Single gauge and dual gauge TO-220

[mike_mike]

Dear Forum,

I recently bought a few LM317T in TO-220 case. I saw that the heatsink of those LM317 is very thin. I found that they are single gauge.
I tried to install one of them on a heatsink, but I cannot install it properly because when I squeeze the M3 nut the lower part of the LM317T is rising from the heatsink and the heat generated by the LM317T is not absorbed by the heatsink, making LM317T to overheat.
What should I do to install those LM317T properly on the heatsink ? I know that I can mount the LM317T using a clip, but sometimes I cannot use a clip due to the heatsink dimensions...

Thanks in advance.

[ArthurDent]

The best way to solve this problem would be to buy some higher quality regulators that are made with correct thickness tabs and scrap the cheap ones. My fear would be if the people who made these knock-off cheap regulators cut corners on tab thickness, what else did they do internally to save money and will I find other problems over time if I use them. 

If you want to try using them (which I don't recommend) you could try using the largest size thick flat washer you can fit under the nut to hold the regulator on the heatsink without distorting the tab. If this works you're still going to be wondering when these cheap parts might fail.

[james_s]

It sounds like what you bought are cheap counterfeit parts, they are probably deficient in other areas as well. I agree with the above poster, you should get some genuine parts.

[floobydust]

This is cheap crappy Fairchild junk, who came up with "single gauge" TO-220 
Tab is 0.55mm thick verses 1.3mm (note F).

It easily bends and doesn't fit insulator bushings. Absolute junk KA317.
Buy another manufacturer's part.

[djnz]

I was bitten by this issue today, and the parts were of known provenance, bought from authorized distributors. Upon investigation, it was clear that this is not a case of counterfeit parts etc; many (all?) manufacturers are supplying TO-220 parts with thinner tabs now, by default, and have re-designated the old thicker tabbed parts to other order codes. For example, ST's version of the thicker tabbed 7805 is now L7805CV-DG, and if you just order L7805CV, you get the one with a thin tab.

[Jwillis]

Shoulder washers.