Steel info

hey, i need a tid bit of help. I did a small search (i'll admit it wasn't too thorough) and couldn't find out what steel to use for my own frame bracing. Now I know 70's japanese steel isn't the greatest in quality but i also know not to use a mild steel. I talked to my instructor about it but he isn't quite sure. He told me to steer clear of high quality strength and hard steels like chrome-moly because it can potentially crack the frame. I really don't feel like just guessing what steel to use. Thanks in advance guys.

I just got a 12x12 plate of 3/8 mild steel to cut up and use for bracing. I'm going to try and get it welded in this weekend. Remind me to let you know how it goes. I'll post pics when it's done.

Why don't you want to use mild steel? And all the pre-made brace kits are 4130 Chromoly. They've been making those kits for years and I've never heard a guy said his frame cracked.

I'm using 3/4" mild steel tubing (not sure the wall thickness) for most of my bracing on my Pro-street. I'm also using mild steel plate for the smaller brackets and the mono-shock linkage mounts.

Later, Doug

The frame is mild steel, nothing special.
Mild steel is perfectly acceptable for frame bracing. I suspect the 4130 spec for frame bracing kits is just used for marketing, just like the "Billet" aluminum aftermarket parts sold.

ill see what happens with don because i get free mild steel at school. concerning 4130 i believe what my instructor was getting at was the fact that using a harder steel would put more stress on the bracing points and possibly causing fractures but really i think he was just kinda saying its overkill for the frames unless someone is using these frames for 130+ hp i dont think it matters other then the fact i don't wanna poor money into chrome-moly when i can pic up mild steel for free.
i agree with the marketing ploy.

The frames of these bikes are 1" x 1/8" wall DOM (Drawn Over Mandrel) mild steel. When welding in bracing, you want to use metal of similar strength/flex characteristic's to prevent the frame from cracking/failing due to stress. 4130 is much stiffer than mild steel and is not something that I would weld into a mild steel frame...you would be setting the frame up to fail.

Second thing to consider is the type of welding to be used. TIG is the preferred method, followed by MIG. The advantage to TIG is the control it allows of the heat and the weld penetration. You need complete penetration of the weld for strength, without too much heat to effect the structure of the parent metal. Any application of heat effects this structure, but too much causes weakness and the potential for stress cracking of the tube at the tube/weld join.

looks like it'll be my TIG project then although my class is a little focused on oxy-acetylene but i could always preheat the frame. I'm not a big fan of MIG; I'm a little too methodical for it. That and i don't have a inert gas for my MIG welder.

Have any old frames or pieces of frames laying around? Cut the pieces you need from those and the diameter would be the right size and the steel would be the same, so that shouldn't cause any problems. Right? I'm no expert on welding.

That'll work...DOM tubing is not that expensive though and you can source it at any metal shop.

yeah id say mild steel,thats all i use but im basically cheap! stick,mig or tig will work depending on your skill level and what you have access to.