Barrel Reamers - home edition

[H Wally]

Wondering what you guys would recommend for a home barrel reamer.

The idea is to make a smooth bore barrel blank by taking a machined steel shaft with a .25 caliber diameter hole bored down the center and bore it out to .40 or .50+ diameter. The goal is to be able to follow this pre-existing hole and ream it out without having the bit wander.

I do not have a lathe or mill to run the reamer, but I can deal with that easily.

What I would like opinions on are what would you use for a reamer? Having the .25 hole already bored will allow me to use a pilot, but I don't have any experience with reamers of any sort. Once I have a game plan I am certain I'll be able to make it though.

I have several ideas.

1) Spade bit style. Instead of the spike in the middle a 0.24 diameter diameter pilot would be soldered or fixed to the end of the cutting bit to guide the cutter down the hole, and progressively larger bits would be used.

2) Carbides: With a steel rod, fit carbide cutting teeth into the rod in a recessed section around the rod. Again, use progressively larger bits.

3) Regular metal bits. Problem is that they cut not only on the face, but down the shaft and could potentially wander, since I don't see how I could put a pilot on it.



Is there a style of already existing reamer that could do this job?

 

[tiriaq]

This is the sort of operation done on muzzleloading barrels, using rather basic tools. There are various books describing the process.
A piloted twist drill can be used, followed by a reamer to clean up the marks left by the drill. Lapping would be the last step.
If you have a look at Brownells, you can see the piloted drills which they sell to open out barrels for liners.
A pilot could be ground on a drill bit, and the cutting edges properly sharpened. A tool post grinder could be used in a lathe. The drill would need an extension.
I would not be surprised if a company like PT&G could not supply tools like these.

 

[H Wally]

True enough, I'm just thinking I might be able to pick stuff up locally or adapt what I can find. I like tinkering like that. Though the brownells bits look good, they're out of my budget for this project. I don't even know if it's going to work.

I hadn't thought of just grinding a pilot onto a drill bit. Don't really know why, just getting over complicated I guess. I'll probably try that route.

 

[BCRider]

You're after the wrong tooling. Reamers classically are only to remove the last thou or less to achieve a dead on size and roundness. They aren't intended to remove that much metal.

You're on the better track with grinding a pilot ont an existing bit. But this isn't a hand tool type of job. You're after a toolpost grinder or something similar mounted in something that will spin that drill bit dead on centered to ensure that the pilot is dead on center to within a tenth or two. That's pretty serious stuff.

If you're setting up tool post grinder to do such a piloting job then you may as well start with a drill bit that is slightly over size and trim down the OD of the drill with the grinder as well as form the pilot all in one setup. That way you ensure that the pilot and the drill bit diameter are as dead on centered as the play in the lathe headstock allows. In other words unless the lathe is in rough shape it'll be superb.

 

[MiltonBradly]

I'd be curious how it might turn out If you just tried a conventional drill bit in the desired size run through the pre-pilot drilled blank. What length of barrel are you aiming for?

It's a shame you're on the wrong side of the country... I've wanted to have a go at making my own blank in much the same manner and then try to do some cut rifling for a ~.36 cal flintlock carbine. I'd let you use my mini lathe to play on if the drive wasn't so far

MB

 

[iconfig]

what you are looking for is appropriately called a gun drill

 

[CanAm]

You may want to read some books or info on gunsmiths such as HM Pope and others who did gun drilling in primitive environs, especially during the 19th century.

 

[mooncoon]

my vote would be for a series of piloted twist drills. Basically go from 1/4" to 5/16 then 5/16 to 3/8. I think trying to drill in in one pass would be excessively slow and I think you want to advance relatively quickly to minimize drift. Silver solder a mild steel extension shaft on each of the pilot drills using V blocks but ideally the shaft should be smaller in diameter than the drill to reduce friction and that would be difficult setting up without a lathe to make bushings etc for the set up. Finally I think you need guides outside the barrel to keep the drill in a straight line on the outside as well as on the inside

cheers mooncoon

 

[Randy B]

what you are looking for is appropriately called a gun drill

Gun drills are no good if you have a hole there already, they are designed to make the hole not enlarge an existing hole. You will need a piloted drill or a series of reamers to bring you up to size. Best to use a piloted drill that leaves a good finish and about .005 then ream to finish or start with a solid blank and a gun drill that leaves the same.005 and ream to finish. More chance to have a good size bore and nice finish with a gun drill.

