Gunsmithing AR lower grip screw threads

[NavyshooterM40]

I need to clean up the grip screw threads in a lower. What size tap do I need.
Thanks

 

[canman]

1/4-28

 

[Skunkworx]

Yep 1/4-28

 

[NavyshooterM40]

Thanks!

 

[strikeeagle1]

Remember you wiil need either a 6"tap or 6" tap handle wrench to get up in that space.

 

[Rocketvapor]

Maybe remove the grip before tapping?

 

[strikeeagle1]

^^ that would be too easy ; don't know what or IF I was even thinking. LOL!
For installation I do use a few tools to hold the slotted fasteners as well as either a hex / torx fastener as keep the fastener
fairly well centered to decrease the chance of cross threading the fastener. The Delrin slotted adapter has rubber fastener head retainer to keep it from falling off during the proces. The Wiha too is pretty good but the magazine well is pretty narrow down deep which only allows a few turns of engagement before you have to release it from the tool.

 

[cas6969]

Wow this thread made me feel really dumb for a moment there. I couldn't figure out what all these special tools for? lol

I tapped an AR grip screw once, an obscenely expensive CNC grease gun mag lower showed up untapped. (I just used a regular old tap and tap holder.) But it was an interesting few minutes and lots of colorful language when I couldn't get the damn grip screw to catch. "Why won't this f@#%ing thing screw in!!"

 

[Rocketvapor]

Being careful you should be able to clean up the threads in a plastic or aluminum lower.
Making new threads might be harder to visually align

 

[larryh128]

What I have used for hand tapping is to make a guide out of MD Nylon with a snug hole to guide the tap. A 1" thick piece of any material with a vertical hole thru it will align a tap properly to start.

 

[strikeeagle1]

^^^ I am generally risk averse when it comes to screwing up (pun intended) simple gunsmith projects. Which is why I use those centering tools, a lot less commotion then cross-threading a fitting. Same situation with shotgun wood butt stock retaining bolts that can break thru a beautiful gun stock if the slotted screwdriver is not seen / set into the bolt slot. Old gunsmiths used to wrap tap about the shaft of their favorite butt stock screwdrivers to center the driver shaft to avoid that situation. I fabricated an entire system of stock bolt centering drivers with variable diameter fittings to keep me out of trouble disassembling / assembling expensive gun art.