Stirling Engine : Laura

PS, maybe grind a junior hacksaw down narrow enough to fit in the die and cut that piece out.

Or put the die in the lathe chuck and very carefully centre drill and drill out the broken piece with a drill smaller than the inside diameter of the die. .

Brian,

all you need to do is back off the 2 outside screws on the holder and screw in the middle one to its fullest then using a pin punch knock the remains of the screw out

it wont damage anything and no need to buy a new die

Make sure its supported underneath when you drift it out

done it plenty of times myself

Trevor

Trevor's idea may work Brian if the holder is slightly over size but usually they are bang on size so the die wont expand at all. Often it's possible to remove the handles from the die stock and machine them out a little. I'd suggest to 0.010" over the size of the die. Too much and there is risk of the die cracking when it's forced open with the centre screw. That's 0.25mm or a touch more.

I was once told that prior to WWII die stocks always came slightly over sized but after that they suddenly all came on size. That's been true of all of the ones I have bought.

A digital calliper is good enough for measuring the the sort of tolerance that is needed. The figure i mentioned should be ok with 1" / 25mm dies. Larger sizes could take bit more and so on.

John

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Hi John

The reason I mentioned the above method was due to the photo he has showing that its a split die which means the holder will have sufficient room to be expanded otherwise the 3 screws would be redundant

cheers

Edited By Trevorh on 26/11/2015 12:56:07

Brian, I see you say the metal is silver steel and by the discloluration you have been getting it hot when cutting with the Dremel, did you by any chance cool the hot bits of metal This would have made it harder to thread, more brittle and also done your die no good.

High Trevor. I have bought more than one 3 screw die stock where the die is too precise a fit in them to allow split dies to be opened up at all. They can be scrunched up a bit in them but that would be pointless.

One thing I will add is that when I have needed to I have opened them up by 0.015" but am a little concerned that some might crack dies if they do that.

John

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Edited By John W1 on 26/11/2015 14:45:23

Hi John

you should find that the die holders are sized to allow the split die to be opened up to give an oversize OD of thread when it comes into contact with the holder and subsequently when fully closed down it should give an undersize thread when fully closed

In its natural shape it should be ok for most applications

I personally have never had one break on me whilst it was in the correct holder

you are of course quite right about some of the tolerances mentioned but in general I find that if I stay away from the imported holders then the tolerances are pretty good, same goes for the dies, as long as they are not the cheap cast variety then all is good

cheers

It might interest you to know that the first 3 that I opened out were at work and not imports or cheap. It was a regular apprentices job when ever more die stocks were bought. One of the early test pieces was a 1/4 bsw thread nice and shiny and checked for dia with a mic and taken with 3 cuts with the die. Another the screws on a pair of toolmakers clamps and screws for a draw filing jig for thin metal. It couldn't be done with the stocks as supplied and as I mentioned pre wwII they didn't have to modify them. From what I have bought or had come with lathes that I have owned they never have significant clearance on the dies.

The mad tasks with the dies can be done but I have the distinct impression that the tolerances on dies has changed. Taps too as they are usually over sized now.

John

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Can't argue with that John, had to do similar tasks during my apprenticship...

trevor

I have been working at night and sleeping all day so my apologies for the delay in replying.

I did successfully cut this thread using the lathe : the tailstock was used to keep it straight. This is my preferred method of cutting threads. But I was not happy with the shoulder so I attempted to clean it up a bit by putting the work piece in the vice and recuttting it ; this is when it broke. I should have left it alone. I did try to cut the thread in the vice from the start but I could not get it to start.

I have removed the broken piece using a hacksaw blade. Unfortunately the die has been damaged. You can see that two of the thread cutting pieces are broken off so I will have to buy another one. I think the damage occurred when I tried to drill it out. My drill press is rubbish ; I should not have even tried to use it for this.

NOTE : the die could not be opened up enough using the centre screw...not even close.