 

[H Wally]

You may want to read some books or info on gunsmiths such as HM Pope and others who did gun drilling in primitive environs, especially during the 19th century.

Funny you should say that. I was doing just that a few weeks ago and found this:

http://www.flintriflesmith.com/ToolsandTechniques/barrel_making.htm

Specifically, rough boring bits, which are forged sharpened rectangular tapered HC steel, then twisted. They are spun opposite to a regular bit to push chips forward rather than pull them back.

And the reamer. It cuts on the two exposed squared edges, and paper is slipped between the wood and the reamer bit to increase diameter the reamer cuts to:

my vote would be for a series of piloted twist drills. Basically go from 1/4" to 5/16 then 5/16 to 3/8. I think trying to drill in in one pass would be excessively slow and I think you want to advance relatively quickly to minimize drift. Silver solder a mild steel extension shaft on each of the pilot drills using V blocks but ideally the shaft should be smaller in diameter than the drill to reduce friction and that would be difficult setting up without a lathe to make bushings etc for the set up. Finally I think you need guides outside the barrel to keep the drill in a straight line on the outside as well as on the inside

cheers mooncoon

I'm with you on that. As for having a smaller diameter shaft for the drill bit, initially I'm going to just have to clean the bore out regularly, but as the bits get bigger I have some stepped bits that I can just use the V block for (leave the larger diameter end of the bit hanging over the end of the vblock)

I honestly don't expect anything all that useable out of this project, but it gives me somewhere to start. I figure I can learn all the steps and pitfalls that would be common to forged barrels without introducing welding and hammering complications and work my way back.

 

[none]

Wouldn't a half inch diameter unibit or step bit self center itself in the original hole and would you pull it through or push?

 

[guntech]

If you already have a straight hole through the material, I would suggest a removable pilot tool from PT & G designed to do exactly what you want to do... I bought one for doing liners and it works so much better than a piloted twist drill which I used for years. If it is not guided by a pilot, it will wander...

talk to PT & G and explain what you want to do... http://www.pacifictoolandgauge.com/products/reamers/bore.htm

 

[fiscus]

How deep is your hole? I have successfully modified regular drill bits to piloted with a dremel, just by grinding the lip down flush with the body of the drill. Depending on the brand of drill it can be a few thousandths or .020". I found that if the pilot was tight in the existing hole it is better to leave a sharp cutting edge on the pilot. So you need a to modify a lot of drills to get a lot of material out, but it is very easy and doesn't take special equipment to modify this way, you just need to find a cheap set of drills. I found it was not too much trouble to just turn the drill with a pair of vice grips and push with the tiny cut it takes.

 

[mooncoon]

I'm with you on that. As for having a smaller diameter shaft for the drill bit, initially I'm going to just have to clean the bore out regularly,complications

I think you misunderstand my concern. You want to remove the bit and clean the chips every 1/4" or so, once the bit is completely inside the hole. Otherwise the chips build up within the drill flutes and jam the drill. The reason for the slightly reduced drill shaft is to prevent rubbing on the sides of the hole you are drilling. If the drill shaft is full diameter for its full length, it would not take much of a chip to bind it

Those bits with the reverse twist I doubt would drill worth a damn and particularly with the 1/4" beginning, you would end up with a jammed drill in no time. The square bit is more of a finishing reamer/burnisher than a drill.

cheers mooncoon

 

[H Wally]

Wouldn't a half inch diameter unibit or step bit self center itself in the original hole and would you pull it through or push?

