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Building a Plinth -- TD-124

Discussion in 'Turntables' started by tromba, May 4, 2013.

  1. tromba

    tromba Super Member

    Messages:
    1,024
    Location:
    Montgomery, AL
    So several years ago I obtained a Thorens TD-124. It's gotten to be time to give it some attention. I decided to build a new plinth, but since I didn't know exactly what I was getting into, as questions about plinths in this thread.

    What follows is a result of things I learned there.

    When I say I built a plinth, what I mean is that I had some idea what I was after and worked with a friend, a master craftsman in building things from wood, and he did most of the work while I "supervised".

    Started with wood and glue

    [​IMG]

    I bought this glue simply because I read somewhere that hide glue was a good choice for gluing layers in a plinth. I asked about that in the forum but no on responded -- so I figured "why not?". I found out from my mastercraftsman, Robert, or Master that hide glue was what many furniture makers used to use because it wasn't permanent. Heat makes it loosen and parts could be replaced. He didn't think there was a particular need for it, but since I already had it, we used it.

    The layers
    I decided I wanted a good plywood plinth so we looked in the Master's wood supply and found an inch thick birch plywood piece that was about 21 inches by 17 inches. Seemed like a good size for me. I had already decided I wanted something a little bigger than the table itself. Also had on hand a half sheet of 3/4 in birch, and that was enough to give us the five layers shown here

    [​IMG]

    Now all we had to do was cut away all the wood we didn't need. We started by using the original Thorens plinth as a guide for cutting the first layer.

    [​IMG]

    Trace the outline

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    then cut. Here a Forstner bit is cutting one of the holes for the "legs"

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    Then a jig saw cut the opening

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    and layer one is cut

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    the openings were cut inside the pencil marks,

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    and the to finish off the inside edges this oscillating spindle sander was used. For those unfamiliar with it like I was, it rotates and goes up and down at the same time.

    [​IMG]

    both surfaces were also sanded

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    To check the fit, the table was inverted and this first layer was placed in position

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    to do the next layer, the high points coming through layer one needed to be checked. For this we placed a piece
    of paper on the turntable and made a rough sketch of the high points

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    setting layer one on top of layer two, we could mark the holes the legs would come through as well as the
    shape of the opening that would continue into layer two

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    newly cut layer two clamped to layer one and a router finishing the edges. The top bearing bit in the router follows the cutout in the top and cuts the one in the bottom -- only here where both pieces will eventually be the same. The large hole lower left will be
    enlarged for where the tone arm will fit.

    [​IMG]

    working on the next layer

    [​IMG]
     
    Last edited: Jan 19, 2016

     

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  2. tromba

    tromba Super Member

    Messages:
    1,024
    Location:
    Montgomery, AL
    continues

    and layer three is done. Of course each layer involved lots of finishing and sanding.

    [​IMG]

    after layer 3 we were past any need for openings, so layers 4 and 5 had openings just enough to allow air to the motor and allow access for the wiring.

    [​IMG]

    On to glue -- we started with layers 4 and 5. To keep the alignment good, we first clamped the layers
    and then screwed them together.

    [​IMG]

    Next the screws were almost removed,

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    leaving just the very tip of the screw through the wood.

    [​IMG]

    Then glue was applied

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    and spread around.

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    and spread some more.

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    Next the layer with the screws was placed back on top, and the small amount of the screw still sticking through met the holes that had been drilled, making alignment of the two layers very easy and exact. The screws were drilled back in and the edges were clamped. One of the reasons for the screws only being near the center was that the clamps don't reach that far -- the screws acting as clamps in the area where actual clamps didn't reach.

    [​IMG]

    So far we had the turntable "leg" holes (these are the long threaded screws on the bottom of the turntable) the same size as were found in the original plinth. Because of the number of layers used here, those screws won't reach through to the bottom so putting a nut on the screw would be very difficult.

    [​IMG]

    In order to attach a nut to them these bottom two layers had those four holes enlarged enough to get a socket into the hole

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    Then a washer could be inserted and the nut then tightened against the plinth.

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    Final clamping of all the layers

    [​IMG]

    After unclamping, the edges needed sanding to remove the glue making it better to run through the joiner. This picture shows the veneer already on the top -- veneer is shown a little later.

    [​IMG]
     
    Last edited: Jan 19, 2016
    doctor fuse likes this.
  3. tromba

    tromba Super Member

    Messages:
    1,024
    Location:
    Montgomery, AL
    And this picture shows that I actually DID do something!!! Sanding!!!

