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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. |
07-19-2020, 08:48 PM | #8 |
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Re: 7/16-14 thread chaser
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07-20-2020, 07:57 AM | #9 |
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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, 08:56 AM | #10 | |
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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, 08:58 AM | #11 |
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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, 09:01 AM | #12 | |
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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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07-20-2020, 09:07 AM | #13 | |
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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 | #14 | |
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Re: 7/16-14 thread chaser
Quote:
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 | #15 |
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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, 07:16 PM | #16 | |
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Re: 7/16-14 thread chaser
Quote:
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, 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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07-20-2020, 08:42 PM | #19 |
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Re: 7/16-14 thread chaser
Most threads in the parts we are talking about (flathead Ford engines) are "standard" class 2 threads as used in assembly line production.This is normally a 77% thread. A class 2 tap will not remove metal from a class 2 threaded hole unless the the female thread is damaged.
Myths get started by very intelligent people "creatively" answering a question rather than spending the time to look up the correct answer. Once a myth gets started, it is hard to dispell. |
07-20-2020, 08:44 PM | #20 |
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Re: 7/16-14 thread chaser
I find that the internet, especially Amazon to have most everything I need at a reasonable price and quick delivery, Even to Vt
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