Walneck's Classic Cycle Trader - March 2009 - (Page 23)

MONTHLY FEATURES ? American Tap and die kits like the one shown are available in inexpensive kits as shown for SAE and metric fasteners but will run you about two hundred bucks for most Whitworth kits. Helicoil kit gets a lot of use mostly to repair stripped alloy threads. Kit generally does not come with the drill bit shown, but keeping the right drill bit with each kit makes mistakes less likely and is a real time-saver when it’s time for a thread fix. Whitworth thread design is shown, complements of Bolt Science. The use of a different thread angle and radiused cuts require appropriately matched hardware. stock of what came out of an assembly as well as what will be used for the repair or build. Be advised also that it is quite possible in many instances to use non-Whitworth fasteners in a Whitworth thread form if the pitch of the thread, the distance between the two adjacent thread high points is the same, but this is not recommended because the angle of the thread is different, 55 degrees for Whitworth as opposed to 60 degrees for SAE. Pay especially close attention when dismantling fasteners that attach to alloy parts as to whether or not particles of alloy come out with the threads. Pay even greater attention to the condition of the thread forms in the alloy. This way, you can spot trouble early, and not experience that sickening feeling of a fastener that refuses to hold, as it should during a rebuild. It is often much easier to repair stripped threads with something like a Helicoil insert on a work bench than it is when the part is installed on a motorcycle. A stripped sump stud hole is an excellent case in point and very common to find during a rebuild. The only safe way to determine what sort of fastener thread you hold in a grime-encrusted hand as I often do is to clean the fastener carefully and then measure it. Cleaning, though, is universal and most easily accomplished using a power driven wire wheel. Clean both the bolt head and threads and then inspect for damage. If damage is found, running the fastener through a matched die can clean up the threads to make them useful again, but a badly boogered set of threads means it’s time for replacement. Blind holes into alloy react well to a liberal shot of something like WD 40 followed by a small bristle brush worked into and out of the hole. Thread forms in alloy can also be cleaned up by running the correct tap into the hole, and many good pros do this religiously to every alloy hole they find to assure a good fit and clean threads. To fix a bolt thread or clean up a threaded hole, a thread gauge must first be employed. Thread gauges are relatively inexpensive for all the thread types under discussion. Once you’ve matched up the thread, use a bit of cutting oil on the tap or die before using it. There is one form of nut and bolt damage that is completely invisible, and that’s hydrogen embrittlement. This can occur during the plating process that can allow hydrogen atoms to invade previously high-strength steel and form weak pockets that are then prone to fracture. The cure is to properly heat-treat plated metal to expel the hydrogen, something a reputable plating shop does but a backyard mom and pop operation may not. WALNECK’S CLASSIC CYCLE TRADER® | March 2009 23 WALNECKS.COM I http://www.WALNECKS.COM

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Walneck's Classic Cycle Trader - March 2009 Contents American The Buzz w/ Buzz Walneck Biker of the Month Motorcycle Tops w/ Mike Brown Mad Man of Marion County Bator International Auctions AMCA Scholarship Program Bench Racing w/ Mark Zimmerman Events Listings & Advertisements Mid-America Auction Results British 1967 Norton 750 Atlas and Scrambler 1923 Brough Superior 1969 Norton Commando S My Classic Cousin > From Mars European Japanese Motorbikes & Scooters Memorbilia Antique Cycle Clubs Parts, Accessories, Want Ads Competition How to Place a Word Ad How to Place a Photo Ad Area Code Directory How to Subscribe Let Us Help With Your Event

Walneck's Classic Cycle Trader - March 2009

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