How to tap thread holes for fastening mcpcb?

AnhTran · 2018-05-24T10:48:33.000Z

Hi, i want to create threaded holes on many of my flashlights but i know nothing about this topic. The aim is to fasten led pcb to flashlight shelf with high quality threads and screws.
Could you please help me with:
-What size of tap is normally used for this purpose, i used notigon mcpcb
-What tools are needed?
-Where can i buy these tools and high quality small screws
I have visited some local shops but the smallest size i could find is M3, and their screw are also big and not high quality.
Thanks

clemence · 2018-05-24T12:37:48.000Z

To simply answer your questions:
-What size of tap is normally used for this purpose, i used notigon mcpcb
For most small flashlights M2x0,4, M2,5xo,45, and M3x0,5 are the most common sizes

-What tools are needed?
Tap(s), tap handle, drill bit (center drill bit or end-mill drill bit), cutting oil, fixed drill stand. For aluminum you can use HSS tap. Remember, the harder the tap, the more brittle it is (prone to breakage). Aluminum is sticky, without proper lubricant it tends to stick to the cutter, making it harder to turn and creates dull/rough finish. WD40 or kerosene is the best cutting fluid for aluminum.
Any good threading always starts with a straight and properly sized hole. Try to avoid free hand drilling at all time. Fixed drill stand or milling machine is the best.

Here’s the link to a good chart: https://littlemachineshop.com/reference/TapDrillSizes.pdf

The easiest threading is through hole type. You can use single tapered tap for this.
Next is semi bottoming thread (blind hole with a small bottom area without threads). Better with a set of 3 tapered taps.
The most difficult is full bottoming thread. You need to get special tap for this. I usually just ground a normal tap using a bench grinder to make it threads the hole all the way to the base.

-Where can i buy these tools and high quality small screws
I can only recommends you to online stores such as Ebay, Aliexpress, or McMaster-Carr since I know nothing about Australia.

I have visited some local shops but the smallest size i could find is M3, and their screw are also big and not high quality.
Find another store then. Or simply shop online

Practice first. Hand tapping is unlike machine tapping. You need to move forward/backward often to break and free the chips. Straight tap insertion is also the key. Use simple jig to aid straight insertion. Creating a small thread is harder than larger thread. Most beginner usually breaks the tap because of:

- wrong drill size

- slanted drill/tap insertion

- wrong/no cutting fluid

- imbalance turning movement

- chips jamming

broken tap teeth

Check youtube, there are lots of manual hand tapping video tutorials there.

- Clemence

DB_Custom · 2018-05-24T12:57:37.000Z

Clemence said it all. Nice work!

I like to use a drill press to drill the hole, then mount the tap in the drill press chuck but DO NOT use the power of the drill press to thread the hole! Instead, turn the chuck by hand. This keeps the tap perfectly aligned with the hole just drilled but it also introduces some problems due to the drill press itself. It may be a good idea to get the tap started with the drill press to ensure alignment then release the tap from the drill press jaws and continue with the tap handle by hand.

Thanks for reminding me that I need to do this to the last light I built from scratch…. today probably! (I’ll still forget)

AnhTran · 2018-05-24T13:27:09.000Z

Thanks Clemence for your answer, that’s much more harder than i thought, i might need some proper researching and practising if dont want to destroy my flashlights

everydaysurvivalgear · 2018-05-24T13:50:51.000Z

To hard no need for complications.
If the shelf is only a few mm thick say 3-4mm and its aluminum you dont even need a tap kit aluminum is very soft metal

Drill a hole in the alloy no lube needed if its small.Or if it’s needed only use the tinniest drop. Use a steel screw to thread the hole job done! If it was a bigger job then go all out.

Only tip i can add is before you drill start the hole with a hole punch so the drill bit stays aligned.

Common size would used be an M3. Bunnings have them but they are like 3mm long i bought some from Ebay i also cut some down with the angle grinder.

