Mounting guide scope on tube rings

[Erling G-P]

Hello all,

I recently acquired a secondhand SW ST80 for use as a guide scope.  It came with the ADM dovetail/rings seen in the photo below.  I need a set of bolts for mounting it on the tube rings of my SW 200P-DS, but am uncertain about the size & type. The ASM dovetail is fairly thick, at 15mm.  Would either of the ones liked to below be the type needed ?

https://www.firstlightoptics.com/dovetails-saddles-clamps/1-4-inch-socket-head-whitworth-bolts-x2-3-4-inch-long.html

https://www.firstlightoptics.com/dovetails-saddles-clamps/1-4-inch-socket-head-whitworth-bolts-x2-1-inch-long.html

[StarDodger]

I think they will be metric bolts probably M6 and not whitworth...

[Erling G-P]

Thanks, so like these, only I will have to find a longer version:

https://www.firstlightoptics.com/misc/m6-bolts-x2-suitable-for-sky-watcher-st80-tube-rings.html

 

[bobro]

1/4" UNC is correct. Same as camera tripod.

[StarDodger]

2 hours ago, bobro said:

1/4" UNC is correct. Same as camera tripod.

UNC are you sure, my skywatcher Mount and scope has M6 bolts....

well am not sure now then.... 🤪🤪

[StarDodger]

23 hours ago, Erling G-P said:

Thanks, so like these, only I will have to find a longer version:

https://www.firstlightoptics.com/misc/m6-bolts-x2-suitable-for-sky-watcher-st80-tube-rings.html

 

Yes I would have thought they were correct, but someone now says not....so 🤔🤔

[Erling G-P]

Thanks for the replies.  Actually got some M6 bolts today, but haven't tested them yet. First the home depot overcharge me for 4 bolts, and then I come home and spot that there's only 3 bolts in the box.  Won't break the seal as it's going back for a replacement!

Incidently, if UNC is the type required; would such be available from home depots too ?   Placed an order with FLO last night and they've already dispatched it, so too late to include the UNC bolts.

[StarDodger]

13 minutes ago, Erling G-P said:

Thanks for the replies.  Actually got some M6 bolts today, but haven't tested them yet. First the home depot overcharge me for 4 bolts, and then I come home and spot that there's only 3 bolts in the box.  Won't break the seal as it's going back for a replacement!

Incidently, if UNC is the type required; would such be available from home depots too ?   Placed an order with FLO last night and they've already dispatched it, so too late to include the UNC bolts.

UNC is a little less used  these days, but they may well have them, but I am still leaning towards them being metric M6.. 🤞

Edited June 18, 2019 by StarDodger

[bobro]

1 hour ago, StarDodger said:

UNC are you sure, my skywatcher Mount and scope has M6 bolts....

My SkyWatcher 150PL scope rings take 1/4" UNC. The bolt looks similar to an M6 but has a slightly larger diameter and a different thread. The photo shows a standard 1/4" camera screw correctly screwed into the tube ring. An M6 bolt won't go in due to the different thread. Perhaps you can find an ebay seller that does them if you don't wish to order from FLO.

Here is a link to a discussion some time ago:  https://stargazerslounge.com/topic/16317-skywatcher-thread-size/

Certainly a confusing issue!

[Erling G-P]

Thanks for the replies guys - had thought the answer would have been a simple one

I'll test the M6 bolts; probably tomorrow and report back what I find.

[Erling G-P]

Have now tried the M6 bolts and unfortunately they don't fit.  Thus looks like I must hunt for some UNC bolts instead.

[StarDodger]

3 minutes ago, Erling G-P said:

Have now tried the M6 bolts and unfortunately they don't fit.  Thus looks like I must hunt for some UNC bolts instead.

Hmmm, so I guess they go in a bit then get tight..?

[Erling G-P]

1 minute ago, StarDodger said:

Hmmm, so I guess they go in a bit then get tight..?

A very tiny bit yes, and then pretty much locks in place.  Haven't wanted to use any force, for fear of damaging the thread.

[StarDodger]

2 minutes ago, Erling G-P said:

A very tiny bit yes, and then pretty much locks in place.  Haven't wanted to use any force, for fear of damaging the thread.

What length 1/4” UNC do you need..? As I have a bag full of them, but mostly Allen head types..

Edited June 20, 2019 by StarDodger

[Erling G-P]

The dovetail is 15mm thick, and I just measured the 'depth ' of the hole in the tube ring to 17mm, so 30mm max  - 25mm / 1" would be fine I think.

[Erling G-P]

Update:

Have now received UNC 1/4" bolts from FLO and it is indeed those which fits.   Next problem was that I don't have an Allen key which fits the bolts - 4mm is too small, and 5mm is too big.  Have resorted to tightening them with a pair of pliers for now, which seems to be enough.