    [​IMG]

    and more sanding. Sanding must be done carefully not to sand through the veneer. Sanding on the veneer started at 150, to 220, to 320 grit.

    [​IMG]

    Now to check the fit...

    [​IMG]

    cutting away where the electronics will go. Most of the holes here were to be filled with lead. The ones for the turntable legs were taped with the blue tape to avoid confusion.

    [​IMG]

    Shown in the walnut shell here

    [​IMG]

    And that completes the plywood layers.

    Veneer on the top

    My original idea was to just sand these plywood layers and varnish. The Master, however, had other ideas. He though it would look best if it had a walnut shell and a walnut veneer top. And as usual, The Master was correct.

    First step was to put the veneer on the top, starting with trimming it to fit. Shown here are two pieces of walnut veneer clamped together with a straight edge.

    [​IMG]

    Router the edges, "unfold" the layers and the two trimmed edges will match.

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    Fit to the top

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    And apply glue.

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    One of the difficulties working with veneer is getting a good smooth seal between the wood and the veneer. The best "clamp" for that is a vacuum. This involved putting the glued top into a plastic bag with the veneer side down against the flat surface and vacuum pressure holds it all together while the glue dries. This machine was a Vacupress (and can do up to whatever side bag you have)
    closer view, showing the veneer being held tight and even against the plywood.

    [​IMG]

    The next day it was time to cut out the veneer over the opening. A hole was made in the center of the veneer and then a bottom bearing bit in the router cut it flush with the plywood. You can also see here where the two pieces of veneer were taped togther -- where it has adhered to the plywood it looks like one piece of wood.

    [​IMG]

    and router the edges

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    At this point it was time to sand off the glue around the sides

    [​IMG]

    until it was smooth like this -- removing the glue allowing it to be finished to perfection later on the joiner.

    [​IMG]

    So that finishes the veneer of the top.
     
    Last edited: Jan 19, 2016
    doctor fuse likes this.
  4. tromba

    tromba Super Member

    Messages:
    1,024
    Location:
    Montgomery, AL
    The Walnut shell

    The Master works with rough lumber and not anything precut. This guarantees that the wood will be the exact dimensions he needs since he's making the cuts. The shell started with walnut that was 5-4 -- the rough dimension is 1.25" thick and normally planed to a thickness of 1"

    The first step is to use the table saw to cut to the approximate sizes.

    [​IMG]

    The primary work to get the sides in the correct shape is the joiner and the planer.The rough walnut is cut slightly oversized and the planer and joiner get it to the exact dimensions. The cut piece is first run on the joiner.

    [​IMG]

    It's purpose is to make one side completely flat

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    Once that one side is flat, the planer is used making the top exactly parallel to the bottom (finshed by the joiner) and at the exact thickness needed. The board is fed through the planer, coming out the exact thickness required.

    [​IMG]

    Now comes the 45 degree angles on the corners. To help prevent errors, the angle of the cuts are roughly marked making the correct angle evident no matter how the board is held.

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    The cuts are made with the Mitre saw. I thought this was the coolest tool in the shop. it has a laser shining on the wood where the cut is to be made

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    Fitting the pieces

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    measuring and checking

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    Back to the saw

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    Getting close

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    The original plan was to use biscuits to hold everything together. These are small pieces of wood that go in specially cut slots, half in the walnut and half in the plywood.

    [​IMG]

    The Master has a special tool just made for creating the holes for these biscuits

    [​IMG]

    When in place, they look like this and will go flush against matching slots cut into the plywood

    [​IMG]

    Biscuits also go into the ends of each board. Shown here are the holes cut but the biscuit cutter

    [​IMG]
     
    Last edited: Jan 19, 2016
  5. tromba

    tromba Super Member

    Messages:
    1,024
    Location:
    Montgomery, AL
    a test fitting, then another cut...

    [​IMG]

    test fiting the side

    [​IMG]

    Now we had to make cutouts in the back for the electrical power and the RCA connectors. The electrical details will be covered later.

    [​IMG]

    Finishing the holes

    [​IMG]

    So that the RCA connector will fit into position, the outside will be the exact dimension of the connector and the accompanying screw will hold it in place. Due to the thickness of the walnut, the back of the hole will be large enough to allow a socket to tighten the connector

    [​IMG]

    Once the position on the back is determined, some of the plywood will have to be cut away

    [​IMG]

    Everything assembled for a test fitting.

    [​IMG]

    To give the top rounded edges, the boards are run through a router.

