Tap n dies

[ace]

Hi all

Having recently broken my soul remaining 6BA tap I am placing an order for some new ones and for a few new additions. My question is which is best Carbon or High-speed steel!. I have purchased most of my tap and dies from either Chronos at the M.E. shows or from an Eclipse deal, and these have often been value for money types and have lasted well, but the BA taps seem to be the poorer quality but I have no idea what type these are. So what is the difference?

Cheers

ACE

[GWRdriver]

Ace,
I know from my reading and correspondence over the years that carbon steel has been preferred in the UK. The usual reasons are that the first cost is less and in case of breakage they can be annealed in place and drilled out.

HSS is typically preferred in the USA, and is my prefernce, first because they are far more widely available at reasonable prices than carbon steel and HSS will hold an edge for longer than carbon. HSS cannot however be annealed, at least in the usual sense, and consequently cannot be drilled out so in case of breakage in an expensive casting it sometimes leaves us with a considerable challange.

[abby]

I for one would never buy CS if HSS was available , drills ,reamers and taps need only be a one time buy for most modellers - breakages excepted , we have all broken small drills and taps , but use a good cutting lubricant and go carefully and this should be a rare occurence. Use the pilgrim method - like they taught at school - two turns forward and one back to clear the swarf. Most important in my opinion is to buy tools by a reputable manufacturer such as Dormer. Most of my taps and dies , infact most of my tools were "borrowed" from my father and are many years old but still cutting fine! I don't know if Trefolex is still available , I have a tin which is years old but I use it for any cutting work involving hand tools. It does what it says on the tin - halves the work and extends tool life.

[Jo]

Hi Ace,

I must say the quality of some of the cheap HSS taps and dies leaves a lot to be desired. If you know of any second hand tool dealer it is worth having a rumage through their old taps/dies box. Normally they do not bother with taking these to the shows as when they are only charging 50p to £1 each they just pour them all in together. Spend a few minutes and you will be rewarded. I have acquired a number of excellent quality taps (brand new SKFs) and dies through this route.

Don't forget that if you have a blunt one that a dimond rat tailed needle file will soon bring it up again. And my tin of trefolex is also going well. Put some in a small lid (I used a spice jar lid until recently) and it is always ready for tapping.

Jo

[ron]

Trefolex is still available but boy is it expensive! if you leave some of Screwfix' tap and die aerosol in a small dish to evaporate it ends up pretty much the same and works very well.
Personally I've always used good quality CS taps & dies, I don't think most amateurs use them enough to justify the cost of HSS ones in this country.
Ron

[albertsell]

Hello ACE,
When I want a good quality and good price taps and dies, always HSS + treflex from my local large supplier of nuts and bolts to industry.Taps purchased at exhibitions at cheap prices are what you buy CHEAP, always look for a name on taps to qualify its source and quality.As already commented by ABBY buy the best ,look after them, they will outlast you.
Albert.

[Tim Bayliss]

Hello ACE,
Carbon steel taps (and dies) are harder than HSS. Being harder they tend to be more brittle and break easier, most noticeable in small sizes (BA, etc). CS taps can also be sharper than HSS due to the better edge taking qualities.
The only real advantage of HSS over CS is for automatic machining where toughness is more important than hardness. For hand use either should be fine but I will agree that, especially in the small sizes, the quality of manufacture does make a difference.
Tim

[chris vine]

Hi,

I find that Rocol RTD, (Reaming Tapping Drilling) fluid (gloop) is very good. I was told to get some Trefolex but did not find it nearly as good as the RTD.

Chris.

[havoc]

I for one would never buy CS if HSS was available , drills ,reamers and taps need only be a one time buy for most modellers

I do have blunt drills and taps. Maybe if you don't work anything else than brass but silversteel and carbon steel can take a toll on your tools. Just the same as drilling xxx holes in some frames. Personally if I can I used carbide.

