We want to use to fix the wooden rails of the drawer. Has anyone come across a case like this?

Discussion in 'Screwfix' started by Andrew34, Sep 28, 2021.

  1. Andrew34

    Andrew34 New Member

    Hello. Has anyone come across a case like this?
    We want to use to fix the wooden drawer rails:

    1) DIN 963 screw or equivalent (countersunk head)
    2) DIN 912 bolt (high cylindrical head) or analog.

    The runners are made of oak.Question: Which option won't cause cracking and delamination of the contact surfaces?

    Besides for the bolt with high cylinder head different lengths are available - 4, 5, 6 mm. What is better to take?

    It is more convenient to make cylindrical holes rather than tapered holes (for a countersunk head). But which is more advantageous in terms of reliability and low cracking?

    Attached Files:

    Last edited: Sep 28, 2021
  2. ejenner

    ejenner Member

    It's pretty simple if you don't want the wood to crack the clearance hole should be identical or slightly larger than the screw and shaped the same way. Countersunk spreads the clamping force across a larger surface area so that will put less pressure on any concentrated areas. You can create the thread before attaching the rail by installing the screw without the rail in place. Take the screw out and then put it back with the rail in place, it should mean you don't have to tighten the screw as much on the second time of tightening it up.
  3. Andrew34

    Andrew34 New Member

    The surface of the oak tree (marked in red), how much load can it approximately support? 1.5-2 mm on both sides. If there is a force along the axis (marked in blue).

    Attached Files:

  4. ejenner

    ejenner Member

    Experiment with some scrap pieces before you work on the real item. The exact measurements will vary from one quality of oak to another so there is no universal answer. I guess you would have to use a torque wrench with a screwdriver bit inserted otherwise you won't know how tight you are turning the screws. Glue is used a lot in joinery as well. These rails could be glued and screwed.
  5. CraigMcK

    CraigMcK Screwfix Select

    It might be better explaining what you are trying to do, it seems very excessive to concern yourself with tensile and cantilever forces if it’s a set of bedroom drawers for example.

    EDIT: PS it’s not normally tensile forces on drawer runners? Unless I’m looking at your drawing in the wrong way
  6. I-Man

    I-Man Screwfix Select

    Agree with CraigMcK - sounds like your over complicating a very simple thing
    WillyEckerslike likes this.
  7. Andrew34

    Andrew34 New Member

    1. Here's why I have this question.
    I use independent milling heads for blind holes. They reduce the risk of punching through the board. It is easier for me to make two cylindrical holes.
    The dimensions of the countersunk screw heads are not adapted to wood joints. They are for steel plates. I have to buy milling heads for metal. So that the surfaces touch evenly. That's an extra cost. And you can also burn the machining surface of the wood.
    2. Kitchen table drawers. Axial loads (along the screw rod) can occur.
  8. WillyEckerslike

    WillyEckerslike Screwfix Select

    Why? Use a drill bit to drill a pilot hole through the rail and into the drawer side, then a slightly larger drill bit through the rail and finally a countersink bit in the rail. Use a bit of tape around the drill bit if you are worried about drilling too deep. Apply wood glue to rail and drawer side (where rail will meet obviously) and screw rail to side using countersunk screws and cleaning off any excess glue that squeezes out. This has taken longer to type than the job will. The screws will act as clamps. Once the glue has set insert drawer.
    I-Man and rogerk101 like this.
  9. rogerk101

    rogerk101 Screwfix Select

    If I were to put as much analysis into each and every DIY task I did around the house, nothing would ever get done.
    I have made many many drawers in really high end furniture right the way through to a drawer mounted fridge in my campervan an all I've ever used are a few countersunk wood screws on each drawer runner. Touching wood, I can honestly say that many years later, with many thousands of openings and shuttings, they're all still just fine.
    Don't overthink and overanalyze ... just do it!
    I-Man likes this.
  10. Andrew34

    Andrew34 New Member

    Some screws will have an offset if several countersunk screws are used at the same time.
    A screw sometimes cannot fit through the hole. The holes will have to be widened. Extra work.

    Quote from an old handbook

    "Of all the types of screws... countersunk or semi-sunk screws with conical heads are the most attractive, as they allow for connections without protruding parts. Unfortunately they also have the greatest number of disadvantages compared to screws of other types. The main disadvantage is the difficulty of combining the two centring surfaces - the thread and the tapered cooking surface. This disadvantage is particularly pronounced in connections with several screws. Due to unavoidable manufacturing errors, the centres of the threaded holes in the housing usually do not coincide with the centres of the tapered sockets in the part being tightened: Only one of the screws of the connection fits correctly in the tapered socket, the heads of the other screws lie in the sockets with an offset. This disadvantage can be partially eliminated by using a backlash fit for the threads.
    Another disadvantage is the difficulty of locking."

    The idea of converting to cylindrical bores arises. It is easier to increase the diameter of the slot. But then the head will not take the load.
  11. AnotherTopJob

    AnotherTopJob Screwfix Select

    Surely this is a wind-up?
    rogerk101 and WillyEckerslike like this.
  12. rogerk101

    rogerk101 Screwfix Select

    Sadly probably not!
    I have friend who has a bachelor degree, a masters degree and a doctorate ... all in electrical engineering, and all from Cambridge.
    He is in his mid sixties and is the most knowledgeable person I know ... about anything and everything, because he spends his life researching stuff. Sadly he has never done anything useful with all that knowledge, and wouldn't even know where to start if asked to make a basic wooden box!
  13. woodbutcherbower

    woodbutcherbower Well-Known Member

    It has to be. I’ve never read anything quite like it. I’m just waiting for the OP to start worrying about the tensile strength and breaking strain of the different metals the screws are made from. Brass? Steel? 316 Stainless? Which grade? Single thread? Twin thread? Cutter? Passivated? Dachrotised? Galvanised? Plated?

    This whole business of fixing two bits of wood together is a nightmarish minefield. I have no idea how I’ve managed to earn a living for 35 years …
  14. I-Man

    I-Man Screwfix Select

    Definitely taking the **** now

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