Drill/Tap Octagon Barrel for Breechplug

[dd832]

I have an unthreaded .45 cal octagon barrel that needs to be drilled and threaded. I have a floor drill press, but I'm not sure how to set it up to do vertical drilling. It seems like trying to accurately position the barrel with the drill spindle is next to impossible. Looks like an 8 hour job to align it. Anybody do this recently?? Thanks in advance. Mike

 

I'm sure that you could come up with a long complex set up to do the job but its end quality would be in question. I work in a machine shop so have access to a lathe and four jaw chuck... Recommend you spend a few bucks to have your local gun shop breech it for you or a local machine shop to help you out...

Thanks

 

[Runner]

Having it done on a lathe is best. If you want to try yourself, take a wooden dowel that just barely fits into the bore and use it to align the barrel by putting it in the chuck and sliding the barrel up on to it. Clamp things up and then open the chuck, allowing the dowel to drop into the barrel out of your way. Mark the correct sized drill for your tap and drill to the correct depth for the breechplug. Too shallow is better than too deep. Now the fun begins. Getting the hole drilled is simple. Getting the tap started straight is the hardest part without a lathe. If the threads are not cut straight, the breechplug tang does not align with the barrel. I bored the one I am working on the other day on my little lathe, but because I had already polished the round barrel, I could not get the chuck to hold it without damage for tapping. I tried to tap it straight by hand. It would be usable, but it is not straight. You will not have the problem with an octagon barrel at least. I ordered a second barrel blank and I am going to do all the machine work before I do anything else this time!

I had a bad day. I ruined a stock, tapped the barrel wrong, and broke the blade of the Damascus patch knife I have been working on all in the same day! I may not be the best person to listen too!

 

[Vaino]

I now buy barrels that are factory breeched but have in the past drilled and tapped the breech hole in a drill press.. Besides a reg. tap drill you'll need a flat bottom tap drill, ctrsk, regular tap and a flat bottom tap. The drill press has to be tall enough to accept the barrel. I clamped the barrel in a large V-block w/ the barrel going thru the dr.press table center hole. Start by just holding the V-block and start to slowly drill w/ the tap drill. Once centered, clamp the V-block and drill w/ both tap drills to final depth. Ctrsk the hole and using a regular lubed tap, turn the spindle on and then off and while the spindle is coasting, bring the tap down into the hole. It'll stop sfter a few rotations. Complete the tapping by hand. Good luck........Fred

 

[loojack]

Try TOTW, I think they'll do it for $20-$25 or so....loojack

 

[Vaino]

I agree in having someone else do it. By the time you buy the drills and taps there's a few bucks tied up plus the headache of doing it... but some guys persevere and have to at least try it once. Also don't forget to send the plug along.

 

[Cherokee]

Like said beofre have a pro do it. Even if you buy the tools and do it yourself you may screw it up. Nothing against you it just works out that way. I would probably screw it up haha
TOTW charges $25 on their website not sure if thats only for their items bought through them or if they do outside work.
Only takes a phone call.

 

[dd832]

Ye of little faith. Nothing is impossible [for the man who doesn't have to do it himself]!!
Thanks to Flehto and Runner for the advice - I used the drill press. First I zeroed the table level with a dial indicator and ran the barrel up thru the center hole in the table. Clamped the barrel vertical to the table with an old drill press vise. I already had the taps, used a 9/16" end mill and a 37/64" reamer to finish the hole. Tapping was the easy part. Measured the threaded plug & took a couple of thou off the end of the barrel with my lathe to match the breech plug. My 9" South Bend lathe only has a 7/8" spindle hole, otherwise I would have tried treading it using the lathe w/ my 4 jaw chuck.
The reason I did it myself is that I bought a 15/16" barrel (.45 cal) from Numrich for $20 & was too cheep to spend more on shipping 2 ways + the machine work. Pre-threaded barrels are definitely the way to go.
I'm making a Kendall/Hilliard underhammer buggy rifle. Will be making the hammer, trigger & springs next. AND NO, I don't have pics, but I do have a dead digital camera. [4 sale, cheep] Mike

 

[mikelange]

DD832 --

I refrained from posting, earlier, because with all the talk about lathes and drill presses and the advisability of just sending it off to be done, I feel like the backward country cousin who can't afford the good toys or the cost of having "people" to just do it for me.

