As does Home Depot.
JB WELD is not thermally conductive, though. There are thermally conductive epoxies available. I suggest using those if you go that route.
Tom
I haven't had any issues with that. The only snag I've come across is that some types of screws aren't shipped from the US to Canada. I think that has to do with the type of steel used for the screws. I'm pretty sure it's the zinc plated screws that won't ship. I haven't had issues with stainless steel hardware.
Of course, these days that can change as the wind blows, so what worked six month ago might be unworkable tomorrow.
I have noticed that McMaster doesn't stock everything in one location. So if the shipping seems high, take a close look where the items ship from. I often find that one item ships from Warehouse A and the rest from Warehouse B. Finding a substitute for the one that ships from Warehouse A can often cut the shipping charge in half.
That said, I would much prefer to shop locally, but my local hardware suppliers don't typically stock small screws like M3.
Tom
M3 screws are cheap here, 3x10 in mild steel are like 25 cents for 100, and $2 US in stainless steel.
Nuts are cheaper.
You could buy a few hundred at a time direct from maker and stock up.
Nuts are cheaper.
You could buy a few hundred at a time direct from maker and stock up.
20 years ago my M3 hardware came from Brafasco at a ridiculous premium. One little box of whatever would set me back $50 to $80.
10 years ago I was buying from China eBAy and Alibaba. Zero compromise in quality and almost ten times cheaper.
Last year and this past winter I stocked up from Amazon. Cheap & good and no wait time.
10 years ago I was buying from China eBAy and Alibaba. Zero compromise in quality and almost ten times cheaper.
Last year and this past winter I stocked up from Amazon. Cheap & good and no wait time.
Two-part JB Weld Epoxy performs 30 times better than a mica washer and thermal grease. It performs exceptionally well at a very low cost and is available.
I have achieved outstanding results clamping LM3886s. The package of the IC is directly connected to the heatsink. All said and done its like the epoxy is not even there when you're done clamping it. It is one of those things you just got to try to believe it. I've been using various JB Weld products around heat sinks for over two decades and always amazing results.
The downside; it is a one-way ticket.
For the tool challenged such as I, glue is a true value proposition. I would not, however, use epoxy to glue semiconductors to a HS. That really is an issue if the semi gets damaged and must be replaced. Don’t want to buy a new HS as well as the semi. The bar hiding the semi to the HS is what I would go for.
The bar clamp and a drill and a tap is a relative easy way and effective. If you can't figure out a tap, you can through-bolt if you must.
The patience and dexterity to to use them is second nature to some and like travelling to Mars for many.
You can bolt through many heat sinks and skip the tap.
Just so you all know, I'm a drill, tap thread person.
The epoxy thing is when you want and need an epoxy solution.
My POINT was/is that JB Weld 2-part Epoxy High Temp IS NOT a thermal barrier or a thermal debate.
Think about it for a second, it's not like it is 1 or 2mm thick when you clamp a 3886 to an AI piece.
I have an old amp piece prototype experiment kicking around here somewhere. I got to resurrect it, fire it up, take some pics and post it to yee. I could remeasure the thermals and take some thermal images and post them. I think some people may find it interesting. Others, good for a laugh.
Interesting!! I'll keep that in mind.
Can you get the chip off by heating up the epoxy? Many of them let go around 200-250 ºC. Of course, there's no reusing the IC after that. 🙂
Tom
Haha I don't know. That JB stuff just gets harder and harder over time/heat(epoxy). I recon it would turn to glass or something similar? IDK ha.
If you are glueing down ICs and transistors, you must be goofing around experimenting or you know what you are doing, I guess.
For me, perhaps, it is a mixture of both. 😉
Am I missing something or the problem is just to mount two TO220s to the Al heatsink? What's the problem with making a tapped hole? You're completely fine with M3 tap in the Al to just hold one TO220, when it's let's say 8mm deep and you cut it clean. With a thin layer of good thermal paste you're good, no need to be brutal with tightening force. I've used rapeseed kitchen oil to drill and cut threads into Al my whole life and never had a problem. And you can always use a threaded insert if you don't trust the tap. Gluing the devices to heatsink is crazy idea to me.
[[What's the problem with making a tapped hole? ]]
1: no drill
2: no tap
3: no motivation ;{
1: no drill
2: no tap
3: no motivation ;{
The approach I favor, if HS permits, is STOXX’s suggestion to drill and bolt the fixing bar.
Or, use self-threading screws, carefully! Less chance of the tap breaking in the HS, although I would follow nearly all the other precautions for tapping: drill pilot hole as determined for the size of screw to be used; use lots of lubrication; go slow in 1/4 turn increments then backing out to clean out chips. I have used this approach twice and it surely works. Not as elegant as tapped hole but good enough for functionality.
Or, use self-threading screws, carefully! Less chance of the tap breaking in the HS, although I would follow nearly all the other precautions for tapping: drill pilot hole as determined for the size of screw to be used; use lots of lubrication; go slow in 1/4 turn increments then backing out to clean out chips. I have used this approach twice and it surely works. Not as elegant as tapped hole but good enough for functionality.
I have lost two taps in the front lines.
You want to talk about things coming to a grinding halt.
You want to see despair.
You want to see a project stop for a few weeks.
Oh boy. Faith tells me I have another one coming someday.
You want to talk about things coming to a grinding halt.
You want to see despair.
You want to see a project stop for a few weeks.
Oh boy. Faith tells me I have another one coming someday.
If you have a habit of breaking taps, I suggest you review your method. Here's mine:
I also don't use the cheapest taps. My current favourite is a spiral fluted, TiN coated M3 bottom tap that I bought at McMaster-Carr. I think it was maybe $10-15 at the time. I've tapped many holes in it in the, probably, 15+ years I've had it.
Tom
- Drill hole of the correct diameter perpendicular to the surface of the heat sink. Use a drill press or drill stand.
- Use the appropriate tap for the threads.
- Use cutting fluid. I use A-9.
- Use a tapping block to hold the tap perpendicular to the heat sink. Mine is just a chunk of 1" thick aluminum with a hole drilled through it.
- And don't force it. Learn to tell when you get a little spring in the tap and stop there. Don't forget to break the chips by backing off every quarter to half-turn.
I also don't use the cheapest taps. My current favourite is a spiral fluted, TiN coated M3 bottom tap that I bought at McMaster-Carr. I think it was maybe $10-15 at the time. I've tapped many holes in it in the, probably, 15+ years I've had it.
Tom
Excellent advice!
Great synopsis.
My 1st enemy was cheap taps. Later I gained proficiency and haste was my enemy. Next, I presume old age or stupidity will strike me a blow.
I know this isn't directly related to the OP's topic but I recently broke a #4 tap off in a copper bar and couldn't extract it. What I finally did was dissolve the ferrous tap out With an Alum bath. Took about 24 hrs. I am proficient in tapping but I applied just a bit of sideways pressure due to the awkward location I was working in.