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Rarkov 2nd October 2002 09:56 PM

Wanted: Aluminium Construction Tips

In the next couple of days, I will be receiving some heatsinks for my monoblocks I'm making. (Not a Nelson Pass design...That's next!)

The heatsinks are aluminium with a base of 4mm thick. I want to screw into this, without reveling the screws on the other side. To do that, I will use my dremel type tool with it's drill press set to a particular level so as not to drill through.

1) Do I need to tap this hole before screwing into it?

2) Should I use a spring washer?

3) Any tips so as not to thread the aluminium heatsink?!



P.S. I'll post if I've forgotten anything! Thanks

mbroker 2nd October 2002 11:54 PM

Re: Wanted: Aluminium Construction Tips

Originally posted by Rarkov
1) Do I need to tap this hole before screwing into it?
Probably, but even a blind M3 tap will likely be too deep for your heat sink.

2) Should I use a spring washer?
I would. It'll help keep the transistor(s) in contact with the heat sink(s) when things heat up. Plus they'll help spread the clamp load over a larger area, reducing chances of breaking a plastic case transistor.

3) Any tips so as not to thread the aluminium heatsink?!
Try epoxy, ala Peter Daniel? There are also clips that hold transistors to heat sinks, but the correct heat sink must be used, or a bar screwed down to hold the clips (check out the usual heat sink suppliers for more info). Could you drill holes into the fins? If the base of the fins is wide enough, you could drill precisely located holes deeper so you can more easily tap them.

Good luck,

Mark Broker

Jakeh 3rd October 2002 11:39 AM

I'm guessing ;) that the heatsinks have two pre-tapped holes offset around the midpoint of the sink, and four in the corners, something like this:


Depending on the number of output devices (and assuming they are flatpacks) I would go with a bar over the flatpacks fastened down with machine screws into the two central pre-existing tapped holes. Saves almost all effort...

So your only problem occurs if you can't fit the number of output devices...

Regards, Jake

Kram 3rd October 2002 11:42 AM

Hi Gaz,

Where did you get your heatsinks from and how big are they?

See ya

Rarkov 3rd October 2002 12:04 PM


Look one post above yours. See that little smile after the "I'm guessing"? That cause he sold me 'em! ;)

They are 150mm by 200mm so I hear. They arrived today but I haven't had the chance to see them yet. Jakeh's description will be about as good as you get until I can get a picture of them. There is a render floating around on here somewhere that I did from the description...

-: Click Here To View :-

The problem isn't really mounting the devices - which are flat pack incidently. The problem is mounting the internal chassis to carry the xformer without threading the aluminium. I am going to make an internal chassis and cover the exterior in wood, with the sinks sticking out of the sides.


Jakeh 3rd October 2002 12:08 PM


In which case are the corner holes no use? Make the former for the case out of aluminium angle, and bolt the heatsinks to it as appropriate.


Rarkov 3rd October 2002 12:16 PM

Yeah, that's an idea.

Are the holes all the way through? If they are - then I could get quite alot of strength into the chassis via the corner bolts and then a few screws for the middle of the heatsink to stop sagging. As long as I bend the chassis sheet metal in all three directions I should get no sag and the corner holes/bolts would take most of the force.

That was a glimpse of the logic that goes around my head 24/7! How sad / mucked up is that?!


Jakeh 3rd October 2002 12:20 PM

They are indeed all the way through.

Not that I can understand your plan!



Rarkov 3rd October 2002 12:25 PM

I'll have to do a render when I get home...Better yet - I could stop designing and get on with it - but that requires travelling down from Newcastle to Ripon in N. Yorkshire to use my Dad's garage / tools!

You'll have to settle with a render! ;)

Travelling down to my parents means eating their detox diet with no meat and lots of healthy things I can't pronouce the name of...It'll have to be when they're away! ;) Sorry mum ;)


pinkmouse 3rd October 2002 01:53 PM

Jakeh- got any of those heatsinks left?

I'm Sarf Lahndahn, where are you?

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