Vent Hole Liner Question

[QuanLoi]

The literature that comes with the White Lightning touch hole liner I'd like to install states the use of a #4 drill.  Looking at conversion charts, #4 sits between 13/64 and 7/32.  Does it matter which one I use?

Thanks in advance...

[D. Taylor Sapergia]

Yes, I'd say it does.  Use the #4, if that's what is required.

[Dr. Tim-Boone]

Numbered bits are different sizes than dimensional bits

[Acer Saccharum]

Center punch the location. Then drill with a "Combined Drill and Countersink". Drill thru with a smaller drill, say, 3/16, then open the hole with successive drills until you get to the #4 drill.

If you use a drill smaller than the #4, the tap may strain and break, or tear threads.

If a larger than specified drill is used, then the thread engagement will not be enough, and THAT will be unsafe for whomever is standing to the right of the shooter.

[QuanLoi]

Thanks again... This site is an invaluable source of knowledge!

Decker

[Meteorman]

It can be confusing.... you will find many tap drill charts that prescribe a 7/32" tap drill for 1/4"-32 bolts.
That gives you about 75% thread engagement IIRC.
I'm with Taylor on this - if they say #4, they want more thread engagement, and why argue with them.
(... but I'm guessing there are MANY who have used 7/32" with no problem ...).
/m

[Dr. Tim-Boone]

When you buy a WL liner from Chambers you can buy a drill and tap for the size you buy...I recommend that you do that..save yourself the problems...

[Acer Saccharum]

Just please start with a smaller drill than the #4.

Why?

If you don't, the #4 will drill oversized. That's what drills do. Drill the next fractional size down, and finish with the #4...you'll get a MUCH more accurate hole.

[Hungry Horse]

I used one of Jim's WL liners for my old Navy Arms 1803 Harpers Ferry. These guns were notorious for slow ignition due to the poor placement of the touch hole. By center punching a new center, and drilling a pilot hole as previously mentioned, installation of the new liner cured the problem. She shoots pretty fast, for what she is. I was able to drill the new hole for the liner, and eliminate the poorly place original touch hole.

                            Hungry Horse

[P.W.Berkuta]

Just please start with a smaller drill than the #4.

Why?

If you don't, the #4 will drill oversized. That's what drills do. Drill the next fractional size down, and finish with the #4...you'll get a MUCH more accurate hole.

What Acer said is "Spot ON" and this method is the best way to drill a hole that is as close to actual size other than using a reamer  .