Rawlplugs for heatsinks?

[gingermrkettle]

Well not Rawlplugs, but being bored of the faff of M3 taps are there such a thing as threaded inserts that will hold a TO220 device to a heatsink properly? I can see the inserts supposedly for plastic but wasn't sure if they would be suitable.

 

[Barrymagrec]

You could use Helicoils - but then you`d have to tap the holes to insert them......

If you can access the other side of the heatsink and it is not too thick you could use self clinching bushes. https://uk.rs-online.com/web/p/clinch-nuts/0827619/

 

[sam_cat]

If you can access the other side simply drill a 3.5mm hole all the way through and use an m3 bolt with nut and washer on the opposite side.

 

[awkwardbydesign]

Nutserts. Basically threaded pop rivets. I use them in all sizes of thread.
https://uk.rs-online.com/web/p/products/7689978/?grossPrice=Y&cm_mmc=UK-PLA-DS3A-_-google-_-PLA_UK_EN_Fasteners_And_Fixings-_-Rivets_And_Riveting_Tools|Rivets-_-PRODUCT_GROUP&matchtype=&pla-417641336608&gclid=EAIaIQobChMI96Kkh4Wx3gIVy0MYCh1_hQ3cEAQYASABEgI6MvD_BwE&gclsrc=aw.ds
Or buy a kit, like this. https://www.amazon.co.uk/dp/B078KFLDW1/?tag=pinkfishmedia-21

 

[Barrymagrec]

Nutserts are good for sheet metal, especially if you can`t access the other side but they don`t go in quite flush so not so good for screwing a TO220 device down on.

 

[martin clark]

Just use a self-tapping metal screw in the blind hole? You really don't need or want much force to hold a TO220 in place.

 

[awkwardbydesign]

Nutserts are good for sheet metal, especially if you can`t access the other side but they don`t go in quite flush so not so good for screwing a TO220 device down on.

Countersunk ones do.

 

[Barrymagrec]

Not reliably so, in my experience, and you have to countersink the hole by exactly the right amount.

In the case of screwing devices to a heatsink nutserts won`t give maximum conductive area close into the fixing hole of a (say) TO220 device.

 

[Shadders]

Just use a self-tapping metal screw in the blind hole? You really don't need or want much force to hold a TO220 in place.

Hi,
Thanks for this - just did a search and screwfix sells them.

I did not know that they existed - are they suitable for power transistors with a TO-264 package and an aluminium heatsink ?

Regards,
Shadders.

 

[Arkless Electronics]

Just use a self-tapping metal screw in the blind hole? You really don't need or want much force to hold a TO220 in place.

Careful now if doing this. A raised area of alloy around the hole is common when doing this so it's best to screw it in all/nearly all the way and then remove it and file it down to flat.

 

[Barrymagrec]

Valid point.

 

[martin clark]

Good point!
Or drill the small hole, run a larger drill in 2-3mm to counterbore / debur with a countersink before Installing.

 

[YNWOAN]

In aluminium you can tap M3 by putting the tap in a cordless hand drill with a tiny dab of grease - I’ve done it hundreds of time (speeds things up enormously).

 

[martin clark]

Agreed, but works best with good-quality taps, not glass-hard cheapo ebay /chinesium specials (which can snap readily under shock, leaving an intractable problem unless you like playing with carbide, or nitric acid...)

 

[gingermrkettle]

Understand on the countersinking, although I still have a reasonable stock of https://uk.rs-online.com/mobile/p/thermal-gap-pads/0446493 which would help.

 

[hp1]

I did 300 regs one time each had 2x m3 threads so 600 taps at 20mm deep only took me 2 days and one dormer tap, trick is to wire brush and oil the tap every 3rd or so tap.