Where to source tinned brass M5/M8 hex bolts connecting the transformer to heat sink?

Q&A and troubleshooting
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1

I’m trying to find replacement M5 hex bolts to connect the transformer wires to the aluminum heat sink on the power board; I managed to overtighten and shear them off by accident when putting my inverter back together. They are copperish/bronze colored on the inside and silvery on the outside, and the repair shop my dealer connected me to told me they are NOT regular stainless but in fact tinned brass.

I have had zero luck trying to find tinned brass bolts to reconnect my transformer to the heat sink. I have been going back and forth with Victron directly trying to find out where they source them from or a suitable replacement, but have not gotten a clear answer.

As a side note, is it acceptable to drill and tap a new hole for an M5 bolt? I unfortunately stripped out the original hole when removing the bolt fragments with an extractor kit, and had to retap it to a larger size. Now I’m thinking a better course of action would be to simply drill and tap a new M5 sized hole instead and attach the transformer lug there, and maybe fill in the old hole with a fresh aluminum screw so I don’t have empty space (if this is even necessary, if not I’ll just leave an empty hole in the side of the heat sink).

2

Hi i don’t know what country your in but i use these guys
Hexagon Socket Screws (trfastenings.com)
You can also buy from Farnell direct.
Most local (to you?) fastening company’s will sell direct too.
Hope this helps.

1 Like
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You use these to connect the transformer lugs to the heat sink? I’m assuming you use the stainless screws, right? If so are those ok to use? I’m worried about heat and corrosion because the originals look like these rare tin coated brass or copper types.

4

Hi there is a good guide on RS here about different Machine Screws, as long as there is no special requirements A2 or if you’re worried about corrosion A4 stainless will be fine (as there is no tensile strength requirement), the tin coated brass is a standard option in many applications and is cheaper that stainless.

I tend to use the best I can for whatever applications it is appropriate for as experience has taught me you can never be too careful.