How to use a die?

I've found solid dies work ok but I'd rather cut slightly under size on the first pass. Is it safe to split solid dies with a cutting disc or are they likely to break if opened in the stock a little?

I think that there are two types of unsplit die.

Hexagonal dienuts are meant for cleaning up therads by hand.

Unsplit round dies are for use in a production environment where faffing around adjusting a worn die or taking multiple passes is just a waste of time. use them till they blunt, then throw away.

This is why they are cheap, they are mass produced for factory use.

Quality wise, you can get good un's and bad un's. I've never had a naff thread produced by my good unsplit ones.

Neil

I have tried the cheap taps and dies and regretted it, they would not cut a clean M6 thread on/in stainless steel 316 once purchase a set of Dormer taps and dies problem solved.

Bob

I thought that most commercial, and aerospace, threads are produced by rolling, not cutting. For those threads that are cut there are assorted self-opening dieheads, which would be much quicker than reversing a conventional die. Having said that both my Britan and Pultra have adaptors that use conventional dies. Although they all have three adjusting screws, as per split dies.

Andrew

In my experience, many modern die-holders are poor. The threads for the adjusting screws are loose, and there is too little metal to get a decent length of engagement. As a result, a split die cannot be opened significantly.

Round stainless tends to be made by rolling and so has work-hardened surface. This is good for some uses, but a die tends to tear the thread, pulling the hard top layer away. A blast with a propane torch to a dull red, cool in air, seems to help.

And now, what advice to you have for sharpening a used die? A Dremel with a cylindrical grinding tip seems to be the answer, but is it? What else might work well?

Cheers, Tim

"Best bet is to get a HSS split die, I would never buy carbon steel taps & dies unless it was for a once only use, I have known the teeth to fall of on the first use on St.steel."

"Sorry these circular dies which are not split are rubbish,(cheap foreign imports) their only possible use is for cleaning up a burred or damaged thread, dustbins the best place for them."

I am sorry gentlemen, I mean nothing personal, but what a load of cobblers. I have just paid a few pence more than £32 for two Carbon Steel dies, do you think I was robbed?

Of course I wasn't. I am sorry, but a blanket statement such as "all Carbon Taps and Dies are worthless" is just so wrong. On so many levels. I regularly thread Titanium and tap Stainless steel and I will ONLY use Carbon Steel. For a couple of reasons. I need to cut more than a couple of threads each time and I need the products I make to actually work. My failure rate threading Titanium with HSS is too high and although it wears the Carbon Dies quite quickly, I don't get any failures.

If any of you have tapped Stainless you will know how bloody minded it can be. High quality carbon steel taps are the way forward. They might cost (in the sizes I use) me £27 a set but they cut through like butter.

Next up - solid dies. Do you think industry has all the time in the world to mess on adjusting dies for each and every thread they cut? Of course they don't. Solid dies are commonplace as the CNC machines need them.

The massive advantage though is I get to buy up all these "useless" tools at a cheaper rate than usual at the engineering shows - because the majority pass them by as "useless". I have just bought a good handful of these "useless" dies that came out of a major aircraft manufacturing plant, bit of a result that was.

For the record, I buy my Carbon Steel threading kit from Tap and Die. They supply Boeing, Airbus, General Electric etc. with these "useless" bits of kit. If you are buying "cheap" taps and dies, half rice half curry powder, you will most certainly get what you pay for.

graham.

edit: spilling

Edited By Oompa Lumpa on 14/03/2015 21:11:01

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An excellent point, Graham [and well made]

I have no doubt that good, properly heat-treated 'carbon steel' can take a better edge than HSS.

It was near Alchemy when they originally made 'Crucible Steel' ... I would be interested to know how it's done now.

MichaelG.

Wow -- thanks for all the great advice. I now know ten times more about using dies than I did yesterday!

I am going to avoid stainless steel for now -- I can use brass rod instead, which I assume is easier to put a thread on, I really chose ss because I had some handy. When I really need to use stainless I will buy some decent dies, as mine were a 40 piece tap/die set for AUD66.

Thanks again everyone -- what a great community!

Aha, well yes. If you can use brass, you will be well pleased. Much more co-operative than stainless.