I've cut the breeches off new and used barrels, and (like you) bought unbreeched tubes because the price was just too good to pass up (latest acquisition was, like yours, from Numrich -- a 30" x 1" .50 caliber). My drill press is a big tabletop model and I don't own a lathe. I clamp the barrel level (I do own a level) into a vise and simply drill a 37/64" hole the same depth as the length of the threads on the plug I've chosen for my latest project. I do enough building to have long-since found it worth my while to acquire both standard and bottom taps in 1/2", 9/16", 5/8", and 3/4". My plugs end up seated to the shoulder of the bore and indexed correctly to the flat of my choice. Sometimes there's a lot of trial and error, filing, and sweat involved, but the cash to cover the labor fee and shipping charges, to have Track or someone else do it, stays in my pocket.

Ye of little faith, indeed. I envy you your better tools, but above all admire your willingness to do the job yourself. :hatsoff:

 

[dd832]

Mongrel, are you also drilling/tapping your barrels thru the table center hole vertically?

I knew I couldn't be the only one out here doing this. Appreciate the encouragement. Mike

 

[Runner]

My Southbend 16/24 is still waiting for a motor that the house electric likes. The one that came with it takes out mains. If it was running, I can do the whole job with no problems. My little lathe has a little over .75 thru the headstock, so the smoothbore is possible, but a regular octagon barrel is not. If I had not finished the barrel before prepping the breach threads, it would have been no problem. Learning experience that killed a 24$ barrel.

 

[JOHN L. HINNANT]

Greetings dd832,

Quite a bit of good advice has been given out here; the best being. have a professional do it.

This is a straight forward machine job that any good machinist can do, but might cost $50.00 or $60.OO, BUT IT NEVER HURTS to visit one and get an estimate.

I have my own lathe and do my own work. I DO NOT DRILL the tape drill size before tapping. Here is what I do.

1. the barrel is centered in a four jaw chuck on the outside flats to a plus/minus .0005"

2. Instead of drilling, I use a stub boring tool to bore to the tap drill size.

With this method, the tap drill hole is perfectly round, perfectly centered, and has a 90 degree flat shoulder inside the tap drill hole. The depth of the hole can also be precisely determined.

If you have somebody do this job. you might ask them about this method. If neccessary, they can contact me for more information.

Best regards and good shooting,

John L. Hinnant

If you are not an NRA Member, why not? I am carrying you load.

 

[Runner]

Are you using a normal boring bar or are you using a special tool?

 

[JOHN L. HINNANT]

Greetings Runner,

Well...... Yes and No.

Now to explain. I use an Enco 4 tool multi-position tool holder. If you are not familiar with this type of tool holder, it will hold 4 tools at one time and can be rotated to different angles to the work piece. This type of tool holder IS NOT REQUIRED to do this boring job.

With this tool holder, I use 3/8" square H.S.S.
tool bits (hand ground to shape by me) or 3/8" square Brazed-on Carbide tools.

Some years back, I purchased 2 dozen 3/8" square X 3-1/2 long, H.S.S. tool blanks.

One end is ground to a standard General Purpose Lathe Turning Tool, EXCEPT..... the Top and Left Side Cutting Edge is ground about twice as long.
The bottom of the tool is greatly relief ground.

The long tool allows me to firmly fasten it in the tool holder and have enough length and rigidity to bore to a 1" depth with a mimimum of tool spring back.

As the inside shoulder is formed by the larger bored tap drill hole, the leading front end of the tool is used to face the shoulder square to the bore and the tap drill hole.

By using the boring method, the end result is a centered perfectly round hole and a nicely squared inside shoulder.

By boring the tap drill hole one thread or so too deep, the end of the threaded breech can be faced with great precision until the tang lines up correctly with a barrel flat and the breech plug face is flush with the inside shoulder.

This may seem like over-kill in fitting a breech plug, but this type of precision work is characteristic of my nature, and is one of the reasons I would never be able to make a living as a gunsmith. I cannot bring myself to work to a lesser standard, and most people will not pay for the labor involved in that kind of work

The tool design is simple, but works well.

Hope this information will be helpful.

Best regards and good shooting,

John L. Hinnant

If you are not an NRA Member, why not? I am carrying your load.

 

[Runner]

I have done much the same in the past making airgun valves. I have a set of carbide boring bars here that would let me drill small and then bore to size. Since the 3/4 16 plug I got is a solid plug, did not worry about it. I just drilled and tapped. I figured to cut the shoulder on the plug to match the drill profile so they closed up together. This is a round barrel with no off center problems, so all I have it a depth fitting. No flats unless I cut them myself. I may cut some flats for about an inch or so this time.
I ordered a stock of the breech plug blanks they sell also. Cutting threads and getting the plug ready to use saves 30$. I ordered some taps and I took a bottom tap to the belt sander so I can cut threads right up to the shoulder in the barrel.
Thanks for the info!

 

[varsity07840]

TOW does outside work. I've sent them barrels in the past for rebreeching, etc.