Hello,
I need to tap two M3 holes in aluminum heatsinks. I have 3 pass 3mm taps.
I don't succeed to have nice threads. They finish "too big hole" and the screw slips in them.
I had the advice to use only the last finishing one, as aluminum is a rather soft metal. This is a bit better, but still not very nice.
I have difficulties to start and stay vertical...
How do you do ?
Any tips to tap heatsinks ?
JMF
I need to tap two M3 holes in aluminum heatsinks. I have 3 pass 3mm taps.
I don't succeed to have nice threads. They finish "too big hole" and the screw slips in them.
I had the advice to use only the last finishing one, as aluminum is a rather soft metal. This is a bit better, but still not very nice.
I have difficulties to start and stay vertical...
How do you do ?
Any tips to tap heatsinks ?
JMF
There are several ways to do this.
1. Tap from the rear. This results in the thread at the working surface being better formed.
2. Fit a suitable metal plate on the face of the heatsink so that the loose hole is taken up in the scrap material.
3. Use a drill press.
1. Tap from the rear. This results in the thread at the working surface being better formed.
2. Fit a suitable metal plate on the face of the heatsink so that the loose hole is taken up in the scrap material.
3. Use a drill press.
It seems you drill the hole to big. I just go very slow to begin with en make sure it's more or less straight. If you have a drill bench that can go very slow then this could be an option.
Thanks for the tips.
I like the scrap metal plate idea.
How do you use a drill press to do the job? I would be afraid:
- either to press too hard
- or to break the tap ?
I drill at 2.5mm for M3, which looks like the "official" value.
JMF
I like the scrap metal plate idea.
How do you use a drill press to do the job? I would be afraid:
- either to press too hard
- or to break the tap ?
I drill at 2.5mm for M3, which looks like the "official" value.
JMF
Taps require a very steady and accurate hand control which is difficult to achieve with taps in the range of a few millimeters in diameter. My advice is to use a drill stand and work very slowly by manually rotating the chuck with your hand. If your holes came out to be too big, use small bolts through the heatsink.
OK, understood.
I take the opporttunity to ask if there is a better tool tu cut heatsink than a Hack Saw (I don't find that they cut thick aluminum so easily).
JMF
I take the opporttunity to ask if there is a better tool tu cut heatsink than a Hack Saw (I don't find that they cut thick aluminum so easily).
JMF
2.5mm is too large for M3
You need to use 2mm.
It took me a while to figure that one out. Once I changed to 2mm I stopped having issues with laxity.
3mm for m4
I second using a drill press
I know its not considered good practice but........
I have also had great success using a cordless drill driver for taping m3 and m4 holes. I find that the freedom from having to provide rotation allows me to focus my limited brain power on jamming the tap as hard into the hole as possible till it bites and then things are easy.
You need to use 2mm.
It took me a while to figure that one out. Once I changed to 2mm I stopped having issues with laxity.
3mm for m4
I second using a drill press
I know its not considered good practice but........
I have also had great success using a cordless drill driver for taping m3 and m4 holes. I find that the freedom from having to provide rotation allows me to focus my limited brain power on jamming the tap as hard into the hole as possible till it bites and then things are easy.
2.5 mm is good, but also measure the final hole. It can easily be bigger. I simply don't see how the final tapped hole can be to big. I have done this a lot, and never experienced this
2.5mm is the correct drill for an M3 tap.
If you use a smaller drill you run the risk of snapping the tap.
If you use a smaller drill you run the risk of snapping the tap.
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Stupid question, but I suppose your are lubricating as needed and turn the tap back half a turn out every 1 or 1 1/2 turn ?
He's not breaking taps, but good point.
WD40 is a good lubricant for cutting threads in aluminium.
WD40 is a good lubricant for cutting threads in aluminium.
In my experience, the less I have to force to cut (using WD40 as mentionned) , the less I "wiggle" thus making a cleaner tap, just saying..
I started lubricating "half way" in my tests, with WD40, and it improved the things. I'm turning the tap back when I have to force a bit more, which is more than every 1 or 1 1/2 turn.
I had the feeling that that back movement could participate to the messing of the threads in that soft material.
JMF
I had the feeling that that back movement could participate to the messing of the threads in that soft material.
JMF
No turning it back breaks the leftover material, which is good and necessary. If you don't do it you can actually ruin the threads.
When the tap starts to force in the very cheap/soft aluminium (for chinese cases that is, I have never had a Modushop chassis so can't comment on the quality of the heatsink extrusion) you are already messing up the thread...even more though if you are tapping a blind hole and bottoming out
It's also very important to clamp the workpiece at these small diameters. And keep the tap very steady and perfectly vertical too. No lateral movement at all in either the workpiece or the tap. Which is hard.
Exactly!
2.5mm is what i use.
Use a stand drill for drilling not a hand drill!
Taping by hand i use w40 for lubricating, turn the tap back half a turn out every 1 turn. If you feel difficult turn, lubricate it again, or turn the tap back completely, labricate and try again.
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Tap drill size chart Metric Tap Chart
+1 for comments by KatieandDad and Coolnose. Always pre-drill to at least 3 mm deeper than the projected bolt length - space permitting. I've always done the tapping by hand for the up to 4 mm(very carefully with WD40) and you must use a blind-hole tap. This is different to a through hole tap. Some videos for reference.
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwiF27nEl-3pAhWNZMAKHXjsAzAQwqsBMAB6BAhfEAQ&url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DKo3CaRw9Ktk&usg=AOvVaw3DUDUG69txrfgl64OXmnUg
https://www.google.com/url?sa=t&rct...=X5Ef-MBSIFI&usg=AOvVaw0E4xLSfut-4iQAg_J_GzYE
Good luck, Kevin
P.S. If possible use a can of compressed air to blow out the hole after you have removed the tap. I also normaly take the tap totally out after every two full turns to clean the hole of swarf.
+1 for comments by KatieandDad and Coolnose. Always pre-drill to at least 3 mm deeper than the projected bolt length - space permitting. I've always done the tapping by hand for the up to 4 mm(very carefully with WD40) and you must use a blind-hole tap. This is different to a through hole tap. Some videos for reference.
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwiF27nEl-3pAhWNZMAKHXjsAzAQwqsBMAB6BAhfEAQ&url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DKo3CaRw9Ktk&usg=AOvVaw3DUDUG69txrfgl64OXmnUg
https://www.google.com/url?sa=t&rct...=X5Ef-MBSIFI&usg=AOvVaw0E4xLSfut-4iQAg_J_GzYE
Good luck, Kevin
P.S. If possible use a can of compressed air to blow out the hole after you have removed the tap. I also normaly take the tap totally out after every two full turns to clean the hole of swarf.
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I also use the drill press (only turning the chuck by hand) for a few threads to be sure of starting vertically.
I can also vouch for the low powered, torque limited, battery drill-driver.
Set torque limiter to a suitably low value. Go slowly. The surest way to break taps is wobbling with the usual tee-handle. Cordless drill avoids this.
Use some lube, back off to break the swarf and completely remove tap if required to clear flutes. Small taps soon clog.
I can also vouch for the low powered, torque limited, battery drill-driver.
Set torque limiter to a suitably low value. Go slowly. The surest way to break taps is wobbling with the usual tee-handle. Cordless drill avoids this.
Use some lube, back off to break the swarf and completely remove tap if required to clear flutes. Small taps soon clog.