Does a flexible auger bit wander?

[rslaback]

I have a piece of old bowling alley that needs to be cross bolted before I put it to use as a table top. I know aircraft extension bits exist but they are pricy. I have a flexible 9/16 x 54" install bit that has a 6" auger on the cutting edge. Do you suppose that you can trust an auger like that to not wander across a 42" piece of material? I know it is risky no matter what I do so I may just go with a metal channel on the bottom but some all thread through the whole thing seems like a better overall solution.

 

[RTM]

If it hits a knot, or wildly varying grain, it may wander. Mine don’t have a center spur, which greatly reduces my faith in them.

 

[cgrutt]

Would something like this work?



Try Lee Valley I bet they have a solution.

 

[RoninB4]

Across 42" one could almost expect some wander unless it has a pilot/bushing of some sort to maintain alignment at regular intervals. What you use to power the auger will also have a great influence as well. Using a drill press will be very different than a hand drill as you're limited by the stroke of the quill length and a hand drill will likely not maintain a constant angle (perpendicularity). Frequent removal of the auger/drill to clear chips out of the hole will be required. The friction encountered at depth will also need to be addressed so you don't bind the auger/drill deep in the hole when it expands from the heat generated.

If cross drilling to fasten all the boards together then the hole is just clearance for a threaded metal rod? What do you plan to power this auger/drill with? I might suggest going 21" from either side to meet in the middle but that may just create a mismatch without proper tooling and a fixturing. Do you have the equipment and skill to re-sharpen the auger/drill? Hard Maple will dictate a re-sharpening more than once, fiberglass will abrade the auger/drill very quickly IIRC.

A simple "yes" would have answered your one question and I've run off at the mouth again so I'll stop here. Your project is doable but likely won't achieve good results by casual methods. I don't know how thick the section is but you have a good chance of breaking out the top/bottom unless you take steps to prevent that happening. JMO

 

[Hakeem]

It’s doable but use a bunch of locking extensions instead. 1/2” auger will definitely leave enough space for the locking barrel to follow, maybe even 7/16”

I’m sure there’s a use for those flexible bit extensions but they’re far too unpredictable for my tastes. I bought one and tried to use it to drill through the top plate from an existing opening in the wall…promptly drilled through the crown moulding

 

[Sinatra]

I would drill a 1/4” pilot hole through first, then follow with your larger bit. You can get a 1/4” x48” bit for under $30. You will need a drill with a lot of torque like a drill press or a Milwaukee Holeshooter. Also will need to continually pull the bit out to clean the hole as you drill. There is nowhere for the chips to escape.

 

[mike93lx]

I can't see how a flexible bit wouldn't wander. Completely wrong bit for the application

 

[gizardlizard]

I’ve built many tops from bowling alley and have always bolted it together on the bottom with angle iron and it doesn’t move. Hopefully yours is from an approach or the first 16 feet of the lane. Everything else down from that toward the pins is soft. You can measure 16 feet down from the line where the ball is released and see the finger joint transition from hardwood to softwood. I would never buy this stuff unless I was able to remove it myself as people will say it’s all hardwood when there is plenty of softwood in part of the lane too. Around here it sells for 5-8 dollars a linear foot.

 

[WillyBoy]

All of the sections of bowling lane that I've worked with were nailed together with hardened nails. Each piece is nailed to the next in a pattern that ensures that you'll hit multiple nails if you're drilling horizontally across the width of the lane.
Cutting a section crossways with a portable circular saw hit several nails. Eventually the blade shed several carbide teeth. That blade is hanging on my wall of "stupid stuff I did", along with broken wrenches and router bits with bent shafts.

 

[RTM]

I’m sure there’s a use for those flexible bit extensions but they’re far too unpredictable for my tastes. I bought one and tried to use it to drill through the top plate from an existing opening in the wall…promptly drilled through the crown moulding

I can't see how a flexible bit wouldn't wander. Completely wrong bit for the application

These guys are right. The flex bits are for drilling thru the occasional fire block or top plate for installing speaker wires, Ethernet cables. Commonly named “bell hanger”s bits were the predecessor, but had a much stiffer shaft, and were slighty guideable. They do make a guide for the flex ones, to try to keep you out of the crown molding, but still not a certainty.

The spade bit with multiple extensions, or a ships auger, might work better, but the nails should be mapped out beforehand to see if you have a fighting chance of not fouling up the tools.

I had forgotten about horror stories from guys who tried this 20 years ago.

 

[Steve_P]

With a drill press, I've drilled thru 4" of wood with a long 1/4"? bit and it wandered. I can't see how it's not going to wander in 42" of hardwood.

 

[no704]

No way to do this. Can you drill each board individually?

 

[PCustoms]

Stupid question, why does the top need a cross bolt?

