Howdy Gents,
I am brand spanking new to turntable building but I am determined and going to give it a try. I have access to a machine shop and some raw materials. My first question is about platter material. Is Delrin or HDPE a good material for a platter? I have a 12" dia., 5" long piece of Delrin and a 12" dia., 6" long piece of HDPE. It would be my luck that they are useless, but I have my fingers crossed. Does anyone have an input? Thank you in advance.
I am brand spanking new to turntable building but I am determined and going to give it a try. I have access to a machine shop and some raw materials. My first question is about platter material. Is Delrin or HDPE a good material for a platter? I have a 12" dia., 5" long piece of Delrin and a 12" dia., 6" long piece of HDPE. It would be my luck that they are useless, but I have my fingers crossed. Does anyone have an input? Thank you in advance.
Delrin could be ok, it does absorb moisture from the air though, so maybe not.
and HDPE, too soft really.
of the two Delrin is the better choice, it's not so much the materials but what you do with them that count .
a 10mm HDPE platter 'mat' could be awesome, but on it's own it will need some support for rigidity...
and HDPE, too soft really.
of the two Delrin is the better choice, it's not so much the materials but what you do with them that count .
a 10mm HDPE platter 'mat' could be awesome, but on it's own it will need some support for rigidity...
HDPE may sag, Delrin is much better. That big chunk was also a good bit of change- Delrin isn't cheap. It won't change much with humidity. I'd be worried about the resonant characteristics, and the idea of scooping it out and maybe potting in some lead shot has a lot of merit. Be sure to balance it when done. Also, like most plastics, it will hold a nice static charge- the reason that if I were diy-ing a table for myself, I wouldn't use a plastic or glass platter unless there was a conductive layer involved.
sq225917 said:
This is just half the story
Delrin which is a trade name for POM does as you say absorb moisture, but that is something that has already happened by the time our Kilowattski friend gets his chubby little hands on it.
It is what is referred to as conditioning.
After conditioning there are no dimentional changes or changes in properties worth considering for a platter.
So Kilowattski, you just go ahead and use your piece of POM for your platter, it will be just fine.
Magura
the issue with delrin really comes in when lathing it, that beatiful flat piece of Delrin heats up,it's mositure content changes and when it cools hey presto.. slightly out again.
if you take a slow thin cut this shouldn't be an issue but you need the right cutting tool for the job.
worth bearing in mind.
if you take a slow thin cut this shouldn't be an issue but you need the right cutting tool for the job.
worth bearing in mind.
I've machined Delrin and what sq3245634531 (!) says is true. Take light cuts at high speed and don't let it get too warm.
If you are careful and mark out some holes symmetrically for the lead shot, then all you have to do is put the same weight of lead shot in each cavity - a la Teres. Some kind of plug then to close the holes. The lead shot should be snug but not absolutely jammed in there. Shouldn't rattle if you shake it. No. 9 lead shot is what you're after, or close to it.
AFAIK Redpoint uses a skin of teflon on their platters so I wouldn't worry too much about the resonance. Sonics will be different with delrin but if everything else is good it will just be different "flavours".
What you do need to worry about is an excelllent bearing, plinth, platter and very important is the drive motor. You can get away without using fancy exotic plinth materials by adding mass and rigidity. I found the bearing and motor drive to be the biggest challenge in making an above par TT.
Fran
If you are careful and mark out some holes symmetrically for the lead shot, then all you have to do is put the same weight of lead shot in each cavity - a la Teres. Some kind of plug then to close the holes. The lead shot should be snug but not absolutely jammed in there. Shouldn't rattle if you shake it. No. 9 lead shot is what you're after, or close to it.
AFAIK Redpoint uses a skin of teflon on their platters so I wouldn't worry too much about the resonance. Sonics will be different with delrin but if everything else is good it will just be different "flavours".
What you do need to worry about is an excelllent bearing, plinth, platter and very important is the drive motor. You can get away without using fancy exotic plinth materials by adding mass and rigidity. I found the bearing and motor drive to be the biggest challenge in making an above par TT.
Fran
One of my neighbors owns a machine shop and has a Haas CNC Mill. I am going to try to sweet talk him into letting me write some G-Code for the Haas to turn a 5" thick hunk of aluminum into a Teres style plinth over a weekend. Wish me luck. I may cost a case of Pilsner Urqell, his favorite beer.
I have started to look into bearings. I have my eyes on a 1/2" ID Sintered Bronze, Oil-Impregnated, Self-Lubricating sleve bearing with a 1/2" case hardened steel shaft that is dimpled on one end for a ceramic ball. If I use the delrin I don't need a thrust plate. Does this sound ok?
For the motor and controller I plan to take advantage of the Motor and Controller group buy being administered by Algar_emi. I will also purchase the motor top plate and pulley. The rest of the enclosure will be made from a turned piece of 6" aluminum rod stock. I will bore out the center on a mill with a fly cutter.
Well, at least those are the plans. Everything is always subject to change due to suggestions by those more knowledgable than I.
I have started to look into bearings. I have my eyes on a 1/2" ID Sintered Bronze, Oil-Impregnated, Self-Lubricating sleve bearing with a 1/2" case hardened steel shaft that is dimpled on one end for a ceramic ball. If I use the delrin I don't need a thrust plate. Does this sound ok?
For the motor and controller I plan to take advantage of the Motor and Controller group buy being administered by Algar_emi. I will also purchase the motor top plate and pulley. The rest of the enclosure will be made from a turned piece of 6" aluminum rod stock. I will bore out the center on a mill with a fly cutter.
