Large wood / steel hs drill bit with small shank?

[T i m]

Hi folks,

I'm trying to make a special drill for drilling out the stump of a 9" sq wooden gate post but want to leave the surrounding concrete intact.

The idea is to drill enough 'joined' holes across it to be able to pull the two chunks out using screw eyes (chain and coachbolt) on some scaffold pipe, car jack etc (Ideas from this list and thanks )

So, I bought a cheap (1 pound. market) SDS 14mm drill that I can use for the SDS part, drill / mig that into some tube (or bar counter bored on the lathe) and then connected to a large (25mm) wood / steel drill bit? (cheap from a boot sale?).

But, because it would be difficult to hold the business end of a drill in the lathe to turn the shank down (or counter bore) for my extension tube / rod system I think I need to find something big but with a small shank ready to go ..?

I nearly bought a cheap (39 quid?) set of such drills recently, going from about 12mm up to 30mm or so but all with 12mm plain shanks but I wouldn't want to risk ruining such a bit (and the set) on this job?

So, any ideas please? (links prices etc?)

All the best ..

T i m

(Someone kindly suggested 'sharpening' a masonry bit but looking at it's design I'm not sure it would work very well through 4.5m (9 holes x .5m deep) of 'good' wood?)

[Cicero]

============== Have you considered a wood auger bit? They come in quite large sizes but even the large sizes have a small shank (about 9mm).

The expensive drill set you describe is probably a set of blacksmith's drills and they're very expensive.

Cic.

[Ian Stirling]

Why not? Looking at one, if you take a fair bit off the top, to leave a

90 degree cutting edge, with some relief, then it will cut fine, though perhaps not as fast as a proper bit. Cutting away a large portion of the bit support that the carbide is soldered into to enhance chip removal would be a good idea. Alternatively, a simple auger worked very well for this sort of thing. If I could have welded it on a long shaft, it'd have been ideal. (it was around 1")

[Dave Liquorice]

As the OP wants joined holes I think an auger bit is the only sensible approach. Any "ordinary" drill is just going to wander into the adjacent hole very quickly. Even so I doubt an auger bit will keep true for 1/2 a meter...

As to the initial problem, interesting. I think I'd end up with a brute force and ignorance approach of some sort, involving lump hammers and long sharpened bits of steel bar to split and break up the timber. Rather than trying to drill accurate 18" deep holes...

[T i m]

Yes I have .. but I was hoping for something fast and these need cranking with a hand brace don't they Cic?

They might if been .. as I said they were about 39 quid (for a set of maybe 7?) and I was going to get them for getting the bulk of material out when boring something on the lathe (press tools etc)?

All the best ..

T i m

[T i m]

That was my thought Ian .. ;-(

I *do* have a 1m long 25mm SDS bit but I didn't really want to muller it just for this job when for similar money I could (possibly) make something more suitable?

Are you talking 'hand brace' here Ian? Well that *is* a thought, would be easy to extend and would be quiet in use but I don't fancy plugging through 4.5m of even softish tannalised timber by hand if I can help it?

Maybe I'll get one of those wood chewing things for the angle grinder, lock it on, throw it into the hole and run away! ;-)

All the best ..

T i m

[donny]

Call me a pyro but I'd try burning it out.

Donny.

[T i m]

The 'idea' here Dave would to drill pilot holes (say 12mm) with a long extension so that I can get the fairly upright and at say 60mm centres. Once they start to go there shouldn't be much to send them astray. If I then follow up with the 25mm 'superdrill' that should follow the the pilot holes and then some rabid diagonal drilling after that to eat away the 'bridges' ?

Even so I doubt an auger bit will keep

I fell a hand cranked bit is less 'easy' to keep vertical than an electric one? I could ecen set one of those caravan 2 direction levels on the back of my SDS drill to keep it steady all the way down. If thay can join two tunnels half was across the channel, *I* should be able to keep a .5 m run straight (ish) shouldn't I?

I used that approach the last time I did the same to the other post Dave. Just didn't fancy spending any more time than necessary laying on the pavement with my hand down a hole up to my shoulder like some old gold prospector ;-)

The other 'problem' here is *I* set these posts originally (some 26 years ago) and I remember exactly deep they are and how much concrete is around them. (*my* fences have all survived the same storms that sent everyone elses 6' panels flying down the road .. just the rot thing that has let me down ..)

My *dream* is to walk out there with my large tool (titter ) and have the old post out cleany and in double quick time. To that end I don't mind spending time and (some) money making (if needed) a tool (or tools) to help me do so?

All the best

T i m

[Ian Stirling]

Maybe. I too have a 1m long 25mm SDS bit, but probably don't treasure it as much, as it only cost me ten quid.

Actually, not.

Mains 600W drill, worked fine. If it was longer, it'd have been a lot easier, as I ran into problems with it hitting the sides of the hole. An adaptor for the much slower turning more rugged SDS drill would be just about ideal. You do of course have to beware of hitting the concrete at an oblique angle. Hitting a flat end, or hitting a side at a very shallow angle doesn't do too much damage.

Those are fun. I needed to abrade off the gel-coat from a fiberglass pond, and it made the job almost trivial, providing a really nice key all over. (the existing gel-coat was flaking) At least a hundred times faster than a wire brush in a drill.

[Ian Stirling]

It won't. If you can get a long enough drill, it reduces to more or less making it swiss cheese, then hitting it with a sledgehammer/drift, and picking bits out.

