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Forum topic by groland posted 11-06-2011 02:07 AM 1215 views 0 times favorited 12 replies Add to Favorites Watch
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groland

152 posts in 2877 days


11-06-2011 02:07 AM

I am making a new base for a turntable (record player). The “deck” that the turntable mechanism mounts on will need to be made out of plywood, probably 1/2 inch material. This plywood has a cut-out in its center that is a complex series of curves. I have made a good paper pattern, at size, to work from.

I have tried free handing this cut out with a router with mixed results—less than perfect curves, a bit of burning, etc. I’d like to do better. I am using birch plywood from The Home Depot for the first few trials—to try to get a suitable technique down. This plywood is of fairly poor quality—paper thin veneer poorly glued on, but it’s okay for trials.

Anyway, I have a few questions:
1. I was thinking of trying to make a template, 1/4 inch tempered masonite, and switching to one of those router bits with a bottom mounted flush bearing that might ride on the template resulting in smoother cuts. Is this the best way to do this? Ought I to cut away as much as I can with a jig saw then use the router, or just wail away with the router?

2. Would baltic birch plywood be better for this kind of routing, or is trying to rout any plywood just not a good idea.

3. If I don’t use a router, what’s my best bet—jig saw and drum sander?

4. If I want eventually to use a nice hardwood veneer—maybe cherry, would that necessitate different techniques?

Thanks,

George


12 replies so far

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Trapshter

64 posts in 1859 days


#1 posted 11-06-2011 02:26 AM

Hello groland 1 st I would make the template from M D F . Mark out the pattern in pencil after you like the shape and design. Cut it out on a band saw or jig saw .leave the line . Then sand to the line . The best way is using a spindale sander, but you can use a rasp to rough it in then sand by hand to clean it up . This part must be very smooth as the router bit will transfer the imperfections to the work piece. When you have it the way you want it.your ready to mount it to your work piece. Attach your template to the work piece . You can use double stick tape or screw it to the underside of the work piece provided it will not be seen. I like to screw when I can. Trace the shape to the work piece and remove the template. Rough cut the piece just as you did the template leave the line!!!! Re attach the template then use a flush trim bit with a bearing . Align the bit so the bearing will follow the template. Then route your piece following the template.. I am sure you will like the results

Jm

-- Smile and wave boys just smile and wave

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fussy

980 posts in 2516 days


#2 posted 11-06-2011 09:39 AM

What JM said is good, but I would suggest you use baltic birch 3/4”; the better and thicker, the better. The reason for this is problems you may have with resonance; feedback caused by vibrations from a less than ideal mounting being picked up and amplified by the cartridge. This is a classic feedback loop, especially if you’re a headbanger.

Steve

-- Steve in KY. 44 years so far with my lovely bride. Think I'll keep her.

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knotscott

7216 posts in 2841 days


#3 posted 11-06-2011 09:23 AM

I think following a template with a router bit is your best bet, whether MDF or hardboard. I’d go to a hardwood supply place to get good plywood.

-- Happiness is like wetting your pants...everyone can see it, but only you can feel the warmth....

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ajosephg

1878 posts in 3026 days


#4 posted 11-06-2011 01:43 PM

Using a template as described is ok, IF you are going to make more than one or two. Otherwise the time spent making the template could be used to make a one off base using a saw (jig, Sabre, scroll) and a drum sander.

3/4 Baltic Birch is the way to go – if you can find it. If it were me, I think I would glue two 1/2 inch pieces of BB together to end up with an 1 inch thick piece.

Since it won’t be visible MDF might even be better because of its density.

-- Joe

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bunkie

412 posts in 2612 days


#5 posted 11-06-2011 02:03 PM

Is the deck going to support the turntable platter and motor? If so, I would use much heavier material than 1/2” plywood. If you look at all of the higher-end turntables, they all have massive decks. This is to lower the resonance of the assembly. Light materials invite low-frequency feedback and poor bass response.

