How to identify M2 first, second and third tap

But doesn't the drill throw up a burr too ?

Not in my experience, a quality carbide spotting drill leaves no detectable raised burr.

Andrew

What about an ordinary drill bit ?

Not if it's kept sharp!

Russell

I don't bother with spotting drills. If that sort of thing is needed I use a centre drill in the drilling machine. They are available in a variety of sizes. I don't believe in throwing money on things that in practice aren't needed.

2 turns down is way too much - as I have mentioned before even 1/2 turn down before reversing to break the chip is to much really and that gets more and more important on finer taps. This is likely to be why you are raising a burr - the tap back cutting. But carry on abusing your tools if you like.

While a drill can be used to remove burrs an hss countersink will make a much better job of it.

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I use 2 types. One is the usual fluted one the other is the cone with a hole in it more for use on the lathe on larger holes. The fluted one is what you need. I have one size but it's extremely pointed and for some reason 16.5mm dia but will do all diameters I am likely to need. You could make a handle for one if needed. I usually stick it in a small morse taper drill chuck that I have kicking about when and if I need to use it by hand. If it has to be significant and super neat I use the depth stop on the drill. - Countersunk headed screws etc.

Drill size - measure the drills and the tap and adjust the 1.6mm accordingly erring on being over size. You should have picked up from other posts that it's not that critical providing that the roots of the tap are clear. Zeiss ain't too good in that respect. Number drills add a whole host of different sizes few of which are needed but if say a No50 was bought the actual size may not be exactly as it should be. I shouldn't have mentioned it really as metric by 0.1mm offers similar accuracy at this size.

John

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''two turns down is way too much'' : no wonder I have broken two taps !

A bit more than the number of flutes on the tap is safest Brian - so if 4 a 1/3 of a turn max and if it's a very fine tight tap even that might break it. I would have thought it would be ok on M2 though.

John

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Edited By Ajohnw on 13/03/2016 13:40:55

My biggest mistake previously was not making the hole deep enough. This is a blind hole so if I want 6mm of thread then I should drill out to 8mm or even 10mm. I was tapping right down to the bottom of the hole before. This along with too many turns in one go and the tap was certain to break. I know better now : drill further than you need thread for and only 1/3 of a turn at a time. Some tap magic does not go astray either.

The kit should have provided shorter screws Brian if the M2 ones needed 6mm of thread. There is a need to watch for swarf being trapped at the bottom of blind holes too. I usually just blow and shake it out. Some use an air line with care as it might enter their eyes.

As I have one this might help blow bits out. They give a fine powerful blast of air. Something similar should be about in Oz

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I'd say that the bulb is around 2" or more across.

As I have mentioned I do have a tin of tapping fluid but find hand soap is better. Might be because it's a very old brand - Knight's Castile and may be pure old fashioned hand soap with lanolin or something similar in it. It's also great for getting grime of my hands. My wife buys it when ever she see's it. Usually in packs of 6 or more.

John

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If you drill a clearance diameter for about one thread deep you can start spiral taps safely.

I regularly tap brass with M2 and M2.5 and do it with a guide block to start and usually without looking!

80 holes in one session is not unusual.

Do you have a photo of your guide block ? Do you use Tap Magic or similar ?

I recall one of the "known" writers on Model Engineering and Home Workshop Shop topics advocating casting some form of solid lubricant into thin strips or wires to be inserted into blind holes before tapping. Providing the diameter is made close to that of the hole the threading lubricant pretty much fills it so as the tap proceeds down the hole it pushes the lubricant back out forcing it into intimate contact with the cutting edges of the tap and driving the swarf up out of the hole. I imagine the inside of the flutes would also be well lubricated so making it easier for the swarf to escape. Only obvious drawback is that you'd need to work hard at getting the tapped hole clean if intending to use a thread locking compound.

Maybe someone on here knows the source and what solid lubricant was advocated. Something waxy I guess.

I find smearing the inside of the hole with tapping compound, I use Trefolex, with a rod or wire makes things go much easier.

Clive.

Guide block is simply a lump of 1.5" square MS with a hole drilled squarely through to just clear the tap shaft diameter.

Brass tapped dry, Templex Blue Foam, Rocol RTD or Dormer Supercut, dependent upon the material, thread diameter etc being cut.

Cast bacon grease into round shapes.