I have a big problem. I broke the tapping bit in the hole, It ruin my heatsink. How can I tap small holes like this without breaking the bit? I already back off to clear the filings half way tapping already, should I use oil?
I broke it on the 4th hole, I cannot afford to keep breaking it. Every time I break one, I have to move the pcb and start all over again. Please help.
Thanks
I broke it on the 4th hole, I cannot afford to keep breaking it. Every time I break one, I have to move the pcb and start all over again. Please help.
Thanks
You need to do two things. Use some tap oil, synthetic motor oil is acceptable. For every turn of the tap go back 1/4 turn.
Yes, I agree with Joel. If the tap is breaking the drill bit is too small. The tap should have a numbered drill bit size etched onto it. 4-40 would use a no. 44 for a tight fit and a no. 43 for an easier fit.
Unless the tapped hole is shallow, it's common machine shop practice to use some kind of tapping oil/fluid.
jeff
jeff
thanks for all the reply. It's the tapping tool that broke. The drill bit comes with the tapping bit. It's Irwin Plug Tap and Drill set. The drill bit is #43 for 4-40.
I since watched videos on Youtube. I should have turn in 1 turn and back off 1/2 turn, also with oil. I just cranked like 5 turns before backing off. I learn my mistake now.
Luckily I decided to build a prototype amp on a wood board instead of build right into the expensive chassis I bought with heatsink on the side. It would be devastating if I did it on the real chassis and broke the bit.
Is there any magic way to back the broken bit off? Luckily, the hole is for mounting the pcb. I can forgo that. It would be much worst if it's the hole for the power transistor.
Thanks
I since watched videos on Youtube. I should have turn in 1 turn and back off 1/2 turn, also with oil. I just cranked like 5 turns before backing off. I learn my mistake now.
Luckily I decided to build a prototype amp on a wood board instead of build right into the expensive chassis I bought with heatsink on the side. It would be devastating if I did it on the real chassis and broke the bit.
Is there any magic way to back the broken bit off? Luckily, the hole is for mounting the pcb. I can forgo that. It would be much worst if it's the hole for the power transistor.
Thanks
No, but some nitric acid will in most cases do the trick. It basically partially dissolves the tap to the point where you can back it out. Take all the usual safety precautions, as you're dealing with a highly corrosive liquid.
jeff
On VERY rare occasions the tap breaks off leaving enough stub that you can grab it with, e.g., locking jaw ("Vise-Grip") pliers and back it out of the hole. Or the tap advanced far enough before breaking that you can grab the pointed end and back the tap out.
The tap itself is hardened to the maximum and you will not be able to drill it out with any drill available to us mere mortals. I have heard that a few machine shops specialize in removing broken taps, using electro-discharge machining (EDM) techniques. (EDM uses an electrical spark to vaporize metal near an electrode.)
There ARE tools made for extracting broken taps. I have never owned nor used one, though I once saw one used to extract a broken tap from an engine block. I suspect they are not available for small sizes like #4, but a little shopping may prove me wrong.
The general topic of home-shop tapping has been discussed on this Forum, e.g. at " http://www.diyaudio.com/forums/construction-tips/220877-hand-tapping-tool-2.html#post3189349 " or " http://www.diyaudio.com/forums/construction-tips/268997-amp-enclosure-screws.html ".
Dale
Not worth the expense, unless you're using some exotic extrusion for a heatsink.
jeff
If the tap is made of HSS a carbide drill bit may break it up. I did this a couple times to save a hole I could not afford losing. The drill bit will most likely be sacrificed. Make sure the hole will have sufficient undamaged depth left before deciding drilling out the broken tap. You must go very slowly on the drill press as the carbide snaps easily.
Aluminum can get "sticky" when not using fluid when cutting threads, and this can create a lot of resistance torque. When I'm in a hurry tapping a few holes, I pull the dip stick out of the car and that drop of engine oil would be all that's needed.
Aluminum can get "sticky" when not using fluid when cutting threads, and this can create a lot of resistance torque. When I'm in a hurry tapping a few holes, I pull the dip stick out of the car and that drop of engine oil would be all that's needed.
There is a tool called a tap remover. It has four small 'fingers' that slide into the gaps in the tap, then a collar that pushes down over the 'fingers" to hold them in place.
http://www.amazon.com/Walton-10043-...3456173&sr=8-11&keywords=walton+tap+extractor
Failing that you can use a small drill bit in the three flutes. Drill through the aluminum beside the tap and the the tap should loosen enough to twist it out.
http://www.amazon.com/Walton-10043-...3456173&sr=8-11&keywords=walton+tap+extractor
Failing that you can use a small drill bit in the three flutes. Drill through the aluminum beside the tap and the the tap should loosen enough to twist it out.
I've never been able to reliably use a #4 tap, even with plenty of oil and proper procedure, and now only use #6, 8, and 10 hardware.
Unless you can grab the stub with pliers and unscrew it, it may stay in there.
Use a 2.5 mm drill for M3 bolts.
Use a cutting oil on the tap shaft.
When making thread go in 2 turns then back off 1, then 2 turns again back off 1 until thread is completely done.
Its very rare for me to snap a tap.
Use a cutting oil on the tap shaft.
When making thread go in 2 turns then back off 1, then 2 turns again back off 1 until thread is completely done.
Its very rare for me to snap a tap.
Never use oil when tapping aluminium it will clog the flutes. As suggested kerosene or one of the specialized tapping fluids for aluminium. Also what type of tap are you using. 4 flute taps break the easiest. Buy good quality spiral point (NOT spiral flute) machine taps. Even tapping by hand these will last longer and be easier to tap.
Make sure you're using the correct drill, and the correct tap wrench. Too big a wrench and you will easily break a tap. Also make sure you tap square to the hole.
These are some of things I learned 32 years as a tool maker.
Make sure you're using the correct drill, and the correct tap wrench. Too big a wrench and you will easily break a tap. Also make sure you tap square to the hole.
These are some of things I learned 32 years as a tool maker.
Thanks guys and gals for the advice. I received the new tapping tool, I watched the video on youtube, I use just oil, forward 3 turns and back 1 turn. Easy, I did both heatsink in 30 minutes without any incidence. Very smooth.
The hole with broken tap is only one of the pcb mounting hole, I have 10 transistors on top of the remaining two holes to hold onto the pcb, it's not going anywhere. This is only an experimental platform only, it's all good.
I just tested over 50 of the MJL3281 to match the Vbe. they can easily be matched to 1mV!!!! Next step is to solder the transistors on. I am glad I messed up on the experimental heat sink. If I break the tap on the real chassis, I'll be crying!!!😱
The hole with broken tap is only one of the pcb mounting hole, I have 10 transistors on top of the remaining two holes to hold onto the pcb, it's not going anywhere. This is only an experimental platform only, it's all good.
I just tested over 50 of the MJL3281 to match the Vbe. they can easily be matched to 1mV!!!! Next step is to solder the transistors on. I am glad I messed up on the experimental heat sink. If I break the tap on the real chassis, I'll be crying!!!😱
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