search for a Mechanical Engineering design guide.  The hole already there meets theses min specs.  I would use that a min guideline. They already took into account the various forces that will be applied to the material during it's id'ed lifetime.  Forces = stress, strain, thermal cycles and vibration,,,  Engineers also use a min of 2x life  (breaks but not safety critical) to 4x life (life safety)    There's other reasons for failures but the joke in my business is it's impossible to design for "stupid"     

I personally wouldn't do it.

If you are swarn to doing it I would fish plate a piece of 3/16 material compatable with that arm, the length and width of the arm widening the fish plate to mimic the original piece on the end,a piece of cake for a professional  welder.....jj. 

GPatrick wrote:

I think if you look at the picture you posted you are staring at the answer.  Look at the cross section where the current bolt hole is and I would think that you would need that amount or more since you are shortening the arm.  If you have a sacrificial spare you may want to look at cutting and re-welding.  There were a series of posts a while back on someone who modified a pitman arm for a home-built P/S mod and from what I could see, they did a good and safe job.  With proper welding, heat treatment, etc., you may end up with a better/safer arm than drilling through a somewhat narrow cross-section.  But I'm sure others have opinions to offer - I just thought I'd throw the first one out.

That was me and thanks for the compliment. 

Daze, I think you have two considerations:  you need enough steel around the hole and you need a machined surface.  I think you also have two ways to accomplish that: you could cut it and weld it like I did my pitman arm, or you could drill the hole where it needs to be and run some beads around the sides of the hole for strength, and the top so it can be machined.  In this case, I'd do the latter since the former requires making a jig to hold everything in place.  I'm not a pro welder so I took my pitman arm to a pro and had him preheat it to 450 F.  As soon as he was done, I buried the pitman arm in kitty litter so it would cool slowly.  Were I at home, I'd have popped it into a preheated oven and gradually reduced the temperature.  Also, as I noted I'm not a pro welder, but I do know that a special rod is needed for optimal strength.  I seem to remember 7018, but double check me. 

BTW, don't forget that many aftermarket suspension and driveline components are welded and no one gives them a second thought.  Do a good job and it will be safe.

Last edited by jkordzi (5/08/2015 10:54 PM)

Not on 60s ford spindles but on earlier 56 ford spindles I've seen it done to them. But the few that I've seen they heat up the arm and flatten it out and then drill out the new hole. Most times or they just drill it out. I would think you'd be fine there's several other spindles out there that have far less material thickness and have large wholes for the tie rods.  on newer ford and some gms spindles they have have a straight hole for the tie Rod. So I don't see a problem with it.  Down side how ever you might have to move the rack assembly forward to accommodate the for shortening the steering arm.  Also if you have shortened the steering arm enough you could even use a Ford Taurus rack and pinion escourt or even a later j rack with end mounted tie rods. The later j rack puts out 6" 1/2" less then the earlier center mount jrack.

Last edited by True74yamaha (5/08/2015 11:55 PM)

Could the arm be machined parallel on both side and then make a piece that mounts inboard but sandwitches the steering arm, then welded, bolted or both. Would have to shorten up some threaded section of either the rack or tie rod end. But if mounting the tie rod end hole inboard loses some turning radius due to mechanical interference then I guess the idea was no good haha.

Give it a swipe with a file, and if it cuts easily, it is not hard. If it is hard and the file won't touch it, I would go to plan B. If is cuts fairly good with a file, it is still ductile and should be tough enough based on base material and not heat treat. I have seen many steering arms re-drilled or cut and welded without issues. I cut off the end of some and drilled and tapped for a screw in end so I could adjust them.It worked great, even when I crashed and bent everything on the track. The screwed in joint held up perfectly, but the spindle broke off at the inner bearing.