Thorens 520 armboard--drilling hole for tonearm

[will shade]

I have a Thorens 520 that's been on a shelf for a few years (main turntable is an LP12) and I've been working on setting it up. The arm is an OL RB250 and I had it set up with a somewhat kludgy VTA thingie that I would like to remove. The armboard accommodates the VTA sleeve, but the hole is too wide for the Rega arm, so I need another armboard. I bought the armboard, which is made of rosewood I believe, from an outfit in Taiwan.

These armboards aren't easy to come by, but there are a couple of Swiss gentlemen selling them on ebay--usually drilled for SME or some other arm, acrylic, and rather pricey. I am comfortable doing diy stuff, including woodworking, and could easily make a new armboard myself (I think), but I'm not confident about getting the 9" tonearm centered correctly with the spindle. I'd happily pay someone to do it to know it was done right, but again, I really should be able to do it myself. Do people drill their LP12 armboard themselves? Any words of advice, encouragement, etc? (Searched Thorens 520 in the forums and it appears to be an uncommon 'table here.)

 

[matt j]

There's usually an LP12 armboard pre drilled to suit most of the common arm fixing standards so generally speaking they don't require DIY drilling.

It's a shame you've already bought it, you could probably have bought one pre done from the UK. A chap called Steve at Magna Audio makes tons of arm boards (as well as lots of other nice stuff) for all sorts of TTs, drilled for any arm you like.

 

[Craig B]

Almost seems a shame not to be taking advantage of the greater girth of TD-520, by not fitting a 12" tonearm. Regardless, I have what I like to call 'hard and fast' rules for doing arm boards with minimal scope for error.

1. Assuming the new board has its 3 mounting holes pre-drilled, simply mount the blank board on the deck and then, using the tonearm maker's supplied template, mark the centre of the spindle to pivot point. Often this is more accurately achieved with both platters off, with the spindle hole of the template enlarged such that the sub-platter/spindle can be inserted through. This allows for a perfectly flat plane between centre of axis of platter and tonearm pivot point, negating the possibility of error using the typically suggested pin through pivot point extending down to the board from platter height.
2. When deciding where the hole should be along the circumference of the spindle to pivot arc, make sure to take into consideration front and rear clearances with dustcover on and down. Rega's template indicates the necessary clearances. This is not generally a problem with plinths the size of TD-520 combined with circa 9" tonearms, so the final position can often be selected more from an aesthetic perspective.
3. Under no circumstances use anything other than a proper drill press with fresh bit to drill the hole(s). Small cabinet shops are always equipped with a free-standing drill that the proprietors are often happy to allow access to, or do the drilling for you FOC.

HTH,

Craig

 

[Seanm]

It doesn’t have to be accurate to the millimetre, as the arm has slots in the head shell to compensate for minor inaccuracies.

I can’t quite remember how I did it when I was making an armboard for my TD125: I think I either tied a bit of string to the spindle, and to a pencil at the other end, or I used a strip of wood with holes drilled at either end, 222mm apart, one for the spindle and one for a pencil. Then drilled with a hole saw bit. It was all quite easy, and I don’t have a clue.

 

[will shade]

Thanks, that's helpful. I think I'll try to drill a new one myself.