Stirling Engine : Laura

[pgk pgkParticipant @pgkpgk17461]

In my limited experience you might get luckiest/simplest with a pair of self locking pliers (molegrips) and heating the brass first for some expansion differential.

I've tapped very few m2's in metal in this hobby and being lazy I bought machine taps I use by hand as a one stage (I'm sure I'll get criticised/unlucky soon). But I have tapped loads of tiny holes in small bones and it takes a delicate touch in some brittle species to avoid shattering (the bone).

[Brian JohnParticipant @brianjohn93961]

I have already tried various pliers but no luck at all. I was sure I might be able to screw it out slowly bit by bit but it will not budge.

The tap is very small so heating the brass would probably heat the tap equally…wouldn't it ?

I am also surprised that it was the third (finisher) tap that broke and not the second tap. I have not been using the first tap on brass.

NOTE : these are serial taps.

Edited By Brian John on 01/02/2016 09:21:45

[pgk pgkParticipant @pgkpgk17461]

It'll heat the tap too but brass expands more than steel.

[HopperParticipant @hopper]

Dont cut the tap off. You need that end to grip on. +1 on vice grips and a bit of heat.

You won't drill a tap out. It is made of steel as hard as the average drill bit. A solid carbide two-flute drill bit might do it though. Somewhat expensive. Sutton make good ones. (dont get a chinese cheapie it will break off in the job!)

The old timers used to make a mix of alum and boiling water and soak the brass in that over low heat. It would dissolve the steel tap but leave the brass or bronze untouched. I'm sure if you google around you will find the exact technique somewhere (probably on this forum at some point over the years!)

[AjohnwParticipant @ajohnw51620]

You can more or less forget drilling it out Brian. A carbide drill might do it but would probably snap. You could try drilling down the flutes with something in a Dremel but if it tries to remove material from the tap you will probably finish up with something else stuck in it. The perfect answer is spark erosion.

Looking at the photo I would have thought a decent quality pair of 8 or 9" engineers pliers would get it out. Mole grips too as pgk suggested. Try and find a old major brand name.

Tapping M2 is not like M6. It needs more care, tap square and more frequent reversals to break the chip.

Usual reasons for breaks.

Tap not square to hole – I suggested that you should check to see how square your drilling machine is to the table and adjust if needed – a large 300mm adjustable spanner will undo the nut. They can usually be bought in sets of 3.

Not reversing often enough. People are inclined to never do that often enough and get away with it until the try very small sizes. It's obvious really. Think about the width of the flutes and how much of a turn is needed before the chip has to bend. The tap will bend the chip but it's easy to ask it to bend too much.

Wrong sized hole – check the sizes of drills. Don't assume that they will be correct at small sizes. Brass tends to cut very cleanly so this may well be your problem. Taps at this size shouldn't take much effort. If you measured a 1.7 rather than 1.6 you might find it's 1.65 so that would be the one to use unless the 1.6mm was definitely 1.6 dia or slightly larger. You'll probably find it's undersized. They usually are.

Here is a source of engineering tools for you

**LINK**

Those pliers are ajohn approved but sadly lack the notch in the side for cutting thick wire.

If you want to get some locking pliers the rs pro ones should be ok

**LINK**

Their adjustable spanners are a bit expensive. As a company they tend to sell high end and ok stuff and no junk. They did sell Chinese lathes at one point but dropped them – too many complaints.

I use a set of ones that are similar to these also the plain ones without plastic on the handle. The main thing is the material they are made of

**LINK**

John

–

[HopperParticipant @hopper]

Here you go. You could use an aluminium saucepan or heatproof glass jug I suppose. anything non-steel.

Edited By Hopper on 01/02/2016 10:33:08

[Brian JohnParticipant @brianjohn93961]

The Alum ( Aluminium Potassium Sulphate) looks fascinating. I will try heating and the pliers again tomorrow with my big burner and if that does not work I will try Alum.

I have NOT been reversing the taps. I found the second tap went into brass very easily. I did not use a first tap either. Obviously now that I have broken a tap I will do things correctly ie. use all three taps and reverse them constantly. I will check the drill bits too. As you say, they all seem to be undersized in the smaller sizes.

[AjohnwParticipant @ajohnw51620]

I mentioned a type of square to Brian at some point. It and maybe a larger conventional engineers square is all that may be needed really plus a protractor. It looked like China had missed the squares as I could find them by a main manufacturer at a very steep price Chronos have had them though

**LINK**

Usually the only measuring blade is the narrow one.

