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striped worm carrier cap head bolts


Singlin
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One of the holes in the dec base that accepts the worm carrier cap head bolt is striped.

What would be the best method of fixing it?

Can i temporarily still use the mount with 3 bolts on my dec axis?

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Helicoil does seem like the obvious first choice. I'd have thought the mount would be ok to use for a short while though it may struggle a bit with accuracy in DEC depending on which bolt is missing.

James

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You would need the appropriate helicoil "spring", the correct drill bit, the correct helicoil tap and a helicoil insertion tool. Being as the mount will have to be drilled anyway, it might be more straightforward to retap the existing hole to the next size up.

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I think you really need a 7mm hole to tap an M8 thread. Going M6 to M8 really has to be taking out too much work for the tap, I'm sure. I'd be tempted to see if you can find a local engineering company who can stick the mount in a drill press and do the job for you for the price of a few beers.

James

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Would the Helicoil method produce a stronger thread?

I have never overtightened the bolts, they might have been overtightened by the previous owners.

If I need to drill a larger hole then maybe placing a helicoil might be more stable solution?

I will have to do this myself as any specialized shops are two hours away.

My thoughts now are maybe purchasing a helicoil kit for a m6 bolt.

Do i have to buy the kit with a specified thread size and if so what thread size do these bolts have?

Edited by Singlin
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Depending on where it is, I think I might be tempted to go for the helicoil option. There's not a lot of metal around some of threads to be able to drill them out much larger.

I'm fairly sure (from memory) that those bolts are all M6, but it would be sensible to check first. The easiest way is probably to put a known M6 bolt into one of the other holes and see if it goes in smoothly. Otherwise you can measure the bolt -- easier if you have vernier calipers. As far as I'm aware the helicoil set tells you the size and length of the thread you want to replace, so M6 x 15mm for instance. I've not bought one in the last ten years or more though, so don't take my word as gospel on that.

James

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I have used helicoils to repair sparkplug threads in cylinder heads, they fit a steel spring as the thread so theoretically should be stronger than an aluminium thread but you need enough

thickness of metal to take the insert.

Personally I would drill and tap for the next size bolt if theres room.

Dave

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I ordered the following Helicoil kit from e-bay

http://www.ebay.it/i...#ht_3066wt_1037

The drill bit of 6.3mm supplied in the kit was perfect .

When screwing in the Helicoil just make sure that you screw it in about 1mm below the top of the bolt hole otherwise chaffing will occur when screwing in the bolt.

Whole job took no more than 5 minutes with a very strong and secure fit using the original bolt.

Edited by Singlin
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