Thread: Nice contract for someone

Originally Posted by Bushmiller

Good thought, but the style of drill is a little different. I think it is more akin to masonry drilling. I feel it involves percussion by means of "down the hole hammers."

Boring holes in the end grain of timber is particularly troublesome. I suspect the only way to do it would be to bore a relatively small pilot hole around 25mm dia and then enlarge it perhaps in stages to 100mm and finally 200mm. This would be done with a fly cutter using first the 25mm hole and then the 100mm hole as a guide.

The biggest hurdle is chip removal, but this could probably be done with either compressed air or vacuum or a combination of both.

Of course you would need a fair sized motor to drive the fly cutters.

Ironically, I think the initial hole would present the most problems with chips or sawdust being the bad guy.

Regards
Paul

Paul

the initial hole "could" be bored with a ships auger, I'm not sure how well it would go into end grain, but it should follow the pith as the line of least resistance.

as to geotech drilling, there's basicly two types
hammering akin to a masonary drill, and
reaming where a cutter is rotated while being pulled through the material

in wood, the reaming "could" be done with either a fluted drill or a saw tooth forsner
in both cases you would need a pilot hole in the order of 1-1/2 inch through which you'd thread a 1" rod -- I'm guessing the size of rod needed to convey the necessary torgue without twisting -- to power the auger

Originally Posted by ian

Paul

the initial hole "could" be bored with a ships auger, I'm not sure how well it would go into end grain, but it should follow the pith as the line of least resistance.

as to geotech drilling, there's basicly two types
hammering akin to a masonary drill, and
reaming where a cutter is rotated while being pulled through the material

in wood, the reaming "could" be done with either a fluted drill or a saw tooth forsner
in both cases you would need a pilot hole in the order of 1-1/2 inch through which you'd thread a 1" rod -- I'm guessing the size of rod needed to convey the necessary torgue without twisting -- to power the auger

Ian

The problem is the end grain and keeping the hole straight over such a distance. Whilst the auger is very happy to pull itself into cross grain, it is equally reluctant to do the same in end grain.

Initially in end grain it will pull in, but as soon as the auger is retracted to clear the flutes it will not bite again. Basically the "thread" has been lost. From that moment the drill has to be pushed. I think it would be quite important to keep the hole central (within, say, 10 to 15mm) and that is hard to do. You are absolutely right that the bit will take the line of least resistance, but as the heart of a log is infrequently concentric, the drill will deviate at the first opportunity.

None of this is insurmountable, but it is a problem.

I have noticed that twist bits in larger sizes don't seem to perform well in timber, but that could certainly be explored further.

The forstner bit has two problems. The main one is the ability to stay straight over distance. It just isn't designed for deep holes. The second is that there is no provision to remove sawdust. This is not a particular problem over a 25mm deep hole, but a big issue over a 2500mm deep hole!

Another issue is the position of the drilling: Horizontal. Gravity wants to exert its influence. In soil drilling mostly it is vertical and gravity helps here. I expect that some geotech drilling is done horizontally, but I am not familiar with that and I presume that absolute accuracy may not be of paramount importance. I think I have heard of bores going off like bananas.

Probably the best way to drill would be vertically upwards, but we are talking about really special machinery, tall workshops and lotsa money. I did hear a report that mercedes cars were doing their drilling operations in this manner, but that is unconfirmed and if they are, few of their engine blocks are 2.5m tall.

I guess we are mostly in agreement on one thing at least. This is not your average, straight forward, easy job.

Regards
Paul

Paul
I have some famliraity with horizontal geotech drilling -- last year we spec'd a job that requires the drillers to stay on line and level -- to within about 200mm over 80m -- as they drill a drill a 50mm pilot hole which will be back reamed to 300mm. The drillers will do it using a steerable drill guided by ground penetrating radar. They have to repeat this about 30 times, but the first hole will be the most difficult.


In terms of your logs, a modified earth auger might be the go, the log of course would need to be constrained in a pit and the torque involved will be something fierce


alternatively, in another thread a method was described where a skilled operator using a modified chain saw could "drill" a deep round hole.
Given that bars as long or longer than your logs exist, step drilling with successively bigger chain saws might be a way forward

Originally Posted by ian

Paul
I have some famliraity with horizontal geotech drilling -- last year we spec'd a job that requires the drillers to stay on line and level -- to within about 200mm over 80m -- as they drill a drill a 50mm pilot hole which will be back reamed to 300mm. The drillers will do it using a steerable drill guided by ground penetrating radar. They have to repeat this about 30 times, but the first hole will be the most difficult.


In terms of your logs, a modified earth auger might be the go, the log of course would need to be constrained in a pit and the torque involved will be something fierce


alternatively, in another thread a method was described where a skilled operator using a modified chain saw could "drill" a deep round hole.
Given that bars as long or longer than your logs exist, step drilling with successively bigger chain saws might be a way forward

Steerable drill sounds interesting. How does that work?

With an auger of any description we are talking big. Big motor, big restraints and huge torque.

Having plunge cut with chainsaws (normally the smallest one I put my hands on) and cut freehand with a 42" bar, using a chainsaw to cut the holes is not something I would relish. I would fight shy of trying one hole that way. I believe the contract is initially for 80 logs with a possibility of more to follow. I not sure too many would be putting their hands up for that one and I have seen some very clever exponents with a chainsaw.

Regards
Paul

Here you go Paul. Directional boring - Wikipedia, the free encyclopedia

Originally Posted by

Here you go Paul. Directional boring - Wikipedia, the free encyclopedia

Thanks .

Regards
Paul