The quote for Delrin just came back. For 3 platters, with 12 holes drilled/bored around the perimeter, BUT NOT TAPPED, $775.00/ea plus shipping. As one might imagine, the holes add considerable time to manufacture.
Note that the price of polymers is tied to the market price of petroleum which is currently at a four year high. No deals on Delrin.
I’m about 95% certain that I am going with aluminum bored for shot loading. I’ll anodize it black and be done with it.
Note that the price of polymers is tied to the market price of petroleum which is currently at a four year high. No deals on Delrin.
I’m about 95% certain that I am going with aluminum bored for shot loading. I’ll anodize it black and be done with it.
Just some thoughts. Not sure what type of plugs you are going to use. You could have the machine shop cut some aluminum round stock approximately .125 thick and with a larger diameter. Then bore down the holes the plugs diameter to .125 deep. This will leave a nice ledge for the caps to seat to. Then loctite if slip fit or interference fit them. If you ever want the caps out loctite would be the easier option. From a strength standpoint the holes would be on top for the caps. No lead weight pushing down on caps. You will probably use a mat of some kind so cosmetics may not be a concern.
The threading sound kinda cool but it is a lot of time. Also if you cap on the top do not use any magnetic material. Even stainless has some magnetic pull.
Hope this gives you some ideas. If you go with threaded please post the process. Always looking for new processes.
Enjoy the ride
Tom
The threading sound kinda cool but it is a lot of time. Also if you cap on the top do not use any magnetic material. Even stainless has some magnetic pull.
Hope this gives you some ideas. If you go with threaded please post the process. Always looking for new processes.
Enjoy the ride
Tom
Another option, which I have already done, is make the platter 2 piece. Then bolt it together to make the thickness you want. Say you want 3.000 thick platter make bottom out of say 2.000 and top 1.000. drill the holes for or lead on bottom and use top to cap the holes.
Could use a delrin top and not even use a mat. I am going to do this as I have a 2 .375 thick delrin piece which I will cap with a .500 aluminum plate on the bottom.
Not sure how the delrin will mate with the aluminum but it's a hobby for me and I have the machines. On my two piece aluminum platters you have to look really hard to see a line but that is after I bolted them together and I turned them on a lathe. You could ask your machine shop guy about dowel pins.
The combos and sizes are endless maybe use whatever you can get a deal on. If you are going to get the materials talked to the machine shop to make sure they can do what you have in mind. I assume you have a teres bearing to show them.
Enjoy the ride
Tom
Could use a delrin top and not even use a mat. I am going to do this as I have a 2 .375 thick delrin piece which I will cap with a .500 aluminum plate on the bottom.
Not sure how the delrin will mate with the aluminum but it's a hobby for me and I have the machines. On my two piece aluminum platters you have to look really hard to see a line but that is after I bolted them together and I turned them on a lathe. You could ask your machine shop guy about dowel pins.
The combos and sizes are endless maybe use whatever you can get a deal on. If you are going to get the materials talked to the machine shop to make sure they can do what you have in mind. I assume you have a teres bearing to show them.
Enjoy the ride
Tom
I have decided to go with an aluminum platter with 12 holes for shot around the perimeter. As the shot will be in a highly viscous damper bath, the holes must seal perfectly.
I really don’t see that happening with Delrin.
At one point in my life i managed an injection molding facility. Polymers are not the uniform, inert, easy to work with materials most people imagine them to be. They can be hygroscopic, they have flow patterns, entrained air, Delrin especially has grain direction etc. They warp and deform over time. Delrin is in that class of material that is hard to join to anything including itself especially if an oil-tight seal is required. Also, polymers don’t age well especially in sunlight and this will be the last turntable i ever build ...........(right). Expect that a 3 inch thick section of Delrin will have vastly different characteristics at the surface(s) than in the center. Cutting, milling and boring will release tensions and change dimensions and probably balance. I could go on. But hey.....maybe it’ll sound slightly better.
Now, if you are just loading with shot and there is to be no oil, then maybe some specie of acceptable press fit can be achieved.
Interesting that you mention the sandwich option, as i am paying a machine shop to do this, that would likely drive the cost higher than my budget allows. But i like the idea of different densities/resonance patterns in the platter.
I really don’t see that happening with Delrin.
At one point in my life i managed an injection molding facility. Polymers are not the uniform, inert, easy to work with materials most people imagine them to be. They can be hygroscopic, they have flow patterns, entrained air, Delrin especially has grain direction etc. They warp and deform over time. Delrin is in that class of material that is hard to join to anything including itself especially if an oil-tight seal is required. Also, polymers don’t age well especially in sunlight and this will be the last turntable i ever build ...........(right). Expect that a 3 inch thick section of Delrin will have vastly different characteristics at the surface(s) than in the center. Cutting, milling and boring will release tensions and change dimensions and probably balance. I could go on. But hey.....maybe it’ll sound slightly better.
Now, if you are just loading with shot and there is to be no oil, then maybe some specie of acceptable press fit can be achieved.
Interesting that you mention the sandwich option, as i am paying a machine shop to do this, that would likely drive the cost higher than my budget allows. But i like the idea of different densities/resonance patterns in the platter.
TomWh.. I did the shot and silicone fluid when I built my turntable. I have the bore with the shot/ oil above that I have a counterbore for a o-ring and above that I have a counterbore for the 0.125" thick aluminum plug that had a press fit. On top of that I have a 0.875" thk. piece of graphite in the shape of a donut..Like Redpoint and Galibier designs have.
Seth...I built my table 10+ years ago and I anodized my platter silver and I can see a wear line from my 0.500 wide mylar belt....you may want to reconsider the black anodizing.