Hmmm.. Might. Though there is still a cutting edge on a self centering bit that could interfere... unless I'm missing something again, which I am prone to.

If you already have a straight hole through the material, I would suggest a removable pilot tool from PT & G designed to do exactly what you want to do... I bought one for doing liners and it works so much better than a piloted twist drill which I used for years. If it is not guided by a pilot, it will wander...

talk to PT & G and explain what you want to do... http://www.pacifictoolandgauge.com/products/reamers/bore.htm

Hmm. That's a good thing to know about - thanks! Actually, might be perfect, if a little expensive.

How deep is your hole? I have successfully modified regular drill bits to piloted with a dremel, just by grinding the lip down flush with the body of the drill. Depending on the brand of drill it can be a few thousandths or .020". I found that if the pilot was tight in the existing hole it is better to leave a sharp cutting edge on the pilot. So you need a to modify a lot of drills to get a lot of material out, but it is very easy and doesn't take special equipment to modify this way, you just need to find a cheap set of drills. I found it was not too much trouble to just turn the drill with a pair of vice grips and push with the tiny cut it takes.

Final goal is to have a short rifle barrel, so 18.5 inches minimum. Initial hole is slightly oval, and lots of material needs to be removed. I'm going to give it a go in the next month or so with basic tools to see what I can do. If a halfway decent result occurs and I proof the barrel with no ill results, then it'll be on to slightly more refined attempts. This is mostly just to satisfy my curiosity so I'm not worried if it takes a while. I'll be learning in any event.

I think you misunderstand my concern. You want to remove the bit and clean the chips every 1/4" or so, once the bit is completely inside the hole. Otherwise the chips build up within the drill flutes and jam the drill. The reason for the slightly reduced drill shaft is to prevent rubbing on the sides of the hole you are drilling. If the drill shaft is full diameter for its full length, it would not take much of a chip to bind it

Those bits with the reverse twist I doubt would drill worth a damn and particularly with the 1/4" beginning, you would end up with a jammed drill in no time. The square bit is more of a finishing reamer/burnisher than a drill.

cheers mooncoon

Yep - understood you on having the smaller diameter drill shaft. I'm just really bad at conveying what I'm thinking

The webpage I got the pics of the rough boring bits said they were run in reverse of regular, so they would push the chips ahead of them, and that they had to be cleaned regularly. It is true that they're working from very close to final diameter though, as their barrels are formed on a mandrel, so not really applicable to my use, but interesting nonetheless.

 

[trevj]

I gotta go with guntech on this one as the best choice being a piloted machine reamer on an extension.

A drill with a ground, accurately centered, non-cutting pilot is a close second. This is what the drills sold for installing liners are. Drills modified without the benefit of a tool and cutter grinder are pretty much just plowing more or less random holes down through the material. Which may be adequate for the needs at hand, or not.

For making and using the barrel tools as shown at the flintlock site referenced above, the video Gunsmiths of Colonial Williamsberg (Williamsburg?) is worth watching. The barrel in this video is also welded, but around a rod, spirally, and then they make and use the reamers as well as the square reamer to final size. Seeing the tools made and used, makes their use a lot clearer. Worth tracking down a copy!

Cheers
Trev

 

[Pepperpopper]

That's a great site! Funny though, at one point in the forging sequence he is rounding over in a swage block, price one of those out! Cheaper to make the barrel maker in that two tape set!

 

[ciphery]

You're after the wrong tooling. Reamers classically are only to remove the last thou or less to achieve a dead on size and roundness. They aren't intended to remove that much metal.

You're on the better track with grinding a pilot ont an existing bit. But this isn't a hand tool type of job. You're after a toolpost grinder or something similar mounted in something that will spin that drill bit dead on centered to ensure that the pilot is dead on center to within a tenth or two. That's pretty serious stuff.

If you're setting up tool post grinder to do such a piloting job then you may as well start with a drill bit that is slightly over size and trim down the OD of the drill with the grinder as well as form the pilot all in one setup. That way you ensure that the pilot and the drill bit diameter are as dead on centered as the play in the lathe headstock allows. In other words unless the lathe is in rough shape it'll be superb.

