit a 2 man job? 1 to work torch and other to hammer and dolly?

can u overheat the area and harden the metal?

Can u give us a brief take on heat shrinking to remove dents and depressions in panels?
maybe what to do if u accidentally cause a panel to suck in  or oil can?

Cheers

Ed

[Glenn 'Stinky' Stankevicius]

Hey Ed, ya gotta watch the mouse when typing, the prompt follows the arrow. If you pushed the mouse up whilst part way through a msg you'll start typing in the subject and a CR will post the msg.

[streetneat]

Ok then I will try my best to explain heat shrinking. In a nut shell if you work with metal and especially panel steel you get to know its properties and limitations...
This  knowledge is only gathered through experimentation....years of it.... so to try and explain it  here is a bit difficult - so here goes... The more times a panel is heated and rapidly cooled it will become "work hardened"  ...this means just what is says... its hard to work and get to move around the way you want it to.... also it changes the properties of the steel so this means it will become brittle and will crack easier... This is  desirable when tool making
( hardening ) but not when working with shaped panels. The first thing to remember is that the panels  are formed under pressure... up to 50 tons of it to be exact.. so introducing heat or even sandblating will stress relieve the steel and it will look for the easy way to relax itself... This presents itself as the oil canning that was mentioned ..the easiest way to counter act this is by heat shrinking... Heat shrinking is an aquired art form... Basicially it involves heat a small patch of steel, without moving the acetylene torch at all until a "cherry " or heat spot starts to rise up. This is quickly hammered down after the torch is with drawn in a circular motion working in towards the center or away from the centre of the cherry.. depending on what you are trying to achieve..... The panel is quickly quenched with a damp water soaked rag and even this is applied in  a circular motion, mainly to arrest the heat from escaping  into the rest of the panel. This action causes the molecules of steel to rush toward the cooling source and this is the main element of the shrinking process. The heated cherry, as its hammered with a suitable dolly backing it, is also prelimarily shrinking the steel.The panel is then cast over with a steel body file and high and low spots are addressed...  This is only a brief response to a wide ranging question. I cannot stress enough that this requires years of practise to master perfectly and even after all these years of panel beating ( nearly 20 of them) I am still learning the properties of steel and what happens to it when heat is applied...Cheers streetneat