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07-19-2020, 10:46 AM | #1 |
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7/16-14 thread chaser
Did a search on the forum here and found a set of thread chasers for reasonable money. In all my years with cars and as a machinist, I only needed one once for a spark plug hole, and that was MM. So I only need a 7/16-14. I know I can make one, but would prefer to buy it. Any sources a for single thread chaser tap. Have done an internet search and all the comes is regular taps. Thank you Fordbarners
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07-19-2020, 11:06 AM | #2 |
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Re: 7/16-14 thread chaser
Here's a good deal.
https://www.summitracing.com/parts/s...yABEgJLAvD_BwE |
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07-19-2020, 11:08 AM | #3 |
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Re: 7/16-14 thread chaser
Mac tools. I have a Mac tool thread restoration kit & it is in kit. You can purchase it from them individual.
Cheers Tony |
07-19-2020, 11:15 AM | #4 |
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Re: 7/16-14 thread chaser
USA-made UNC kits including 7/16-14 on Amazon for $15.50.
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07-19-2020, 12:52 PM | #5 |
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Re: 7/16-14 thread chaser
McMaster-Carr
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07-19-2020, 06:00 PM | #6 | |
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Re: 7/16-14 thread chaser
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07-19-2020, 08:34 PM | #7 |
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Re: 7/16-14 thread chaser
Here are few things to think about for head studs.
A thread to be properly used needs to be CLEAN bare metal. No corrosion, rust or scale. Any of these will corrupt a torque reading. A thread chaser is essentially an under size tap which will clean out MAJOR rust and corrosion. This device can not produce a correct size CLEAN thread. Like it or not, the laws of physics apply here. Head stud holes in a block need to be cleaned with a standard tap which will make the thread size as it came from the factory. This operation needs to be done with a fixture that holds the tap in perfect vertical alignment or a machine such as a mill or large drill press. If the hole does not clean to bare metal then it is too rusted/corroded to hold proper torque and needs to be repaired. While sometimes not visible, corrosion can account for up to 20% corrupt torque readings before the thread fails. A sealer such as high temp. RTV can be used on the dead end but a thread lube absolutely must be used on the fine thread end. The sealer should be allowed to dry for at least an hour before assembly. Head stud holes in a block can be tested before final assembly of the engine with simple home made tools. A 3 inch diameter by 2 inch thick steel slug (BOTH SIDES PARALLEL) with a 1/2 inch hole in the center, a HEAVY HARD steel 7/16 washer, a HARD high nut and a proper length stud. You install the stud through the slug with the lubed nut and washer on top and torque to 80 for a model A or flathead V8. If the thread is good, the torque wrench will have a solid feel. No “floating” or wanting to keep turning. Good threads will easily go over 100 if you are wondering. |
07-20-2020, 08:56 AM | #8 | |
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Re: 7/16-14 thread chaser
Quote:
Just wondering your thoughts on head BOLTS on an 8ba? I always heard never to clean the holes with a tap only to use a cleaner tap. Also per the machinist very experienced with flatheads use number 2 Permatex to seal the threads.
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07-20-2020, 07:16 PM | #9 | |
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Re: 7/16-14 thread chaser
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A problem with bolts is, you sometimes have them seep water with no sealer on the thread. If you use sealer instead of lube, the torque readings will be off. |
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07-20-2020, 09:01 AM | #10 | |
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Re: 7/16-14 thread chaser
Quote:
Thanks, Gary in N.Y. P.S. We actually test ALL the head bolt holes when we mount the block plate either during a pressure test session or for finish honing the bores, but they ALWAYS get checked way before the final assembly time! Occasionally we'll do singles also (photo below).
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07-19-2020, 08:48 PM | #11 |
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Re: 7/16-14 thread chaser
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07-20-2020, 07:57 AM | #12 |
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Re: 7/16-14 thread chaser
Thank you. And thanks to Pete for the insight. I would use #2 non hardening Permatex on the end of the stud. What about "thread lube" for the USS end in the in the block ?
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07-20-2020, 08:58 AM | #13 |
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Re: 7/16-14 thread chaser
Can we circle back to the idea of using a tap and not a chaser? I understand the difference and get the physics aspect of this in regards to cleaning out all the rust and scale.
Caveat: This is what I've read, but have not actually compared. I thought the thread pitch Ford used for their head stud holes is not the same standard pitch we use today. That's why some say to make a chaser out of a an old head bolt by cutting flutes into the side. I'd really like to know is this fact or fiction. |
07-20-2020, 09:07 AM | #14 | |
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Re: 7/16-14 thread chaser
Quote:
It's just the diameter that ford held tight. You can buy taps that are correct to match the ford thread spec, but a general purpose one bought willy nilly will probably not be to that tighter spec. Someone did post the correct spec once on this forum but I can't remember who it was or the title of the thread. I use a set of blue point thread chasers. They have proved invaluable over the years. |
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07-20-2020, 09:54 AM | #15 | |
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Re: 7/16-14 thread chaser
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Agreed on the thread chasers. I got mine from Sears, but they are made by Apex. My friend is a Snap On dealer and he confirmed they are the same as Snap On/Blue Point, just a different sticker on the plastic case. Exactly the same. |
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07-20-2020, 10:16 AM | #16 |
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Re: 7/16-14 thread chaser
I would not use a tap in fear of removing parent material, BTDT. Use a thread chaser.
This article explains it well. http://https://www.autoserviceprofes...stener-threads Last edited by glennpm; 07-23-2020 at 07:16 PM. |
07-20-2020, 07:29 PM | #17 |
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Re: 7/16-14 thread chaser
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07-20-2020, 07:42 PM | #18 |
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Re: 7/16-14 thread chaser
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07-21-2020, 08:56 AM | #19 | |
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Re: 7/16-14 thread chaser
Quote:
I'm assuming you mean the type of tap that you might possibly purchase at a typical hardware store maybe?? Thanks, Gary in N.Y. P.S. It all boils down to the "H-limits" of each individual tap. Conventional hardware store taps are generally the H-3 series! For tighter threads you would use an H-1 or maybe an H-2? It all depends, the taps come as high as H-5's, maybe more, not 100% sure!
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07-21-2020, 02:05 PM | #20 | |
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Re: 7/16-14 thread chaser
Quote:
Class of Threads, H Limits Classes Of Threads There are (3) established Classes of Thread, designated in the unified series by adding: "A" for Screws and "B" for Nuts (or other intenal threads) to show definite limits and tolerances. Class 1B Thread Is wherea 1A screw can run in readily for quick and easy assembly. The hole is classified as 1B. The fit is a 1B thread, (very seldom used in modern metal working) Class 2B Thread Consists of a 2A screw in a 2B hole. 2B thread has wide applications. It is used to accomodate plating, finishing and coating to a limited extent and threfore, has fair tolerance allowances. Class 3B Thread 3A screw in a 3B nut or internal threaded hole, used where tolerance limits are close. GH Numbers GH Numbers are listed below. "G" designates Ground Thread. "H" designates the pitch diameter is on high side of basic. These two letters (GH) are followed by a numeral indicating the Tolerance of Pitch diameter oversize. H1 = Basic to Plus .0005 H2 = Basic Plus .0005 to Plus .0010 H3 = Basic Plus .0010 to Plus .0015 H4 = Basic Plus .0015 to Plus .0020 H5 = Basic Plus .0020 to Plus .0025 H6 = Basic Plus .0025 to Plus .0030 H=Above Basic H7 = Basic Plus .0030 to Plus .0035 L=Below Basic |
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