A Thread Repair Solution That Saved My Ass

Don’t Over Torque Your Screws!

When I finally received my first Leupold scope from the USPS, I was excited. I immediately unwrapped the packaging to install it on my new Thompson Center ProHunter .17 HMR barrel. I sat down at my desk like a little kid getting ready for to put together his new Lego™ set. Assembling to Leupold dovetail scope mount appeared simple and using the FAT wrench seemed so easy – what could go wrong? I screwed all four screws into the barrel by hand, set the FAT wrench at 30 lbs. p/sq. in. (as suggested by midway) and then proceeded to torque them. I turned and turned – waiting for that click. Nothing happened. Instead of thinking about what was going on, I made one last twist that suddenly gave way – I stripped the threads on my brand new T/C Encore barrel.

Attempting to salvage what I had going on, I took out the remaining two screws I didn’t torque. I sat there bummed out not exactly sure about my options. I searched the Intarweb to look up any local machine shops that might be able to help me out. I even attempted to contact a local freelance gunsmith. However, it was Labor Day weekend and any correspondence wasn’t expected.

After realizing the source I have at my disposal, I searched the Specialty Pistols forums. They specifically focus on those unusual handguns and rifles varying from break action firearms, single shot carbines, and more! The handy dandy search function led me to the Brownells’ oversized 6-48” screw kit.

Item description from the Brownells webpage:

“Saves Your “Tail Feathers” If A Hole Gets Stripped. Slightly larger in diameter than the common 6-48 scope base mounting screw. Most holes ‘ruined’ while drilling or tapping can be fixed; just retap to .146″-48 and install. No need to re-drill base or gun. Thanks to Doug Knowt for his tip.”

This kit seemed to be the answer to my trouble. The shop kit includes 48 pieces of .146″-48×1⁄2″ (12.7mm) slotted machine screws, blued finish with Fillister and Weaver-style head, 1 taper tap, 1 bottom tap, and 1 Screw Gizzie in a bench box. The kit seemed complete, but one must also remember to get the T-handle in order to cut out those new threads. I picked the Starret T-wrench for no particular reason – there are plenty of other options.

Here’s a quick blurb about the contents inside the kit. The taper tap is for holes that do not have threads. The taper tap allows you to screw it in straight and with much more guidance. The taper tap is used with more frequency and can be used for holes that are drilled through the material. The bottom tap however is used to continue a set of threads down a blind hole, or a hole that is not drilled through (no light = blind hole). In my opinion, both are recommended for rethreading scope threads – it’s much easier. The screws are ½”. In most instances you will have to grind them down to size. I needed my screws to be ¼” to fit correctly. The Screw Gizzle holds the screw while you grind the threads down to size. Avoid using pliers, vise-grips, etc directly on the machine head – they just mess them up.

The taps worked very well! I didn’t have to drill a new hole and they were relatively easy to use. With the base nested with one good screw, I started off with the tapered taps. The base provided a guide into the mangled threads. I used Break Free CLP for lubrication to avoid any binding with the metal. You may want to use another lubrication that’s more suitable if you happen to be more aware of one – I just grabbed what I had laying around. As soon as the first few threads were cut, I switched to the bottom tap to finish off the threads. After each turn, I reversed the rotation to prevent crowding caused by the excess metal. Failure to do so may break the brittle taps.

My two holes were rethreaded and ready to go. I just needed to cut down my threads so that they will clamp down on the scope base. I eye-balled it with the original screw length and grind material away at the threads. Be sure to stay consistent so that any surrounding threads aren’t damaged. Use a file for small modifications (raised/uneven threads) if necessary. Inserting damaged threads into holes you just tapped is a horrible idea.

As soon as I was done, I felt relief and a moment of pride. I learned something new, avoided purchasing a new barrel and the hassle finding someone willing to drill a new hole to re-tap it for me. Learn from my mistake and don’t over torque your screws. I set the torque at around 25 lbs. and that is likely to be plenty for a rimfire rifle.

I was really lucky it was something I could fix. It was Brownells and their oversized 6-48” screw kit that made it possible.

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Categories: Firearms, Guns

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4 Comments on “A Thread Repair Solution That Saved My Ass”

  1. suscuncfeeddy
    April 24, 2009 at 4:41 am #

    I’m the only one in this world. Can please someone join me in this life? Or maybe death…

  2. reerboata
    September 22, 2011 at 8:55 pm #

    Hello! what about ?

    !!

    ?
    ???

  3. ZHK
    April 30, 2018 at 12:34 pm #

    Very useful information.

Trackbacks/Pingbacks

  1. New Glass, Shoddy Threads « - March 27, 2009

    […] I looked through my tool box and discovered that I already had the 6×48 dies from my last mishap.  It was simply a matter of cleaning them up.  I was further disappointed in Savage Arms quality […]

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