Welding grade 8 bolts w/ 4130 steel

[Matt Gignac]

We are planning on using 4130 welded uprights this year, with single shear studs to attach the a-arms. We've looked at making our own studs from 4130 round stock, but I'm a little sketched out about lathe-cut threads, even though the threads would not be in bending.

Has anyone tried welding a bolt to 4130 steel to use as a stud? We would weld the head to the inside of the upright, spaced about half an inch to the mounting face of our a-arms' spherical.

I am assuming this is possible as long as the carbon content is similar, and although I haven't found a definite percentage for a typical grade 8 bolt, everything i read says medium carbon alloy steel, so I'm thinking a 4130 or 4140 would be ok.

Matt Gignac
McGill Racing Team

[Brian1]

Welding a grade 8 bolt without any extra treatment for strength will make the bolt very brittle near the weld. We welded a grade 8 bolt to 4130 (similar method to what you described) for part of our chain tensioners and the bolt itself broke near the weld after some use.

[Jersey Tom]

Grade 8 is high carbon, high alloy. I think. In any case, welding it straight, as Brian said, will result in very poor matreial properties in the HAZ.

Lathe cut threads aren't that bad, certainly if theyre not in bending and not that heavily stressed (tighten for shear load only). May even be able to find a roll die for it.

[Wright D]

There are places that you can buy special 4340 bolts. 4340 might weld a bit better then grade eight, if you have fallen in love with welding bolts. http://www.reidproducts.com/na_series.php

[LU-Bolton]

Please don't weld any bolts to a 4130 upright without heat treatment. Actually, don't do it at all. Check out UWA's single shear uprights if you need some help. Welded steel stud into the upright. And knowing UWA's attention to detail, they also probably heat treated their uprights to gain back the strength lost from welding. I would without a doubt, if I chose that design path. We also have run single shear in the past with no problems. Ours consisted of threading the bolt into the upright and counterboring to allow the shoulder of the bolt to take the bending loads, not the threads. It works, although it is not an ideal solution. Hope this helps. Good luck.