Thread strength for long arms, mat'l Q.

Ted Z · Jul 30, 2003

I am considering having male threaded inserts made up of chromoly or another mat'l not sure yet. I have access to someone who can grind the threads for me. Would this be stronger than allthread?

I am curious cuz i have seen a few pix of long arms with bent allthread.

I am talking about the blue part in this drawing. (the red is the arm DOM tubing)

4ward · Jul 30, 2003

Grinding isn't any stronger than having them cut on a lathe,but it's more expensive if you like to blow your money. Rolled is stronger, but only in the thread area. It's not applicable to what you are looking for.

CRASH · Jul 30, 2003

The key with the threaded portion of the arm is to keep it as short as possible, and use B-7 grade all-thread. Not that the bent ones you see had a fairly long exposed portion of thread.

CRASH

xj4rocks · Jul 30, 2003

And obviously thicker diameter is more resistent to bending. but ditto on the B-7 grade stuff. I bought 6" long studs from http://www.mcmastercarr.com/ worked like a champ. I think mine were 1"-8 or something like that.

Bender · Jul 30, 2003

Why don't you just go up a size?? i.e. larger diameter thread

CRASH · Jul 30, 2003

I'm using, 1.25", B-7 stock, btw.

CRASH

Vug · Jul 30, 2003

Ted,

I agree with crash and xj4rocks. The B7 or B7M studs available from McMaster-Carr are a chrome-moly alloy (4140).

The problem I see with making the adapter as you designed is the undercut that will be at the end of the threaded portion. This will be your weak point.

McMaster-Carr is your friend. They carry about everything.

Vug

Bender · Jul 30, 2003

Another route would be to buy some grade 5 bolts (120 psi instead of the B7's 105 psi) that are long enough so you can cut the heads off, slip the unsplined portion in your tube and weld it in. For the adjustable side you can either

1) tap some tubing,
2) weld some nuts together and have them machined down to fit inside some tube,
3) butt weld some nuts to the end of some tubing approximately the same O.D as the nut, grind down any extra nut material sticking out farther than the tube O.D. and sleeve the entire butt welded nut/tube with a larger tube with an I.D matching the O.D of your butt welded tube.

I'd say go at least 1.25" O.D for your rod or bolt assuming a lower control arm of length >30".

Weasel · Jul 30, 2003

buy the B7 stuff everyone else said. Having your own ground would probably end up with a weaker thread then if you just bought reagualr all thread. Grinding is ok but it cuts acrossed the grain giving a weaker thread as rolled thread don't disrub the grain flow. And I would be careful welding anythign as you could make the parts more brittle.

Ted Z · Jul 30, 2003

so we can rule out grinding.... Now do i weld the B7 into a tube or directly to my RE Superflex housing or weld a threaded adaptor onto the RE SF housing? basically should i avoid welding the B7 completely?

Weasel · Jul 30, 2003

According to Carroll Smith when you weld 4130 you must pre heat the part first then after welding heat the weld up to between a dark or medium cherry and allow to cool in still air or covered in dry sand. This will ensure yur weld has been stress relived and not more brittle then the rest of the part. Or you could just use jam nuts on both ends.

xj4rocks · Jul 30, 2003

I welded the B7 stud right to the Johnny joint housing. Never had any problems with it. I've seen some weld a BIG nut to the JJ/bushing housing and then thread the Stud into it and then weld the stud to the nut. This puts the load on the nut which probably isn't B7 and the weld between the stud and nut is to keep it from turning.

Thread strength for long arms, mat'l Q.

Ted Z

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4ward

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CRASH

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xj4rocks

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Bender

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CRASH

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Vug

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Bender

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Weasel

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Ted Z

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Weasel

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xj4rocks

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