Thread: Big Jack Hammers.

I dug a large grease trap (1.5 long x 1 wide x 1.5 deep approx) in basalt with a makita. Short answer it's very hard slow work.

Probably took a week. Short of a bigger jack hammer an excavator with a hammer would be the next thing. Might be better renting one for a day and not spending $3000 on a tool you may not need again.

You a paying for a professional quality tool. If you only need occasional use outside of this job buy a $300 Chinese special.

What's the actual job you are doing.

Have you seen this cheapie?
https://www.bunnings.com.au/full-boa...ammer_p6290254

There's quite a big difference between a demolition hammer and a true jackhammer.
On the worksite I was, for a while, chief demolition man fixing mistakes made by the concrete formworkers.
If the concrete was still a bit green i used a big electric Hilti but when it came to big cured stuff like 1m x 1m concrete beams I used an air powered unit otherwise it took me all day.

The 1700W Kango has a 27 Joule impact energy, the Hilti I was using had more than 50J and I don't know what the air powered one was but it went through reinforced concrete like a hot knife through butter.
The main worry was hitting the 1"+ rebar which fair gave your arms and teeth a rattle.

One problem with air hammers is have you got a compressor big enough to drive it? They start at about 15 CFM and go up quick from there.

Thanks Chris & Bob for the replies. The tools that I've been looking at are the biggest electric hammers from the various manuf's. All around 2kw draw, 30kg weight & quoted at from 62 -73J of output. I suspect there's less difference than similarities between them all.

I agree that $3k is a lot to spend, but have been offered a private "new old stock" example for approx 40% of this price. Since I still have a DeWalt Max combo hammer, it really doesn't make a lot of sense to me to replace the slightly bigger Kango that was nicked with another which is effectively only slightly bigger & more powerful than the DeWalt. Esp. as neither is used "professionally" any more.

I've used air hammers a fair bit in my youth, building a wharf during uni holidays, for patterned quarry blasts, road and bridgeworks as a forester & in the CMF (6RAE). Air hammers are lighter, but tougher to drag, & the punch can be (too) vicious.

Being now somewhat older & hopefully less silly, I use my smaller Max hammers in compacted soils (perfect), for loosening rocks (ok) & breaking rocks (hopeless). With such powerful, heavy tools it makes sense to limit my exposure to short periods only. This unfortunately makes hire less financially viable if it's required several times over an extended period, plus almost all of the purchase price would be offset by my insurance claim.

With several excavation jobs to do over 2 properties, I can foresee much extended but intermittent breaking of all those deep, large 100kg+ basalt & dolerite stones, both too big & too heavy to move manually

Where appropriate a 10t excavator will of course be the preferred alternative for those bigger &/or more accessible tasks.

From what you've stated so far, I gather that an electric hammer of approx 70J energy will be a rather slow but effective breaker. Do you concur?

Originally Posted by Ratbag

From what you've stated so far, I gather that an electric hammer of approx 70J energy will be a rather slow but effective breaker. Do you concur?

Yes.

BTW a $100 pair of gel pad filled leather gloves will save a lot of tingles. I got them for my big old chainsaw and they work a treat. New big Chainsaw has much lower vibe on it but the gloves still help a lot

I wish that sort of stuff was available when I was 17!!!!!!! Probably wouldn't have the start of Arthur itis or hearing loss now.
Kryn

Originally Posted by Ratbag

With several excavation jobs to do over 2 properties, I can foresee much extended but intermittent breaking of all those deep, large 100kg+ basalt & dolerite stones, both too big & too heavy to move manually

From what you've stated so far, I gather that an electric hammer of approx 70J energy will be a rather slow but effective breaker. Do you concur?

Can I suggest that you need to work smarter, not harder?

the "ancients" could break a 100+kg boulder with not much more than a hammer and chisel.
The trick was knowing how. Chisel a groove on one side of the rock, and pound on the opposite side with the hammer. The groove concentrates the internal stress from the hammer blow leading to the rock splitting along the groove.

using current technology, the groove would be cut with a diamond wheel in an angle grinder or demolition saw.
and hammer blows supplied by (possibly) your DeWalt.

another alternative is wedge and feather -- again using the Dewalt (or Ozito) to drill the initial hole

Thanks for the advice. I'm up for any short cuts or work-arounds!

Originally Posted by Ratbag

Thanks for the advice. I'm up for any short cuts or work-arounds!

Well since you asked.

Bluestone.. you will be there until the rest of the year.

Core hole it and blow it if you have access to the good stuff

Then use the digger to remove the loose material, and drill again.

But that might be a bit hard to get these days

There is also the option of renting a stone breaker for the digger, had to listen to them for 4-5 weeks as they dug a basement in a new house few years back. but it did the job, but not cost effective for personal works

Ear protection and something to protect the wrists are a must if going old school with a jack hammer.

Originally Posted by ian

Can I suggest that you need to work smarter, not harder?

the "ancients" could break a 100+kg boulder with not much more than a hammer and chisel.
The trick was knowing how. Chisel a groove on one side of the rock, and pound on the opposite side with the hammer. The groove concentrates the internal stress from the hammer blow leading to the rock splitting along the groove.

using current technology, the groove would be cut with a diamond wheel in an angle grinder or demolition saw.
and hammer blows supplied by (possibly) your DeWalt.

another alternative is wedge and feather -- again using the Dewalt (or Ozito) to drill the initial hole

Good luck getting a boulder to a position where you can access both sides with a saw. Trying to rotate or support very large rocks is a good way to hurt your back or crush your ankle.

I once had a powdermonkey's ticket. But that was most of a lifetime ago. Half a stick of Alfred Nobel's finest, backfilled with an ANFO slurry works a treat. Not, however in such close proximity to my neighbors. In one instance 3 domestic dwellings & in the other a corner store, 2 schools & a hospital.

Much of my work involved "manicuring" large stone in bridge embankments & abutments, & in disposing of large "stags" too rotten & dangerous to fall around the edge of regeneration burns.

Ammonium nitrate is a much "slower" explosive than trinitrotoluene, making it better for heaving & cracking, & not so good for shattering. It was the Nazi's preferred bomb-fill in preference to high explosive. A well-placed 1000 kg ANFO device could render an entire street uninhabitable during the blitz. Recall Tim McVeigh's handiwork in Oklahoma City. That was a seriously big ANFO truck bomb. The allies instead tended to prefer incendiaries (the Nazis used incendiary bomblets too, but less frequently or in such a co-ordinated fashion) to achieve a more sterilising effect on a city-wide scale.

Nevertheless the concussion & possibility of fly-rock despite the use of matting is a risk too far, & not particularly conducive to cordial neighbourly relations.

Even big rocks can be moved & manoeuvred using levers, whereas when lifting the laws of physics (specifically gravity) tend to work against rather than with the operator. Whilst they can be moved within the excavation, they can't be easily removed except in smaller pieces.

Originally Posted by Ratbag

Thanks for the advice. I'm up for any short cuts or work-arounds!

you might find this interesting
http://www.quarryscapes.no/text/publ...factsheet5.pdf