Reaming a bore after drilling

[Tokarev]

For a long time I have an insatiable urge to build a rifled 410 over-under from scratch. The barrels will be 12-13" long and I have 6, 8 and 14" bits to drill.

Yes, our convoluted Canadian gun laws make it legal to manufacture a short barrel for a hand operated rifle/shotgun as long as it was first made that long (or that short) as opposed to cutting down a longer barrel which is a no-no under 16".

But still no idea where to find a long enough piloted reamer. Does anybody make them or would soldering a regular chucking reamer into the drilled end of a round bar work?

[Outpost75]

Brownell's sells long piloted deep hole drills used to install barrel liners. I don't know if they can ship these to Canada.

If not, your idea to solder a chucking reamer onto a long bar will work if you are careful.

[CastingFool]

I once made a 36" long 3/8" diameter carbide drill bit by taking a 3/8" cold rolled steel rod, facing one end, center drilling it and drilling it about 1" deep with a 5/16" bit. Then, I took the 3/8" carbide tipped drill bit, chucked up on a lathe, and turned the end down to about .310"-.311", about 3/4" long. Silver soldered them together and cleaned up the joint on a belt sander. It didn't wobble when used with an electric drill. I'm sure this would work to make the reamer longer, just remember it's almost a permanent fix. BTW, the lathe I used had collets, not a 4 jaw chuck

[country gent]

It does work and as Casting Fool did the mating shoulders is a big plus to help keep things straight and true. When possible I preferred to reverse it and put a smaller shank into and behind the drill. this allows for better coolant fow and chip removal as there is more room around the shank.

[John Taylor]

You can get bore reamers from Pacific Tool and Gauge. These reamers are mounted on a tube, designed to be pulled though the barrel in a lathe while cutting oil is pumped through the tube. I have several in carbide, cost about $200 each.

[KCSO]

I had at one time plans from Starr on making your own shotgun reamers. If you work careful you can ream a LITTLE at a time by hand. I have some long shanks that fit an adjustable reamer set for smoothing bores.

[country gent]

If your drills cut uniform and decent a lappcould be made to smooth and polish the barrel also with various grades of lapping compound. It would be more hand work but also would leave the polish lines parallel to the barrel rather than radial

[Tnfalconer]

If your drills cut uniform and decent a lappcould be made to smooth and polish the barrel also with various grades of lapping compound. It would be more hand work but also would leave the polish lines parallel to the barrel rather than radial

I like that idea a lot. I read all the posts and immediately wondered why a boring bar couldn't be used if the OP has a lathe? I have bored lengths up to 16-18" with my small lathe. Seems as if it could be drilled and then bored to make it concentric. Then lapped as Country gent described.

[country gent]

The only real problem is the boring bar to fit in that size bore will have some chatter and spring issues if long enough to go thru. But chip removal may be easier than a drill or reamer with out high pressure coolant flow thru the drill. For deep holes we would use a special drill flat ground and pulled thru the hole. this gave great results but it the stock walked under stresses then the hole still wasn't straight.

[Tokarev]

So making some headway: ordered and received several drill bits of different lengths. They would be perfect, if the manufacturer has not forgotten to grind the step along the outside of one of the flutes on the longest one!
I do not know how to describe that, but if you look at the cutting edge of the flute, there will be a narrow step along its spiral edge. One flute is fine, the other one is missing this step.
Is this critical for drilling quality? I'll see if I can talk the manufacturer into sending me a replacement w/o having to return this bit, as shipping would be prohibitive.

[Willbird]

As a career machinist I have drilled quite a few smaller holes to a depth/diameter ratio that was greater than what you are trying to do. We used to drill 1/8" holes about 8" deep into H13 steel which is a nasty gummy steel to machine (IMHO).

The key to drilling deep is to get everything lined up perfectly, the drill should be perfectly parallal to the spindle axis on a lathe (if you are doing it in lathe) and you want a very good drill to begin with, Ghuring or Titex parabolic drill IMHO.

Then for a .410 I would drill 25/64(.390) and ream 13/32(.406) and call it done. But first I would drill about 1/2" deep at 11/32(.343) and carefully single point bore until the 25/64 drill just barely slipped in. This will give you a perfect zero runout start. Then drill say 1/4" to 1/2" at a time, withdraw and remove all chips, brush on oil, feed deeper. Try to NOT "push" the feed to much as you will bow the drill.

Here is the type of drill you want, some shopping may find it cheaper

https://www.jtsmach.com/jtswebshop/Pr_CuttingTools/D144.asp

[Jedman]

I just finished a similar project. I bought a antique rook rifle that was said to have a smooth bore.
When I got it you could chamber a crimped 2 1/2" 410 shotshell and the extractor worked perfectly with the shotshell but a fired shell would not chamber fully so the chamber was about a 1/8" short. The gun was a rifle at one time and had a long 28" barrel. Someone had drilled out the bore probably for a liner as it was drilled from both ends and there was a tiny step halfway down the bore where they met and where off by a few thousands.
The drilled bore was about .387 but not very smooth and I could not figure what I could shoot in it the way it was so I decided a 410 shotgun would be the easiest choice to try.