Take a look at the Pro-ject or Music Hall turntables. They use at least 2-3” of MDF.

Perhaps you could post some photos of the mechanism you are using?

-- Altruism is, ultimately, self-serving

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groland

152 posts in 2877 days


#6 posted 11-06-2011 02:27 PM

Thanks to all of you for your advice. Fortunately for me, I guess, is that I have two 48×96 x 3/4 inch sheets of baltic birch plywood sitting in my garage. At one point I was going to make some speaker cabinets, but that project has become unnecessary since I have speakers I like very much now (Quad ESL-63s).

The turntable in question is a Thorens TD-124 Mk I. It has recently been fully restored and runs like silk. I had a base for a 9” tonearm, but recently got an SME 3012 Mk II in really nice condition, necessitating a new base.

I was going to use 1/2 ply for the deck because that’s what the previous one was made of, but I think I will take everyone’s advice and move to 3/4 inch for my final version. The next deck attempt will be number three…time consuming but fun!

George

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bunkie

412 posts in 2612 days


#7 posted 11-06-2011 02:59 PM

Ah, nice vintage stuff. If memory serves, the TD-124 is a spring-suspended platter, right? I have a TD-165 on which the platter/motor sub-assembly also serves as the base for the tonearm. This was a common design back a few decades ago. Modern design has a rigid base to which the motor and tonearm are mounted which necessitates the massive plinth.

The SME arm is a lovely piece. I owned one a long time ago but never got to use it. I wish I still had it. Quads are in a class by themselves with certain kinds of music. You might still want to build speakers one of these days should you develop a taste for Stravinsky with his love of speaker-torturing dynamic range ;-)

Please post some pictures when you are done, I’d love to see them.

-- Altruism is, ultimately, self-serving

View StumpyNubs's profile

StumpyNubs

6856 posts in 2266 days


#8 posted 11-06-2011 03:47 PM

I think plywood was invented in ancient Egypt. I wonder if they used routers back then?

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Moron

5032 posts in 3359 days


#9 posted 11-06-2011 03:57 PM

MDF……….cheap, smooth,………stays flat, no voids

-- "Good artists borrow, great artists steal”…..Picasso

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devann

2201 posts in 2158 days


#10 posted 11-06-2011 07:32 PM

ditto what moron said.

Lots of goood advice above, using a bandsaw, jigsaw or some other means to cut close to your finished shape. You mentioned using a router bit with a guide bearing at the bottom of the bit. You might try a router bit with the bearing at the top of the shaft, with patterns these bits will give you better results.

-- Darrell, making more sawdust than I know what to do with

View jumbojack's profile

jumbojack

1667 posts in 2090 days


#11 posted 11-07-2011 12:44 AM

I am with Moron MDF for your deck. Comes flat and stays flat. Mills very nicely with a router bit. your routed edge will be sharp and crisp. Either use a pattern router bit (the ones with a bearing) or a bushing that fits in your router base. Get your pattern perfect and your product will be perfect.

-- Made in America, with American made tools....Shopsmith

View jerkylips's profile

jerkylips

273 posts in 2036 days


#12 posted 11-07-2011 11:40 PM

“Thanks to all of you for your advice. Fortunately for me, I guess, is that I have two 48×96×3/4 inch sheets of baltic birch plywood sitting in my garage. At one point I was going to make some speaker cabinets, but that project has become unnecessary since I have speakers I like very much now (Quad ESL-63s).”
If you consider doing speakers in the future, don’t use plywood – in my early 20’s I built a lot of subwoofer enclosures for cars, etc. Everything you read on the subject tells you not to use plywood because it’s too resonant – can create weird sounds. I can’t say that I experienced the issue, because I always avoided plywood, but it seems to be an accepted fact. MDF is what was always recommended for anything that speakers go into. Back then, we always covered with some sort of indoor/outdoor carpet or something, but I suppose you could use a veneer if you’re doing speakers for your home..

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