Stirling Engine : Laura

[JasonBModerator @jasonb]

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.

[AjohnwParticipant @ajohnw51620]

Posted by Trevorh on 26/11/2015 12:55:15:

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

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

–

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

[TrevorhParticipant @trevorh]

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

[AjohnwParticipant @ajohnw51620]

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

–

[TrevorhParticipant @trevorh]

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

trevor

[Brian JohnParticipant @brianjohn93961]

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

[HopperParticipant @hopper]

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

[Neil WyattModerator @neilwyatt]

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

[Brian JohnParticipant @brianjohn93961]

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

[AjohnwParticipant @ajohnw51620]

Posted by Neil Wyatt on 27/11/2015 07:12:10:

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 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

–

[Ian S CParticipant @iansc]

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

[Brian JohnParticipant @brianjohn93961]

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

[Neil WyattModerator @neilwyatt]

Posted by Brian John on 30/11/2015 06:40:47:

The 3mm stainless steel rod I have is oversize too at 3.15mm

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

Neil

[Brian JohnParticipant @brianjohn93961]

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

[Ian S CParticipant @iansc]

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

[Brian JohnParticipant @brianjohn93961]

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.

[Brian JohnParticipant @brianjohn93961]

The smaller parts continue to cause problems. This time it is part 30 ; there are six of them to hold the base of the engine above the wooden plinth. The dimensions are not crucial as it is not a moving part of the engine. The instructions call for them to be made out of aluminium. This is awful stuff to drill and tap which is not helped by the fact that my tap wrench is no good for small 2mm taps. I just discovered this today ; it will not grip small taps.

In the end I decided to just drill through at 3.2mm and the engine will be held in place with M3 X 30mm socket cap screws which will pass through part 30 down into the wooden base. The M3 nuts will be located in a counter bored hole. This is the way I normally do these things and it avoids unnecessary tapping.

I was lucky that I have a brazed carbide tip tool which is exactly 8mm wide ; it is perfect for making the recess cuts.

Do you find that aluminium clogs small drill bits and taps ( 2mm or less) ?

I will be buying one of these to use with small taps :

http://www.ebay.com.au/itm/TAP-WRENCH-tap-handle-T-wrench-Tap-Holder-1-16-to-5-32-1-5-to-4mm-/110750239680?hash=item19c93a8bc0:m:m96W8p_1PeS9VuZf94q40Kg

 

 

Edited By Brian John on 02/12/2015 06:20:41

Edited By Brian John on 02/12/2015 08:36:28

[Ian S CParticipant @iansc]

Brian, those bits could be made of anything, wood would be quite OK, drilled right through, and either a bolt through the base board, and nut underneath, or a wood screw into the base board.

Ian S C

[Brian JohnParticipant @brianjohn93961]

Yes, I know. I even have some M2 X 14mm brass spacers already drilled and tapped which would also work. But they are a hexagonal shape and I decided to keep closely to the original shape. I also wanted to try out that carbide tool on something

[JasonBModerator @jasonb]

Brian, you can grip the taps by the round shank, the advantage is that if things do get a bit tight then hopefully the tap wrench will slip before the tap snaps. You can also lightly grip tbe bit of exposed round shank in the drill chuck which will help guide the tap true to the bore.

Kerosine when turning, tapping fluid when tapping and as the flutes are not very deep on small taps take the tap out often and clean off the swarf

Edited By JasonB on 02/12/2015 13:13:52

[Brian JohnParticipant @brianjohn93961]

I was using the bar type tap wrench which will not grip the smaller taps. I have ordered the T handle type with the chuck for use with smaller taps in future. This was my first attempt at tapping aluminium ; I have only done steel and brass before. I thought aluminium would be easy because it is so soft but I found that it ''sticks'' to the drills bits and taps.

[AjohnwParticipant @ajohnw51620]

You should rotate the tap backwards every 1/4 / 1/3 turn to break the chip Brian. A few full turns to start the thread are usually needed but the chip size is small then due to the taper on the tap. There is also the question of how much downward pressure to apply. Can't help you much on that aspect but some is needed otherwise the teeth that have already cut will cut some more due to the cutting forces caused by the new threads that are being cut – they try and push the tap out rather than in. A little pressure is needed in practice, around the same amount that is needed to get the thread to start cutting "crisply" when most of the taper has gone in.

I've generally managed by just using 2nd cut and plug taps. The 1st cut one is definitely needed on very hard materials and can be a good idea when very fine tapes are being used. I don't see M2 as being very fine just bordering on that area.

The pressure aspect applies to dies too.

I have my tin of supa dupa tapping lubricant as well. I'd guess many have. Can't say as I am impressed. I often scrape a bit off a bar of hand soap onto taps. It's a type that has some sort of moisturiser in it. LOL I've mentioned cutting oil several times.

People often mention paraffin / kerosene for aluminium. The key word is more volatile than substances used on other materials. It's oily and evaporates readily and that aids cooling which helps prevent the aluminium from melting at machine tool cutting speeds. In practice I have never seen it used. Oil mist and suds yes but never paraffin. The suds tank would have to be emptied and filled up with it. I'd guess if any one really ever used it this way they would also mix in some sort of oil. All I have ever seen been used even when grinding it is lots and lots of suds.

John

–

[Neil WyattModerator @neilwyatt]

I use a neatcut type oil when tapping aluminium. I've had no problems tapping down to 8BA. 10Ba is trick in ally, but only because the thread is so shallow.

[AjohnwParticipant @ajohnw51620]

I wonder if some of the problems with fine taps is down to the depth they are used to. There is one thing common to just about any screw fixing done correctly and that is the relationship between the diameter of the screw and the engagement length with what ever it's screwed into. Nut thickness is a typical example. The relationship us usually just over 1 diameter. Tool rooms I have been involved with shorten bolts if needed so the engagement length is in the range of 1 to 1 1/2 diameters, same order as a nut in other words. Maximum strength. There is no need to tap much deeper than that.

Must admit 1D gives me the wobbles so always go for a bit more and also often can't be bothered to shorten screws and bolts. On the other hand 10BA only needs fully tapping to a depth of an 1/8" tops really and that is very likely to save breaking taps.

John

–

[AjohnwParticipant @ajohnw51620]

Taping lubricants always remind me of an instructor that probably trained as a tool maker in the 1930's. He had managed to get a bit of sperm whale oil which was reckoned to be the ultimate tap and die lubricant. It fell into disuse for obvious reasons. From the wiki it seems a "greener" alternative with similar properties is jojoba oil.

**LINK**

This would have the additional advantage of rejuvenating skin and hair and curing all sorts of things as we grow older. Just rub it on or take a bath in it etc.

John

–

[Author]

Posts