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Stripped insert, repair methods


Steve Dold
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Well, I really did it good this time. I was putting bindings on my brand new Renntiger tonight and stripped a middle insert. It stripped really easily, it wasn't cross-threaded and I didn't put much torque on it at all. I had even greased the threads of the screw slightly, so there was no galling going on. The screw looked allright, so I suspect the insert might have been defective.

Anyone have any ideas? I'm thinking of tapping it with a 1/4-20 bottoming tap, but I thought I'd better check here first.

Would this weaken the insert much?

Steve

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Guest Jagger

Steve try using A 6 mm Helicoil thread repair, Ive used them in the past and they work well and then all your screws are still the same then youdon't have to worry about using the wrong screw in a re-tapped hole.

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I'll second the helicoil option. I have not done it myself, but I watched a competent person install one on my board. It is neither difficult nor time consuming, but requires a great deal of commitment. Once it is done, however, you should have the equivalent of a new insert.

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Date: December 09, 2002 10:26 PM

Author: Fin (fin@bomberonline.com)

Subject: Threads-O-Roma

Mark,

I would suggest fixing the damaged insert. You could do a "quick fix" and put a washer under the bolt but then you are effecting the amount of thread engagement. You want at least 3 full turns of engagement.

So the thing to do it just retap the threads. However, the key is to use a "bottoming" tap. The taps you get at your hardware store are generally not bottoming and have a "pointy" tip. This helps start a new threaded hole but will bottom out before it can thread those last few threads in your damaged insert. Find a good tooling shop or catalog a get an M6-1.0 Bottoming Tap. Works like a champ. We have revived many a lost cause boards here at Bomber with this guy.

After you chase the damaged threads check that bolt every so often to make sure it holds a good tension and stays tight. If it keeps coming loose, you need to go to the next ( and slightly drastic) step which is to over size the threads to 1/4-20 standard threads. Easy to do with the right tools. Not going to go into it here but e-mail or call me if you need to go this far.

Or just do more skidded turns as those are generally easier on the inserts ;)

Fin

BomberOnline.com

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Thanks, guys. The Helicoil sounds like the best method, as long as the insert has enough material for the process. I hope it does!

I can live with having one 1/4-20 hole if it's better structurally. Or 1/4-28?

I guess what I'm wondering is, which method removes the lease amount of material.

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From a purely mechanical point of view, I'd try re-tapping it to 1/4" first. You won't remove as much material.

Then, if that fails for some reason, you could try the helicoil. You could not go back to 1/4" if the helicoil fails though.

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As one of the contributors on that thread I pointed out some of the problems w/ the helicoil. I've done a lot of them in my work as a auto tech. Such as; can you get one short enough to fully insert into the exsisting insert, you cannot find a bottoming tap the size of the O.D. of the tap you use to prepare the hole for the insert, and the one mentioned already, the hole will not be able to be tapped out to 1/4 N.F. thread after the repair in the remote possibility of another stripped insert. I know, I'm looking at the glass half full, but you gotta see it both ways before you start! The up side of the helicoil is you will most likely create the strongest insert in your board if it is done properly.

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Guest Pre School Rider

O.K.,here's the 'action plan' in steps intended to NOT do something irreversible or permanently damaging to the insert and board.First,get a bottom tap in M-6 1.0 threading(this threading is 25.4 tpi,but of course the Euros don't use inches).That should re-groove the original threading if it's not too hashed out, second;If the insert dosen't like the original threading(say the threading is total mush 3-4mm down into the insert),then 1/4-28-tpi is the next closest thing you'll find.A bottom-end tap is again the tool for the job.Going to machinist-supply companies like Mc Master-Carr will get you taps and bolts(preferably in Stainless Steel). [ I could toss in 7 mm 1.0 bolts/threading/taps,but you probably won't see these stateside,and rarely elsewhere to boot. ] IF by this time nothing works,then Helicoils are ...a possibility.By now,you'll have used up most of the insert's metalurgical integrity on it's outer casing.The next threading(not counting the unobtainable 7mm)would be a 5/16-24-tpi tap with a helicoil of 1/4-28-tpi. If THIS fails,go talk to Sun Valley Ski-Tools and buy one of my old insert replacement kits,which are drilled Through the board and are to be epoxied into the deck.I believe they make/sell both 6mm and 1/4-20-tpi versions still.Don't bother with the plastic stick-on plugs,never did stay put...

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