posted May 12, 2007 20:27               

I was wondering what the thread is called of the Dexta bolts and stuff.
Is it UNC,UNF,Whitworth,BSW?
Or maybe a bit of everything?

The reason for my question is that somewhere in the future i need to overhaul the engine.
I want to put it on an engine stand just like Stefan did.
I know by experience that this is a comfy way of working on the engine.
But how to bolt it to the stand?
Are there holes behind the startermotor?
There are 3 thingies which look a bit like the cover on the peepinghole through which you check the timingmark on the flywheel.
Could they be covering boltholes?

MMM many questions...

Anyway i hope someone can shed a little light on this.

Thanks guys!

Greetings from the rainy Netherlands.

posted May 12, 2007 21:04               

Thanks again.

posted May 12, 2007 22:56               

Further to Brian's reply you will need UNC and UNF taps and dies from 1/4" up to 5/8", including 7/16" and 9/16". If you only require to clean up the threads then you dont need a full set of taps and dies, I would recommend a good quality 2nd taper tap and a die nut of each size. A die nut being hexagonal is far more useful than a die as it can be run down a stud in situ using a suitable socket.

If you scan Ebay you will usually find a selection of taps etc. and if you don't intend to start the overhaul for some time it will allow you to build up a set. Failing that I can recommend Tracy Tools Ltd.
at www.tracytools.com, I have been dealing with them for over 25 years and have always had excellent service from them.

The Dextas use UNC threads on bolts and studs screwed into the castings, and the other end of the studs are threaded UNF.

If you look at the cylinder block below the generator you will see two plugs slotted for a pozidrive screwdriver, the bolts on Stefan's engine stand screw into these holes which I think are 1/2" UNF. The stand is then bolted to the 3/8" holes at the back of the engine which normally secure the adaptor plate to the block.

A word of warning, the engine less flywheel and adaptor plate is a very heavy lump and if you intend to make the stand yourself make sure that the welds are up to it, if in doubt get your local fabricator to weld it.

If you require more information contact me as I have two engines stripped down at the moment and can easily take photographs of them and the stand which I have made.

You also require an extra deep 11/16" AF socket for tightening the cylinder head in way of the six studs which hold the injectors in place.

Regards

posted May 13, 2007 10:33               

Yes i know that the engine is heavy.I read something about 350 kilos.
In the past i worked on a couple of V8 engines,those were heavy too.
So i bought an engine stand.I can "melt" steel together,but i know that doesn't make me a welder...

So i take it that UNC and NC are the same?
And then i need UNF and AF.
Ok that can be arranged.

posted May 13, 2007 12:21               

UNC = Unified National Coarse
UNF = " " Fine
That's all you have to worry about getting.

posted May 13, 2007 13:06               

UNF (Unified National Fine)and AF (American Fine) are the same threads. I think you will find that AF was the terminology used when Brian And I were serving our time and it has now been superseded by UNF.

There are other threads used on the Dexta,
the injection pipes are M12, the fuel line connections from the tank to the filter and lift pump are 1/2" UNF. And to add further confusion the hole in the block for the oil pressure switch is tapped 1/4" NPT. NPT, National Pipe Thread is an Americam standard tapered thread which is not compatible with BSP, British Standard Pipe.

Regards.

posted May 13, 2007 15:23               

As for the engine stand,i'll start looking for some solid steel...

Thanks again,greetings from the still rainy Netherlands.
Rob.

[This message has been edited by Dunggatherer (edited May 13, 2007).]

posted May 13, 2007 17:26               

In fact UNF, UNC and metric threads are 60 degrees, whilst BSW and BSF are 55 degrees.

When I was at sea it was standard practice during any overhaul to run a tap through all the nuts and run a die nut down all the bolts or studs and I continue this practice whenever I overhaul any machinery here at home. Having stripped my Dextadown I can assure you that the majority of the threads on the Dextas are either UNC or UNF.

If anyone requires further clarification on this subject I have some charts which I could post on this site.

Regards.

posted May 14, 2007 00:28               

NPT = National Pipe Tapered
NPS = National Pipe Straight

quote:

---

Originally posted by Tubal Cain:
Rob,

UNF (Unified National Fine)and AF (American Fine) are the same threads. I think you will find that AF was the terminology used when Brian And I were serving our time and it has now been superseded by UNF.

There are other threads used on the Dexta,
the injection pipes are M12, the fuel line connections from the tank to the filter and lift pump are 1/2" UNF. And to add further confusion the hole in the block for the oil pressure switch is tapped 1/4" NPT. NPT, National Pipe Thread is an Americam standard tapered thread which is not compatible with BSP, British Standard Pipe.

Regards.

Gerald

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