Kingston

Hello,

a bit of a practical problem here. I have several 1U rack cases where I have to mount the toroid in with the center bolt to the bottom of the case. The thing is, this bolt is just way too big fat one, and the case bottom would become lop-sided and won't actually quite fit in a rack either.

I was thinking of making a dent in the case bottom, where the hole for the bolt will be. But how to make this dent cleanly? I've seen this kind of dents in many cases in all kinds of electronics. How do they do that?

Say, a dented circle, diameter of maybe 2-4cm, depth maybe 5mm?

(then finally a drilled hole in the middle)

Mike


Viitalahde

I'd drill the hole first and then place something bigger, wooden & rounded (harjanvarrenpätkä!) on the hole and knock the dent in with a hammer.

keefaz

You can also try to place a large metallic circle/cylinder on the other side of the plate while hammering the bottom,
to act like a hole punch

Silvas

I´ve had this exact problem with my anteks...That´s what i done : i got some flat head screws, they were a bit undersized compared to the original one but it seems that the screw i used is strong enough...then i drilled the appropiate conical shape hole, using a big drill bit. Big enough so the screw´s head fit and is perfectly flat with the chassis bottom. It looks clean enough for me and works wonders. You have to experiment with the screw length and find which length works best for your case without being too long or having the screw touching the top of the case. Let us know how it worked ! the dent solution seems unnecesary to me if you mount the toroid this way...and will look better i think
Camilo Silva F.
Camilo Silva F. Mastering
Chia, Colombia

Tungstengruvsten

I thought and tried the punch-a-dent thing as well but after wasting quite few evenings trying to perfect it and make a tool that would do it I found an easier solution - a bracket that mounts to the side of the case - simple L-bracket that bolts to the side/back of the case and the torroid bolts to.  I put a small rubber foot on the bottom so the weight of the torroid wasn't strictly on the bolts(not that it would matter)

Check out the first NEQ I have in this thread - there is one mounted on that....
http://www.groupdiy.com/index.php?topic=33133.0
Is that a real poncho or a Sears poncho?

thedirtroad

I used #6 stainless steel flat head bolts and a regular counter-sink bit in my drill.
Drill the hole size you need and then use the counter-sink bit to well, counter-sink! The screw obviously goes on the outside of the case, pointing in and the nut goes on the top of the trafo.  I mounted the trafo in my GSSL this way.
I do this for all of my #4-40 PCB standoff's as well.  Works like a charm.

Tungstengruvsten

Here's a couple better pics:

Here's the torroid bracket -



...and i'm pretty excited as on this S800 case I don't have to put any bolts top or bottom leaving them smooth!   ....to be scratched by the gear above and below it...
Is that a real poncho or a Sears poncho?

Gus

google rivnuts. 

The rivnuts thing might be the best idea with Tungsten a close second.
But what I thought when I read your question was that instead of "punching" the hole, try "pulling" it. You have a lot more control than hammering. First drill the hole you need, then take a countersink bolt and pass it through the bottom. Flip the case and pass a steel tube with an inside diameter matching the outside diameter of the dent you want to make, put a washer and nut on it and start tightening the nut until it creates the dent.  Depending on the strength of the steel case, you may need power/air tools, but I think it would work fairly cleanly. As a first experiment you could use an appropriate size socket as the tube, but the cleanest would be to have the inside of the steel tube tapered to match the "dent."  If you use a slightly smaller bolt for fastening the toroid and nothing should protrude from the bottom. 


AudioJohn

A technique I have used on occasion with 1U high rack cases is to use the dished mounting plate washer that comes with the transformer - and mount it on the under side of the case. You need to drill or punch a fairly big hole for it to fit - and you still have the thickness of this on the bottom surface - but the mounting screw is now well recessed.
This method is quick and provides a very secure fixing - but you will need another washer for the top - as most transformers only come with one!


Kingston

Thanks to everyone.

Rivnuts look ok, but I would have to order them from quite the specialist stores.

I have to try that pulling thing. I have all the parts and equipment for that already.

The toroid L-bracket looks good and has the added bonus of extra magnetic shielding, depending on the metal of course. I'll have to do that sometime as well.



Completely off topic,

I was googling for those rivnuts and found a big store selling them and bumped into this: http://www.gen-aircraft-hardware.com/site_tips.asp#Why_is_the_Web_Store_closed_sometimes

That must work so well in the global economy. And also, does it mean he has definitive knowledge that god lives in Pacific Time Zone?

1954U1

Completely off topic,

I was googling for those rivnuts and found a big store selling them and bumped into this: http://www.gen-aircraft-hardware.com/site_tips.asp#Why_is_the_Web_Store_closed_sometimes

That must work so well in the global economy. And also, does it mean he has definitive knowledge that god lives in Pacific Time Zone?