    [​IMG]

    This gives the top a nicer look

    [​IMG]

    As it turned out, it wasn't possible to get a really good fit with all the biscuits, so The Master decided to just use biscuits where the corners meet. Before gluing, tape is applied to protect the wood from the glue.

    [​IMG]

    Now the outer frame is glued together separately creating the walnut frame. But not using biscuits to join the walnut to the plywood, the walnut can, if ever necessary, be removed from the plywood. A corner here:

    [​IMG]

    Showing the unfinished, unsanded corner

    [​IMG]

    Yet one more finishing aspect, The Master thought it would look nice with a trim molding on the inside around the veneered surface against the walnut. Here one of those pieces is being shaped by a router

    [​IMG]

    The inside small trim before being cut into a strip.

    [​IMG]
     
    Last edited: Jan 19, 2016
  6. tromba

    tromba Super Member

    Messages:
    1,024
    Location:
    Montgomery, AL
    Before adding that trim, the walnut frame in place

    [​IMG]

    The Assembly

    A view of the bottom with the holes drilled for the lead shot. The tape over four of the holes is to not confuse those holes, which are for the legs from the turntable, with the lead shot holes.

    [​IMG]

    plywood strips are fixed to the bottom. Screws will go through these strips into the walnut to hold the frame in place

    [​IMG]

    The four lead holes in the corner were filled and sealed first (more on the lead in the next section)

    [​IMG]

    We now have the finished base ready to add the walnut sides

    [​IMG]

    The sides are put in place

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    Correct length screws are selected

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    All assembled to check fit, then screwed into place

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    The inner trim is glued, only to the walnut, not to the veneer top. Although it may never be necessary, it then still remains possible to remove the outer walnut frame

    [​IMG]

    trim in place

    [​IMG]

    and clamped

    [​IMG]
     
    Last edited: Jan 19, 2016

     

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  7. tromba

    tromba Super Member

    Messages:
    1,024
    Location:
    Montgomery, AL
    The Lead

    As has been mentioned, holes were drilled in the plywood base for adding lead for additional mass

    [​IMG]

    Where does one get lead shot? I went to a sporting good store and asked for lead shot and they wanted to know what I was going to shoot!! I told them I wanted the smallest size, since it seemed this would give the most mass in the smallest space. So I ended up with 25 lbs. of No 8 chilled lead shot!

    [​IMG]

    As can be seen, this is small shot

    [​IMG]

    and there are lots of them!!

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    Here's a view of one of the corner holes, which, as was mentioned earlier, were the first filled and sealed.

    [​IMG]

    To prevent any noise from the shot, it seemed like a good idea to mix glue in with the shot,

    [​IMG]

    so it was layered in with the shot.

    [​IMG]

    shot, glue, shot, glue

    [​IMG]

    Did I mention that I bought more glue than I actually needed for the wood?

    [​IMG]

    Then the shot holes were sealed and glued with a plywood cover.

    [​IMG]

    Then clamped.

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    A view of the bottom showing the holes about to be filled with shot as well as the cutouts in the base for the electronic connections

    [​IMG]

    hole filled

    [​IMG]

    Holes covered with plywood glued in place.

    [​IMG]
     
    Last edited: Jan 19, 2016
  8. tromba

    tromba Super Member

    Messages:
    1,024
    Location:
    Montgomery, AL
    some trim was necessary in these plywood hole covers to keep the leg holes completely open.

    [​IMG]

    Add the glue

    [​IMG]

    Put in some screws...

    [​IMG]

    My first thought was that we had too much lead and would have some left over. As it turned out we had none left over and a few holes remaining. I remembered that when I was a kid we came across a demolished piano and found all these little pieces of lead on the ground. Years later I learned that these were weights on the piano keys. I imagine I might have had all 88 at one time, but only 50 or so remained.

    [​IMG]

    This was back in the day when we all played with lead, lead soldiers, molded our own lead toys, etc.So having this piano lead it seemed like a good musical end to this lead to use it in a turntable plinth!!