This post has some crucial information:

All of the sections of bowling lane that I've worked with were nailed together with hardened nails. Each piece is nailed to the next in a pattern that ensures that you'll hit multiple nails if you're drilling horizontally across the width of the lane.
Cutting a section crossways with a portable circular saw hit several nails. Eventually the blade shed several carbide teeth. That blade is hanging on my wall of "stupid stuff I did", along with broken wrenches and router bits with bent shafts.

 

[rslaback]

Some answers. It needs a cross bolt (or something) because of glue joint failures in a few spots. A flexible auger bit has a shaft that flexes but there is essentially a 6" auger bit at the front. It is my understanding that while a traditional twist, forstner or spade bit is pushed into the material, an auger feeds itself. This means that the shaft simply provides rotation which is why it can be flexible. The reduced diameter of the drive shaft section provides clearance for many of the chips and reduces the need for a larger drill due to lateral friction on the bit shank. Driling each board is not realistic. Neither is meeting in the middle. A cross bolt is more cosmetically appealing but I might just slap two or three lengths of shallow unistrut to the bottom of it.

 

[mike93lx]

Some answers. It needs a cross bolt (or something) because of glue joint failures in a few spots. A flexible auger bit has a shaft that flexes but there is essentially a 6" auger bit at the front. It is my understanding that while a traditional twist, forstner or spade bit is pushed into the material, an auger feeds itself. This means that the shaft simply provides rotation which is why it can be flexible. The reduced diameter of the drive shaft section provides clearance for many of the chips and reduces the need for a larger drill due to lateral friction on the bit shank. Driling each board is not realistic. Neither is meeting in the middle. A cross bolt is more cosmetically appealing but I might just slap two or three lengths of shallow unistrut to the bottom of it.

The only reason for the flex shaft on that auger bit is to allow it to be used into a wall cavity. The shelf feeding part is because it will be hard to apply pressure in that situation

If you want it to have a chance of going straight, the shaft needs to be ridgid

 

[RTM]

A flexible auger bit has a shaft that flexes but there is essentially a 6" auger bit at the front. It is my understanding that while a traditional twist, forstner or spade bit is pushed into the material, an auger feeds itself

If you have one of these, I agree, your odds of success go up with the longer straighter body. When I googled Flexible Auger Bit, the first thing that came up was not lead screw equipped (Diablo), which is the style that I think both of mine are. The next three were different flavors of true auger, with lead screw, from long straight bodies (Klein) to short tapered bodies (Greenlee), with an Amazon in the middle.

Again, hope you don't hit a nail.

 

[PCustoms]

Some answers. It needs a cross bolt (or something) because of glue joint failures in a few spots.

Will a bar or pipe clamp close the joints?

Spread them a little, drip some glue in and use a vacuum from the opposite side to pull the glue through. Then clamp it all tight.

If you need extra support I'd recess in a piece of steel on the bottom.

 

[rlitman]

...The reduced diameter of the drive shaft section provides clearance for many of the chips...

No, it doesn't. Drilling horizontally, once the auger flites are buried more than an inch or two, that hole's going to completely clog. If you can somehow contrive a way to drill UP with this, getting gravity to pull the chips out, you'll get a few inches deeper, but even then auger chips are so large that they'll eventually clog the hole without active assistance. There's a reason ship augers are fluted all the way back, but even 36" ship augers only have the capacity to drill a little beyond their 24" of flutes. You're not getting through 42" like that.

And all that's forgetting about staying centered in the wood (NOT happening with something so flexible you have no way to guide it, and even if you could, it would be damned near impossible to stay that straight), and don't hit any nails (also not likely).

For a hole that deep, you could turn the wood on a lathe (that'll guarantee you stay in line) and use a gun bore (these have a port for compressed air to be sent to the tip to force chips out), but that's probably out of your reach tooling wise (and most of us for that matter), plus that still wouldn't react well to the dozens of nails you'll find on the way through.

My suggestion would be to forget this through bolting idea anyway. It's passe. I have an old-school butcher's block in my kitchen, and in the original construction method the maple was assembled with sliding dovetails and then through bolted. Today, they eschew the bolts in favor of glue, all on foot long long-grain joints that are repeatedly subjected to moisture from one end alone (this is a worst case scenario, so if it works for Boos, it's got to work for you too). Bowling lanes are much thinner, so getting sufficient clamping pressure for a good glue-up should even be within the reach of most hobbyists. Half a dozen pipe clamps should provide enough force to close a few inches of gap. Alternate them top-bottom-top-bottom to keep from warping. Titebond III has the thinnest consistency of the Titebond series of wood glues, plus offers the longest working time, so I'd go for that. Use something like a piece of aluminum cut from a soda can to drag glue down (or the vacuum).

And when you're done gluing it, it'll stay together. The metal support underneath isn't to hold the sides together, it's to keep it flat.