Hi, I need to tap a 4-40 blind hole at the back of an aluminum front pannel that is 0.2" thick only. I can only tap a hole less deep than that. My problem is if you look at the tapping bit, the fluke is tappered...that is the diameter is smaller at the tip and gradually getting larger..for very good reason for normal tapping. But if I can only go less 3/16 deep, it's not going to work.
The only thing I can think of is having a second tapping bit, break the tip off. Then first use the normal bit to tap first, then use the broken bit that has the right diameter to retap the hole again.
Any other advice I can do?
Thanks
The only thing I can think of is having a second tapping bit, break the tip off. Then first use the normal bit to tap first, then use the broken bit that has the right diameter to retap the hole again.
Any other advice I can do?
Thanks
There are taps made with flat ends for blind holes, but you may need to rethink your plan. At 3/16"hole depth and with a 1/32" chamfer to start the tap straight you will only have 5/32" of pilot hole depth and will have at most 4 or 5 threads. Taps start out with partial height threads to get them started then gradually rise to full height so at best only your first thread or two will be fully formed. It may work but you will want to tighten those fasteners very carefully once it's done.
Chances are it's 6063 aluminum which is the most common grade in general use. I'm in agreement with Kevin here, trying to use a bottom tap for threads that shallow is iffy at best. If you must go that route, I'd seriously consider using a threaded stud epoxied into the aluminum, and using washers and nuts to fasten in place.
Mike
Mike
Thanks for the replies, sorry I did not get back here because I was tied up with the thermal issue.
M3 threads are finer, does that help any so I can get more than 4 or 5 threads?
How do people do that? The panel has a few blind M3 holes.
M3 threads are finer, does that help any so I can get more than 4 or 5 threads?
How do people do that? The panel has a few blind M3 holes.
You can do a good shallow threaded hole using a form tap. The tap drill size is different (larger) and the taps cost more, but they work great in soft heat sink aluminum. Look up Balax.
Do you mean this kind?
http://www.amazon.com/Screw-Thread-...6937207&sr=1-4&keywords=M3+thread+forming+tap for M3
http://www.amazon.com/gp/product/B0...rue&ref_=ox_sc_act_title_2&smid=ATVPDKIKX0DER for 4-40
Thanks
M3 has 0.5 mm thread pitch. 0.2" = 5.08 mm. If you drill a 4 mm deep hole and use a bottoming (or closed-end hole) tap, you may end up with threads in about 1.5-2 mm of that. So you'll have 3-4 threads. That's not a lot... If you do go that route, I'd try to get a flat bottom drill so you can make a counter bore and thread that rather than using a regular drill bit which will leave a hole with a taper at the bottom.
McMaster-Carr has all sorts of taps. Part number 8305A52 would be a good fit for your needs as far as I can tell.
Another solution would be to use a threaded boss or pem-nut. McMaster can likely help you out with those as well.
Tom
McMaster-Carr has all sorts of taps. Part number 8305A52 would be a good fit for your needs as far as I can tell.
Another solution would be to use a threaded boss or pem-nut. McMaster can likely help you out with those as well.
Tom
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Here are the two taps I'd recommend:
Thread Forming Taps | Travers.com
Thread Forming Taps | Travers.com
If you can drill the hole, then finish it up with a flat bottom as described above (regrind a drill to look more like an end mill), you'll get very close to the bottom. Remember, form taps use a different size drill- see manufacturer's charts.
One of the taps you listed is a screw insert tap, like Helicoils. Those aren't great for very shallow holes, but they're extremely durable and can fix it when the soft threads strip out.
Thread Forming Taps | Travers.com
Thread Forming Taps | Travers.com
If you can drill the hole, then finish it up with a flat bottom as described above (regrind a drill to look more like an end mill), you'll get very close to the bottom. Remember, form taps use a different size drill- see manufacturer's charts.
One of the taps you listed is a screw insert tap, like Helicoils. Those aren't great for very shallow holes, but they're extremely durable and can fix it when the soft threads strip out.
When you tap, be sure to use oil. Also, practice on a scrap piece of the same thickness until you're confident in your ability to do this.
Another way people do this is with flush head PEM hardware-
PennEngineering: Studs and Pins for Sheetmetal
http://www.pemnet.com/fastening_products/standoffs.html
That works best if the panel gets painted, but if carefully pressed in the circular heads don't look that bad. They also have same-side hardware, but it won't be quite as strong.
Or, go with stainless steel flathead Philips screws. In truth, almost any alternate way of doing this will be structurally better than a shallow thread in aluminum.
Another way people do this is with flush head PEM hardware-
PennEngineering: Studs and Pins for Sheetmetal
http://www.pemnet.com/fastening_products/standoffs.html
That works best if the panel gets painted, but if carefully pressed in the circular heads don't look that bad. They also have same-side hardware, but it won't be quite as strong.
Or, go with stainless steel flathead Philips screws. In truth, almost any alternate way of doing this will be structurally better than a shallow thread in aluminum.
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Yes, the press-in pem nuts may be the best option. Just drill a shallow hole and press it in.
Turn out I don't need it anymore. Received the remote motorized volume control, put it in without needing to tap extra hole.
thanks
thanks
Like others have maybe said:
Have 2 of the Taps on hand. Use the Tapper Tap to start the hole nice and Straight. Get a few good threads going.
Now take and grind the Tapered end back/off on the other Tap (a nice square flat end). You want to grind it back till there is just a couple threads with Taper on them left.
Now you're good to go, just make sure your In the threads you started when you start the new taping(Start this Tap by hand). Keep it straight and aligned and use Lube as been said.
You should need to back-out and get the metal bits out before continuing to the bottom (close you eyes if you use a straw!) ;]
Have 2 of the Taps on hand. Use the Tapper Tap to start the hole nice and Straight. Get a few good threads going.
Now take and grind the Tapered end back/off on the other Tap (a nice square flat end). You want to grind it back till there is just a couple threads with Taper on them left.
Now you're good to go, just make sure your In the threads you started when you start the new taping(Start this Tap by hand). Keep it straight and aligned and use Lube as been said.
You should need to back-out and get the metal bits out before continuing to the bottom (close you eyes if you use a straw!) ;]
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