    [​IMG]
     
    Last edited: Jan 19, 2016
  9. tromba

    tromba Super Member

    Messages:
    1,024
    Location:
    Montgomery, AL
    The Armboard

    The original armboard wasn't in such great shape. It was a little cracked and wrinkled so it seemed like a good idea to make a new one out of walnut. Because the entire armboard will be visible, using a solid piece of walnut is easier than using plywood and veneer. The Master thought a burled walnut veneer (like what's used in Rolls-Royce) would add a nice touch. So the walnut board is selected and the veneer layed out

    [​IMG]

    Not to waste a big piece, the veneer was cut and a joint would be at the hole cut for the arm, making the joint nearly invisible. Here it's taped together prior to gluing. It was then glued and put in the vacuum chamber to dry

    [​IMG]

    For cutting to the correct size, the original was taped with double sided tape to the walnut

    [​IMG]

    Then using a band saw, The Master carefully cut the walnut

    [​IMG]

    to the exact size of the original

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    Next using a Forstner bit again on the drill press,

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    holes are drilled for the arm itself

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    some finish work remains to make the exact size. Note here the condition of the orignal armboard.

    [​IMG]

    cutting the holes for mounting the armboard to the table

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    Using the original armboard to drill the mounting holes for the arm.

    [​IMG]

    Using the router with a top bearing bit (in a router table -- if this were in the hand held router, this would be a bottom bearing bit.)

    [​IMG]

    The bearing follows the outline of the original plinth and the blade cuts the new one to its exact dimensions.

    [​IMG]

    and to finish the mounting hole

    [​IMG]

    Countersinking the holes where the armboard mounts to the table

    [​IMG]
     
    Last edited: Jan 19, 2016
  10. tromba

    tromba Super Member

    Messages:
    1,024
    Location:
    Montgomery, AL
    testing the fit of a screw

    [​IMG]

    The inside of the original armboard has a taper where it fits against the table. Here the taper is "measured" simply by setting this tool (a mitre gauge) to exactly match the taper

    [​IMG]

    Then it's a simple matter to set the table saw to the same exact taper.

    [​IMG]

    And the new armboard ends up being cut to the exact taper

    [​IMG]

    The table sitting on the plywood stack

    [​IMG]

    now with the new armboard

    [​IMG]

    both the new and the old

    [​IMG]
     
    Last edited: Jan 19, 2016
  11. tromba

    tromba Super Member

    Messages:
    1,024
    Location:
    Montgomery, AL
    Varnish

    Two different varnishes were used -- the first (four coats) was combination of polyurethane and oils that are hand rubbed, the second (two coats) of oils and wax that are hand rubbed. This gives a nice satin finish.

    [​IMG]

    Both Sam Maloof brand.

    [​IMG]

    The walnut frame is not yet attached and is varnished separately from the plywood foundation

    [​IMG]

    And the armboard is still separate. Varnish is applied liberally, then wiped off

    [​IMG]

    then left overnight to dry

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    Four coats of the first varnish

    [​IMG]

    and two coats of the second varnish, all applied by these little foam brushes

    [​IMG]

    followed by a thorough rubbing in - wiping down

    [​IMG]
     
    Last edited: Sep 30, 2018

     

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  12. tromba

    tromba Super Member

    Messages:
    1,024
    Location:
    Montgomery, AL
    The Electronics

    I've never liked the idea of dangling cables and wires while moving a turntable, so I decided to make them detachable from the back of the plinth. Construction of this was shown earlier
    Mounting the RCA connectors with a socket on the backside

    [​IMG]

    For ease of use, this plug was used. No soldering/wiring required. The AC cord from the table plugs into one side, and the other side is a standard 3 wire connector of which I have dozens from various computers over the years.

    [​IMG]

    The plug inserted into the hole prepared earlier

    [​IMG]

    The the RCA connectors attached. Note as mentioned earlier, the backside has a hole large enough to use a socket to tighten the connectors

    [​IMG]

    All in place.... but we needed to secure the AC plug so that pushing a cord into it from the outside wouldn't push it into the plinth

    [​IMG]

    The Master again came up with the solution -- simply screw a wood screw into the plinth, catching the side of the connector

    [​IMG]

    A better view of these screws (I guess the focus could be better!!)

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    Finished view from the outside (plinth is inverted here)

    [​IMG]

    The last external electrical connection is the ground connection. To protect the finish, where this will go was covered with tape

    [​IMG]

    Measuring and marking on the tape

    [​IMG]

    where the ground connection will go

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    an indentation made by an awl to help the drill get started.

