Drilling and fixing oak sleepers

Hi all.Part of my current project is to install 25 oak sleepers to form a retaining wall. I was after people's recommendations for good drill bits to use. I'm going to be using 200mm m10 coach screws countersunk flush with the face of the sleepers. I will be driving them in with an impact driver. I'm looking for a good method to countersink to 10mm and then run in a pilot hole.Thanks in advanceBenedict

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  • I have never pilot holed them ever

    A small flat wood bit would be good to do your countersunk hole
  • PRO
    As James said but if be trying it out on some waste wood first. Also 10 MM is a big countersink as I'm sure the coach screws I've used are not as thick as that in the head
    • PRO

      Coach screws, have always be available in 6mm, 8mm, 10mm or 12mm diam or imperial equiv when they had square heads. And i think you can get 16 & 20mm

      • PRO
        No I don't mean diameter I mean 10mm into the wood.
        And like you say below it needs to be big enough to fit socket on
  • PRO

    Coach screws normally have a hex head, which is flat under the head, so they would't really suit a countersink, but if you use a forstner bit, you'll get a flat surface for your coach screw head to sit on.

    You would also need a bit somewhat larger than 10mm, not just big enough for the head, but also the  outside diam of the socket driver.  It would be advisable to use washers as well.

  • PRO

    create a wooden plug out of off cuts by cutting down the off cut to about 20mm then using a 30mm hole saw cut out a load of plugs, then use a 28mm flat auger bit to recess the head of the bolt at 25mm depth then plug the hole with the pre cut plugs leaving no sign of fixings or holes.

    as said by james you should not need to predrill as not even an axe swung by the best of us would split through a sleeper so no m10 coach screw will.

    also I would only use an impact driver to start the fixing and finish it off with a 3/4 socket or extension bar as the impact driver might shatter your socket bits or adapter so always have a backup.

  • PRO

    Hi Benedict

    we have just finished a job using oak sleepers to form a series of retaining walls. We used 200mm long Timberfix structural wood screws. We fixed straight down through the top sleeper into the course below using a corded SDS drill. Where the last course was visible we fixed the sleeper diagonally from the rear.

    Hope that helps

    • Yes that's exactly how I do it so that the faces are left clean. I also add either 3x3 or 4x4 posts behind the wall and then fix timber fix screws through the posts into the top sleeper, countersunk, although this is overkill as the posts usually sit about 4 inches shy of the top so when you backfill they are completely hidden. I've seen some people use M10/12 threaded rod right through all the courses, but I can imagine this would be a bitch of a way to do it. When I put them in vertically they get concreted in, then 1 single length braced across the length of the wall if the dimensions allow and then M10/12 threaded bolt driven through pilot holes in the brace diagonally down and through 4x4 short posts which have again been concreted in although you can just dig a hole just big enough for these support posts then pack with sand and you'll be amazed how well they hold, obviously I'm talking about a retaining wall no higher than 2ft here. Any higher and you probably would want to concrete the support posts as well. I did this recently for a timber retainer wall that was leaning over. As you turn the front nuts on the threaded bolt it pulls the wall towards and in the direction of the support posts, thus righting the wall to a perpendicular/level position. Cheers and good luck;-)
  • PRO

    Hi all, thanks for your replies. I am happy with how I am going to fix the oak and the construction of the wall. I'm after peoples recommendations for brand of type of bit for long life. I don't want to change to a new bit every couple of holes. 


    • Trust us on the timberfix. They are the way forward. As long as you've pilot holed and counter sunk every hole, itll be a breeze getting the timber fix through the oak. It has a hex head and you get a hex head bit with every pack you buy although you never need another bit once you've bought your first pack. Only reason I've ever held onto every hex bit I've ever got is because I'm very good at "misplacing" them (losing)! Go for timberfix you won't be sorry and neither will your client when they know they are getting a good solid screw!;-)
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