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Ted
12-01-2005, 10:12 PM
I need to replace some threads (3/8 in.) on the side of a drill stem. This set of threads will secure a collar holding bolt on a boring machine(machine used to bore under roads, etc. for cable companys). My question is, will the heli coil threads hold up under daily disassembly and reassembly conditions? If not what do I need to do?

ScottS
12-01-2005, 10:41 PM
Hi Ted.

I never had had much luck with the wire helicoils. I have been a recent convert to keensert type thread repair.

http://www.keensert.com/

Here is their website. They are a little more user friendly. You can use normal Taps with them there is a chart for the correct size drill to use. Go through the site to see the directions and see if they will work for you.

rsr911
12-01-2005, 11:26 PM
Also look at Timecerts, these are used extensively to repair or reinforce Aluminum engine blocks for studs. They are called Timecerts because the inner and outer threads are timed to each other so they have relatively uniform wall thickness in a smaller diameter insert.

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-Christian D. Sokolowski

John Garner
12-01-2005, 11:35 PM
Ted --

My experience matches Scott's, wound-wire thread repair inserts haven't done as well by me as have solid inserts.

Key-locking inserts such as the Keen-Sert brand that Scott mentions are excellent, but they sometimes need standard-but-uncommon tap sizes and always need special tooling to set the keys.

An alternative to a key-locking insert is one that is retained with an adhesive. The commercial version is the E-Z Lock insert, and they have a good website at www.ezlok.com (http://www.ezlok.com) OR a homemade insert glued in place with an anaerobic thread locking compound (Loc-Tite being the best-known brand) or an epoxy (J B Weld usually works well) may be your ticket out of a jam.

John

WJHartson
12-02-2005, 08:41 AM
As others have said the wire helicoil may not be your best option for this application. You said that this is for the locking screw in a collar. Since it is a locking collar can you just drill and tap another hole somewhere else on the collar for the screw.

Joe

DR
12-02-2005, 09:48 AM
"My question is, will the heli coil threads hold up under daily disassembly and reassembly conditions? If not what do I need to do? "

I believe there are different varieties of Helicoil brand inserts. They're all wire type, but some may be designed for frequent removal conditions.

I say this because I make a customer's part in which he inserts Helicoils. While perfecting the design he showed me a few Helicoils, all appeared to be identical to me. He explained they had subtle differences depending on the intended useage.

My customer purchases Helicoils in large quantities, whether the different varieties are available to the small quantity purchaser is another question.

radish1us
12-02-2005, 06:15 PM
To answer the first part of your question.
Heli coil inserts will start to deteriate very quickly with constant retentioning of the screws/bolts, they are mainly used in a once tightened then left alone situation.
By undoing and redoing the bolts, the actual heli coil thread will start to eat into the parent metal and then everything becomes loose again, only this time there is a far larger hole to try and fix up.
For a fix it once and do it RIGHT, go for the Keenserts, the best, bar none.
Had a lot to do with these two brands with a nitro fuel bike and the best were, without a doubt, the Keenserts.
This machine needed constant attention and after each pass, it was ripped apart to see what damage had been done and then put back together again very quickly.
KEENSERTS were the ONLY thing that could handle this.


radish

coles-webb
12-02-2005, 06:29 PM
I have to agree, I have put hundreds of Heli-coils in things and they are great as long as you don't take it apart. You can get helicoils with a locking feature (2 of the center wires are crimped to hold in the bolt). Keenserts are good but remember that the tap drill size is not a standard tap drill size (as standard taps are used, unlike heli-coils). If you use a normal tap drill size you will never get the keensert in and will bend the pins. The only thing about keen serts that sucks is replacing them. Time serts are good also. And yes ther are different types of Heli-Coils, locking and non-locking, magnetic and non-magnetic.

http://www.timesert.com/index.html

http://www.emhart.com/products/helicoil.html

http://www.manufacturingtalk.com/news/hec/hec103.html

http://www.keensert.com/

Mike

[This message has been edited by coles-webb (edited 12-02-2005).]

[This message has been edited by coles-webb (edited 12-02-2005).]

[This message has been edited by coles-webb (edited 12-02-2005).]

Ted
12-02-2005, 07:55 PM
Guy’s I appreciate the input. I was worried that the frequent use of this application would be more than the heli-coil could take.

Looks like about everyone else feels the same. I like the feedback on the other options and I plan to try the keensert brand.

I’m glad we have a site such as this one, to call on each other’s expertise.
Thanks again