Matabele
.300 member
Reged: 16/09/10
Posts: 230
Loc: Zimbabwe
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Hi all,
Just a query out of curiosity, but how do you think the raceway for the sliding bolt in a Purdey double underbite system is machined in? It would seem the top tang is obstructing access for a milling machine. Is the tang heated and bent out of the way for this operation? From the guns I've managed to view the recess mostly looks quite rough, so I assume there is a lot of filework involved.
Any ideas?
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twobobbwana
.333 member
Reged: 25/11/11
Posts: 299
Loc: Queensland, Australia
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I believe they're chain drilled and broached till they clean up.
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Matabele
.300 member
Reged: 16/09/10
Posts: 230
Loc: Zimbabwe
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Makes sense twobob, but it seems to me you'd need an overly long drill bit. Interesting stuff this gun building.
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Aaron_Little
.300 member
Reged: 25/09/13
Posts: 109
Loc: Newark, TX
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Modern production would have them sinker EDM the raceway. Drilling and broaching is still a viable means though.
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A.M. Little Bespoke Gunmakers LLC.
Michael08TDK@yahoo.com
682-554-0044
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Waidmannsheil
.416 member
Reged: 19/04/13
Posts: 2510
Loc: Melbourne Australia
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You can only broach a through hole, not a blind hole as the broach must be pulled through the workpiece. Originally they would have used a slotting type head which would have shaved it out a thou at a time. The Italian Gun Makers Piotti have such a machine and you can see it in use on their website although it is cutting the slot for the lumps. It is the same principal however. Aaron is correct, these days it would be done with EDM.
http://www.piotti.com/en/lavorazioni/la-meccanica/
Waidmannsheil.
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There is nothing wrong with vegetarian food, so long as there is meat with it.
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tinker
.416 member
Reged: 12/03/05
Posts: 4835
Loc: Nevada
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FWIW, there's a slotting/shaper attachment for Bridgeport type milling machines - that is one way to mechanically achieve this kind of blind metal removal in the toolroom or machine shop.
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--Self-Appointed Colonel, DRSS--
"It IS a dangerous game, and so named for a reason, and you can't play from the keyboard. " --Some Old Texan...
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Matabele
.300 member
Reged: 16/09/10
Posts: 230
Loc: Zimbabwe
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Thanks for the replies gents, I found the Piotti link really interesting! What would you call that machine, I'd like to try and find some more info on them?
Tinker I have heard about that option on some Bridgeports but didn't realise what it could be used for. Seems like a great feature to have for a gunsmithing setup.
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Waidmannsheil
.416 member
Reged: 19/04/13
Posts: 2510
Loc: Melbourne Australia
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We have a slotting head for our horizontal mill which is also rotatable. The machine that Piotti use would have been purpose built for the gun trade, a practise which was fairly common in the old days. The large gun making firms such as Mauser, Mannlicher, FN, Winchester etc. used to have their own internal machine design and construction departments which would make machines to suit the design of firearm being built. Often these machines would perform only one single cut before the work piece was moved to another machine. These days a handful of CNC machines can do everything that a whole factory floor of machines were required to do in the past.
Waidmannsheil.
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There is nothing wrong with vegetarian food, so long as there is meat with it.
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Pugwash
.300 member
Reged: 24/03/07
Posts: 113
Loc: Scotland,UK
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The bolt slots used to be drilled,then filed and drifted using a series of hardened drifts.At this stage in the action machining process the strap would have been roughly machined to size then bent upwards out of the way.This process hasn't been used for quite a while and as suggested it is spark eroded now.
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twobobbwana
.333 member
Reged: 25/11/11
Posts: 299
Loc: Queensland, Australia
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Chain drilling, milling then slotting would get it done as long as the top tang was out of the way.
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