Drilling deep?

I have set aside a few pieces of wood that might be pleasing rifle stocks.

Currently, the AR-15/ LR-308 style rifles are catching my interest.

I would like to drill those "Lo-o-o-ng" holes for the A2 stock and receiver extension.

I could see the work going well on a metal working lathe with the stock blank mounted on the carriage.

I'm reluctant to run that much wood on any of my machines, but I suppose a well designed vacuum system would cover the concerns.

My thinking is that the "stock" would be shaped around the drilling. not the opposite.

Suggestions? Suitable tooling? I'm assuming a bell hangers auger is NOT the correct choice, but I could be wrong. ;-)

There is a tool called a lamp auger. It is used in conjunction with a wood lathe having a hollow tailstock spindle. As the name implies it is used for drilling through a lamp base. Check the catalogs for woodworking supplies. The auger will not notice the difference between a lamp and a gunstock.

Illinoyance said:

There is a tool called a lamp auger. It is used in conjunction with a wood lathe having a hollow tailstock spindle. As the name implies it is used for drilling through a lamp base. Check the catalogs for woodworking supplies. The auger will not notice the difference between a lamp and a gunstock.

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I'm quite certain that a lamp auger and a bell hanger's auger are interchangeable.

Thank-you for the response, non the less.!

I have had to drill deep long holes in wood before and a hole saw worked well. You have to drill in sections and use a bar the same diameter as the drill bit, once the saw bottoms out just retract it put the bar into the centre hole and rock it to break out the plug remove the plug and repeat. I used a socket on an extension to drive the hole saw deeper into the wood than the spindle on the hole saw would normally allow.

What diameter hole? How "Lo-o-o-ng"? With the grain or across it? What wood?

If someone asked such a vague question on the General forum, they'd be excoriated. We need more info too to be or real use.

richard newman said:

What diameter hole? How "Lo-o-o-ng"? With the grain or across it? What wood?

If someone asked such a vague question on the General forum, they'd be excoriated. We need more info too to be or real use.

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Please forgive me.
I was thinking of first posting this in the gunsmithing forum where the arrangement and configuration would be familiar to most. Then I changed threads thinking to pull from the wood workers alternate views.

The hole is very near inch diameter, Length (depth) is 10 inches.

The hole goes end grain all the way. A close fitting, but not tight, metal tube goes in the hole. This tube is a "standard" item. The hole needs to fit the tube, not the other way round.
There is a tight tolerance relationship between the bottom of the hole, and the surface plane at the start or the hole. Vis. depth to a square bottom.

I've set aside blanks of figured maple and cherry. Call it "North American hardwoods"

The near sized blank would be roughly 12" X 6" X 2".

Agree with Richard.

Guys on pool cue forums use gun drills with high pressure air instead of hydraulic fluid. Probably around the same length x diameter you are looking at, for a long forearm or butt blank. Then again, some cue makers drill + taper bore so they can get the core in close before the glue seizes up, if they are not using epoxy.

If you can make the forearm with a top and bottom, I have built tools (large router bit) for a guy who was in-letting competition match barrels. But in his opinion the barrels should not be bedded much past the receiver. This was a good 30+ years ago and i didn't have an opinion.

Is the hole in your project a bearing, or a "non-influencing" fit? Is it tapered?

smt

Edited: we were both typing at the same time.

1.) your hole is short and fat for the pool cue guys, shouldn't be a problem. I actually do similar length, smaller D with regular twist drills so long as it is in the lathe with the blank turning. I use a regular grind, but probably flatter tip profile. (sorry, never measure, just ground until "that looks about right)
2.0 You definitely need to drill the hole undersize, let the blank kick around the shop including maybe some moderate window exposure time, and let it relax before doing the final bore.

Let me see if i can dig up a picture later....

Cal - this might not be the best example but it shows a few considerations to deep drilling end-wise in wood.

I've done this often enough, but not often enough to be confident saying whether a sheet-metal type point. or a shallow angle std point works better. The idea is to let the bit cut - they tend to diverge in wood because of the varying grain all around the hole, as well as the possibility that the wood may start to warp from released stress as it is drilled. If it becomes clear the bit is diverging, it may be necessary to go up a step in size.

I try to drill the first hole a bit undersize, but not a tiny little one. You want to take advantage of the most stiffness possible rather than start a small hole (as in metal) that in wood may simply cause the bit to wander, and then be practically un-recoverable.

I do c-drill with the largest possible, and them use a taper shank drill if one is close for the first size, to get the most (presumed, lol) stiffness, short overhang, and concentricity. As with metal, it is best to indicate the TS in before starting

https://www.practicalmachinist.com/vb/images/attach/jpg.gif

Then i add an extension to either the same size silver-deming (reduced shank) drill or one that is slightly larger.

https://www.practicalmachinist.com/vb/images/attach/jpg.gif

https://www.practicalmachinist.com/vb/images/attach/jpg.gif

This is actually an unfinished desk leg, so the bore was only 7" deep x 7/8" dia. but from that point i would have been relatively confident to go "a good bit" deeper.

