BA, ME, Metric Coarse or Imperial : which taps and dies to buy ?

[Ady1Participant @ady1]

Are there a few sizes which keep cropping up ?

I'm not a traction engine dude yet but have found a 20quid metric HSS tap and die set extremely handy for general duties

You can buy metre lengths of threaded bar from B+Q up to 12mm for a few quid each

In many cases you don't even need any nuts, the threaded parts simply screw flush into one another via the bar

[Brian JohnParticipant @brianjohn93961]

1. No lathe yet and not for quite some time !

2. Sorry for the confusion but I am trying to cut the thread on the outside of the tube ie. I am using a HSS 3/16-40 die. The tube is 4.76 mm which I have been told previously is the correct size tubing.

[Russell EberhardtParticipant @russelleberhardt48058]

Take a piece of brass bar, drill a hole the size of your tube (plus holes for other sizes while you're at it) and saw along the centres of the holes like this:

Then put that in the vise to grip the tube without distorting it.

Russell.

[Brian JohnParticipant @brianjohn93961]

The tube is not distorting ; the problem is that the vice is just not gripping it enough. The aluminium soft jaws I am using have notches for gripping tubing but it does not seem to be helping much.

[“Bill Hancox”Participant @billhancox]

Brian

A good fit between your tubing and the vice block is important. When doing work on gun barrels a few years back, I used powdered rosin between the barrel blocks and the barrel with good results. The rosin provides quite a bit of additional grip. I have continued to use the same technique for some of my metal work.

Bill

[JasonBModerator @jasonb]

Brian. try sliding the soft jaws sodeways a bit so the small Vee that you are using is directly in line with the screw of the vice

When the pipe spins do the jaws leave marks all along the pipe or just at the very bottom, this would indicate the jaw is lifting and not applying the same level of grip along the whole length of the pipe

[Keith LongParticipant @keithlong89920]

Might be worth trying a variation on the trick used in turning / milling to get a better grip, wrap a turn or two of paper round the tube and then put that in the vice jaw vs. The paper will make the tube slightly bigger so that the vice has more to grip and will also "bed" into the tube surface and that of the jaws.

Also worth looking to see how tight you've got the die set. Assuming that it's a split die try easing off on the two angled holding screws and tightening the one in the split – don't go to heavy handed you don't want to break the die. If you can get a thread cut with the die opened slightly then it's an easy matter to nip it up and run the die down again to cut a bit deeper if you need to for the female threaded part to fit ok.

Other things that come to mind – is the tube in a hard or annealed state, much easier to thread if it's annealed – how much of a turn are you putting on the die before you back off to break the swarf string. The latter I find has quite an effect but then I'm, usually threading steel with something in the M8-12 range

[BazyleParticipant @bazyle]

The paper trick above might be enough otherwise try rubber from cycle inner tube, old gloves etc, Instead of a V groove in the jaws which only grip along 4 lines try two pieces of wood held together and drilled down the interface, size allowing for the rubber grip, to get all round contact.

However have a think about the cutting action. You have 3 or 4 lobes on the die with say 6 teeth each in contact as you move down all tryig to take a cut ?? deep. That's a lot of force. Hence it is a lot easier if you can get a split die and make several passes. With taps you are stuffed on adjustment which is why taper taps were invented.

[Peter TuckerParticipant @petertucker86088]

Hi Brian,

Are you using any lubrication on your die? This can make a big difference.

Peter.

[Neil WyattModerator @neilwyatt]

Tubal Cain advocated Russell's device, but made from ebony from an old bowling ball*.

Neil

For bowls rather than bowling, I imagine.

[IanTParticipant @iant]

Sorry Brian – I've just tapped some tube (as an extension handle) and my 'brain' was still in tapping mode (e.g. internal threads)

However, dies also cut easier if the thread engagement is lower. If you had a lathe you could have tried 'easing' the tube diameter slightly – or if you are using a split die then you could try opening it up (over size) to get the thread started and use several passes as suggested by Bayzle.

