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  1. #16
    Join Date
    Feb 2020
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    Perth
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    I thought that I'd add in that this table will be an outdoor table, not an indoor table. And when I say outdoor, it will be in an undercover entertaining area that won't get wet or have direct sunlight.
    Just in case that changes any design opinions..

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  3. #17
    Join Date
    May 2007
    Location
    Sth Gippsland Vic
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    4,355

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    Quote Originally Posted by thirstyvessel View Post
    Cheers for the feedback, Auscab.

    Just so I get it through my noob head, you're saying that another option would be to use a steel plate as the fixing of the leg to the base of the table top. This steel plate would be approx 10mm thick, say 150mm wide and 950 long, effectively spanning the width of the table. The plate would be fixed to the legs from the top using a number of screws, say 4 or so, through the top of the plate into the guts of the leg. These screws would be quite long and hard, possibly similar to the ones you showed in a previous photo. Then, the plate would be fixed to the underside of the table top by, let's say, 10 bolts or screws, 5 evenly placed on each side of the plate. These can only be about 35-40mm long though - at maximum.

    Does that sound like what you had in mind?

    The weak point there would be the 4 screws holding the plate to the legs, if my engineering memory is correct. You wouldn't be worried about the shear forces that may be placed upon the table and unsettle these hold-fasts? The table top weighs about 150kg, so I'm just concerned about the inertia and shear forces that will be placed on these screws.

    I'm not trying to diss your idea here, I'm just trying to get it through my head and remove doubt.

    Thanks for the feedback!

    Whats going on with me getting involved here is . Your design has me thinking of a design Id like to make and I'm running through the construction thinking of a clean minimal simple way to build based on whats in my mind as well as your design.
    So I'm not necessarily right of course. I just like running through with a design thought and see if I hit a snag . If I do hit a snag things revert back a step or go traditional . If it works out to be a good way I remember it as a solved problem for later builds .

    What happened two days ago was I discovered those screws . Same day as I was walking around thinking of a trestle design, plain and simple with just a top and two leg ends. Your thread got me started but its something Ive been stuck on a number of times . My son pulled out a bag of the screws that he collected off a building site . They were left spread discarded in the dirt . He told me the screws were used by the guys who were working on the stud walls. And I thought that screws like these would hold a table like that together well .

    The screws are 11mm wide at the thread , the shank is 8mm with so 1.5 mm of thread sticking out each side . The counter sunk head is 8mm high so needs at least an 8mm steel plate . Their about 16mm wide , I didnt measure that. And their a high tensile hard modern steel . Huge holding power! I googled them from the info on the head of the screw shown in my picture . I got a number and rang the Aussie supplier and he told me . "The screws were used by the guys delivering the stud walls, to hold the plates on top of the wall frames that the crane picks them off the truck with .
    They get unloaded , the plates come off and get discarded with the screws and the stud walls go into place . "

    He also said they come up to 600 long ! I asked the guy about sizes ,50mm up to 200 mm long, and the cost, and he said he will get back with an email soon .
    If they dont come in 50mm then cutting down a longer screw is the go.

    So your question above .
    Yes, 8 to 10mm plate and set in around 90 mm from table edge .

    Yes, 4 or 5 screws 200 long if possible holding plate onto legs but with hole pre tapped by using a screw possibly, with a deep groove cut in side to cut a thread in timber . Used by driving in and taking out a number of times . That way the thread gets a full bite . Your not going to be able to drive such a big threaded screw down into a hardwood like Jarrah without some extra work .
    When screws installed in leg to hold plate , inject some poly glue in the holes .

    Yes , ten screws 45 + 8mm long for the top 53mm . or 50 . Cutting a 50 out of a longer screw gives a thread all the way to the end . You have to be careful if that's done because if the hole is to short by any amount in the top it breaks through the wood when it touches the end of the hole . A pointed screw doesnt do that . The point breaks through if its to long .

