I'd like to create a few M4 or M5 threaded holes in some pieces of brass and aluminium that I've got. Ideally the holes should be about 8mm deep and blind, not "all the way through". I've never used a tap or die, but this seems like a good excuse to add to my tool collection have have a play.
Is buying a cheap set such as
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in order to gain experience a good plan? Are the eye-wateringly expensive sets that RS sell necessary for DIY use? Is it worth buying a set that includes drill bits in the exact sizes needed, eg 3.2mm, or will drill bits in 0.5mm intervals be OK?
halfords do a reasonable mixed set, as do machine Mart... if you know you will only want M4 & M5 then go to a trade tool outlet and but the size you want ... You need 2 taps per size Taper & Plug (or bottoming) then importantly you need the right size drill .... for M5 you need a
4.2mm drill for M4 it would be 3.3mm Yes you can buy what may seem odd sizes ... I have a 2 drill sets providing 0.1mm to 20mm in 0.1mm increments.
Although as you are going into soft material, go to nearest size down, and take your time, clear out swarf frequently.
Brass and aluminium is pretty light work for taps - drilling with the next standard undersize and going gently with the tap should be fine. High quality (e.g. Presto) taps and dies make a difference when working somethiing hard and particularly where there must be no f***-ups, e.g. engine repairs.
The set you point to has only taper taps. The problem is that you want to tap blind holes, so you need both taper and plug taps (the plug tap cuts the last few threads parallel at the bottom of the hole) otherwise the tapings will tighten up as you screw in the bolt. Better still a taper, second, and plug.
See
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you want to do just M4 and M5, you would be advised to buy just those sizes of good quality taps, and the corresponding correct drills.
Most brass doesn't need a lubricant (IIRC), but I think aluminium does, but I can't remember what it should be.
The trick is to go very slowly, and back out a little very often to break and clear the swarf. You can get a rhythm going.
Cheap tools are almost never a good idea. In any case, that set seems to provide only one tap per size, probably a taper tap, and they are thread cutting taps. For any blind hole you need, as a miniumum, a taper and a plug tap, preferably taper, second and plug taps. While cutting taps will work fine with brass, they are not the best choice for aluminium. For that, you need lobed taps, which distort the aluminium into the thread form, without cutting, and the associated work hardening makes the thread much stronger.
Best is to go to an Engineers' Supplier, or a real specialist, like Drill Services (Horley) Ltd.
You should always have the right size tapping drills. Undersize pilot holes make tapping difficult and may lead to breaking the tap. Oversized pilot holes reduce the depth of thread, making it more likely you will strip the thread when tightening something into it.
Probably not - certainly not if you know the sizes beforehand and you only need a couple of sizes.
It _might_ be useful for Gross Bodgery if things come into the workshop where you never know what size you'll be needing next. OTOH, the Screwfix ones are really bad quality and they're metric only. M12 in carbon steel ? The thing is going to last about an inch, if that much.
Yes. Although you can get them for less than RS' prices.
The simple rules for taps and dies:
Are you now, or have you ever been, a reader of Model Engineer? if you haven't, then you only need a couple of sets of metrics and you're sorted forever. You can afford these, even in good quality.
HSS. Carbon steel is a bad joke.
Presto, or similar quality, and made in England (or Europe at least). Don't waste your time and metal on cheapies.
Almost any amount of effort to avoid breaking a tap is easier than the trouble of removing a broken one.
Taps. You need taps, not often do you need dies. People without lathes very rarely need dies.
Taps come in sets of 3 (taper, second, plug), not sets of 2. Real ones, that is. For small taps then you can manage with only second and plug quite adequately (no taper) but the 2-tap sets are often somewhere between "taper-second" and "chamfered plug".
2 fluted taps will break if you bend them sideways. Nearly all very small taps will be 2 fluted, but get 3 fluted if you possibly can.
Dies are adjustable in size. Set them correctly, or you'll have loose / tight threads.
A set of Zeus tables is useful, but you can often pick up freebie equivalents in better toolshop.
There are two metric pitches (for most threads).
Tapping drills are magic sizes. Now drills are cheap, so buy extra tapping drills just the right size when you get your taps. Keep them with the taps and don't use them for anything else.
Get a nice tap wrench. Get several, of different sizes. eBay.
Get a squirt bottle of RTD (cutting goop) if you ever tap steel. If without, then at least use _something_ greasy or oil. Brass often needs cutting lube to clear the chips away too (back the tap out and wipe it).
Use the right tapping action - two flutes forward, one flute back. Pretty spirals look nice, but they'll bind and break your tap.
Spiral taps make a great bargain at an auction, but they're machine taps and there's a reason why few people buy a second one for hand use.
A tapping machine is very useful, especially for fine work in aluminium. Use a drill press with the belt off and maybe the feed spring unhooked, at least until you have the thread started square.
If you use the same size over and over, then keep spares on hand. Particularly M3 !
On Mon, 12 Jun 2006 20:25:20 +0100, Simon wrote (in article ):
Really the equation is what level of quality do you want and whether you can get it for the price you are willing to pay. That doesn't correlate to whether the use is DIY or not.
I was looking for a similar thing myself a few months ago, and rejected the cheap sets that are around because generally they have only one tap per size which is sometimes not good enough.
Eventually I bought a boxed set from
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has proved to be good quality (i.e. not carbon steel) for just over £100.
I don't need the longevity of a professional engineer's set costing about three times the price and more but the accuracy and results have been fine.
Don't bother with expense of looking for a set with a second tap ... unnecessary, I have never had to use one, and threaded hundreds of holes in just about all materials ... a taper & plug are what you need. Use some white spirit as the lubricant, and follow advice by previous poster .. slowly doe sit.
I found dies quite useful for cleaning the threads on slightly buggered screws, open up the die, spin it down to a good part of the thread, tighten it up till it just touches, then back it out, often all that is needed for unusual screw sizes. (or material)
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