Stock number SS125. Odd that there aren't many used ones about as they were very common in toolmakers chests. A bit of a must have.

John

[pgk pgkParticipant @pgkpgk17461]

I like the alum idea..looks cool.

Other thoughts … I've heard of folk chipping out broken taps on the grounds they are more brittle.. by shattering them with punches and picking out the bits… but doubt that would work this small.

I dreamt up another couple of ideas if you had access…chuck it in an ultrasonic bath which might mobilise some of the chips jamming the tap (we used those for cleaning instruments prior to sterilisation)

Or if there is some way of creating a heat resistant dam around the brass surface to stop flux getting between tap and brass.. then you might be able to solder a nut to the tap stub: just like welding a nut to a broken stud.

It's also possible to get tiny core drills and drill a core aroud the tap.. remove, then plug the hole and redrill.

[Ian S CParticipant @iansc]

You may have to go to the Chemist Shop to get the Alum, I needed so a couple of years ago. After I got it I was looking through the stuff in the garden shed, and found a 1kg bag of it from a garden shop, so that's another place to look. Just make a solution of the Alum and water in a glass jar, put the brass in the jar and put it somewhere warm, if the level goes down just top up the water, it might take a few days, but it does work. Your problems only really start when it happens in a bit of sleet or cast iron.

After I finished removing my broken tap, I put a lid on the jar, it just needs a bit more water and it's ready to go again.

Ian S C

Edited By Ian S C on 01/02/2016 12:35:58

[Andy HoldawayParticipant @andyholdaway]

I've just bought a Kg of Alum for this very purpose, should be delivered today. I broke a 2.5mm drill bit in a piece of aluminium about 20mm in. I managed to chip out the majority of it but the tip remains deeply embedded. As I don't want to have to remake the part (cylinder head for a hit & miss engine) I thought it was worth giving the Alum a try.

Youtube has a number of videos showing the technique, and it seems to work a lot faster if you can heat the solution to about 90°C. I'll let you know how it turns out.

And no, Brian, I still haven't got my Laura engine to run, although I found a tight spot the other day which may be the cause. I'll fettle it and have another go, although work has decided that I need to be in Scotland for the next couple of days so it won't be immediate!

Andy

[Brian JohnParticipant @brianjohn93961]

I tried to buy Alum in Cairns today but no luck : two chemical supply companies, three pharmacies, one hardware store and one health food shop. Nobody even knew what I was talking about even though I did give the full name and the abbreviation. So when I got home I found that a M2 nut would just fit over the broken tap that was sticking out. I screwed it down and then attempted to hard solder the nut to the tap. Disaster : not only did the solder not take (no idea why) but where I had soft soldered to make a repair earlier (see above), this ate its way into the brass completely destroying the whole thing. No need for a photo, I am sure you get the picture !

Anyway, I still have two more work cylinders that can be used. I was looking forward to using the Alum ; I will have to buy some online in preparation for next time.

I am still waiting on my M2 X 16mm socket cap screws. These things take a long time to arrive from China now. I may be better buying from the UK in future.

I have also decided to paint the inside of the flywheel red as per usual so I have given it two coats of etch primer. The first coat of Killrust red will go on tomorrow. I could have left it unpainted as it looked quite nice with the machined and polished outer surfaces contrasting nicely with the rougher inner surfaces.

I also took apart the cylinder holders (parts 3 and 4). I suspected that the Hylomar I used had got into the groove which connects both cylinders ; it oozes everywhere when you tighten things up. Sure enough, the hole was blocked so I spent one hour cleaning all the Hylomar from both pieces and all the screws. Even with the recommended methylated spirits this stuff is messy and sticky. I do not think I will be using it again. As I am not soldering these two pieces to the base plate as per the instructions, I can try it without any sealer and see if it works. If there is a problem then I can easily take it apart and try something…gasket goo perhaps ?

Andrew : what did you use to seal parts 3 and 4 ? Are you sure the connecting groove on part 3 is clear ?

Edited By Brian John on 02/02/2016 07:02:55

[Ian S CParticipant @iansc]

Ya Didn't try the garden shop did ya, they should have it there.

Ian S C

[HopperParticipant @hopper]

Posted by Brian John on 02/02/2016 07:01:24:…

I am still waiting on my M2 X 16mm socket cap screws. These things take a long time to arrive from China now. I may be better buying from the UK in future.

…

Kung Hei Fat Choi. (or maybe Gong Xi Fa Cai on the mainland.).

Officially the New Year starts Feb 8 but there are already 100,000 people trapped at Guangzhou railway station trying to get home for the season. Things will move very slowly now for about three weeks or so. Hopefully your bolts got dispatched before the madness started.

