Self-tapping screw sizes

Discussion in 'Mech Tech' started by Skater 8, May 23, 2020.

  1. The front belly pan is held on by 2 sizes of captive-washer self-tapping bolts, one takes a 10mm socket, the other 13mm. I believe they are called Acme bolts. I guess that as the self-tapped holes have got wider, the the PO has migrated from 10 to 13mm. Now it is a bugger matching holes to bolts and changing socket size.
    To my mind it would be sensible to bang in 13mm everywhere.
    Where does one get 13mm hex-head captive-washer self-tapping screws, they don't seem to exist!

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  2. Try ebay
  3. Tried

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  4. Thanks for the effort, but that only goes up to 10mm not 13mm.

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  5. Riv nuts and M6 bolts
  6. A rivnut is what you need - and a tool to insert it. NB bolts are usually measured by their thread size as opposed to the hex head, so your 10mm head is an M6 bolt (means 6mm std pitch thread) and your 13mm is an M8. Hope that helps.
    mikedjames and Skater 8 like this.
  7. x3 for rivnuts
    Adrian1975 likes this.
  8. Baysearcher

    Baysearcher [secret moderator]

    If you use rivnuts (which are better) make sure you buy a decent tool. The cheap ones disintegrate after about 2 uses.
    Skater 8 likes this.
  9. What are these rivnuts of which you speak
  10. They just about do an M6 before disintegrating in your hand. Trouble is, proper ones are expensive.
    Skater 8 likes this.
  11. IMG_20161009_154307.jpg
    That's what they look like when you cock um up
    jonbott and snotty like this.
  12. Rivnuts or Jacknuts or caged nuts then.
  13. Don't use macadamia. They simply don't work.
    Norris and MorkC68 like this.
  14. The Memfast rivnut tool is the DBs
    (My Xmas present last year)
    snotty likes this.
  15. Expensive too
    snotty likes this.
  16. Also dont forget that you need a tool that is man enough for using steel rivnuts.
    With the aluminium ones , they will corrode out through dissimilar metal corrosion or the threads will strip as you pull on them.
    I was doing some on my roof yesterday and three times I pulled out the threads on an M4 aluminium rivnut. I managed to snap the M3 tool completely in the past.

    Problem is if you are used to pop rivets, the point where you have to really squeeze on the tool to "start" a pop rivet is where you STOP with a rivnut.

    Unfortunately the wreckage when you drill them out is now rattling around inside the roof..

    So I have been forced to buy more downlighters for the poptop so I can fill in the holes I am going to have to cut to get the bits out...
  17. Mine's held on with 4 bolts ..3 at the rear, 1 at the front.
    I use the same button head Allen key type bolts that I have on my tinware.
    Thought this was standard...certainly looks original.
  18. I don’t think so. The fasteners were those big self tapper things, I think.

    Mine’s held on with three big self tappers and a riv-nutted M6 bolt at the front now.
    Last edited: May 24, 2020
    Skater 8 and Betty the Bay like this.
  19. If you are going a-rivnutting, as Mike said, use the aluminium ones, not stainless. Stainless are rock hard and will bust the cheap rivnutters in five seconds.

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