I did reduce the piece down to 1.9mm before cutting. I did put it in the lathe to keep it square. I initially had the dremel tool set too high and as you can see it burned the metal a bit ; I have now lowered the speed. Today I cut another three of each of parts 10 and 11 ready for the 2mm dies when it arrives from the UK. I also cut some pieces in stainless steel rather than silver steel. I will see how that goes when the die gets here.

Making these smaller pieces is turning out to be more difficult than the larger pieces. My camera is terrible at close ups.

Edited By Brian John on 27/11/2015 06:13:56

Edited By Brian John on 27/11/2015 06:15:26

Edited By Brian John on 27/11/2015 06:18:58

Ah yes, the old "I'll just give it one more tweak and get it perfect -- POP!" trick.

Don't worry, we've all been there.

Edited By Hopper on 27/11/2015 06:41:56

That die doesn't look suitable for splitting - the holes are too small and it would be nigh impossible to spring it open with the adjusting screw.

I always put a short taper on the end of anything to be die threaded to help the die have an easy start.

Neil

I still couldn't get it going in the vice ; I had to put it in the lathe. I have just purchased a die hold to make it easier to do it in the lathe.

I really must make a spindle handle soon.

Edited By Brian John on 27/11/2015 08:09:58

I would expect to see a bit of a lead in on the die, might be on the other side. However at times there isn't one.

On sizes like M2 I usually file a small chamfer on the end that takes it down to a bit less than the core diameter. It's no critical and also helps nuts etc fit. Same with tapped holes usually with a countersink by hand.

When cutting threads with a tap or die the usual reason for breakages is not reversing them to break the chip that's been cut often enough. A usual rule is every 1/4 or 1/3 of a turn. It's possible to feel when the chip actually breaks off. With aluminium and brass it's usually possible to do it less often than that but care is needed on low diameters. Taps are available that are intended to be fed in one go even so when using these by hand it's still a good idea to reverse them to break the chip.

I did have a problem once with an M2.5 die refusing to start. Turned out that it was well under size. Especially in small sizes the only sure way to check them really is a screw with the same thread having mic'd that first.

John

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I think most of the die stocks made today are made to fit the unsplit dies, so need minimal clearance. To use them with split dies, do as suggested and open the holder out .010" / .015". Some of my dies have an adjusting screw in the split.

Die stocks, and tap wrenches are good  things to start with when you first get your lathe,  I made a number of them when I started, Sold the presentable ones, kept the rest.

Ian S C

Edited By Ian S C on 28/11/2015 09:43:31

I have ordered two of the 2mm dies from Arc Euro and they should be here in about 10 days. I thought I better order two dies as the postage cost is the same.

I made two of part number 17 today. I seem to have a problem getting small parts to run true in the chuck before I start machining them. Is this where a four jaw chuck would be useful ? The four jaw chucks are still on their way from China...on a very slow boat !

The 3mm stainless steel rod I have is oversize too at 3.15mm and does not fit the bush so I have ordered some more from Hong Kong. I am hoping that it will be slightly undersize. I could bore out the hole a bit more but I was worried about making the walls too thin.

Edited By Brian John on 30/11/2015 06:42:18

Edited By Brian John on 30/11/2015 06:42:40

Is it really 1/8"? (3.17mm).

Neil

I was told that it was 3mm but obviously it is not. The rod I have ordered from Hong Kong is marked as 3mm / 0.12'' so I am hopeful that this time it is correct. It is marketed to be used in RC cars and helicopters.

Edited By Brian John on 30/11/2015 11:38:21

Edited By Brian John on 30/11/2015 11:40:19

Brian, the four jaw chuck will not, without packing close cpmpletely, your little one might go down to 6 mm or 8 mm. If you need smaller, you can drill a little bush, and slit it length wise , then you can handle the small stuff, I suppose that's why so many of the guys use collets.

Ian S C

Aha... so I need a collet for these small items ! I can get it done as is in the three jaw and it turns out okay but a collet might help me get a better result.