The sickening crunch of breaking kit.

[trazor]

A 10mm bolt would require over 3.5 tonnes of tensile force to fail, for 2 to break seems remarkable.

Enlarged pictures of the break would be good to see.

[Carbon Brush]

Sorry to hear of the failure.

Sadly failure of chinese fixings is not uncommon.

Like Glowjet, I have replaced many of the fixings on china built kit. Whether it be scopes/mounts, garage door opener, computer monitor bracket, or whatever.

Threads are often a bit wobbly when mating parts because of poor tolerances. It is often easy to twist off a hex bolt head if the cheese they are made from has not matured fully.

I first did screw swapping on the chinese EQ5 mount supplied with an Orion Optics (UK) scope. Then I modified the tripod fixings. On it went. That was over 10 years ago.

Stainless (and other) fixings are readily available at low cost from the likes of ebay. I have found them always far superior to the originals.

Stainless also looks good after a few years of use. 

[hgjevans]

... A bog standard Sky Watcher 200P Newt  ...

...

... The bolts are a bit bigger though not massively so (M10 rather than M12

Since I also have a bog standard SW 200P Newtonian (albeit just on an EQ5 - but I presume the rings and dovetail are the same), I've been following this thread with some concern.

I've just had a good look at the mountings on mine, and unless I've misunderstood which bolts have actually broken then the first thing I would say is that they're not anything like as big as M10 - more like M6. But in fact they look like 1/4" Whitworth bolts to me, which would make sense as this is used for the camera mountings in the equivalent position on the other half of the rings. The attached photographs show the mounting for the dovetail on mine. The two smaller Allen-head bolts either side of the central 1/4" bolt would appear to be there to stress the dovetail and effectively lock the whole set-up. They look like M4 to me or maybe M5. I'm not keen to dismantle them to check, but anyway it occurs to me that if someone thought they were actually under tension - i.e. gripping the rings, they might have tightened them up with an Allen key, thinking that would hold the dovetail even more strongly, when in fact they would only be putting a lot more strain on the central bolt.

So, having checked the mountings I'm a bit less concerned than I was. I've been using all sorts of heavy cameras and lenses mounted with just a 1/4" Whitworh screw for over forty years now (though in truth I prefer 3/8" for the bigger stuff), and although I've seen plenty of sockets ripped out of cameras (not mine, I hasten to add), and scores of stripped threads on flash brackets and the like, I've never yet seen a tripod mounting screw break. Usually something else is weak enough to fail before that does. 

But I admit, a 200mm Newtonian - possibly with heavy eyepiece and/or a DSLR piggy-backed does seem like a lot of weight on quite a long lever to be held by just two 1/4" bolts.  

[trazor]

Since I also have a bog standard SW 200P Newtonian (albeit just on an EQ5 - but I presume the rings and dovetail are the same), I've been following this thread with some concern.

I've just had a good look at the mountings on mine, and unless I've misunderstood which bolts have actually broken then the first thing I would say is that they're not anything like as big as M10 - more like M6. But in fact they look like 1/4" Whitworth bolts to me, which would make sense as this is used for the camera mountings in the equivalent position on the other half of the rings. The attached photographs show the mounting for the dovetail on mine. The two smaller Allen-head bolts either side of the central 1/4" bolt would appear to be there to stress the dovetail and effectively lock the whole set-up. They look like M4 to me or maybe M5. I'm not keen to dismantle them to check, but anyway it occurs to me that if someone thought they were actually under tension - i.e. gripping the rings, they might have tightened them up with an Allen key, thinking that would hold the dovetail even more strongly, when in fact they would only be putting a lot more strain on the central bolt.

So, having checked the mountings I'm a bit less concerned than I was. I've been using all sorts of heavy cameras and lenses mounted with just a 1/4" Whitworh screw for over forty years now (though in truth I prefer 3/8" for the bigger stuff), and although I've seen plenty of sockets ripped out of cameras (not mine, I hasten to add), and scores of stripped threads on flash brackets and the like, I've never yet seen a tripod mounting screw break. Usually something else is weak enough to fail before that does. 

But I admit, a 200mm Newtonian - possibly with heavy eyepiece and/or a DSLR piggy-backed does seem like a lot of weight on quite a long lever to be held by just two 1/4" bolts.  

If that central bolt is the only one attaching the scope ring, and the other 2 act as locking screws, then that seems a poor design.

I would suggest a minimum of 2 attachment screws per scope ring, to prevent rocking.

A heavy OTA,  plus  2 x 1/4 screws of possible poor quality, on that type of attachment, is asking for trouble. 

If that was mine, I would drill and tap the 2 locking screw positions, and bolt each scope ring on with 3 screws.

[hgjevans]

If that central bolt is the only one attaching the scope ring, and the other 2 act as locking screws, then that seems a poor design.

True, but it must be said these scopes with their rings and dovetails have been on the market for many years now, and have had a lot of field testing. I first started checking them out on the net about three years ago, and even then they had been around for years. And since that time I was scouring the web looking for whatever tales of woe there might be about them, right up until the point when I bought mine last autumn. And this is the first incident like this that I've come across. Doubtless there may be others out there, but if it were common for the mountings to fail I'd expect to have seen a lot more reports of it - even if they were just secondhand accounts.

[Lonestar70]

If that central bolt is the only one attaching the scope ring, and the other 2 act as locking screws, then that seems a poor design.

I would suggest a minimum of 2 attachment screws per scope ring, to prevent rocking.

A heavy OTA,  plus  2 x 1/4 screws of possible poor quality, on that type of attachment, is asking for trouble. 

If that was mine, I would drill and tap the 2 locking screw positions, and bolt each scope ring on with 3 screws.

The purpose of the 2 outer bolts is to permit adjustment for cone error... they are not meant for locking.

 I agree it is a poor design and the bolts supplied are generally of poor/dubious quality.

Hope the OP manages to get back up and running soon.

Best regards.

Sandy.

[hgjevans]

The purpose of the 2 outer bolts is to permit adjustment for cone error... they are not meant for locking.

Ah, thanks for clarifying that. TBH I'm happy to just leave them be on mine - I don't do imaging so it won't much matter for my purposes. But does that indeed suggest a likely cause for over-stressing the bolts on the OP's scope?