[Brian JohnParticipant @brianjohn93961]

Peter : Yes, they were sent on the 16th January. I am hoping that they are out of China by now. Where do you buy Alum in Cairns ?

Gong Xi Fa Cai is correct

Ian : why would they have Alum in garden supplies ?

Edited By Brian John on 02/02/2016 11:44:46

Edited By Brian John on 02/02/2016 11:45:18

[Ian S CParticipant @iansc]

Brian it's use to lower the PH of the soil, so garden shop or agricultural supplies. Health food shop may have it, or the super market among the preserving stuff, it is used when drying fruit. It is also used in a perfumed form as Bath Salts, so you can go and soak in it.

Ian S C

[Andy HoldawayParticipant @andyholdaway]

Brian, I used a silicone adhesive/sealant that sticks like ……! It probably is worth checking that the slot is clear, but I was quite sparing with it.

Alum is also used as a deodorant (apparently) and is what styptic pencils are made from (old school wet shavers will know what they are!).

My tub of Alum has arrived but I'm currently a few hundred miles from home in a very cold and windy Scotland. I'll let you know if it's successful when I'm back tomorrow night.

Andy

[Andy HoldawayParticipant @andyholdaway]

Well, being the eternal sceptic I didn't really believe the alum trick would work, but I dissolved a couple of tablespoons in about 1/4 litre of boiling water, sat it on an old camping stove and brought it up to a simmer.

Dropped the part with the broken drill bit in and poked the hole with a cocktail stick to make sure the solution had fully entered the hole (probably didn't need to do that) and watched it fizz for about 15 minutes. Lo and behold, no more broken drill bit!

The offending hole is the one at the bottom of the piece. You can hopefully just see the bubbles emerging.

I washed it thoroughly, and found there was a sort of grey coating on the aluminium, but it rubs straight off with a cloth. Slapped it on the pillar drill and tentatively drilled down the rest of the hole. Nothing but aluminium swarf and a nice neat hole. I shall save the solution in a jam jar for the next time!

Andy

[Brian JohnParticipant @brianjohn93961]

I wonder how long it takes without boiling the solution ? Nice to know that it works but I still can't buy any Alum in Cairns. I called five gardening supply places today and nobody knew what I was talking about so I will have to buy it on ebay.

Edited By Brian John on 03/02/2016 17:09:38

[Andy HoldawayParticipant @andyholdaway]

I don't know how long it would take without heating, I'm impatient! Probably a few hours I would have thought.

As an aside, I definitely had a saturated solution as I let it cool so that I could put it in a jar for future use. The Pyrex jug had a clear liquid in it until I moved it, and the Alum suddenly re-crystalized back to a white powder. Took me back to chemistry lessons at school!

[Ian S CParticipant @iansc]

Andrew, you can grow the cryslals in the same way as copper sulphate(blue stone).

Ian S C

[Ian S CParticipant @iansc]

Brian, you could ask at the botanical gardens, if they haven't got enough to give you a few grams, they may be able to tell you where you might get some, it might be E Bay, but it is handy to have.

Ian S C

[Brian JohnParticipant @brianjohn93961]

Moving into the final stages of assembly now that the M2 X 16mm socket heads have arrived. They were a bit long so I cut them down with the Dremel tool to make things a bit neater. I have order some M2 X 14mm and M2 X 12mm but I am not going to wait 3 to 4 weeks for them to arrive.  I know I will be using a lot of M2 socket heads in the future so I have ordered many sizes to have on hand. I have also ordered two more replacement sets of M2 X 0.4 HSS taps in the event of future breakages…and still looking for Alum !

I think this is a much better idea than soldering it all together :

Edited By Brian John on 05/02/2016 06:02:39

Edited By Brian John on 05/02/2016 06:03:59

[HopperParticipant @hopper]

Looks good with the screws holding it together. I agree better than solder.

No idea where you would get alum in Cairns. I do know that it is used in boiler water treatment to settle out soilds, or used to be, so not sure if a pool shop might have some for clearing murky pools??

[Danny M2ZParticipant @dannym2z]

Posted by Hopper on 05/02/2016 07:24:07:

Looks good with the screws holding it together. I agree better than solder.

If you wish to buy decent quality screws and stuff in Cairns, have you tried this place? **LINK**

(Go to the store locator on the home page)

I buy heaps of fasteners from the my local branch, they are very inexpensive by the box and much better quality (ISO traceable) than some of the cheesy imports.

* Danny M *

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