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Discussion Starter · #1 ·
Anyone know where I can source a thread repair kit or 'chaser' for 3/8 UNC tapped hole. Its a 'blind' threaded hole in BBC ally cylinder head with a dodgy thread (caused by cross threading) don't want to use use taper, int and plug taps in case I rip remaining threads out (and its not at 90 degrees to machined inlet face)
 

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Discussion Starter · #3 ·
Anyone know where I can source a thread repair kit or 'chaser' for 3/8 UNC tapped hole. Its a 'blind' threaded hole in BBC ally cylinder head with a dodgy thread (caused by cross threading) don't want to use use taper, int and plug taps in case I rip remaining threads out (and its not at 90 degrees to machined inlet face)
Group components in walthan abbey do helicoil kits.
Thanks for that - have a Helicoil kit in that size - wanted to avoid things getting bad enough to use!
 

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I got my kit from E-bay, cheaper by far!

You could have it drilled out and a double threaded put in...

To make a chaser, use a triangular or half round file and cut into a bolt of the right size down through the whole thread depth to generate a cutting edge and use that. Great for cleaning head bolt threads in the block and exhaust bolt threads too.
 

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As above or use a little cutting wheel in a dremel type thing, quicker than a file and you can hold an angle to make the cutting edge. Have several of these at work for cooler lines.
 

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Discussion Starter · #8 ·
As above or use a little cutting wheel in a dremel type thing, quicker than a file and you can hold an angle to make the cutting edge. Have several of these at work for cooler lines.
Not a bad idea in fact! - years ago I would do this with a low grade steel bolt and case harden it or use a high tensile steel bolt and conventionally harden and temper it. Using ARP stainless bolts so I guess they will be tough enough but will need to grind the flutes. I had wondered if a thread 'repair' kit used a tapered thread and easier to use. Must do this with spark plug holes. Brodix heads have tight threads and can be a bastard to screw the plugs into. Studs for header flanges - Corvette - BBC - Hooker Super Comps - no friggin' chance!
 

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I got a complete set of male/female chasers of MAC tools a few years back which covers most common sizes including 3/8 unc, they only have a small lead in taper so can reach bottom of hole if not too deep, snap do sell them individually. quite useful kit, might do the job !!!!
 

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I got a complete set of male/female chasers of MAC tools a few years back which covers most common sizes including 3/8 unc, they only have a small lead in taper so can reach bottom of hole if not too deep, snap do sell them individually. quite useful kit, might do the job !!!!
I've got a (nearly complete :roll: ) Snap-On set of these and use it a lot - great tools and don't actually remove any material other than what's in the wrong place.
 

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Discussion Starter · #14 ·
Thanks for replies on this guys - I took a stainless ARP 3/8" ANC bolt and using a Dremel ground a couple of flutes down the side - didn't stop the thread becoming f*c*ed though. Fortunately but removing a washer there was just enough thread left to get a bit of torque on bolt. Next time it'll need to be Helicoiled !
 

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Next time dont use a stainless bolt. SS is softer and tougher than mild, so its no surprise it didn't re cut the thread. If you can get a HT bolts the same thread, and then do the dremel thing..Just some advise, thats all.
 
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