Barrel Lining - Attaching Drill Bit to Rod Extension

[sign216]

For a barrel lining; when attaching an extension rod to the piloted barrel liner drill bit, I've heard you silver solder them together.
Is that brazing with a hi-temp torch and a 55% silver solder, or a low temp solder with a tin + 4% silver solder, like Brownells Hi-Force 44 solder?

Brownells instructions say to silver solder, but the write up looks likes it's brazing with an oxyacetylene torch.
Web search shows a man who joined them w low temp silver solder, and it worked fine for him for multiple jobs.

Which is correct?

Joe

 

[4v50 Gary]

Brazing is very high heat. Soldering is much lower. I'd go with low temp, high force.

 

[sign216]

Gary,
I hear you, but Brownells' instructions specifically mention using an oxyacetylene torch to to form the bond.
Which sounds like brazing, right? Do you think they are being overly safe, and requesting people to unnecessarily use the strongest technique?

 

[Blue68f100]

What kind of joint are you going to use to join the 2? Just butt them together, or drill and insert ? The last thing I would want to happen is the bit comes loose in the bore. Use a high temp silver braze A min of 10%. This will require a oxy/acety to heat it up in a short period of time. Your shooting for ~1400F. If you have access to a lathe turn the shaft of one and insert in to a pocket to keep everything on center.

 

[jmorris]

I have TIG welded extensions to drill bits in the past. It helps a lot to have a lathe to machine the two for fit and post weld ensuring it’s 100% true.

 

[sign216]

Most instructions says to use a lathe to machine a hole and matching stub in the two butts. I don't have a lathe, so I filed
a trench and matching rise in the two ends (see photos).

 

[doubleh]

I have a lathe and and machine a 60 degree angle on the bit and extension, center drill the other end of the extension so it will on a dead center in the tail stock and then set both up in the lathe to assure they they are straight and braze with a A/O torch and bronze brazing rod. I use drill rod for the extension because is is straight. Turn the brazed joint dwn to the same size as the drill and you are done.

A real machinest might find this method mickey mouse but it has worked well for me.

I would guess Brownell's torch recommendation is based on the fact that type of torch gives you excellent heat control and is fast. It's a rather expensive set up except in hobby torches if that type is still available. Gas and bottle cost or rent is the main expense. Propane gives adequate heat for silver soldering but is not as controllable as A/O. Think a small flame that comes to a point and gives 5000 degrees of heat to do this job. TIG welding would be excellent but again, an expensive setup.

Tremors have removed my ability to do almost anything like this so have at it your way.

 

[jmorris]

The easiest method is drilling a hole in the center of bar stock, then insert the bit and weld (top) but that will only get you further from the machine, not a deeper hole.

#2 is drilling out the bottom of a bit and inserting rod (2nd down)

#3 is welding bit to same size drill rod (3rd from top).

Don‘t forget folks offer longer bits, like the bottom 3.



As well as extensions one can a fix drill bits to, like this 12” B&D extension but again are limited to how small of a bit they can follow through a hole, 5/8“ for that one.

 

[jmorris]

Do you think they are being overly safe, and requesting people to unnecessarily use the strongest technique?

That depends on if someone has ever come across a broken off bit in a very deep hole. I have and would probably use the strongest method I could come up with, if there is a remote chance I could break one off a foot deep + in a small diameter hole.

It doesn’t cost that much more to do it right and if you can’t get it out yourself, someone that could is probably going to “break it off“ in you. Because at that point, what else can you do?

 

[sign216]

Doubleh and Jmorris, thanks for your replies. You both describe great techniques, from a well equipped shop. My technique is to do this without the expensive torch or lathe. I am buoyed by the account of others (from another site) that it can be done simply. We will see.

Joe

 

[a5werkes]

The "easiest" solution is to just purchase "aircraft length" drill bits, not very expensive and many hardware stores have some selection, or endless choices at McMaster Carr. I have a bunch them.

MrPete222 / Tubalcain has a great and entertaining recent short video about long length bits, them as well and shows a welded / brazed extension in his collection; "desperate men will do desperate things" as he characterizes the fabrication.

https://www.youtube.com/watch?v=ZgL1Ure47yg&list=PL6HIFled82YXOnt4YhGvYPBQ40XO3ITRk&index=19

 

[sign216]

A5Werks,
At first I had a hard time finding aircraft drills with the piloted point, and the rifle has a 24" barrel, so the common 12" aircraft bits won't do.

This got started during covid when shops had nothing, including Brownells. From Ebay I was able to source the correct piloted drill, and drill rod, and started the project with plenty of mistakes, and stops n starts along the way. Now Brownells has piloted long-length drills bits in-stock for $67!

I've put so much time and money that I'm loathe to buy a pre-made drill bit. I may regret it if my solder joint fails, leaving the bit stuck inside the bore.

Joe

P.S. Thanks for the video, looking at his collection, I have "bit envy."

 

[a5werkes]

I may regret it if my solder joint fails, leaving the bit stuck inside the bore.

that's the devil for your project!