[jeffhills]

A word of warning, I bought loads of far eastern CS taps from RG tools as I had no ME sizes, they cut so far oversize they have all gone in the bin! I have replaced with CS British made from Polymodel, they are OK but like all CS taps I have seen are 'cut thread' ie the tread is cut, then its hardened and then sharpened along the flute, so the diameter and form of tread produced is defined by a 'rough' area of the tap. Most HSS taps are HSS GT. ie ground thread, where the tread form is ground on after hardening, this type of tap produces perfect result, but prices for BA (specially odd sizes) are just stupid as production quantities are so low. Is it time we switched to metric size treads on our models?
Jeff

[alanstepney]

Over the years I have collected loads of taps and dies.

Just keep your eyes open at car boot sales, auctions, and the Tracy Tools specials at ME shows, and soon you will have plenty of every size possible, with duplicates or multiples, of all of them.

[Tel]

Same here AJ, tho' generally speaking I prefer the carbon steel as they give a much cleaner cut.

[SteveW]

Guys,

I've noticed that a lot of the cheaper HSS tap/die sets only include 'second' taps. These are somewhere between a taper and a plug tap. Generally this is fine unless you're doing a blind hole.

I've also heard/read that HSS taps are ground to have a clearance angle behind the cutting edge. This can make for the more aggressive cut needed by industry but does not always suit our purposes.

I also use the Screwfix spray taping gue, it's a lot easier to manage and get rid of than Trefalex and similar and doesn't glue the swarf to everything.

[ace]

Well thanks chaps for the grand replies, I haven't had trouble with tapping holes before, I broke the 6BA tap not due to lack of lube or over-doing it but through having bought cheep c**p. They, being the BA set have mostly broken off at the top near the end of the thread where the shank tapers in. I must confess that I bought these on impulse as they were cheap and the set covered the full BA range. One learns from ones mistakes. I have however always managed to utilize broken taps before by regrinding them to a shorter length for use in jobs that require a limited depth such as cylinder glands and other blind holes. I guess its time to reach deep into the pocket and buy some quality this time. ;D 'O' and my mistake the other taps are mostly Dormer not Eclipse.

ACE

[baggo]

One tip I picked up some time ago was to increase the size of the recommended tapping drill slightly, especially if you are tapping in steel. This gives a finished thread depth that is still plenty strong enough but gives the taps an easier life as they have less metal to remove. Also use a 'second' tap rather than a taper as there are fewer teeth cutting, again reducing the loading on the tap. Like Chris, I use Rocol RTD all the time. Most of my work (2½" gauge) involves 8,10, and 12BA and although I do sometimes break taps (usually through carelessness!) it's a fairly rare occurence.

John

[alanstepney]

The drill sizes that the makers quote are based upon machine tapping.
For hand tapping, a thread engagement of around 65% is sufficient and the reduction in strength is minimal, whilst greatly reducing the incidence of tap breakage.

Tubal Cain wrote extensively on this subject (in ME), and went into the maths of it in depth.

Tapping drills for many threads showing the low-engagement tapping drill sizes are on my website, and the main link page for threads is at:

www.alanstepney.info/page8.html

[abby]

Alan - had a look at your web-site , some good stuff but your tempering chart -when viewed in safari on a mac - runs from straw to cherry red.

[ilvaporista]

I can only confirm most of what has been said above, by all means start off with a cheaper set but as the opportunities come along grab yourself better quality tools. At many shows or even car boot sales you come across single taps at good prices. Yes I know that unbroken 14BA taps lying in loose boxes for 20p don't exist but keep searching. From a workshop clearance on another ME site I bough a job lot of old taps and dies for £20. Best money I ever spent.

I find Rocol RTD the best in ferrous materials and for brass/gunmetal etc I use a mix of olive oil and parafin.

To avoid tap breakages I have a poor man's George Thomas Tapping and Staking Tool. Copied from my good friend Romeo in Naples, it started life as a cheap Chinese drill press. Pics are again on my site under Attrezzature halfway down the page. www.ilvaporista.it

[alanstepney]

Abby, I tried several times to get that particular chart in a form that would print "true to colour" on any system.
Never seem to have got it right, or perhaps I am trying to achieve the impossible.

Thanks for the information though.
Maybe I'll try again, or perhaps it is best deleted if I cant get it right.

[Lurkio]

Alan,

Have you come across the 'Web Safe Colours' or 'Browser Safe colours' before? Maybe you have.
A set of colours supposedly recognised and reproduced accurately by any browser.
Thought this may be useful to you.

Lurkio.