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Old 05-12-2016, 06:52 AM   #21
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Perhaps brush standard

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Originally Posted by seasidemom View Post
I have a 1982 Bristol trawler, 42'. We have removed all of our stanchions and toprail, and have now refinished the cap rails. Some of the flat head machine screws we removed in the process are not reusable. I cannot find anything like them anywhere! They appear to be 5/16" diameter, but not quite; or #8 metric, but not quite. Neither of those sizes (new) will sit flush in the stanchion base plate b/c the heads are far too large, nor will they fit the threads on the tapped plate under the cap rail. The original screws are 1-1/2" long, brass or bronze. They are definitely NOT standard (at least, anymore), and custom made replacements are $7.75 each (OK) and require a 4-week lead time (not OK). Alternatively, I could have all the stanchions re-bored, the cap rail holes re-drilled, and the inside plates re-tapped. I would much rather find the darned machine screws! Where did these odd fasteners come from? More importantly, how can I get some?
While working on my boat, i decided to change hull zincs. One of the mounting bolts appeared bent and the nut mis threaded. I took the bolt to a place specializing in bolts and learned that the old one was something called brush standard, which the company could not match.

Gordon
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Old 05-12-2016, 06:52 AM   #22
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Greetings,
Mr. FF. Thanks. I was unaware of the "manufacturing/finishing" process. That being said, one would think that a home finisher would source commonly available fasteners. Even today, metrics, for example, are not all that common. More readily available to be sure but you have to look for them.

Perish the thought that some bozo actually used Whitworth nuts and bolts although it's not out of the realm of possibility... https://en.wikipedia.org/wiki/Britis...dard_Whitworth

Mr. GJ. Could brush standard be British Standard?
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Old 05-12-2016, 06:53 AM   #23
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My heading should have read British standard... Not brush.

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Old 05-12-2016, 07:06 AM   #24
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Back when the Bristols were built owners frequently "worked up" in size to a larger vessel.

So many folks had a "20 year box" of goodies from past adventures to use.

Unlike today where a credit line will put a newby in a 60 ft bucket.

Happily world trade is reducing the number of fasteners, Metric will probably win over the coming decades.
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Old 05-12-2016, 07:12 AM   #25
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Many bolts on my Albin are a British standard something or other.....

No known sore for all sizes...someone might have the source (British car enthusiast in NY state)....don't have it in this computer.

My suggestion is to figure out how to convert to standard.....you have and will probably have spent more time searching than just bite the bullet and convert.
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Old 05-12-2016, 07:27 AM   #26
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Used to deal with BST stuff once in a while back in the days when I worked in a friends body shop. He had lots of older Britsh cars.

http://www.metricmcc.com/catalog/ch10/10-1008.pdf
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Old 05-12-2016, 08:06 AM   #27
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Originally Posted by RT Firefly View Post
. . . . There HAS to be something that readily fits.

. . . . attempts at re-tapping could be a quick journey to hell IF the nut starts spinning
I'm with RT on both counts.

And: If the countersunk head is too large, don't file down the edge, it won't help; the face will still stand proud of the stanchion base-plate. Use a countersink bit in an electric drill to deepen the recess.

I strongly recommend using a pillar-drill, and always clamp the workpiece. Never hold it by hand - it doesn't work and the blood gets everywhere!
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Old 05-12-2016, 08:17 AM   #28
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Regarding BSW screw sizes

Comment is these locomotive 19th century bolt sizes you may be able to use UNC bolts as they will fit.

https://www.britishfasteners.com/threads/bsw.html

British Standard Whitworth (BSW)

These are the original, 19th Century, coarse-threaded industrial bolts designed to hold locomotives together. Because of their coarse pitch, they are more prone to vibrating loose, so are little used on motorcars. Except for threading into aluminum (e.g. crankcase studs), where a coarse thread is less prone to stripping than a fine one. It turns out that, except for 1/2" (where the British use 12 threads per inch (tpi) and Americans use 13 tpi) the thread pitches for the rest are the same as for American Unified Coarse (UNC). However, the thread form is different; Whitworth = 55 degrees; UNC = 60 degrees. In spite of this, mismatched nuts and bolts mate nicely, so you're likely to find UNC bolts or studs where BSW should have been.

Then there exists BSF thread, which is just more TPI.

If this is BSF, then just retap if you can do so. I would retap every one of those suckers.

Since they should fit regardless British thread to UNC thread, and they do not as you have said, then likely you do not have British Standard Whitworth bolts.
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Old 05-12-2016, 09:39 AM   #29
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The origin of this boat was India, but I don't know which parts were completed there. If it was one of the owner completed boats, it seems to me that it would be just as likely to include OTS parts. I guess I have been assuming that they used to make these machine screws and something changed such that they aren't made anymore. I hope I am wrong about that.
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Old 05-12-2016, 09:52 AM   #30
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OK, I am chasing the BSW lead....the literature even mentions that they used smaller heads. And India = England in terms of manufacturing, right? Give me some hope!
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Old 05-12-2016, 10:31 AM   #31
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If you'd like to put this whole mystery to bed once and for all take 2-3 of these screws to a local tool and die maker(master machinist). Walk in Monday morning and offer to pay him to precisely identity your fasteners. It'll take him about 5 minutes with thread micrometers, pitch gauges and a machinists bible to end the mystery once and for all. While there he will likely be willing to tell you what size to modify to. He can also order replacements for you for a fee.
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Old 05-12-2016, 10:47 AM   #32
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Quote:
Originally Posted by seasidemom View Post
OK, I am chasing the BSW lead....the literature even mentions that they used smaller heads. And India = England in terms of manufacturing, right? Give me some hope!
BSW is the same diameter and TPI as UNC thread, only difference is thread angle, and the web link says UNC thread easily pairs with BSW.

https://en.wikipedia.org/wiki/Unified_Thread_Standard
Basically standard US thread should have worked if it is BSW.
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