# Drilling And Tapping Holes



## tibbittsjim (Jun 21, 2011)

I am planning on drilling and tapping several small holes (caseback, faceplate, etc) into a custom stainless steel case.

I bought some cheap micro drill bits and a tap set on EBay to practice on plastic.

Even on plastic I bent and broke some taps and bits on a few attempts.

Probably because I tried using a pin vise hand tool.

I learned my lesson and bought a drill press.

Now I wish to buy better/stronger bits and taps.

Any suggestions where and what to look for?


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## taffyman (Apr 26, 2011)

tibbittsjim said:


> I am planning on drilling and tapping several small holes (caseback, faceplate, etc) into a custom stainless steel case.
> 
> I bought some cheap micro drill bits and a tap set on EBay to practice on plastic.
> 
> ...


hi rather you than me but try using tungston drills they should be better as for taps use plenty of coolant and all i can say is take your time. all the best haydn


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## harryblakes7 (Oct 1, 2010)

Hi, interesting that you broke some taps going into plastic...... as you are probably aware cutting threads is a bit of an art, exact drill sizes and working with the tap using a good cutting compound.

You will need a starting tap, then intermediate, then finishing tap in a very good quality steel, especially if you are cutting into a stainless steel case. The tap must be screwed in gently, ideally using a right angled square to get it exactly upright to the hole, then screw gently in, perhaps half or three-quarters of a turn, before coming out completely and then doing the process again and gradually cutting the thread, you cannot go straight through in one cut. Even after cutting the thread you may wish to charge up a piece of pegwood with some cutting paste and run that through the hole as well.

Certain watch tool wholsalers like Cousins and Meadows & Passmore will have what you want, but if your breaking steel taps whilst cutting into plastic then you need to re-asses how you cut the threads and the twisting force you are using may be too much..... I have cut many threads into watch plates and the trick is to be gentle, take your time, and measure everything twice and use the exact size tap and thread pitch you need

Hope it all works out for you.


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## Billtr96sn (Jun 15, 2011)

Get yourself a Zuess book which gives you the tapping drill sizes to use for any thread you want. Set your drill press as fast as it will go.Ise micrometer blue to mark out your cases and go easy.

When tapping the thread, as has been said, use a good cutting compound (I still use tallow and haven't found anything to beat it yet) and keep backing the tap right out. If you are not doing through holes then you will need a bottom tap after the starting tap.

If you can find some scrap steel of the same grade to practise on.


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## Billtr96sn (Jun 15, 2011)

I have uploaded a Zeus here for you to download


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## tibbittsjim (Jun 21, 2011)

This is all good information.

Thanks for the comments and the .pdf.

I will report back once I experiment more.


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## Blackthou (Aug 13, 2011)

I've drilled and tapped many a hole but never anything as small as a watch thread. Out of interest, how do you manage to obtain the revs to get the drill to cut? The smallest hole I've drilled is 0.2mm (didn't need tapping) but needed a spindle speed of 90,000 rpm.


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## bry1975 (Feb 6, 2004)

Generally speaking you need to drill the hole about 0.85 times the thread diameter so a M10 would

be 8.5mm drill size, M5 4.2mm drill size etc etc.

Take your time use decent tools the best you can afford and try and keep the tap perfectly perpendicular to the surface, check with an engineer's square always use cutting grease or fluid.


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## BondandBigM (Apr 4, 2007)

I'm betting most of the tools sold on eBay are cheap far east rubbish. If you have a local engineers merchant close by pop in and they should be able to sort you out with some proper drills and taps. Personally I would use the drill press for drilling and tapping. After drilling the hole swap in the tap and then you do it by hand a bit tricky but it keeps the tap nice and straight to the hole.

Does the newer version of the Zeus book go down to such small sizes ?? I couldn't be bothered to wait for the download.

Mine might be a bit out of date :lol: :lol:


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## BondandBigM (Apr 4, 2007)

You need a small version of these, centre drill to give your drill a start, countersink to chamfer the hole to go with your drill & tap set. I'm not sure you'll be able to use the starter or intermediate tap on such shallow holes though. You need some cutting compound or fluid and a suitable vice firmly fixed to your drill press table and off you go.


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## tibbittsjim (Jun 21, 2011)

Thanks again...this is all good information.

I started a new thread about trying to find the right size taps for a "mini hand tapper" i bought.

Please check it out and let me know if there is a place to buy taps that fit this tool.


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## Dick Browne (Dec 16, 2008)

I wasted a couple of taps before realising what I was doing wrong - as you tap the thread, the material you're tapping into will curl off, if you don't break these tangs off, you're going to jam the tap and it will eventually snap. I generally tap into softer material than stainless, and find that half a turn forward, a third back, then half forward again does the trick. On a bigger hole you'll see the tang spiralling inward and you'll know when to reverse, you will also see it snap off. On something as fine as you propose, I'm guessing you won't see anything (or possibly feel much increase in resistance) until the tap snaps.

Backing the tap out entirely isn't a bad idea with small-bore holes in stainless.


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## tixntox (Jul 17, 2009)

A bit of grease on the tap will catch loose swarf and save it from going "everywhere". :lookaround:

Mike


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