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

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

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 !

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

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

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.

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.

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

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

.

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.

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

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

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

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.

.

Brian,

I stand by my observations at [1] and [2] in my previous post.

A slightly tight die, applied with a small angular mis-alignment will give exactly the problems you are describing.

MichaelG.

Brian definately slacken it off for a first cut then tighten up to do the finishing cut. I do find that their UST prethreaded fittings are a bit tight on ME threads so always put a plug tap down the fitting thread to open it up a bit so the male thread does not need to be so small.

You could always make a shorter version of Russel's jig to take a single size of pipe which would make it easy to cut with your junior hacksaw. As well as reducing the risk of crushing the jig also has far more metal in contact with the pipe than the 4 contact points of a Vee jaw so the extra friction also helps hold the pipe.

J

All I'll say is that I don't buy from Tracy Tools anymore; make of that what you will.

Andrew

Brian,

It's possible Russell didn't cut his brass jig in half with a hacksaw - he may have just clamped two pieces of brass together and then drilled them to carefully placed centre punch marks.

I don't know what Russell actually did - but it's what I'd probably do.

IanT

Hi Brian,

Looking at your set up, I think your vice clamping force might be increased if you added a tube of the same diameter at the opposite side of the vice jaws or move your work piece to the center of the jaws if possible. Another alternative would be to clamp more of the tube perhaps horizontally clamped if you have the room to turn your die holder.

Ed.

Ed : No, it will not grip horizontally. I have already tried that.

Andrew : Well if you do not buy from Tracy Tools then who do you buy from ? I did order from ''another mob'' once and ended up paying more in postage than the cost of the items ordered so I will NOT be doing that again.

Ian : Okay, two pieces of brass held together in the vice and drilled...worth trying