As can be seen, the blank needs to have a nose turned on it for a ring for the steady, or else a steady with BB contacts Use a 4 jaw at the driver end to dial it in parallel to the bed ways.

Or there is the gun drill solution as the pool cue guys use.

One other point - when setting up to do this on an un-replaceable part, i make at least one blank in a similar grain common shape to prove every step. Centering, cutting the nose, drilling, all of it. Or, if it works in ash which is pretty cheap these days, it will probably work in anything. Walnut and cherry should be a lot easier, ime.

smt

CalG said:

I'm quite certain that a lamp auger and a bell hanger's auger are interchangeable.

Thank-you for the response, non the less.!

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Not so. A lamp auger is a spoon bit while a bell hanger's auger is a twist drill on a long flexible shank plus a cross hole in the web for attaching wire to pull it back through the hole.

Illinoyance said:

Not so. A lamp auger is a spoon bit while a bell hanger's auger is a twist drill on a long flexible shank plus a cross hole in the web for attaching wire to pull it back through the hole.

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Which of those defining features do you fell would be most advantageous to the application of this topic?

Note: I did not write the two augers were the same tool, but rather they might be interchangeable in the application of drilling a rifle butt stock.

Any chance a hex-shank Forstner bit with an extension would work? Just throwing that out. I have used Forstner bits some, but not with an extension.

JLarsson said:

Any chance a hex-shank Forstner bit with an extension would work? Just throwing that out. I have used Forstner bits some, but not with an extension.

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That will likely be my first effort.

In the drill press, stock clamped to the table tilted 90 degrees (vertical)

A simple guide mandril that will allow repositioning the stock in order to achieve the required depth. A fence may be enough.

Flat bottom hole, with a small pilot. Two strong pluses!
I can see producing the extension in such a way as to include an air blast pipe of some type. Chip evacuation at the bottom of the hole may be an issue.

That sounds like a good approach Cal. I'd probably use a round shank rather than hex, and make as sturdy an extension as possible. And the air blast will really help when you get deep. You won't be able to retract the bit far enuf to clear chips, so blowing them out as you go is important.

Another possibility is a spade bit. They are cheap, but surprisingly effective. Plus its easy to adjust the diameter by filing or grinding. But you have to take the entire cut at once, can't go in steps.

If you have to have a really accurate hole, I'd be tempted to drill undersize as Stephen recommends and use a boring bar for a final cut.

The fact that a twist drill will initially be guided by it's perimeter can be either a plus or a minus for drilling wood. The wood may warp as it is drilled, causing the constricted bit to diverge. In a lathe situation, the forces cause a bit to cut to center, sometimes dramatically in metal, say when using a non-completely-centered or worn (drooping) TS. The bit can readily be seen to bend, retracting in and out of the hole. It makes a bellmouth, but tends to keep tracking fairly straight until the bit breaks. In an un-centered situation with wood, the forces initially tend to push it to center, but after a period, the stiffness of the bit compared to the material starts it whittling the weakest area of grain and then it diverges and keeps getting worse.

A Forstner will go the direction it is aimed. Including around curves if aimed that way by hand. So if the set up includes a very good fixturing & aiming system, and a very good concentric extension, it should work well.

Whatever method you use, wood moves as it is cut & areas of stress are relieved. You have the advantage of (I presume) air-dried blanks? which tend to be low stress compared to kiln dried. You mention drilling the hole and building the stock around that geometry. I agree. So long as you understand that some highly figured blanks may well still move as they are carved. Especially when most of the carving is off one side of the larger piece of wood. I hesitate to say this because for some reason, a lot of people who are not sure what they are doing have very good luck, at least the first time. Those of us who "supposedly know what we are doing" can't cheat even a little bit, or every gremlin in the book creeps out. But you may find that if you drill the hole to size, and if it is a close fit, after you carve the stock, the hole may have warped. Or maybe not.

If you air dryed the blank yourself, and if the MC is higher than 10% when machined, it may warp some as it dries or after the completed rifle is kept in heated living space for a full set of seasons. This is part of the reason some guys who prefer traditional wood stocks for competition, believe the wood should never touch most of the barrel. The other reason is differential heating causing the barrel to diverge as it warms up and heat is rejected faster from one side than another. "Sounds good" but I'm not knowledgeable enough on shooting sports in general to have much opinion on that part of the equation.

I just gave a kid a 2 x 6 x 21" long blank of aluminum for a similar app, this past spring. I gather he's trying to do a more "militarized" version or whatever is cool with kids these days. Reminds me i should check in if he has made any progress.

smt

Can you clamp the stock to a mill or mortiser table, drill the first inch or so with a forstner, then come back with increasing lengths of drill bit? A 6" long 1" diameter bit is going to be pretty stiff, and starting the hole square is going to be the deciding factor.
When drilling really deep hole in wood, 2-5' like for a propshaft, the boatbuilders would use a barefoot ships auger- no spurs, no point, just a flat cutting edge- supposedly it kept the drill from being led by odd grain. not sure I would recommend it but worth a thought.