Threaded rod to flat bar

  1. ChrisBailey

    ChrisBailey New Member

    Messages:
    8
    Location:
    Kings Lynn, Norfolk, UK
    Hi, this is my first post and Im a total beginner. My welding experience to date is a plug weld to hold a plate to box section and tacking a tab onto sheet metal to hold an accelerator cable. This was on an old Clarke 90 mig, about 10 years ago.

    As I have a project car under restoration, I got myself a new welder (clarke wasnt mine). Its a TecArc c181. Ive got a 10ltre adams gas 5% co2 argon mix, argon regulator, a cheap ADF helmet and some new gloves. 15Kgs of wire too.
    All baught after lots of reading on here and the hope it will be the only welder I ever need.

    So, first project is to fix a performance pedal box to the car. Now the car is based on a classic beetle, its had welding done before me where they reinforced the floorpan by welding box section all around and across the underneath.
    To get enough room in the car for comfortable seating, Ive had to cut into the napoleon hat (see classic beetle) to move the pedalbox as far forwards as possible. Now in this location, I cannot put bolts or set screws through the floor pan as the holes line up with the reinforcement bars.
    My brainwave was to weld threaded rod (m10) to the floor pan, then put nuts on to fix the pedalbox down.
    As the floorpan is made of sheet steel, I thought it was a good idea to put some flat bar down to hold the threaded rod (gives a bit more to weld to).
    I think the easiest way to weld this would be to drill a hole into the flat bar, clamp the threaded rod perpendicular and then plug weld.
    Do you think this would work?
    Any problems?

    I may also need to put in some reinforcement to the napoleon hat that I cut earlier.
    Im thinking some box section to create a square frame. Pedal box will just sit upto this frame.
    Any better ideas?

    Ill try and put some pictures up tomorrow.
    Its hard to describe.

    Anyway, this will be my first welding project. Ill also put some pictures of the welding up.

    Thanks in advance
    Chris
     
  2. Arclikeharrypotter Member

    Messages:
    1,100
    Location:
    Northampton
    You could drill and tap the flat bar to m10 then plug weld. Help keep it straight and add some piece of mind.
     
    8ob, wyn, Ashley Burton and 1 other person like this.
  3. Spark plug

    Spark plug Member

    Messages:
    3,602
    Location:
    Durham, England
    Or drill and countersink the flat bar and weld a countersink bolt in from the back before welding in place.
     
    anjum and 8ob like this.
  4. evobilly666 Member

    Messages:
    178
    Location:
    New Forest
    As spark plug says above. Also, I advise you do some practice runs using similar materials and then do some destructive testing. Pedal boxes are safety critical and should be approached with caution. That said, it’s perfectly doable, even for a first “real” project. Welcome btw.
     
  5. gaz_moose Member

    Messages:
    988
    Location:
    tamworth staffordshire
    don't use threaded bar. buy some 'counter sunk bolts' grade 8.8 M8 minimum. then drill and counter sink the flat bar from underneath and run a bead of weld around the bolt head. don't buy BZP finish but chemically blackened. drill the countersink a bit deeper then you can grind it flush once welded.
     
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  6. ChrisBailey

    ChrisBailey New Member

    Messages:
    8
    Location:
    Kings Lynn, Norfolk, UK
    How thick should the flat bar be to use counter sunk bolts?
    Ive only got 3mm flat bar to hand.
     
  7. tom2207 Member

    Messages:
    1,604
    Location:
    uk northern ireland
    thread bar is horrid stuff if you only get it at a diy place , often galved , which does not help ,
    pic may help
     
  8. ChrisBailey

    ChrisBailey New Member

    Messages:
    8
    Location:
    Kings Lynn, Norfolk, UK
    The threaded bar I have is stainless steel (I know probably going to make first time welding even harder). It seems OK, nuts run up and down it without catching.

    I'm tempted to give it a go with the threaded bar, at-least just one of the four fixings. I'll smack it with a hammer and see if it stands up.
    I've got a quote for some more flat bar steel (5mm by 30mm by 6m) and some box section 25mm2 1.5mm thick and 6m long.
    £36 if I collect, its 10 mins from me.
    I'll have to order some counter sunk bolts and some other bits to do it the way you are all suggesting.
    Maybe next week now?