Incredible!
He's somewhat right, because God is telling to him, who live in Pacific Time Zone, to respect the 10 commandments.
But its not enough..
He sould  not sell anything also to people doing orders in their Sabbath time.
But maybe he's ok about dealing with sinners.

mad.ax

Why not using something like the one on the upper right corner of this pic?

I don't even know the name of this thing in French, so I cannot translate it in English! But you should find it easily at any store who sells stuff for plumbers.
Just drill a bigger hole in your case and use this as a washer...

Axel
« Last Edit: April 25, 2009, 04:50:13 PM by mad.ax »

doubleroger

That plumbing washer is a great idea!

AudioJohn, I don't really get it, do you mean the hole should be a little less than the size of the washer and so the washer would get stuck when one fastens the screw, or should the plate be under the transformer or what?
Please explain.
Arthur.

Re: mounting toroid to case bottom. bolt too big and case won't fit in rack
« Reply #14 on: February 11, 2016, 09:05:40 PM »
for reference - i think the 'proper' way to do this is to build a 'form' first - can even be a piece of plywood etc with a 3/4" or 1" diameter sunken hole in it (at least the depth of the thickness of the bolt head) and then 'punch' (with a smaller diameter like half inch or so - should be at least the size of the head of the bolt) into the recess making a recess with angled edges. Ideally maybe the depth of the recess could be a bit more than you need for the bolt head in order to get the trafo OFF the bottom sheet of the chassis...

Whoops

Re: mounting toroid to case bottom. bolt too big and case won't fit in rack
« Reply #15 on: February 11, 2016, 11:52:49 PM »
for reference - i think the 'proper' way to do this is to build a 'form' first - can even be a piece of plywood etc with a 3/4" or 1" diameter sunken hole in it (at least the depth of the thickness of the bolt head) and then 'punch' (with a smaller diameter like half inch or so - should be at least the size of the head of the bolt) into the recess making a recess with angled edges. Ideally maybe the depth of the recess could be a bit more than you need for the bolt head in order to get the trafo OFF the bottom sheet of the chassis...

It would be nice to get some pics of that.

I'm using this:
http://www.cmc.pt/public/images/Porcas-de-Rebitar-Estriadas.jpg
http://www.screwcenterbrooklin.com.br/rivkle/porca_rebite_cabe%C3%A7a_plana.gif
http://www.kive.pt/media/catalog/product/2/0/2010213120034_1.jpg

CJ

Re: mounting toroid to case bottom. bolt too big and case won't fit in rack
« Reply #16 on: February 12, 2016, 01:47:25 AM »
JB Weld a nut to the bottom of the chassis,
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

gswan

Re: mounting toroid to case bottom. bolt too big and case won't fit in rack
« Reply #17 on: February 12, 2016, 02:20:31 AM »
Not sure how much internal clearance you have, but I've solved this problem by mounting the toroid to a 3mm aluminium plate using a countersunk bolt and then screwed the aluminium plate to the chassis base with 4 M3 countersunk screws, which can be made flush with the bottom of the chassis.

Gene Pink

Re: mounting toroid to case bottom. bolt too big and case won't fit in rack
« Reply #18 on: February 12, 2016, 03:15:33 AM »
instead of "punching" the hole, try "pulling" it. You have a lot more control than hammering. First drill the hole you need, then take a countersink bolt and pass it through the bottom.

That's the route I would take, with a variation.

If you can get it mounted in a vise with deep enough jaws to get at the appropriate spot, squeeze it.  Been there. done it like this for one-offs:

Assuming an SAE 1/4-20 flathead screw, use a 1/4" drive socket as an anvil, helps in centering everything. Socket #2 is only for clearance for the end of the screw, not necessary if you have an arbor press with clearance. You can work your way in iterations through the socket sizes for precision, or just use one about 1/8" bigger than the screw head O.D. and be done with it. The sheet metal may split a bit, and likely will if aluminum, but so what?  The end result may be a bit rough, but it will be flush.

Gene

Audio1Man

Re: mounting toroid to case bottom. bolt too big and case won't fit in rack
« Reply #19 on: February 12, 2016, 02:24:12 PM »
Sometime you can’t see the forest because of the trees. Try to think outside the box.
Dimpling the chassis typically requires 3-5 ton’s of force for 16ga CRS Installing a Pem stud fastener may take 1500 lbs. Both require some special tooling and machinery that may not be easily obtained. Why not look at a strap the can clamp the toroid to the side(s) of the chassis. This can fabricated using a vice and hammer.  The toroid height must not exceed 1.60 to fit into a 1U chassis. Get a strip of 1’ steel / alum / ? and go to work.

Duke :)


 

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