Also another cheap option if you have an impact driver just use self tapping metal screws.

DB_Custom · 2018-05-24T16:33:16.000Z

I normally side-step the whole issue and glue the MCPCB down with Arctic Alumina Thermal Adhesive.

clemence · 2018-05-24T19:25:25.000Z

AnhTran:

Thanks Clemence for your answer, that’s much more harder than i thought, i might need some proper researching and practising if dont want to destroy my flashlights

There are easier ways to make threaded hole. But to learn how to do it properly (manually) in the first place is invaluable. After you have mastered the basics, you can modify the technique according to your needs - this is what engineering is all about.
Here’s one of a useful video to help you start with threading:

Goodluck,
Clemence

MRsDNF · 2018-05-24T20:34:12.000Z

What part of Australia are you in AnhTran. I may be able to point out a shop to you.

Firelight2 · 2018-05-25T00:47:55.000Z

Screws to hold down MPCBs? … it’s easy:

I use a small drill bit to drill a hole for the screw, then just screw it down. Pretty much any small machine screw will self-tap into the shelf below the MPCB just fine.

This probably isn’t as durable as doing it the right way, but it seems to get the job done. I’ve done this with many lights and have yet to have any of the self-tapped threads strip.

MRsDNF · 2018-05-25T03:32:47.000Z

MRsDNF:

What part of Australia are you in AnhTran. I may be able to point out a shop to you.

PM me if you like.

DB_Custom · 2018-05-25T03:34:52.000Z

Because of this thread I actually got the DBC-07 light drilled and tapped for the MCPCB, thank you! Didn’t take all that long and I won’t have to worry about the emitter overheating now.

AnhTran · 2018-05-25T03:44:08.000Z

Hi i’m in Melbourne, I tried Bunnings but they don’t have small tap and screws, what is your recommendation? Thanks

clemence · 2018-05-25T03:51:16.000Z

Bought mine from here:
http://s.aliexpress.com/uAfiyMfQ?fromSns=Copy to Clipboard

- Clemence

NeutralFan · 2018-05-25T19:34:12.000Z

If you drill a hole into the shelf and then just screw the screw in, I would double check to make sure the surface was not raised next to the hole which could cause the MCPCB to not sit flat. And if it was raised, counter sink the hole a little or make sure the hole in the MCPCB is wide enough to clear the bump.

MRsDNF · 2018-05-25T20:18:28.000Z

I cant find an industrial supply shop in your area. I’d suggest to start with a 2mm taper tap and 1.7mm drill bit. If your not careful both can snap off without warning.
2.5mm is another size that would be handy.
These small taps in a quality brand can be quite expensive.
I use this shop for most of my tool requirements. They will have all the taps drills and most of the screws you want. Saying that id do buy lots of screws of ebay as they are a lot cheaper.

waughs.com.au

Waugh's | Industrial Supplies

Waugh's Industrial Supplies is an industrial engineering equipment specialist in Australia. We're and industrial supply group based in Victoria.

I’m quite happy to help you out any way I can.

DB_Custom · 2018-05-25T20:25:46.000Z

Pass another cold one mate, that’d be most helpful, thank you!

MRsDNF · 2018-05-25T21:03:31.000Z

It’ll have to be a soft drink or water.

CNCman · 2018-05-31T23:56:07.000Z

You can google suppliers online or nearest you.
Everyone should use thread forming taps in areas where you will be disassembling things often, if possible. Most production environments use them because they last a long time, don’t break as easily as cutting taps do, and the treads are much stronger. The flashlights you already own were most likely tapped with them. Premium taps are made by Guhring, but they are not necessary to buy and are not cheap.

https://www.mscdirect.com/browse/tn/Threading/Taps/Thread-Forming-Taps?navid=12106038

Thread forming tap drill chart

http://media.guhring.com/documents/tech/Charts/FormTapDrill.pdf