1. Please take 30 seconds to register your free account to remove most ads, post topics, make friends, earn reward points at our store, and more!  

Mounting ears : Finding the right screw size for pre-drilled holes

Discussion in 'Amps and Cabs [BG]' started by zortation, May 8, 2020.


Tags:
  1. zortation

    zortation

    Dec 26, 2011
    Toronto, ON
    I've got an old amp that came with the ears un-installed. I try to put them on but discover that some yutz at the factory used the wrong size tap for the mounting holes on the amp, the thread holes are too big and the supplied screws just keep going in circles. The screws are the original screws for the amp.

    How do I find out what thread size is in the hole?
     
  2. Make and model of the amp will help a lot.
     
  3. zortation

    zortation

    Dec 26, 2011
    Toronto, ON
    AG500SC
     
  4. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Gently try an assortment of screws. Note that some manufacturers use metric, and be sure to check what's going on inside before sticking a screw in any chassis hole.
     
  5. The other possibility, I think more likely, is some yutz supplied the wrong screws with the ears. You might first try to find out what screws were supposed to be used and compare that with what you have since it's a whole lot easier to measure screws than threads.
     
    zortation and Jim C like this.
  6. rufus.K

    rufus.K Supporting Member

    Oct 18, 2015
    SoCal
    I have an Ag500 somewhere. If its reasonable to get to i will have a look.
    Post a photo of which holes youre using, as i dont have rack ears for mine
     
  7. With metric threads I think you mainly find the 'fine' pitch variety.

    If you have to take a stab at it you could measure the size of the hole. Across between opposite tips of the threads will be slightly smaller than the nominal bolt size, by about the pitch of the thread.
     
  8. rufus.K

    rufus.K Supporting Member

    Oct 18, 2015
    SoCal
    15890642063555497129787007506454.jpg Theyre 10-32
    Likely the same pitch as the rack rails you'll be using. The threaded portion is shallow, 3/16 to 1/4"
    15890643286316761558934811577391.jpg 15890643286316761558934811577391.jpg 15890643646401749769381838231260.jpg
     
    zortation likes this.
  9. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Be VERY careful with the length, especially on the right hand side.
     
    zortation and fdeck like this.
  10. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    Also beware that M5-0.8 and 10-32UNF are extremely close to one another. They might match if the nut is just a few threads deep, but then jam up if you go further. One of my rules from repairing a lot of bikes is to make sure a fastener can be threaded all the way on with the fingers before using any tools.
     
  11. Begs the question of @rufus.K whether it's a dead certainty

    Is that stage right or amp left?
     
  12. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Horse right, I'm a FOH guy after all.
     
    wcriley and Rich Fiscus like this.
  13. Not to be an Ass but to be clear you mean not the one in the pic above that should not be sent in too far for fear of contacting amp guts?
     
  14. I've seen guys drive screws into transformer windings, circuit boards and wiring harnesses by putting screws back in the wrong places, or using aftermarket generic screws that were too long.

    A good way to check length is thread it in until the threads catch; then measure how much more threads there are between the panel and the screw head. Anything more than 3/16" or 5mm is potentially too long.
     
    Last edited: May 10, 2020
    agedhorse likes this.
  15. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Looking at the front of the amp, the right side where the power switch is located.
     
  16. rufus.K

    rufus.K Supporting Member

    Oct 18, 2015
    SoCal
     
  17. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    The supplied screws might have been intended for mounting the ears to the rack. Some racks have threaded rails.

    Check that the rack ears are indeed the correct ones. The three holes should align on both the ears and the case.

    Use a toothpick or to gauge the available depth inside the cabinet or take the cover off and look.
     
    zortation and agedhorse like this.
  18. Jim C

    Jim C I believe in the trilogy; Fender, Stingray, + G&L Supporting Member

    Nov 29, 2008
    Bethesda, MD
    Seems like it would be easy enough to check in with Aguilar for proper screw diameter, thread pitch, and length.
    If I had to guess, I would start with a US thread (only because they are a US company which is no guarantee), and buy a fine and coarse thread at you local neighborhood hardware store with the appropriate diameter. May as well buy a metric screw as well. As per fdeck, gently thread the screw in knowing that two of them are wrong.
    As far as length, a general rule of thumb is go 1 1/2 time the diameter of the screw for the exposed section going into the amp. This needs to take material thickness and any flat or lock washers into the equation.
    Better yet, pull the lid after you've discharged the capacitors or. unplug and don't turn power up for 24 hours before popping the top.
     
    zortation likes this.
  19. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    agedhorse likes this.
  20. zortation

    zortation

    Dec 26, 2011
    Toronto, ON
    I just looked at them, they're wood crews! I'm going to give Aguilar a shout tomorrow. Thanks!
     
  21. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
    Feb 27, 2021

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.