Posted: 8/25/2025 8:26:51 PM EDT
[Last Edit: maggiethecat][Edited]
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How would you thread 9/16-18 7" deep? The longest tap I can find is 6" OAL. A proper size tap extension will be too big to fit in the hole. I thought about turning down the tap to fit ina 1/2" tap extension drill .500, ream .510 is the easy part. tapping full depth is the issue Here's a drawing, YES- I know it has wrong diameter on it. 
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Originally Posted By giantpune: you check to see if they make a tap extension that fits your tap and hole? McMaster has a bunch of different sizes. Mcmaster tap extension for 9/16 has a max diameter of .687. Well above the hole size of .510 tapextension.com has a max diameter of .625 (buy from them, awesome people!) a 1/2" tap extension from tapextension.com has a max diameter of .500 which will fit in the hole, but will not work with an unaltered 9/16 tap |
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https://www.strobelssupply.com/9-16-18x8-high-speed-pulley-tap/?srsltid=AfmBOop13peCXg3yx3Oilimh5QSQdKjYA8XITT_ybhxdhDJgZvY4ZyMv But you'd have to find a way to reduce the shank diameter. Does it really need that much thread length? |
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Originally Posted By paul463: https://www.strobelssupply.com/9-16-18x8-high-speed-pulley-tap/?srsltid=AfmBOop13peCXg3yx3Oilimh5QSQdKjYA8XITT_ybhxdhDJgZvY4ZyMv But you'd have to find a way to reduce the shank diameter. Does it really need that much thread length? Yes, it needs that much thread length |
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I turned down a 5/16-18 tap at work to get the threads deeper. I used a carbide turning tool, ran it slow and took .005 off the diameter at a time. It didn't take very long. |
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Everything you need to know about the left was on display during covid . -RC03
Everything you need to know about the left was on display during covid . -RC03
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Originally Posted By paul463: https://www.strobelssupply.com/9-16-18x8-high-speed-pulley-tap/?srsltid=AfmBOop13peCXg3yx3Oilimh5QSQdKjYA8XITT_ybhxdhDJgZvY4ZyMv But you'd have to find a way to reduce the shank diameter. Does it really need that much thread length? Thanks for the link. I think if I have to turn down shank I'd rather use the standard length and 1/2" tap extension |
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I vaguely recall that they used to call the reduced shank ones "nut taps" - try that search term too. Also "extended taps" and "extension taps." Might get lucky. A tap extension is not likely to work, the OD of the portion that contains the female square drive socket feature will almost certainly be larger than your thread's minor diameter, so as you noted, it won't be able to enter the hole. Using an extension with a 1/2" OD in a hole nearly the same size is not something I'd recommend... Likely to get caught up on the smallest chip and possibly cause a catastrophe. Better to have as much clearance as you can get in a deep hole, IMO. The reduced shank pulley tap would be a much better choice, even if you need to turn it down. I'd be inclined to skip the square if you're going to power tap it. Just back the tap out a lot to clear the chips out. Once you get in there a ways, maybe every 4 or 5 turns. |
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You need to braze (Not Weld) an extension to get deeper. The link to McMaster-Carr is 6" OAL, that would give the Brazed portion less stress using it by not having too much torque when using for the deeper portion. https://www.mcmaster.com/products/deep-hole-taps/ |
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