I have a bunch of taper pin reamers so I took a No. 7 taper pin reamer and mounted it between centers in my lathe and with a angle grinder I ground down the flutes at the front end to a point where the starting diameter was about .385 and ground off the flutes past the point where it measured .412 for clearance the reamer shank was about .400".
On the front end I turned a piece of a old barrel for the pilot and heated it red hot and drove it over the front end of the ground off flutes for a heavy press fit.
I then put the reamer back between centers in the lathe and turned and polished the pilot to .385 diameter and was running true with the reamer centerline.
I thought about how I was going to drive it since I needed a long extension to go thru the full length of the barrel with the action still attached so I bought a 3' length of 5/16" round stock and turned one end to silver solder to a coupling between the reamer and the extension rod.
I again turned the reamer between centers and with my angle grinder I ground down the shank of the reamer until it was mostly round and a diameter smaller than 5/16" to fit the coupling I made from a scrap piece of barrel.
I put the round stock thru my lathe chuck with about 6" sticking out and tapped the coupling on about 1/2" and tapped in the reamers ground end in the other end of the coupling and put the live center in the front of the reamer so it could be rotated and lined up true inline with the extension and I silver soldered the joints while in the lathe.

My lathe has a large enough spindle bore that allowed me to put the barreled action thru the spindle with. the muzzle end sticking out the back side centered in a spider and the breech end with the action still attached in the 4 jaw. I had to remove my tailstock from the lathe to have room to use this nearly 4 foot long contraption I made.
I ran the lathe at 60 rpm and with a large drill chuck on the end of the extension to hold on to I fed the reamer slowly by hand and about every 1/4" I backed it out cleaned off the chips and reoiled the reamer. It was a very slow process as the reamer was enlarging the bore almost .030 at one time and that's a lot. It probably took more than 2 hours to get to the muzzle end of the barrel where I stopped reaming to give the barrel some choke with the taper on the reamer.
The bore came out good, not as smooth as most shotguns have so I decided to hone the bore with a flex hone.
Again I needed to make a coupling to silver solder on to the flex hones twisted wire shank so I could use a 8/32 cleaning rod to drive it and polish the full length of the bore. It worked well,
the bore is smooth the full length and I am pleased to only spend less than $20 for everything needed to do the job.
I didn't take any photos of the process as I usually don't for any of my projects but when I seen this thread I thought I would respond and I did take a pic of the tools I used.

Jedman

[Ballistics in Scotland]

You can get bore reamers from Pacific Tool and Gauge. These reamers are mounted on a tube, designed to be pulled though the barrel in a lathe while cutting oil is pumped through the tube. I have several in carbide, cost about $200 each.

That sounds by far the best solution for a professional who will be doing the job again and again, but hardly worth it for the amateur's one-time job. I do like the idea of pulling the reamer through, rather than pushing. I'm guessing now, but I expect yours have flutes extending all the way to the rear so that the chips can be left behind rather than fine their way out at the drill end.

I have drilled reamers and end mills with carbide drills, but what I would use now is a modified rotabroach, or rotary broach, which you will see illustrated on eBay. The former will get you the brand-name original, but I think the patent, if there was one, has expired.

With a lathe and carbide drills you can drill a hole in the tip of a high speed steel hand reamer, which has the advantage over a machine reamer of having around a sixty-fourth of taper at the tip. I don't know whether it is due to different expansion characteristics or building up a temperature which degrades lubricants, but I find carbide drills will very easily seize in hard steel. So it would pay to have two slightly different diameters, and drill a little at a time with each alternately.

Get an inch or so in, and you can solder the operating rod. Barrels are seldom hardened, and I found that enough hardness is retained in high speed steel after slow, careful heating with Brownells 355 silver solder.

[john.k]

Im surprised Mr BIS didnt explain "spill boring" ....a much cheaper process than buying expensive tooling.BSA used to advertise that every barrel was spill bored up to the bust in 1973.Spill boring also straightens cockeyed bores up to the finished diameter.

[Ballistics in Scotland]

Spill boring is a laborious process, best suited to large bore shotgun bores. A square toolbit was supported by a hardwood spill, shaped to match the opposite side of the bore, and separated from it by an increasing number or thickness of paper shims.

Nobody has mentioned adjustable reamers, and rightly so if used as designed. They have the advantage of a reduced shank which can conveniently be soldered, pinned or epoxied into a long tube, but they are unloveable things, extremely inclined to chatter or produce slightly star-shaped holes. What could be done with one, however, is to use it with one blade in the manner of spill-boring, and a brass shim attached to either the reamer or the tube. The blade could even be bevelled at its front end to produce your choice of choke.

Another thought though, if you just want a cylinder bore, is that I have made good bullet sizing dies with two drills. The first is just a conventional twist drill, followed by one just a few thousandths larger, with the corners rounded off with oilstones.

[john.k]

Every 577,45, and 303 barrel made at the Enfield factory was spill bored ,excepting a few experimentals,up until 1940.Millions.BSA centrefire barrels were always advertised as spill bored,claimed to be an important factor in accuracy......The square cutter has one sharp edge and one curved "burnishing" edge,producing the mirror finish......The British makers claimed the Pratt and Whitney method of fixed reamers tore the metal and opened cracks in the surface.