    There is a weak spot I can think of .
    Your legs are only 50mm thick . If the screws go down 200 mm dead middle for the top plate and take up 11mm width, your left with about 19mm each side . If the table got a big enough hit the screws could come out through the side . It'd need something like a car crash maybe ? But I think that's a weak point . Getting the screws down dead middle is possible but a little tricky as well . When I do similar stuff I make up drill bits by welding extensions to them BTW .

    If I may . What I dont like about your design is the 50mm thick legs . Even before thinking of the screwing weakness that's hardly there and may not be a problem.
    Nice table design IMHO has a support system underneath with more meat than the top Probably between 90 and 125 somewhere thick at least would be what I'd do . Either by laminating up dry Jarrah or building a solid box and covering with re sawn 5mm Jarrah . Both those options are not such a good idea for an outside table though. (Edit . I did laminate 10mm Jarrah to my 90mm pine out door veranda posts on a house with two pack and they never shifted with full rain but not much sun , so it would work done right ) Finding some solid similar timber would be the go . like dry old sleepers , leaving them rustic or dressing them , gluing and pinning them together to get the width . Steel pins possibly . With a matching wider steel top plate holding it to the top , it would be something special !
    I'm also not into live edges . But if I did have one it would most likely be on an outside table .

    Ive actually got a similar table to build one day . I bought two Red Gum 50mm thick slabs around 3.6 x 1.2 wide about 15 years ago. One is a clean solid and the other split in two down the middle . It'll have to be my outdoor table as well if I get around to doing it . I need a new deck first .

  4. #18
    Join Date
    Feb 2020
    Location
    Perth
    Posts
    8

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    Hi, I apologise for the delay in my response.. things have been a bit mental around here!

    So, I took everyone's suggestions on board and came up with a solution that I think/hope will work.

    What I had made for me was 5mm mild steel plates in an offset 'T' shape. I'll upload my schematic plan so you can see. To compensate for the weakness in the legs if just screwing down the middle, we put a plate on the inside and will screw the plate to the legs from the inside as well. This, couple with the other legs should provide the necessary pull/push in case of any unwanted movement on the table.

    Auscab, I liked your idea of the structural screws, so I'm planning on 100mm screws down the middle of the legs and fixing screws, 38mm long into the body of the legs and also to fix the plates to the table.

    So yeah, I'm hoping that'll all stand up to everything. I'm going to put together the bench seats this weekend and give them a test and a shake-down. If they prove to be solid enough, then I won't be putting in any supporting braces.

    I'll also throw up some pics of the table top and my 2 pac application and subsequent struggles (but that's for a different day!)
    Table bracket.jpgScrews.jpgTable_sanding.jpgFirst Coat 2pac.jpgFirst Coat 2pac 2.jpg

  5. #19
    Join Date
    Jul 2008
    Location
    geelong
    Posts
    359

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    Much things are about guesswork as much as anything else. sounds chunky with very strong wood. hows about still have provision for a centre support that can be done if needs must be.

  6. #20
    Join Date
    Jul 2008
    Location
    geelong
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    As far as I can understand this - Yes at least some sort of centre support for this kind of length -despite the thickness - lots of things happen with this kinda length.

  7. #21
    Join Date
    Jul 2008
    Location
    geelong
    Posts
    359

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    It will want to move the BAD thing is to try to stop it. - Let it move -IE slotted screw fittings or otherwise - sliding dovetails are a thing too and can be of whatever lenghth.. have tried to stop such things as an experiment -in the weather 4x4" half lapp hardwood -polyurethane-basically NAH sort of held together - but good 1/4 " movement

  8. #22
    Join Date
    Aug 2014
    Location
    Geelong, Victoria
    Posts
    282

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    Not sure if this has been said but i think these tables are sometimes over-engineered to hell. On the support question you have a 50 mm slab of hardwood that is used to build bridges. A span of 2.5 m by my calculation does not need more support. The key issue with the undercarriage is racking. I agree that the practicality of assembly needs to be thought through and a free-standing undercarriage is good in this regard. So it comes down to design of joinery to create a rigid base. The racking forces are probably not huge. If you have a strong, free-standing base you probably don’t even have to worry about fixing the base to the top. It is not going to move about!

    Bruce

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