Dies, damned dies, and cheap dies

[classicsteve]

I was thinking of "There are three kinds of lies : Lies, Damned Lies, and Statistics"

I needed to make a 1/4 UNF brass threaded thumb screw the other day, and after cutting the female thread, realised I only had a UNF/UNC tap/die kit from the car workshop to provide a die. I presented the female die a nice 1/4 brass shaft with a decent lead in and it would not cut a thread at all - and I really tried, and it was held in a tailstock die holder in the lathe. I tried reversing the die and still nothing, yet I could wind the die up a UNF bolt OK.

I looked very carefully at the die and couldn't see if it had clearance angle one way round or the other. I gave up and cut the thread on one of my lathes, and then used the die to clean it up, and that worked.

So are there two sort of dies? True dies, and dies in cheap car tookits. One to be used in one direction only to cut threads, and another only being suitable for thread cleaning - (and I am talking about a proper looking split die here, not a die nut)?

Or maybe the cheapo dies are just badly made. So if you have a proper well made die, is there a convention that you always have the die's face with the labels on, on the face that is leading ?

Hope you know what I mean.. I have a right old collection of old dies and it is time to sort the wheat from the chaff, and buy proper replacements for any garbage. I think my metric dies are equally naff, but I am not sure how to tell just by looking at them.

Thanks, Steve

[jasonb]

The side with the size engraved on it should be the side that leads as the first few turns will have a slight taper.

Cheap carbon steel dies can blunt quickly if used on hard materials like stainless and for brass you bo need a really sharp cutting edge. Also expand the die on the first cut by winding in the central screw on your die holder.

For dies you are likely to use often its worth paying the extra for HSS ones.

Jason

[Deleted]

Steve. You are spot on about the cheap dies being mainly suitable for thread cleaning: I have some cheapo metric die nuts which are just useless!
Tracy tools have been selling a 'Frustrated Export Order' for many years now, comprising a full set of BA dies in HSS for less than £20. They are excellent: I know, I have some! Only trouble is they are a non-standard OD so I had to make a tailstock die holder to suit.
I'm slowly (very slowly) going over to small metric screws, and I bought recently Machine Mart's set of small metric HSS taps and dies. These go from 1mm to 2.5mm, and include two taps per size. Amazing value at £36, and their ease of use and sharpness bely their humble (Rolson) origins.
Hope this helps you,
JB

[ettingtonliam]

Hi
As Jason says, one side should have a taper on the the first couple of threads, this is the side to start cutting with, the other side is virtually square, and is used, if necessary, to give a full thread up to a shoulder. I'm not sure if its always the case that the side with the writing on is the taper side, you will have to look and make sure. With old dies, the taper side will have been the one most used, so sometimes you can find the 'square' side cuts best, simply because its sharper. As always, make the first cut with the die opened up as far as the holder will allow, then gradually close up until you get a good fit.
Those sets the car shops sell are pure rubbish. if you've got a Dremel mini grinder or similar you could always try running a small grindstone up the cut outs on the cutting edge to see if that improves things, but I wouldn't be too hopeful.

Regards
richard

[weldsol]

Yep where have all the good old british die makers gone.
Had a rush job the other week and need a die so off to the local tool supplier and got sorry have not got that size but I can get it by this afternoon, sure enough got a call it had landed.
Got back set up the tailstock holder put in the nice new die (made in Japan stamped on it) did up the screws to set open the die got about three turns on the thread then bang the die had split when I miked up the die (now in two pieces ) it was a good 1mm smaller than the holder.( note this was not sold as a cheapo )
Went off and located a british die and low behold it was only 0.2 mm smaller than the holder
The moral I suppose is get british if you can

Paul

[pendembu]

The same set of small metric taps and dies in HSS as Machine Mart sell for £6 is available from Chronos for £20,even more amazing value!

[classicsteve]

Thanks for the help guys, I am surprised to hear good about machine mart stuff, I thought it was all cheap and cheerful.

I think I should make sure this particular UNF/UNC tap/die set stays in the garage, and probably both my metric sets, as I knwo in one of them the taps are rubbish. They will cut one or two threads before they blunt, and then you tend to lean on them, and ping !

However I am modelling in imperial and BA as all my machines are imperial. With BSW, BSF, UNC, UNF, BA, and ME threads I have plenty for most purposes. I will just need to improve my collection of UNC/UNF taps and dies. I like the slightly finer thread offered by UNF, combined with easy availability of bolts and screws. In this case I am making a grinding jig.

Steve

[bookworm]

If you think Chronos is expensive for the Metric tap & die set sold by Machinemart, then take a look at the price Maplin's are charging for them. Now that is expensive!

[jonkett]

What standard are these dies made to, checking in our catalogue the relevant standard is BS1127, if they do not advertise this then who know's what they are buying. Many of these suppliers do not have the faintest idea what you are talking about.

If you are going to buy a chuck ask them what standard of accuracy they are supplying, i have not had an intelligent answer yet.

[pendembu]

I feel I must correct the error in my previous post.Machine mart charge ££36 for the Tap and Die set. Chronos at £20 are of course much better value.