[rcag_ils]

Don't mean to keep beating the dead horse, but does anyone have any experience fabricating a MKIII plinth? For the MKIII owners, would you kindly post the thickness of the MKIII plinth if you know it?

Question, are the springs used on the MKIII same as the MK4? I don't think they are since the MK4 has a heavier platter, but don't know for sure.

I purchased the springs for my 19 Jr., comes to find out, the Jr wood plinth may be too think for the springs, and it's not two pieces, so I plan on getting a piece of acrylic, and cut it to size to make it fit.

If anyone know of a good acrylic company that would do the work, please post it here.

Thanks in advance.

[Wayner]

How are you going to cut the acrylic? It really likes to crack, so unless you have CNC machines at your disposal, you are barking up a bad tree.

[Bob2]

How are you going to cut the acrylic? It really likes to crack, so unless you have CNC machines at your disposal, you are barking up a bad tree.

CNC..Really?

Lots of ways to cut acrylic. Drilling holes is more of an issue. An improperly ground drill bit will break acrylic very quickly. Zero rake angle will prevent drill bits fracturing acrylic.

How thick is it?
Find a craft store that has a laser cutter. They use them for engraving different materials. If it has the capability of producing 100 watts it will cut 1/4 inch in one pass. Thicker in multiple passes... You can purchase the materials from a variety of sources and take it and a drawing of what you want to them. Lots of machine shops can make that with cnc but charge upwards of $150 an hour (in my area)
plus programming and setup charge.

CNC is not required unless you plan on making a few hundred or thousands of pieces.

[rcag_ils]

I am planning on finding a plastic company, online or locally to do the work. But I would have to drill the holes myself since I don't plan on doing drawing and all. If the MKIII owners don't mind telling me how thick the MKIII plinth is, I know it's bonded on a piece of stainless steel.....

[billc]

I have a HW-19 Mk IV, and have replaced the springs (which potentially have an effect on sound) with Herbie's Audio Tenderfeet.

http://herbiesaudiolab.net/compfeet.htm

I use the tall ones.  I find them better than the springs, and the height may solve your plinth height issue.  This is a typical use for the tenderfeet (i.e., on VPI plinth support).

Worth checking out, and perhaps less expensive than a new plinth. 

Call Herbie, he is very helpful.

Bill

[rcag_ils]

Also there are companies online would sell you a pre cut piece, the prices aren't too bad, but I'll need to know the dimension.

[Bob2]

rcag_ils,
you should have no problem drilling holes yourself if you have the drill bit ground properly.
A local machine shop would probably do it very cheap or for nothing as it only takes less than 30 seconds to modify it.
What size hole?

Looks like billc has a good suggestion.

[rcag_ils]

I think the hole for the bearing would be about 1", then the rest would be 10/32 holes.

[Bob2]

#21 drill for taping 10/32.  Could be bought here..http://www.mcmaster.com/#number-jobbers'-drill-bits/=un0zre # 2901A194  $1.84. Clearance hole size for 10/32 screw use #7 drill bit also ground properly.

1 inch size here..http://www.mcmaster.com/#reduced-shank-drill-bits/=un11c8  # 8772A11 This will cost about $55.93 plus shipping.
Keep in mind that a hole for a bearing, if it has a particular "fit" cannot be drilled to size... Reaming or boring may be required!

If you have a machine shop grind the drill bits be sure to tell them what material you will be drilling.

Do this in a drill press, this ensures that the tool is perpendicular and easier to control. Either will fit in a hand drill with a 1/2 inch chuck but could easily get away from you.. Run this about 200 rpm and lubricate with soapy water or wd40.

Can be done with hand drill but use light pressure. Fracturing usually occurs just as the tip of the drill starts to exit the material.
By grinding the drill bit properly it will not try to pull itself through the material....

I have cut and drilled thousands of acrylic parts with the methods I have described.

[Bob2]

CNC works great for complex geometry...... like this!


but it sounds like your project is fairly straight forward.

[rcag_ils]

Thank you all for the tips.

[Bob2]

Your welcome. Good luck with your project and let us know how it works out!!