Probably just a personal thing Tom but my ME and (best) BA taps and dies are only used on brass/bronze - I don't use them on steel - let alone stainless.

When I say "best" BA taps and dies - I generally reserve my newest ones just for brass but once (if) used on steel they are marked, kept separately and then only used for steel thereafter unless I have no other alternative. I simply don't use my ME (32/40tpi) set on anything but brass/bronze. Not sure this is absolutely necessary in practice (and I may be wandering perilously close to superstition in this area) but It's what I do. Fortunately, I have enough BA taps/dies in the sizes I use regularly to be able to afford this luxury and it only takes a little discipline to observe the rule...

I don't worry nearly so much (well not at all in fact) with my BSW/BSF/Metric/other screwing kit but then they are used mostly on mild steel anyway. But if I was going to be regularly cutting small/fine metric threads in brass or bronze - I might keep some to one side for that specific use too.

Anyone else have this practice or is it just me?

Regards,

IanT

You are not alone Ian, I keep my ME and BA mostly for steam fittings so they are never used on anything ferrous. I do the same with milling cutters, new ones are used on brasses, bronze and ally and then set aside for steels before going for resharpening when viable.

I also have a set of number drills that again are only used with the ME and BA taps.

For brass, good quality carbon steel taps and dies will last for ever.

Ian S C

When I stated that the solid dies were rubbish,and then a contributor stated I was talking cobblers,Well I had in mind the sets of c--p cheap taps and dies usually oil blacked all over and available from auto jumbles,motor trade distributors,cheap retail outlets etc. I have been around a long time and I have nothing against carbon dies /taps I bought a lot of me/brass size taps/dies from Stuart Turner 50 years ago,they were by good known English manufactures and they are still in good conditition, I also have a 9/16 to 1 inch whitworth tap and die set ex WD dated 1940 superb English quality ,all carbon steel ,guided die holders and really good tap wrench .The problem nowadays is finding threading tools of the same quality, The English manufacturers have gone ,and it is difficult to find good reliable suppliers,known names on tools nowadays can be misleading ,they can be made anywhere in the world and somebody possibly bought the company name. I have an unused (until I got them)pairof molegrips,possibly 60 years old and made in Birmingham thats before they went to Wales, I also aquired a pair that were made in spain ,I think after Stanley aquired the brand name,not very good compared with the old ones.

When ever possible, when I thread I do it either in the lathe or milling machine as a drill press.

In the lathe, with the rod blank held in the headstock chuck I place the die in a die holder made to be held in a drill chuck.

After mounting the die in the tailstock drill chuck I present it to the rod . Lubricate the part, use the tail stock ram to apply gentle but firm pressure on the die while slowly turning the lathe chuck by hand to start threading. (IMPORTANT: before doing this turn off power to the lathe and place the headstock in neutral so that chuck is free wheeling)

Carefully maintain pressure on the die as it progresses on the rod, pausing frequently to lubricate, back up a turn or so to clear chips. Like a lot of this kind of work practice brings skill and a sense of touch.

The process works the same way, in principle, in a drill press or milling machine.

The advantage for me is this method allows excellent control of the part and die while ensuring that the threads are started correctly. While it may seem overkill, it is really helps, especially on larger rods.

Everyone has their own way, so find what works best for you.

Edited By Roland GAGE on 16/03/2015 18:29:45

Properly heat treated carbon steel will take a keener edge than HSS but for a machine cutter will lose that edge the moment things get a bit too hot. HSS can keep its edge at much elevated temperatures and makes a very robust turning tool or milling cutter. A tap or die for hand threading does not need to perform at high temperature so I wonder why it has become so popular for hand threading. Maybe HSS being a more expensive material it is bypassed by the bottom end of the market so poorly made taps and dies have become associated with carbon steel. HSS ground thread taps and dies are a premium priced product but I wonder whether a well made carbon steel item will cut just as good a thread or better. Tool life is another factor and I think is probably the main reason HSS displaced carbon steel as the toolbit of choice before carbide took things to another level. For most of the work we do a well made carbon die will give a very useful sevice life, if we need extended life the extra investment in HSS may be worth while.