Better and/or stronger work holding may well be the solution to your problem here but whenever I find myself having to use (excessive) force, it's normally time for me to stop and think again. Are you sure your tube diameter is the same as the nominal size of the die or is it just over?

It doesn't take too much 'over' to start causing problems. Just a thought.

IanT

[Ady1Participant @ady1]

External threads are a lot harder than internal threads which have the hole to support and guide the tap

External threads are made a lot easier by using a lathe to skim down the starting point and cut a rough thread which is dead straight, then the die simply finishes the job off

[Brian JohnParticipant @brianjohn93961]

Thank you for all the suggestions ; I will be trying some of them next time I set up the vice. The paper wrapped around the tube seems any easy one to try first.

I am not using lubricant because if any gets on the vice jaws then the slipping problem could get even worse. This is only brass so I thought I might be able to get away without any cutting lubricant….but perhaps not !

[Bill PudneyParticipant @billpudney37759]

A friend of mine makes dental implants from Titanium, they are very very small. He uses HSS cutting tools that are honed before use. He gave me a load of taps and dies between M2 and M3 "because the biggest thread he uses is M2"

For a cutting oil on both male and female threads he uses coconut oil from the health food shop. The coconut oil is kept warm using a pyrex dish on a cup warmer. Even up here in sunny Australia coconut oil tends to go solid, which is why he uses a cup warmer to keep the oil liquid, but as he says "slimy".

cheers

Bill

[IanTParticipant @iant]

I'm not sure I've seen what size your brass tube is Brian (or the thread you are trying to cut) but one other idea that may (or may not) help you. If you are cutting the thread on tube which has not yet been cut to final length, then you could possibly drill a hole just past where you will eventually cut it off and place a pin through it to stop any rotation (again assuming the tube is not really long). Works for rod too. Personally, I don't generally use any cutting pastes on brass but the taps/dies do need to be sharp.

Sorry, sometimes hard to help when you are not actually present to touch and see the work!

Regards,

IanT

[Brian JohnParticipant @brianjohn93961]

Thanks for the tip Ian but this is not what most people do …is it ?

I really think I might be in need of a better quality vice.

[Gordon WParticipant @gordonw]

I often get this sort of trouble. Check the OD of the tube you are threading, if needed reduce diameter to under the thread dia. File or emery will do.Make a simple clamp from a bit of wood, similar to shown earlier, just drill a hole, split with saw and clamp in vice. If this does not work you need new die.

[IanTParticipant @iant]

Well Brian, generally if I was working on 'tube' (and it depends on its diameter and length) I'd be holding it in a lathe collet chuck and threading it with a die or tap held in the tailstock guide. But you don't have a lathe and sometimes it's not possible to do this anyway.

I have a set of fibre jaws on my vice that grip most things fairly well – but round objects do tend to slip when twisting forces are applied. With thin tube it's also possible to crush the work if too much grip is applied. So (assuming I'm using the correct die/tap and the tube wall was thick enough) in this case I would probably find it easier to simply drill a cross-hole and slip a pin in (the work of a minute or two) rather than make a custom 'holder' of some form. Of course sometimes this isn't possible (larger diameters, thin wall, already finished to length etc.), so other means would be required. There are a lot of "ifs", "buts" and "maybes" because everything I make is one-off generally – all my jobs tend to be different.

So, no, this may not be what "most people do" but it is what I have done occasionally and it does work. Given your problem and available resources – it might also work for you too.

Regards,

IanT

[JasonBModerator @jasonb]

For those that missed it in the earlier posts Brian is using 3/16" nominal tube, size comfirmed at 4.76mm. HSS split die 3/16x 40 ME thread. Pipes will need threading at each end so cross drill is a no no.