[rcag_ils]

Hey Bob2, one more question, how would you bond a stainless steel plate to the acrylic sheet? The MKIII plinth is 1/4" stainless steel plate bonded to 1/2" of acrylic, or I can just get a 3/4" acrylic sheet, but it wouldn't be the VPI spec.

Very nice table you have there, you must have spent tons of time on it.

[Bob2]

racg_ils,
Follow the links to Mcmaster Carr. They do sell some adhesives they claim will join acrylic and ss.
Might have to dig around a bit but it should be there.

The 3/4 material could be machined down to a specific size, all it takes is some money!
Acrylic machines ok. Just need to keep tool velocities in check and keep the material cool.

Thanks and yes, I do have a bit of time in that.

Keep us posted!

[Wayner]

1. He does not have a machine shop. It also sounds like he does not have a drill or drill bits.

2. Describe to us what is exactly a "properly" ground drill bit, since you have done thousands of units like this. Perhaps you can provide a detailed CAD drawing of the bit that is needed.

3. I don't know of any craft store around here that has a laser.

A CNC milling machine has all of the tools required to create such a plinth. It has many different types of bits for machining, they are easily programmed, and the outcome will be successful. The cost will be significant, as there is only 1 unit.

I've been in manufacturing for 40+ years, experienced with many types of plastics, steel and aluminum. If you do not have the tools to do the job, the success rate will be next to zero.

[Bob2]

Very apparent that the op does not have a machine shop. This is why I suggested going to a machine shop to have the drills ground properly.

Craft stores do have laser cutters, so do community colleges and plastics fabrication/sign shops.

One would think that with all your years of manufacturing experience you would know what a zero rake angle actually means.

Blanket statements that something must be done with cnc is simply not true. There are other methods that will do what the op wants to do. This is based on my 40 years of combined actual hands on experience as a journeyman toolmaker, fabricator, certified welder and 28 years of teaching college students in Mechanical Engineering classes as well as Solar Car, Baja and Formula car projects.

I appreciate your experience and knowledge. Just keep in mind others here also have some chops.

[Wayner]

I make recommendations to people that have positive outcomes. I've known rcag_ils for a long time and I know that he is a smart guy. We occasionally PM each other on other topics. His expertise is not machining. This is something that I would not even attempt to do (if I wanted a successful outcome). That is why I recommended that he find a shop with machining capabilities. You don't have to tell them that it takes .159 diameter hole to tap a 10-32 thread. rcag_ils probably doesn't have a tap, either.

Or, maybe because your so experienced, he can send the acrylic to you and you can machine it for him......

[Bob2]

Like you I'm trying to be helpful.
It appears to me you just want an argument.
What do you say we just let it go?

[galyons]

Most larger cities have a "plastics shop". Here in Northern California the chain is Tap Plastics. They will cut and " machine" all types of plastic material for a nominal cost.  Had them make a cover for my VPI TNT over 10 years ago. still looks like new today, ( an occasional polishing helps!). 

Acrylics are pretty easy to cut, drill, glue, (read "fuse").  But one needs some basic tools.  For the VPI plinth not much more than a table saw, ( or  a hand held saw and fence) and a hole saw.  And patience.  Tap, as would other similar shops, sells an adhesive to glue to metals.

Really NOTHING to get ones nickers in a twist over!!

Cheers,
Geary

[Wayner]

Like you I'm trying to be helpful.
It appears to me you just want an argument.
What do you say we just let it go?

I'm trying to be helpful, too. I don't think that rcag_ils is a DIY guy to the degree that he has all the tools necessary to make the plinth. So telling him what kinds of drill bit tips and machining jargon like that isn't going to help get it built. A drawing and a good fabricator will. BTW, a company I do work for has several lasers and they will not cut plastic, because the fumes screws up the laser head and the drippings from the plastic fouls up the cutting bed. For those that think acrylic is easy to machine without mishap, I say to the contrary. Polycarbonate is easy to machine. Acrylic is not polycarbonate. The Plinth on my VPI is about 1" thick, so I would assume that he should keep to that thickness as well, especially with the heavier platter.

And then I have to ask, does VPI not have a plinth for you in their stock room? By the time you get done screwing around with all of this, a plinth from VPI might be better and cheaper. Have you called them to find out?