[T i m]

Hi Donny the 'Pyro' ;-)

This was put forward as an option to a similar question I asked recently (same problem, different 'angle'), but:

It's right on the public footpath

It's quite deep

I don't know how it would 'breathe' (so probably go out without blower asistance). Maybe if I got some sort of thermal lance fitting for my BOC Portapak I could take the bottles back empty!) ;-)

It's probably 'damp' ;-(

I think I tried it last time and it was very slow ..? ;-(

I don't want to crack the surrounding concrete (I want to refit a smaller steel post)

I may well have missed a technique on any of the above (I've thought of Semtex) though?

All the best ..

T i m

[BigWallop]

Have you thought about sharpening the end of a piece of threaded rod ? The rod comes in all sizes and sharpening the end into a point and cutting a couple of straight slots for few inches up the length would give you a cutting point that could be drilled in and pulled out a few inches at a time.

I think I saw some on the Screwfix website that is 1mtr long X M10 and was 94p a length. B&Q also stock it at roughly the same price or not much more.

[T i m]

My set of 3 were only 15 quid but I visualise a more 'suitable' home made tool only costing a fiver (my time is free) and would probably do a better / quicker job?

So one of the spiral wood augers with the tip like a woodscrew and the vertical cutting blades either side of the lifting edges? On an electric drill? Surely if that 'bit' it would attempt to drill down at a fair rate, even with a drill set on 'low / slow'?

Well that was the thought re the SDS .. slower / torquier, HS bit (tough / designed for speed and easy to sharpen) and l o n g extension so I could possibly work standing up and save my old knees / back ?

Sure .

I bet! I have used those angle grinder wirse brushes with the 'bristles' made of what looks like 3 twists of coathanger ... nasy bit of kit but pretty effective on rust ;-) You just don't want it catching your sweatshirt or finding the hole in your jeans .. ;-(

All the best ..

T i m

[Ian Stirling]

It does. It is controllable though.

Combined with a slow, high torque SDS drill, I think it'd be a good match.

I think I would avoid working standing up if I could. Poorer control. Get a nice thick kneeling mat.

Wire brushes at high speed are NASTY. Somehow the sharp end of any falling out bristles lands in exposed flesh at high speed. The carbide grit disks are much kinder and gentler, though not a good idea on metal.

:)

[T i m]

Hmm, that's a new idea, like a very long starter 'tap' ;-) I do have various lengths / diameters of 'studding' in the workshop ... ;-) I'm not sure how well it would 'clear' though but I can see the idea (I was probably going to have Henry working in there as well) might work. I would imagine this would be very good for breaking up nearly rotten timber but if this one is like the last one I did it will be clean solid timber about 1" under the rotten end?

As you say .. pretty cheap experiment in any case ..?

All the best ..

T i m

[T i m]

I think mine were the same as the eBay ones but were from the Friday market at the top of the road so no carrage ;-)

Fair enough ..

I only have one (well two actually) of the cheapo SDS's (1 from Argos

19.95, the other from Makro, 14.99 + Vat) and am not quite sure how slow slow is (or even that it has more than one speed?)

And get a smack in the gob when it jams ;-) (I get your direction though)

Of even non exposed flesh .. I found they go straight through a sweatshirt sleeve!

All the best ..

T i m

[Dave Liquorice]

I doubt it but your plan with pilot holes will certainly help.

[T i m]

Hi all,

It's funny what comes to you in your sleep ;-)

I was trying to think how I could put a small(er) shank on a large hs twist drill for my project (assuming I can't buy one ready to go) and how to hold it in the lathe ..

Just thought .. if I hold the plain shank in the 3 jaw, turn a section down from the chuck towards the tip of the drill then saw the section that was in the chuck off afterwards? The only way this wouldn't work is if it's got a morse taper rather than a parallel shank?

With that attached to my SDS fitting via a .5m length of tube / bar (bored) and the ends tacked in with the MIG I should have a high speed, reasonably tough, true, re-sharpenable post stub drill ;-)

Now, when's the nearest boot sale for a large, cheap drill bit .. ;-)

All the best ..

T i m

[Tony Williams]

Bizarre sideways thought.....

Could the stump be pumped out hydraulically, or at least freed enough for a straight lift?

Drill one hole down the centre, about an inch dia, and right through the bottom. Fill the hole with water until it will take no more. 1 inch steel bar as the piston, and a sledgehammer.

[T i m]

Hi Tony,

Sideways yes, bizarre, possibly not!

I was considering a 'straight lift' one I'd given some of the wood somewhere to go. (ie, create a 'gap' across the middle by chain drilling. collapse one side onto the other (creating some 'space), extract chunks using screw eye (coach bolt) on long lever (scaffold pole) over hole?)

I like it! ..

Only reservations (ever the pessimist)

I can't remember how 'sound' the bottom of the hole is and therefore it might

1) blow the 'bottom' of the hole *if* it is intact.

2) Simply force the water down / sideways into the surrounding ground.

I assume of the piston 'stroke' can be made long enough (depending on how much energy you can apply to the 'piston') the effort would still be applied to the bottom of the post by a huge ratio even with some 'losses?

Post = 9" x 9" = 81 sq inches. Assume piston 1 sq" = 80:1 mechanical advantage. If this was backed up with some vertical 'pre-load' (scaffold pole tension lever from above ..) Hmmmm ;-)

The other neg might be the post being soaked my swell up and jam itself back in the hole?

Brilliant idea though!

All the best ..

T i m