Scott
Seth...I built my table 10+ years ago and I anodized my platter silver and I can see a wear line from my 0.500 wide mylar belt....you may want to reconsider the black anodizing.
Scott
We can definitely play with mats. I was just about to do some arithmetic to ball-park the weight. Standby. BTW, i was looking at images of original Teres acrylic platters. They are agreeably transparent. Looks like the holes for the shot are not all that deep. If you want to see what i’m seeing, PM me. Don’t want to rip off an image and get banned.
Did this fast and it’s only a very rough calculation:
Weight of a 12 inch dia. 6061 disc 3 inches thick: 33.23 lbs
Remove 12 cylinders of aluminum 2.5x2 -11.5 lbs
Weight of 12 cylinders filled with lead shot 2.5x2 +35.59 (!) lbs
Total: 68.82 lbs
That ought to do it for mass don’t you think?
TL;DR - adding lead shot nearly doubles the mass
Weight of a 12 inch dia. 6061 disc 3 inches thick: 33.23 lbs
Remove 12 cylinders of aluminum 2.5x2 -11.5 lbs
Weight of 12 cylinders filled with lead shot 2.5x2 +35.59 (!) lbs
Total: 68.82 lbs
That ought to do it for mass don’t you think?
TL;DR - adding lead shot nearly doubles the mass
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Nrenter - that was most timely. Also thanks to Scott for that note regarding anodizing. I will take both into account. I had the quote modified to reflect 24 holes 1.25” in diameter bored but not threaded. The charge for the holes adds $245.00. The cost of the basic platter in aluminum per Chris Brady’s drawing is $748.00 of which $350.00 is the cost of material. So.....~$1000.00. I think that’s a fair price considering the scope of work, cost of material and accuracy required. What say you?
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I don't think that's too unreasonable. If your machinist is up for it, I'd be willing to purchase an aluminum, drilled platter, too (provided it's black anodized). A couple questions:
Do you trust your machinist to produce this to spec (and that the finish will look professional)?
Have you determined appropriate caps for holes? Should countersinking of the selected cap lip be considered?
I'd like to know the anodization is very black
And a last question to the DIY community...Are there any "lessons learned" or considerations before committing to machining? The basic shape / design is set, but would you suggest any modifications to the top (platter / record interface)?
Do you trust your machinist to produce this to spec (and that the finish will look professional)?
Have you determined appropriate caps for holes? Should countersinking of the selected cap lip be considered?
I'd like to know the anodization is very black
And a last question to the DIY community...Are there any "lessons learned" or considerations before committing to machining? The basic shape / design is set, but would you suggest any modifications to the top (platter / record interface)?
Nrenter - all excellent questions. I will have the platter anodized in Connecticut where the shop is. Was going to ask the group here about surface finish. I would think something slightly grippy would be in order, or, does anodizing give what is wanted? Never seen what I’d consider a highly polished anodized finish.
I’m more concerned about the precise dimensions and absolute squareness of the bore for the bearing. I’m sending him my NIB Teres bearing to ensure proper fit. The drawing spec is +- .005. That won’t do. If -.005 the bearing won’t fit period. If +.005 it’ll be sloppy and all the precision machining in the bearing itself won’t matter. Don’t want to have to use Locktite to make it work.
I’m more concerned about the precise dimensions and absolute squareness of the bore for the bearing. I’m sending him my NIB Teres bearing to ensure proper fit. The drawing spec is +- .005. That won’t do. If -.005 the bearing won’t fit period. If +.005 it’ll be sloppy and all the precision machining in the bearing itself won’t matter. Don’t want to have to use Locktite to make it work.
Boy did I get sucked down a rabbit hole. 1.25 inch NPT taps can be had for less than $30.00 in carbon steel. Polymer chemical resistant pipe caps in that dimension are less than $3.00/ea from McMaster.
But....I don’t want plastic pipe caps on my thousand dollar platter. Also, the finished platter would have to be fixtured in such a way as not to damage it. Then one would have to tap 24 holes without screwing one up.
So...bronze? Couldn’t find any that big and they get expensive fast in the 1.00” dimension they seem to top out at. Think $12.00-20.00/ea and I need 24. Could just buy a 24 inch length of 1.25 inch aluminum round bar that would have to be parted off in a lathe and tapered slightly.....24 Times. Not cheap either. Ideas?
But....I don’t want plastic pipe caps on my thousand dollar platter. Also, the finished platter would have to be fixtured in such a way as not to damage it. Then one would have to tap 24 holes without screwing one up.
So...bronze? Couldn’t find any that big and they get expensive fast in the 1.00” dimension they seem to top out at. Think $12.00-20.00/ea and I need 24. Could just buy a 24 inch length of 1.25 inch aluminum round bar that would have to be parted off in a lathe and tapered slightly.....24 Times. Not cheap either. Ideas?
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I don't think tapping is necessary, particularly since the platter isn't transparent (and you won't see how the plugs secure into the holes). As long as the plugs don't protrude more than 1 mm or so from the bottom, and they stay snug, they won't impact spin (and won't really be seen). Granted, I'm not planning to use oil / silicone along with lead shot, so the seal (for me) won't need to be liquid tight. YMMV.
Slightly grippy (matte) is probably good (no need for mirror polish).
I agree with your concerns with the bearing dimensions - and is why I don't think the costs are that egregious. I may be able to have a platter made cheaper, but that machinist wound't necessarily have a bearing in-hand to ensure a perfect fit. Buy nice, cry once.
Slightly grippy (matte) is probably good (no need for mirror polish).
I agree with your concerns with the bearing dimensions - and is why I don't think the costs are that egregious. I may be able to have a platter made cheaper, but that machinist wound't necessarily have a bearing in-hand to ensure a perfect fit. Buy nice, cry once.
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