J

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JasonB on 31/10/2014 11:16:00:

For those that missed it in the earlier posts Brian is using 3/16" nominal tube, size comfirmed at 4.76mm. HSS split die 3/16x 40 ME thread.

.

At that size; with a decent die properly adjusted and a touch of Rocol RTD, it really should be very easy … I regret to say that I remain somewhat dubious about the die and/or the material.

[Brian] Have you tried using the die on other material ?

MichaelG.

[Brian JohnParticipant @brianjohn93961]

This is a good quality HSS die from Tracy Tools. I did try the carbon steel dies first but got nowhere at all.

I think the first thing to try is to wrap paper around the tube and the next thing is to try a small amount of lubricant on the die. I will also expand the die a bit and make a second pass if needed at a tighter setting.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Brian John on 01/11/2014 03:12:34:

This is a good quality HSS die from Tracy Tools. I did try the carbon steel dies first but got nowhere at all.

I think the first thing to try is to wrap paper around the tube and the next thing is to try a small amount of lubricant on the die. I will also expand the die a bit and make a second pass if needed at a tighter setting.

.

Brian,

It is difficult to advise you at such a great distance but; as you are evidently satisfied with the quality of the die, I can only assume that the problem is with its adjustment or use.

Forgive me for labouring this:

1. a cutting die must be open sufficiently that there is some [small] clearance between the thread profile and the diameter of the tube that you are threading … otherwise it will jam. To check this [with the limited equipment at your disposal], get a piece of commercially threaded tube or rod, and check that your die will run over it like a nut [i.e. without cutting].
2. the axial alignment of the die with your tube is critical and [again, with the limited equipment at your disposal] you are very likely to experience difficulty. There are devices to guide a die mechanically, but these might be difficult for you to make at present.

It's an unconventional approach, but please humour me by trying the following:

• First, check that the die is correctly adjusted [1]
• Now take a drill chuck [preferably mounted on a screwdriver-style handle, but just the chuck would probably do] and use it to hold a short lemgth of your tube.
• [if you are right-handed] Hold the die-holder in the palm of your left hand, and the drill chuck in your right, and gently screw the tube into the die … You should, with a little practice, get to feel when it is properly aligned and cutting freely.

A slight chamfer on the end of the tube will help, as will some RTD or similar … but without proper adjustment and alignment, you will never cut a decent thread. … You need to experience the feel of the tools working.

… Sorry if that is a bit too "Zen" for some tastes, but I am serious.

MichaelG.

Edited By Michael Gilligan on 01/11/2014 09:38:33

[Russell EberhardtParticipant @russelleberhardt48058]

Further to my earlier post:

I was not suggesting that your problem was that you crushed the tube. I understand that the tube is turning in the vise and needs to be held more securely. You therefore need to grip it harder. If you just tighten it in a vise with "V" slots in the jaws as you tighten it further it will start to collapse and thus reduce the holding pressure even if the distortion is not permanent.

The split bar I suggested allows you clamp it securely and apply a lot of pressure without distortion. It does need a lot of pressure to hold it still.

Here's one I have just done:

That is a 1/8" diameter tube threaded 5 BA and took about 2 minutes to set up and do and another five minutes to find my camera. Note however, the big heavy vise. Rocol RTD compound might help as suggested above but I only find it necessary for steel, not brass.

Hope that helps.

Russell.

Edited By Russell Eberhardt on 01/11/2014 09:43:49

[Brian JohnParticipant @brianjohn93961]

Michael : I do get it to cut but there is so much drama with the tube turning ; I do end up with a cut thread on the tube eventually but it takes me about 5 times as long as it should if the tube was not turning in the vice so much. Next time, I will open the die up and try that. Nobody else seems to have these problems which is why I am asking about it.

Edited By Brian John on 01/11/2014 09:46:30

[Brian JohnParticipant @brianjohn93961]

Russel ;: How did you cut the brass in half ? That looks like a big job with my tiny hacksaw . But yes, that could solve my problem.

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