Mike

I don't understand what that means, or why it should be so? Can some-one explain?

Andrew

It's been a long held belief on the "craft" side of our world Andrew (e.g. by many 'craftsmen'   that a properly tempered and honed carbon tool can take a keener edge and therefore give a finer cut than HSS. The downside being that the carbon tools don't like excessive heat, which is why carbon tooling was generally abandoned when HSS came along.

Not being a metallurgist I can't explain why this might be but I do use 'carbon' steel cutting tools - mostly when I need a shape (or size) of tool that I cannot get in HSS or that I don't want to grind to shape or size!. In these cases I can shape (file or machine and then harden/temper) a tool in some kind of carbon steel (e.g. old files, silver steel etc.)

For my particular needs these tools can cut very well, so are very good for occasional/specialist use but they do need care to avoid overheating - not so much when turning but when working very small section tooling on the grinder or with any milling tools. I don't generally hone most of my HSS cutting tools but do so on some carbon ones - especially the smaller 'custom' tools where I want to get a very clean finish.

There has been some debate over the years about the need to hone a cutting tool (at all) but (and again this is a laymans view) if you are cutting very small work (with a small tool) then it seems to stand to reason that a 'smoother' cutting edge will give you a better finish. A carbon tool can take a very keen edge and it seems to take it easier than HSS - which you can also hone of course - but this is a very subjective view. I am sure there will be clockmakers and other people better qualified than me to explain the 'physics' of all this.

Of course, I don't 'hone' my dies and given the choice I'd always buy HSS dies/taps but I do have some larger carbon dies/taps purchased from new, which were about half the price of their HSS equivalents at the time - but which I only expected to use a few times, so the lower price was the clincher.

I guess that I've never worried too much about "why" things work, being much more concerned about whether they actually do (or do not). I think it's also worth remembering that our needs (as hobbyists) are often very different to those of Industry.

Regards,

IanT

(Could use a pre-view function - would avoid re-editing)

Edited By IanT on 17/03/2015 10:48:00

I have heard many times that carbon steels take the best edge, I imagine it is related to greater ductility reducing the tendency of a very fine edge to crumble and depends on good tempering.

The best explanation I could find was from a chef website. Apparently chromium gives stainless steels poorer 'edge qualities' than carbon steel. As you've probably notice HSS stays bright and this is partly because of its high chromium content...

Neil

According to Tubal Cain's excellent book 'Hardening, Tempering & Heat Treatment' (MEW Practice Series #1, Appendix 2 ' Carbon Steel Cutting Tools' pp. 113), properly heat treated carbon steel has a finer grain structure than HSS and is harder than HSS below temperatures below 270°C.

Not very good for production work when things get hot, but eminently suited for a tap or die.

Indeed, I have noticed that my keenest knife blades are made from carbon steel, and I believe that many top quality chef''s knives are so manufactured.

The downside is of course the old enemies of heat and rust - not insurmountable problems though.

The reference above is very informative and also includes some very useful colour plates of tempering colours.

Well worth a read.

* Danny M *

Edited By Danny M2Z on 17/03/2015 12:00:38

Most of the claims for "keener"(??) blades in carbon steel are for knives by the looks of things. There's no obvious reason for making a knife from High Speed Steel (the clue's in the name) unless you are particularly nimble in the kitchen / woodworking shop.

I note that quite a few top end knives are rust free, which presumably means they are not simple carbon steel. I expect there are any number of steels used in the kitchen - just how similar some of them are to what we call HSS may be a question of semantics.

Neil - if the blade is hardened and tempered, surely the word "ductility" no longer applies?

If you buy professional quality dies made by named manufacturers, they are likely to be of reasonable quality. So I tend to buy the likes of Presto, Dormer etc. I might be wrong but generally I've only seen (noticed) the HSS versions from those sources. I'm open to the possibility of some carbon dies being just as good or even marginally better but I prefer to play safe. "Keenness" in a die doesn't really address the challenges I face when cutting threads with a die.

Murray

PS: Here's some info about knife steels. Not a trivial subject!

Edited By Muzzer on 17/03/2015 13:08:12