    Here is some pictures of the task at hand.

    [​IMG]
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    [​IMG]

    [​IMG]

    [​IMG]
     
  9. ChrisBailey

    ChrisBailey New Member

    Messages:
    8
    Location:
    Kings Lynn, Norfolk, UK
    So after a few attempts, I got this.

    [​IMG]
    [​IMG]

    My very first attempt, I drilled smaller holes and tried to plug those. I missed the threaded rod and just filled over the holes.
    The rod just fell off.
    Tried once more, but the rid just snapped off when tightening the nut.

    I then grind it all off and redrilled the holes to 10mm same as the rod.
    Put the rod in about 1mm and turned the volts up to setting 5.
    This time much better. It stopped splattering and was easier to control.

    Ive tried to tighten a nut up on it with a half inch drive. It didnt snap.
    I also smacked it with a hammer, mainly to try and straighten up one of the rods. They dont move.

    I think i either had the wire speed too high, i had it set to 3.5 or the volts too low as the weld is pretty bulbous.

    Im going to do another one for the other side tomorrow.
     
  10. ChrisBailey

    ChrisBailey New Member

    Messages:
    8
    Location:
    Kings Lynn, Norfolk, UK
    The other side was much easier using the same settings as yesterday.

    I put nuts on all of the rods and tightened them up, they wont snap under reasonable force.

    Here is my attempt at welding on the floor pan.
    Using the same 3mm flat bar to aboutvthe same thickness on the chassis.
    I think i got one good bead, but i found it too difficult to move the torch. The access is horrible as the body is still on the floorpan just jacked up a bit.

    [​IMG]

    [​IMG]
     
  11. qwakers Member

    Messages:
    428
    Location:
    cornwall, united kingdom
    buy a rivnut tool and a box of assorted rivnuts.. by far the most useful tool i own :D bar the hammer, of course.
     
  12. eddie49 Member

    There are a few good beads that have connected well to the top surface of the new 3mm flat bar. Some of your spots/tacks are too large - I think you are holding the trigger on for too long. It looks like you're using the "thin metal technique", which is correct for 1mm steel, but welding new 3mm bar to a sound 3mm "Napoleon Hat" chassis component ( if it really is that thick ) should accept a longer continuous bead without burning through. However, those beads look like they are only penetrating the new bar, they aren't joining onto the original chassis. All I see of it is black paint and rust and holes.
    You need to cut back and clean up much more of the existing metal. The inside has to be clean at the joint too, otherwise the weld will get contaminated and will be weak. Do VW restorers normally consider this frame component to be patchable? If so, I think you will need to fabricate patches of the correct shape, flat bar isn't sufficient.
     
    Last edited: May 31, 2020
  13. ChrisBailey

    ChrisBailey New Member

    Messages:
    8
    Location:
    Kings Lynn, Norfolk, UK
    Yeah I skimped on the cleanup.
    Ill grind the welds back and reweld the bits that havent penetrated.
    Ill also clean up the weld area better with a wire cup brush.

    You can get patch pannels for the chassis. The rusty rotten bit on the right is a drain hole. Im thinking about choping this out and putting a new skin over it with sheet metal.
    Id have to replace the hole napoleon hat if i were to buy a patch pannel. Id like to avoid that.
     
  14. tom2207 Member

    Messages:
    1,604
    Location:
    uk northern ireland
    be careful that once you have ground back , ready for a re weld , you dont just do the same again , I would strongly advise you get some off cuts the same sort of thickness and practice your technique on parts that dont matter first , its way easier to throw them away than start cleaning up your car , every time you grind clean its getting thinner , your welder is well up to the job in hand so you have no problems here ,,,
    also you mention putting patches over ,,, that tends to lead to problems further down the road , you will be better cutting out the bad parts then setting a patch into the hole you cut not over the one thats there ,,, its not as tricky as it sounds , but again practice first ,,, and get a bit of copper bar its very handy for this kind of work. I do lots of this kind of work.
     
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