tapping/thread repair

Discussion in 'Cars, Bikes 'n AFVs' started by theblindking, Mar 5, 2012.

Welcome to the Army Rumour Service, ARRSE

The UK's largest and busiest UNofficial military website.

The heart of the site is the forum area, including:

  1. Dull one this:

    I've managed to **** up the thread in a chain tensioner screw hole. Obviously I need to drill it out, tap it and put an insert in but I need advice on what size I need to drill in order to recreate the same bore.

    It was originally an 8mm hole. What size do I need to make it in order to take an 8mm helicoil insert? I assume about .5 of a mm bigger?

    Thoughts would be appreciated and also any advice from those that have done this before in terms of potential issues. I've tapped before but I've never had to repair an existing thread.
  2. LancePrivateJones

    LancePrivateJones LE Book Reviewer

    Go on to the REME thread and ask if anyone has a Zeus Precision Data Chart, most fitters carry them and I believe the info you require is in there.
    BTW, you may be able to drill out the hole undersize and re-tap to original specs without having to helicoil it, the book contains data for this procedure as well.

    This is the book ;


    You can get them for about a fiver.

    As to doing a helicoil, just make sure that the hole is as clean as possible and grease the coil prior to insertion.
    Make sure it goes in below the surface of the hole or it will stand proud and if you break the internal tang you will have to remove it and repeat the procedure.

    Having said that, it is a piece of piss.

    Good Luck.
  3. Helicoil recommend a 21/64" drill for an 8x1.25 insert. So you need an 8.3344mm drill bit, or 8.5mm for government work.

    There's a load of Helicoil shite here and in the various links at the bottom of the page.

    Helicoils are easy just screw them in and away you go.

  4. 8.4mm if memory serves, although we used 8.5mm if that's what we had available (and I don't recall any bad outcomes):thumright:

    What's the chain driving?

    edit: Christ, beaten to it... twice :|

    Still, found this to make sure my memory wasn't giving you a bum steer (page 17): http://www.helicoil.in/pdf/HeliCoil%20Catalogue.pdf
  5. If I remember, having done a bit of diy car thingy stuff, if you buy a heli-coil kit it will come with the drill, inserts, installation tool, and tap. Even by Aussie prices - which are a rip off, shouldn't be too costly affair.

    Just added some techo 'stuff' that should answer all your questions.

    Attached Files:

  6. You are all the finest of men. Cheers.
  7. On the other hand if that fails theres always emetal......ok forget the field repairs from us VM's theres good advice above :)
    • Like Like x 1
  8. Cant remember the name of it, I am sure soemone else will but there is another type of insert that is sometimes recommended over helicoil.
  9. Recoil | Recoil Insert System