Damaged Front (axel) Spindle Threads

[grant lyon]

Any recommendations on how to repair damaged threads on a front axel spindle? The first two (outboard) spindle threads have flattened crests. The corresponding clamp nut is damaged too (it won't thread properly onto the other spindle).

Is this something I can clean up with std Sear Metric die (and tap) tools? I ask because the spindle threads are ~17.8, say 18mm but the pitch seems to be finer than the garden variety Sears catalog tools.

I think, but don't know the previous installation was cross-threaded. Bugs me. I'm quite sure I backed of the clamp tightening screw before turning the clamp nut itself. The clamp nut was relatively hard to unscrew -- like a cross thread. Any way I could have caused a cross threaded condition in the process of removing the clamp nut?

Based on the damage, it looks to me as if the spindle is much harder steel than then clamp nut. I hope this is true, so the nut is sacrifically damaged to save the spindle.

[surflvr911sc]

I’d get a new nut and dress the threads w/ a very fine file. Of course this is only if the nut will thread on past the bad threads once it’s back together. If the nut ends up sitting right on the damaged threads you might need to replace the strut if it’s that bad. If you can, post a pic and the guys should be able to help w/ that determination.

You can get an inexpensive jewelers file set at Sears or Harbor Freight.

[grant lyon]

I was thinking along that line -- except for that downside of trashing the whole strut. The threads are not that bad, just flattened down about 1/3 of the crest for those 1st two threads. That flattening plus some distortion is what I figure causes the problem with the good nut. If memory serves me, I could probably take those two outer spindle threads off completely and still have plenty of threads to grip all the clamp nut threads.

Hoping there's a way to get split die (not sure of the term) up on the good threads and use them as a guide to reform the buggered threads. I've done the file trick elsewhere; maybe I'm just being a nervous Nellie here.

[grant lyon]

photos, two resolutions

[surflvr911sc]

I think you' re fine. Dress them up, put a new nut on there, and you should be good to go.

[fred cook]

If you can't get a die to start correctly on the threads, you might be able to cut a (wheel bearing) nut in half with a dremel, place the nut on the spindle behind the bad threads, clamp the two halves of the nut together and slowly/carefully back the nut off the spindle. Once you have done this a time or two, the rethreading die should start straight on the threads.

Good Luck,

Fred Cook
'80 911SC coupe

[Boss]

There are threading dies (really cleanup dies) available just for spindle threads. Probably not a sears item but any professional tool place should have them.

snap-on example

Note - this is just an example, I don't know the correct size/pitch offhand.

Considering the cost of a new, or even used, strut and the hassle of replacing it, I would be very careful to avoid messing it up worse.

Hope this helps.

[dad911]

I bought the snap-on kit. Covers std & metric. http://buy1.snapon.com/catalog/pro_det.asp?tool=all&item_ID=56049&group_ID=1148&store=snapon-store&dir=catalog

The Thread Restorer Files are made with the correct pitch.

[IROC]

I second the mention of a "thread restoring file". They will fix threads based on thread pitch and will work on any diameter. I have used one of these to fix things like this when nothing else would work.

Type in part number 8309A11 on www.mcmaster.com for an example.

Mike

[grant lyon]

Just a message of thanks to all with suggestions. A thread restoring file from McMasters-Carr did the trick.

[grant lyon]

Just a follow-up message of thanks to all those with suggestions, and some comments on my lesson. A thread restoring file from McMasters-Carr did the trick. Some comments for posterity. I enclose two photos post filing rework. For reference: looking a the right end of the spindle the groove is at 1200. I had to take off a partially formed thread from 0900 to 1200 and start the new thread at 1200-->0100 (on the groove side away from the viewer). Also, as it turned out, I started about midway down the spindle where I thought I had good threads and worked to the right to correct the flattened threads on the rightmost side. When I tried to thread the nut on it didn't mesh properly with the untouch threads. So, I had to also run the file back up on the left 1/2 of the spindle threads to get the locking nut to thread past ~ the 1/2 point. Point being, I think the restoring file starting from a little more to the left (on better threads) would have been the optimum solution. Also, I doubt a die would have been able to get good grip on good threads to guide the re-forming of the buggered threads. I could be wrong, but the thread restoration file looks to be a sufficient if not necessary part of the solution for this problem. Car is back on the road. Much appreciate your help.