OK - then I should try your original hard balsa wood cage idea then.
Just cut to size with a Stanley knife and drill a hole in the centre slightly larger than the sphere?
thanks
Jim
Why not get a brass pipe end slightly smaller size than Xanthe original pic?
Also you could get some ptfe machined to sit tight in the brass with a central hole a bit bigger diameter than the ball or wouldn’t that work?
Yes, the sliding hasn’t been too much of an issue, once set up it’s been fine unless you knock it hard. The glass can slide on the ball bearing anyway.
That sounds like it would work.
Can you just order that online at low cost?
Would save time if I could get the sizes right first time.
You could get the ball beatings and nuts and then change the nuts later if needed, they cost next to nothing.
Hi Xanthe
Situation Report:
10 x 1/4 inch diameter grade 5 silicon nitride balls and 2 slightly larger chrome-plated steel ball bearings have been delivered. (Please don’t tell me the chrome-plating was a mistake - unless it was!)
10mm toughened glass, cut to size with polished edges - due for local collection in the next few days.
Brass stop ends - the 1st fleabay supplier you mention above is not currently open, and the 2nd supplier doesn’t take enquiries. So I’m struggling currently to find any of these online.
I may try a local ScrewFix or other hardware shop locally?
Just wondering how deep the dents in the brass base are likely to be?
Less than 1mm?
I know that depends how hard I hit them, etc.
But if I buy blanking discs that create a cup with walls that are 4mm in height from the base, do you think that will do it?
How high are the walls on yours?
Any tips appreciated - or even a hint as to which actual discs worked for you if poss.
thanks
Jim
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Chrome plated ball… the chrome plating makes no difference, the ball needs to be through hardened, and preferably made from bearing steel (i.e. not mild steel or stainless steel, both of which are too soft and may get a small flat spot where they are impacted by the hammer). I’d also recommend having the ball used to make the dent at least 2x the diameter of the nitride ball.
Dropping a 4lb club hammer onto a 16mm ball from 400mm gave a dent about 4mm diameter about 1/2mm deep.
Although the brass fittings are technically stop ends, the fleabay listing describes them as “28MM COMPRESSION FITTING BRASS BLANKING DISC”; searching for that should reveal them - the seller is “wwltd7779” and they are based in Weston-super-Mud.
The walls on the cups I made are about 4mm above the floor of the internal recess.
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Yes, I’ve found those 28MM COMPRESSION FITTING BRASS BLANKING DISCs.
So the 1/4 inch spheres you use minus the 1/2mm dent should stand up about 2mm higher than the wall.
thanks
Jim
Yes, about right (I haven’t measured it though, I’m not quite that obsessive!).
As long as the glass rests only on the spheres, it’s irrelevant how close the brass wall is anyway. 
Are there any tricks to installing it?
So place the 3 cups and spheres on the shelf and then put on the glass, and then slide the heavy boxes into place without dislodging anything!?
Sounds a wee bit awkward, but doable, preferably with someone else holding the glass in place to keep things steady?
Put one disc and sphere near each front corner - and the other one centred near the rear edge?
Yes
.
I do it the other way, I place the cups & balls on the shelf and place the component on the glass; I then move the glass and the component into position and (carefully) lower it onto the balls (or temporary wooden supports - see below).
There isn’t much room for fingers below the glass, so you may want to put temporary wood blocks in place to support the glass whilst you position it; then, in turn, lift the glass slightly, knock out the wooden support(s) and gently lower the glass onto the ball (I found this relatively easy to achieve). To fine adjust the glass, just lift it slightly, reposition and lower it, then raise the glass a little over each ball in turn to allow them to centre into the depression in the brass.
Using temporary wooden supports also has the advantage of allowing the system to be re-cabled whilst the components are supported in a more rigid manner.
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Thanks again, Xanthe.
You are my spirit guide in the War on Vibration.
Well, as your spirit guide, then I recommend a good armagnac. 
6 Likes
When you drop the weight onto the brass cup, does it bounce and make more than one dent?
In 20 done so far, yes it bounces but only once have I got 2 dents.
Do you fancy bashing my stop ends if I post them with an SAE Jiffy bag and some steel balls?
What size silicon nitride balls do you have?
Well the whole set have been installed now (rather than just the 272), and all the glass upped to 10mm thick.
Compared to the original 8mm glass and 10mm dome nuts there is quite a significant improvement, not night and day, not as big a change as a full black box upgrade, more like the difference between MP3 and FLAC; so for less than £150 (both the glass and home made isolators) it’s something of a bargain upgrade.
3 Likes
5mm diameter silicon nitride balls.
(And I’ve got 3 steel balls too of various larger sizes that I bought to make the dents).
Assuming the inner diameter of the recess in the brass you have is 23mm I’ll use my own 5/8" bearing steel ball to make the indentation as that way I can use the jig I made to hold the ball in place during the impact (thinking about it the fact that I’m using a relatively rigid jig may be the difference as to why I don’t get double dents!).
The recess in the brass I have is 4.3mm deep and the ‘dent’ is about 0.3mm deep (by 3.5mm diameter), so with 5mm balls you’ll only have about 0.4mm clearance between the rim and the glass. You’ll need to ensure that the brass cups sit level, you won’t have much tolerance in the leveling.