I made my tool post grinder by welding the appropriate size nut to a piece of bar stock, then threading my dremel into the nut and using the bar stock as a tool post in my south bend lathe.this is all a mute point since the webbing is too thin to jump drill sizes properly AND have a pilot of correct size. I suppose that you could make an undersize pilot then make an oversize collar to go on over top of it held on with a grub screw and red loctite or silver soldered then compressed air cooled. Then turn the collar to its final size once the loctite has cured. This will ensure concentricitty with the drill bit. I would not personally reduce the diameter of a drill bit as when this occurs all of the relif is lost and the entire OD of the bit is now scraping the hole being drilled. Also there needs to be adequate fluting to allow for chip removal and coolant/cutting oil to enter. Moreover the angles of the fluting will be changed with OD reduction. If you notice the flutes are shaped in such away so as to not only carry chips backwards out of the hole but keep them from getting caught between th drill and wall of the hole. In either case the drill bit will have to be ground perfectly symmetrical or it will pull.
I would use a virgin drill on a reduced diameter extension with extended fluting and go slowly with lots of coolant forced up from the bottom of the work piece(once a through hole has been established) and a steady rest on the drill to reduce flex. then once I got close to size I would use a piloted drill and finally a reamer and lap.
But that's me.

 

[ciphery]

my vote would be for a series of piloted twist drills. Basically go from 1/4" to 5/16 then 5/16 to 3/8. I think trying to drill in in one pass would be excessively slow and I think you want to advance relatively quickly to minimize drift. Silver solder a mild steel extension shaft on each of the pilot drills using V blocks but ideally the shaft should be smaller in diameter than the drill to reduce friction and that would be difficult setting up without a lathe to make bushings etc for the set up. Finally I think you need guides outside the barrel to keep the drill in a straight line on the outside as well as on the inside

cheers mooncoon

No. Fast advancement will cause more flex in the drill bit especially if you have a mild steel extension which I would liken to trying the feat with a wet noodle.
You are correct in the application of proper drill bit size advancement(I would increase by 8ths until 7/16 then ream to 1/2),use of a lathe and a brace(steady rest) to take flex out of both the barrel and unless the tailstock and its chuck on your lathe is the pass through type, a second steady rest on your drill bit. Silver solder a piece of drill rod in place (tool steel). There's a reason is called drill rod. Also protect the lathe bed with some plywood or leather or what have you when soldering, as molten silver solder and its acidic flux can hurt a lathe bed. Put the extension in the tailstock and the drill in the headstock of the lathe now run the tailstock up until the extension and the shank of the drill lightly touch. Now solder and let cool.
Here's why;
1 you will be working with different diameters (big drill, small extension) a V block works on OD, your lathe works on centre. and the head and tailstock are already in perfect alignment.(Hopefully ) Just try clamping dial indicating, shiming,re-clamping,re-dialindicating, etc. To try and set up V blocks to with in a tenth of a thou!
2 As the solder is applied it will pool slightly on the bottom (gravity) this thicker material will pull more as it cools,also difficult to heat evenly from all sides. The lathe chucks will hold everything in perfect alignment with ample working room. Unless the parts are clamped into the V blocks and the V blocks are clamped down to a stable common base there is going to be movement. The V blocks would also need to be perfectly aligned and adequately shimmed to a base with a straight edge to align in the first place.
3 The head stock of your lathe will act as a heat sink keeping the temper in the bit.

You will also need to cut flute extensions into the shank of the drill to allow the chips a route of escape. Do this after you solder on th extension as the full shank centers better in the chuck for the soldering process.

 

[ciphery]

Reverse twist drills(left hand drills) are used in a gang drill press where every other drill head turns counter to the first head thus the drill is turned "backwards". I accidentally grabbed one off the shelf that had not been put in its proper place once. Let me tell you they don't cut worth a #### when turned clockwise! Lol