• Jesse Young

HHIP 1011-0084 31 Piece 5/16-18 Helical STI Thread Repair Kit Review

Updated: Sep 24, 2019



I purchased this on Amazon on September 11th 2019 to repair a stripped out hole in the primary mounting flanges in a aftermarket Harley S&S 107ci Super Sidewinder Evolution motor.

Yeah. So I ordered a "Helical" helicoil kit in 5/16 x 18. I feel like I gambled hard on this one, but you can read my verdict below. It was a little bit of a choice between this guy, and the harbor freight helicoil kit.



5/16 x 18 helicoil kits requires a 21/64 drill bit. One of the complaints other users had was that it was shipped with the wrong size bit. My kit did not have any issue.


The kit includes:


25 Inserts

1 5/16-18 STI HSS Tap

21/64 HSS Drill Bit

1 Insert Driver

1 Tang Breaker




The threads were completely blow out and a faster couldn't hold torque. To aide in cutting I added a few drops of 3-1 household oil.




The bit fit pretty close in the hole. I chucked it up in my dewalt driver and made certain to start straight, going slow and backing off every half rotation to let chips fall out.




The picture can be deceiving, but the drill bit cut fairly clean. You can kind of see debris in the back of the blind hole.




I like to start my taps with a wrench before putting them in a holder, or ratchet. I feel like it gives me better control to get the threads started straight and not at an angle.



Once started, I put a ratchet on the end of the bit and very slowly began cutting the threads. It hit a few tight spots, but overall went in ok. I think the tap was a little on the "not so sharp" side.


Here in the above image is after cutting the OD threads for the helicoil. notice the burr the tap left on the last pass. Eventually I got it knocked off with a pick.




I didn't take any pictures while installed the coil, or breaking off the internal tang. It was started to get hot in my garage and I lost track of taking pictures.


After looking at the above picture. I almost wish I went another full thread deeper.


My Verdict:


The drill bit didn't feel it cut as well on aluminum that other brand drill bits do. It wasn't game changing, but it could have been sharper.


The tap did cut ok, but it retained chips real bad and required 4 back outs and cleaning.


The inserts, driver and punch all worked with no issue.


Was it worth the $20.44? Sure. Would I trust it on harder metal? Maybe not considering how the drill bit didn't cut all that clean on aluminum so I probably wouldn't want to test it on a critical part, or a place with limited room to get it out.




We have no association with Amazon or Harbor Freight Tools. All text is of our opinion alone and not from either company.

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