For the ASP .21. It's not 5mm. It's not 1/4 x 28, but real close, dif threads. WHAT is it!!

Maybe 6.0 X 1.0mm ??

Look near the bottom of this page from Just Engines in the S column of the engine dimension diagram. It is a M6 thread.

http://www.justengines.unseen.org/acatalog/ASP.html

Bill

Do you have a set of calipers or a micrometer? Once you establish the thread OD, ( it will be a little undersized from the nominal size), the the thread cound is a given.

The Magunum line, same as the ASP, brackets your engine. The 28 uses a 1/4-28 thread and the 15 uses a 6MM thread. It has to be one of the two.

Don

Hey , try this Just Engines have all the spares you want and the service they provide is superb...if you can face the cost of postage to the US

http://www.justengines.unseen.org/ac..._Spares_1.html

See if this helps:

http://www.rchelibase.com/propnut/

http://www.boltdepot.com/fastener-in...s/Default.aspx (This one has a printable threads comparison chart named "US-and-Metric-Thread-Sizes")

The [link=http://www.truturn.com/af_asp.htm]TruTurn Adapter Finder[/link] says the thread is 1/4"-28, for all ASP .20-.5x engines.

Either they are right, or they are wrong, but according to them it is not an M6x1.0 thread...

Hey, just walk down to your friendly Ace hardware and browse the metric bins " til you find a nut that fits. Good luck, red

Thanks for the help guys. Everything I've seen said 1/4 x 28, but none of my spinner nuts that size fit. I have an LA .15, and that spinner nut is too small. Tower says that one is 5mm. It must be 6mm x 1, although I don't understand that convention.

Mr. Sieminski,


Although in the past, some engine manufacturers had special bearings produced for them (to make the replacement bearings available only from them...), no manufacturer will make his own thread size on the crankshaft...

It can either be a known metric size, or a known imperial size.


People here are reciting the different threads it can be...
Go to your nearest DIY outlet, with the engine. Ask the person responsible for selling bolts and nuts, to determine the thread size of your ASP...

Dar,
You are the GURU! I was just looking for a spinner type prop nut so I could use my electric starter, but nothing I had would fit. I see the 6mm x 1 prop nuts at Tower, so I'll try that.... but in the meantime I'll head to ACE and try to see what real world dia x thread size it is.
I always use your breakin method, never had one fail, and they always run strong.
Thanks,
Rick

Quote:

ORIGINAL: rsieminski

...I'll head to ACE and try to see what real world dia x thread size it is.

You're welcome, Rick!

Thinking about it, Ace *might* have it. But if they are anything like Ace outlets in this country, they may only have common imperial (1/4-20, 1/4-24) sizes and very few metric sizes... Besides, since you are obviously not buying, they may not be very friendly to you...

Possibly, the place you should address is a machine shop in your nearest industrial zone...

They for sure will have means to take the measurements for you; both in pitch and in diameter. ...And even if they are rather busy, they are generally more friendly...


Just ordering the different sizes Tower has, until you find which is the right one, is pretty wasteful, both in time and in cash...

Agreed, but is there even a possibility that it wouldn't be a std size. I mean it's not 5mm, and it's not 1/4 x 24. Therefore I thought it had to be 6mm??

the 6mm x 1mm convention means the outside diameter of the threads is 6 mm, and it's 1mm per thread. Metric uses mm per thread for the pitch, instead of threads/inch like the SAE system does.

Ahhh, I kinda thought it was like that, but it seemed too coarse. Thanks, good to know!

You can lay two screws together along the threads. If the mesh along the length, the thread pitch is the same. If you lay your 1/4-28 screw, crank end, etc against another the theads will fit . If you lay it along another close, but not exactly the same pitch, the two will not mesh but set tip to tip along the threads. Once you have the thread pitch, the possible nominal sizes are going to be very limited and you can easily eye ball the corect one by compairing your threads to the bin ones. Just be careful that someone hasn't slipped the wrong screw in the bin,

The local hardware store becomes a very effective place to determine pitch. In your case, check the Ace Hardware bins of metric screws and match one to your engine. They will probalby have a nut that fits also if you need one.

Don

Quote:

ORIGINAL: rsieminski

Agreed, but is there even a possibility that it wouldn't be a std size. I mean it's not 5mm, and it's not 1/4 x 24. Therefore I thought it had to be 6mm??

Rick,


I guess you meant 1/4"x28... This is UNF... 1/4"x24 is UNC and will be more likely to loosen...1/4"x20 is UNEC, like those used to connect parts of shelf cabinets, as well as plastic wing-bolts.
1/4"x32, on the other hand, is UNEF. Glow plugs have this thread.

I would consider it very unlikely for a clone manufacturer like Sanye (they make ASP, Magnum, SC and SY engines that are cloned after OS in China), to make an engine that has a non-standard thread size... Even they outsource their prop-nuts from a manufacturer of fasteners...

Can you imagine what would happen, if the known-size prop-nuts they get would not thread on the crankshaft???
Or if a buyer of an engine they make would not be able to find a replacement nut in a hardware store, or have to pay them ~$20 for an *original* prop-nut...

They would not be selling, because no-one would be buying...

It is surely a standard size - you just have to determine which one...

Oil the shaft and press it against a piece of paper to print a track of the thread.

Then measure how many clean spaces fit within ½�.

If 14 spaces, the thread is ¼�-28

If 13 spaces, the thread is M6-1.0

According to the table of post #6, it should be ¼�-28 for that engine.

I know, everything I've read says 1/4 x 28, but it'll screw on a few turns, but binds. I'll try the paper trich, and take it to ACE tomorrow. This one is Generation 3. That may be the difference.

It could be that the thread on the shaft is slightly damaged, so the 1/4" nuts don't fit all the way.

Wish you luck!

That would be my guess too! If so, before you buy a new crankshaft, try running a 1/4"-28 die over the threads. That might be enough to clean it up so that you can still use it.

Allow me to correct you. The American Unified Standard Thread Series classifies UNC Unified National Course as the 1/4-20 size NOT UNEC
UNF is Unified National Fine 1/4-28 and UNEF Unified National Extra fine as 1/4-32

There is NO UNEC Unified National Extra Course designation for American Threads...

NO No NO. Trying to chase the thread with a die will only result in screwing up the remaining threads. If it isn't 1/4-28 as suspected running a die along it will absolutleyruin the crank.Even if it is 1/4-28, and the treads on the end are damaged, trying to chase thethreads will most likely result in thedie establishing a different thread pattern. If the nut cant screw on, the die won't eaither an will makeits own path.

A close inspection will tell if the thread is damaged. If they are, a simple file is the best tool to use, Hold it at 30 degrees to the shaft, the same angle as the threads and file pushing the file to the center line of the shaft. Don't even do this though unless you can see that the threads are damaged. Idoubt that they are as rsieminski sates that a nutwill screw on three turns prior to binding. That indicates thestart of the threads are good and what he is seeing is an example of thread pitch being different. As pointedout eariller, the 1mm pitch and the 28tpi are very close and it would take just about three turns to take up the normalthread clearance.

Don't fix something if it isn't broke.

Don

You must use a triangular file on threads

I had this problem with an old Saito 40. Drove me batty because the nut on the engine fit, but nothing else would. Inspection with a magnifying glass revealed a small flaw; after a light touch with a file the problem was solved. The nut on the engine must have had a tiny bit more thread clearance than the other nuts. But the flaw was at the end as Don says and the nut would not go three turns. Still, after all this frustration I would certainly get a lens and examine it. Jim