Tapping Cast Iron

Wow!

Lots of good stuff there. M6x1 tap from the cheap set has long been replaced (probably with another cheap one), though I suspect it isn't up to cast iron any more.

I'll go and have a measure, but I suspect anything much above M6 is going to be too big for the casting.

I'll have a bit of a think, but my gut feel is to use m6. I will either stick to 1mm pitch or use 1mm for the casting and 0.5 for the end which adjusts.

The end in the casting is just to hold in place and if my tapping fails (confidence boy), I will drill out and superglue...

Now to see if the piggy bank will support HSS taps.

Iain

Having (all of us) moaned about cheap tap and die sets, I'm going to ask if there are any decent (and affordable) sets I can get to replace the terrible one I have.

Most of my tapping / threading has been M6, but most other sizes have been used occasionally. On the auction site I can see HSS sets from 20 or 30 quid upwards - which is about the cost of a set of taps from tracy tools!

Are any of them any good?

Iain

Personally I would buy individually, you can still use the tap wrench and die stock that you have and all those odd unsed sizes in the iold set may do one day. Just buy good ones in the common sizes. I like my Dormer E500 series taps in M3,4,5 & 6, have Volkel in M2 and M2.5 the rest of my metrics are the loose in a bag set I got from Tracy tools maybe 30years ago.

> Are any of them any good?

Some of the full HSS metric sets are very good, I bought a set off a market stall and it';s unequivocally the best set of taps I have had. My carbon steel metric set is ... ugh!

Bear in mind that there are probably hundreds (more likely many thousands) of these produced for every carbon steel BA set so the economies of scale are huge. BA is sadly a niche product these days, a shame as it is probably the most 'scientific' of all thread series and a gift to the scale modeller who wants small threads available in close approximation to 'scale' sizes.

Neil

Buy taps when you need them. But always try to buy taps that are boxed, not loose. If any dealer is seller loose cutters just move on. I extend this practice to milling cutters.

JA

Yes; ground thread HSS Dormer E500 series taps get my vote, but be prepared for severe financial pain in the larger sizes.

On a rainy day, if you are not using them, you can pull them out at tea time and just wonder at their beauty.

Above M10, I would suggest "progressive" "geometric" taps like the Dormer E105 series, but they are even more expensive. They make tapping large diameter threads a very low torque process.

I have quite a few Presto taps, bought locally many years ago. Again, they are ground thread HSS.

For less frequently used imperial, ME and MME sizes I have found Tracy Tools taps pretty good.

Sadly; despite what we all would wish, quality costs. But it can be a good investment.

One other thing: in general, I would recommend Trefolex tapping compound. In fact I don't think I have tapped a hole without it in over 50 years. Eases the process, lowers the effort, and protects the tap too.

It's wet here this morning; and its nearly tea break time; so I'm off to polish the contents of the tap drawer with a soft cloth. I think of it as cherishing my investments...

Marcus

Ian, if you visit any of the shows or car boots keep your eye out for sharp branded taps and dies, Dormer, Presto, and others mentioned above, marked HSS GT, check they do not look abused, ie with worn squares or shanks, these can often be bought as a job lot or cheaply. This will take time though. I would avoid non branded tooling for regular use. If you only have 1 hole to do then buy a cheap one, some are better than others, use one of "our" suppliers is best, you have some comeback. I can help with M6 taps but have no surplus dies. PM me if you are not sorted out

Chris Gunn

I've ordered a volkel 6M HSS set from amazon.

It turns out I don't have any 6mm bar, but I do have a lot of 6mm threaded rod.

I shall use that for my first attempt. If the thread cutting fails I will resort to glue.

Thanks for the help.

Iain

The only downside of using threaded rod is that the thread is often cut to a very loose tollerance so you won't get so much thread engagement in the casting but more of an issue is that you will get a lot of play in the adjusting nut. Better to tap the nut and then you can use a split die to adjust the "fit" of the male thread.

J

Cheap taps cost too much time and money. +More aggravation for only one hole.

At the risk of being laughed off the shop:

https://www.aldi.co.uk/p/92750/0

I bought one of these a couple of years back and the quality is pretty good. There is a 6mm die nut in my set, which following a tip from John Stevenson, I converted to a split die with a Dremel...

Double check the quality of course as they might have 'gone off' since I bought mine.

Steve

Lordy, Lord. These model engineering projects don't half take some time!

Mind you the current cold weather is not encouraging me to get out to the shed, in the dark after work!

I've finally finished my tailstock adjuster - photo below.

I've gratefully used a number of the tips from this thread. New Volker taps and no lubricant, brass nut partially tapped and then finished with the actually bolt to be used.. It seems to be tight with little or no backlash, but I confess that I have not yet adjusted the tailstock with it, having run out of my allotted 'me' time.

The design referenced in my original post wouldn't have worked since it was clearly for a different shape of tailstock so I built this as a vertically oriented mechanism and not a horizontal one.

EVENTUALLY, I'll get to an actual project!

Iain