Problem with Marbles R6 sight

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Brianich
Posts: 4
Joined: Wed Sep 14, 2016 9:11 am

Problem with Marbles R6 sight

Post by Brianich » Thu Feb 15, 2018 10:01 pm

I have two model 8s. 25 cal made in 1922 and 35 cal made in 1911. Screw head that holds the Marbles sight on the 35 broke. To my surprise the screw from the 25 doesn't fit--too small.

The screw from the 35 doesn't seem to be a standard diameter. Between an 8 and a 10. We're these screws left up to whoever installed the sight? Called Marbles and they couldn't tell me anything.

Would appreciate any Info and help you can provide.

Thanks,
Brian

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Wildgoose
Posts: 227
Joined: Sat Nov 06, 2010 5:53 am
Location: Nebraska

Re: Problem with Marbles R6 sight

Post by Wildgoose » Fri Feb 16, 2018 3:26 pm

Its been my experience that the original mounting screws were all the same. They are very hard to find and are an odd pitch. If one doesn't get the mounting screw along with the sight it can be a problem. I am wondering if the previous owner of your 35 might have had this problem and re-drilled the hole to a larger size and re-tapped it. That might be the why the original screw from your 25 is too small. Hard to say what the diameter and pitch are. Do you have the broken parts of the screw and can maybe figure out what it was? Another issue with using a non factory mounting replacement screw if you can find something that works is that the chamfer on the head and its length may not fit the chamfer on the sight. The fit up on the sight's chamfered hole and where the replacement screw bottoms out and tightens up are critical to the sight seating properly. If it isn't seated right it will not center up and will come loose when firing. I have run into these issues before in mounting a tang sight using replacement screws.

Brianich
Posts: 4
Joined: Wed Sep 14, 2016 9:11 am

Re: Problem with Marbles R6 sight

Post by Brianich » Sat Feb 17, 2018 11:17 pm

Thanks for the info. Really appreciate it.

Brian

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Phyrbird
Posts: 806
Joined: Mon Jan 07, 2013 10:53 pm

Re: Problem with Marbles R6 sight

Post by Phyrbird » Sun Feb 18, 2018 8:24 pm

From "Old Gun Sights" '98 ::

Marbles R6 sight screw size: Length .328 Head dia .250 Shank .181 Thread size: .182-40
(I finally found a reliable answer after 6yr)
Phyrbird
SOKY

Brianich
Posts: 4
Joined: Wed Sep 14, 2016 9:11 am

Re: Problem with Marbles R6 sight

Post by Brianich » Mon Feb 19, 2018 5:43 pm

Wow. Thanks for that. One of mine is .182 so the other is a replacement. But am I correct in thinking that the .182-40 is between a #8 and a #10. From the tables I've seen an 8 is .164 and 10 is .190 or thereabouts.

So what do you recommend? Drill and tap to the next size up, being mindful of the head shape as pointed out above?

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Phyrbird
Posts: 806
Joined: Mon Jan 07, 2013 10:53 pm

Re: Problem with Marbles R6 sight

Post by Phyrbird » Mon Feb 19, 2018 7:24 pm

Brian,
I suggest one of the following:

https://www.ebay.com/itm/RARE-MOUNTING- ... 1438.l2649

or

http://www.aperturesnmore.com/product.s ... egoryId=31

Use care, for I personally know there are no more taps left. & somewhere on this site there is a reference to 3/16-40 threads. I've not had good luck with the ones I found.
Phyrbird
SOKY

Brianich
Posts: 4
Joined: Wed Sep 14, 2016 9:11 am

Re: Problem with Marbles R6 sight

Post by Brianich » Mon Feb 19, 2018 9:06 pm

Will check them out. Thanks.

Brian

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