Well, at least those are the plans. Everything is always subject to change due to suggestions by those more knowledgable than I.
heavy wall tubing might be an easier option. theres a lot of boring on a solid rod of that size.
Teres motor pod size of about 115mm works out nice in use although you could get away with a bit less, say 90mm. It depends on the size of the PCB for the controller I suppose.
If you can get a machinist to make something like that - buy him 2 cases!!
Teres motor pod size of about 115mm works out nice in use although you could get away with a bit less, say 90mm. It depends on the size of the PCB for the controller I suppose.
If you can get a machinist to make something like that - buy him 2 cases!!
mpmarino said:
I'd say it's arbitrary, though it requires skills to do it on a lathe to avoid flying objects
By milling it you can by todays standards achieve very close to perfect round, and hence the material stress issues are not an issue for something like this.
If you take a look at many of the round pieces I've made over time, some of very high precision, you will see that they are milled, simply for the sake of doing everything in one operation, in order to get perfect alinging of holes, threads and so forth.
http://www.briangt.com/gallery/magura-40stepattenuator
This have been machined on a lathe on the outer faces (simply due to the fact that a lathe removes big amounts of material faster than a mill), but the rest is don in one operation per face on a CNC mill.
You have to keep in mind that we're not in the aerospace business, but just making a box. It need hardly to fit with anything. By todays standards tolerances and so forth are not an issue.
This reminds me I wanted to tell our Kilowattski friend that the above mentioned mashining issues with POM are 99% fear of flying, and the last 1% can be dealt with by simply spraying water onto the tool/workpiece. Before anybody gets the idea that the water is for the sake of conditioning....it's exclusively for cooling
Magura
As Magura says, tolerances are no problem for today's NC mills. I have a friend with a very well equipped shop, and he holds a couple tenths (.0002") routinely on pretty much any shape. Even better when he has to. The mill is appealing if you wanted some fancy cutout work on one side- thinking like the big telescope mirror that Corning made years ago, but even for simple holes it will guarantee almost perfect location and depth. The only place the lathe will win, and not by much, is the surface finish on the OD. You can always see the tool marks from circular interpolation, but with the right tool, the lathe will give close to a mirror.
Thanks for the encouragement gentlemen. I am sure Magura remembers me back from the Pass Labs forum where the same neighbor took me into his shop and and taught me how to use one of his Bridgeports and said I could use it on Saturdays as long as I bring my own raw material, clean up after I am done and put everything back in it's place. Thank goodness the machine had DRO. I built my Aleph 5 chassis this way. I realized quickly that I was not God's gift to machining but I got the job done whitout pulling all my hair out. He has since added the Haas CNC mill and I am teaching myself G-code programming in hopes of running the aluminum plinth and motor casing on the Haas. I have some sweet talking to do. I am thinking of trying a Corian platter based on what has been said here. What do you think gents. I know the project is not going to happen overnight because I am new to all this but I know you guys will help me through it with your posts. A sincere thank you for your posts.
mpmarino said:
I have done a great deal of machining and often worked with Delrin (amongst other materials). Hopefully the following will be of some use.
I certainly wouldn't use a fly-cutter to do the task you mention. I would use a lathe and turn (not lathe - this is not the right term) both the inside and ouside profiles; preferably without removing the piece from the chuck. A specific 'boring' bit is avaliable for turning the inside profile and allows the cutting head to reach inside the piece. This is not a difficult task in machining terms. I see now that you are simply intending to make an enclosure for a motor. However, I would still turn it with a boring bit as it is easier to achieve deep cutts than witha milling cutter - fly-cutters realy aren't suited to this task.
In my experience Delrin is best turned at a relatively high speed (depending on diameter of piece) with a reasonably fast feed and a slightly radiused cutting bit; this gives an excellent finish. Again, in my experience, Delrin is not prone to over heating when turning it and is, in fact, very easy to machine to tolerance. Don't try to turn off too much at once and you will be fine. However, if you are not experienced in using a lathe I wouldn't recomend doing any of these tasks as you are almost guaranteed to make a mess of it.
Of course you could use a CNC milling machine but it would have to be CNC run. As stated by another member very good tolerance is avaliable in this manner but if a very high surface finish and freedom from stepping jitter is required turning gives even better results (but potentially adds complications).
I have had a little change of heart. I am going to try and clone this turntable.
I have ordered a Teres bearing for $295 and have picked up the 3" thick, 13" aluminum round for the plinth for $200. As soon as I get the aluminum I will start. I will start the platter when then the plinth is done. By that time I will have the motor parts from the group buy. This isn't going to be an overnight project so bear with me guys. This I feel will be a little easier for me to build. I have easy access to aluminum and it will be easier to machine. I will be getting quotes on the Teflon platter top. I have built some Pass Labs amps and preamps but this by far will be my most challenging project. But I am determined.
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I have ordered a Teres bearing for $295 and have picked up the 3" thick, 13" aluminum round for the plinth for $200. As soon as I get the aluminum I will start. I will start the platter when then the plinth is done. By that time I will have the motor parts from the group buy. This isn't going to be an overnight project so bear with me guys. This I feel will be a little easier for me to build. I have easy access to aluminum and it will be easier to machine. I will be getting quotes on the Teflon platter top. I have built some Pass Labs amps and preamps but this by far will be my most challenging project. But I am determined.
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