    [​IMG]

    Where the first nut would go was to be recessed slightly, so that was drilled first,

    [​IMG]

    then the hole itself

    [​IMG]
     
    Last edited: Jan 19, 2016
  13. tromba

    tromba Super Member

    Messages:
    1,024
    Location:
    Montgomery, AL
    My ground connection was simply a long threaded piece from Lowe's. The ground from the arm fastened on the inside, the outside going to the phono pre

    [​IMG]

    The long screw had to be cut, so a hole was drilled in a small scrap and clamped to the table

    [​IMG]

    allowing the rod to be cut

    [​IMG]

    with a hacksaw

    [​IMG]

    the nut on the outside

    [​IMG]

    and the ground connection is finished

    [​IMG]

    the added AC plug here is a 3 wire system, and the original Thorens had just two wires

    [​IMG]

    This cord is very old and will be replaced by a new 3 wire cord

    [​IMG]

    As far as I could tell, from the old 2 wire system, it didn't matter which was + or - so the white and black wires were just connected to the two screws on the block

    [​IMG]

    This shows the entire new cord, simply an end cut of an extension cord (I'd actually used the rest of the cord for a White Lightening Moonshine Speaker Cable.

    [​IMG]

    good view of the connections -- the green ground wire was attached to a motor mounting screw.

    [​IMG]

    connecting the internal RCA cable. This cable was fed through the plinth from the upper layer through another hole

    [​IMG]

    Lots of wires on the bottom

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    wires tacked against the bottom of the plinth

    [​IMG]

    the bottom finished

    [​IMG]
     
    Last edited: Jan 19, 2016
  14. tromba

    tromba Super Member

    Messages:
    1,024
    Location:
    Montgomery, AL
    Final Assembly

    These first pictures don't show up as good as I'd like. The top on this one is the finished varnished walnut sitting on a piece of rough walnut similar to what we started with

    [​IMG]

    Another similar view

    [​IMG]

    Bottom is the rough lumber; on top of that is a leftover piece that was planed and sanded; behind those the difference the varnish makes.
    For me it was a very interesting process going from that ugly rough lumber to the beauty of the finished product.

    [​IMG]

    This is the cut out from one of the layers of the plywood. Note the hole drilled in the middle.

    [​IMG]

    Into this hole the spindle fit when turning the table upside down

    [​IMG]

    like this

    [​IMG]

    So for feet, I picked sorbothane, these from Amazon

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    a peel-off back sticks them to the underside

    [​IMG]

    so that they are in position like this. This did cause a significant problem. Due to the weight of this plinth (70 lbs), we didn't allow the feet to be enough below the plinth so that there was finger clearance. I'll later get taller feet, or build up the bottom a little bit

    [​IMG]

    Time to add the arm to the armboard,

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    making the connections first, then screwing it down to the turntable.

    [​IMG]

    Adding the washers and nuts to the turntable "legs"

    [​IMG]

    And we have a finished product

    [​IMG]
     
    Last edited: Jan 19, 2016
    Hipocrates likes this.
  15. tromba

    tromba Super Member

    Messages:
    1,024
    Location:
    Montgomery, AL
    and The Master makes his final inspection

    [​IMG]

    The painted finish of the turntable itself needed some cleaning. An AK member recommended this, and it worked quite well

    [​IMG]

    So it made it home, currently on the floor in front of the rack

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    So if you're wondering what The Master can do other than plinths....

    Here he made a toy for his grandson

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    here's their bathroom where he made it all

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    and here's the ceiling in their new home office

    [​IMG]

    and then there's the dining room table, sideboard, kitchen table, home entertainment center, etc.

    In his spare time he's my dentist and a flute player I do gigs with.
     
    Last edited: Jan 19, 2016
  16. JohnVF

    JohnVF Lunatic Member

    Messages:
    28,767
    You, sir, are an artist as well as a craftsman. Wow! Thank you so much for this. My TD-124 is as impressed as I am.

    This should be a sticky. There's so much in here that is useful for any plinth build not just the TD-124.
     

     

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  17. shardina

    shardina Active Member

    Messages:
    211
    Excellent work, that looks incredible. And great job on documenting it, too! This thread will be valuable for a lot of people.
     
  18. Dandy

    Dandy Super Member

    Messages:
    4,507
    Location:
    North West, UK
    Yes, thanks to you and the master for this great photo essay.
     
  19. Barncats

    Barncats AK Subscriber Subscriber

    Messages:
    768
    Location:
    New Hampshire
    Bravo, not only for the the beauty and utility of the plinth itself, but especially for the thorough documentation via photos and captions. Wonderful, and yes, stickied it should be -- a superb guide for anyone making a plinth for any turntable.
     
  20. ecoak

    ecoak Member

    Messages:
    98
    Location:
    Toronto, Canada
    Thanks for this post! Nice job. May I ask what was the final weight of the plinth assembly? And also, you mentioned that you, or your friends, cast toys as children - did you consider melting and pouring molten lead into the cavities rather than glue with shott?
     

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