Using a demolition breaker

From DIYinfo.org

1 Demolition Breaker, Electric Jack Hammer
2 Safety
3 Types of Bits
4 Freeing a Stuck Bit
5 General Use
6 Author

[edit] Demolition Breaker, Electric Jack Hammer

Quite often in renovation work I need to break up a section of old concrete, or dig some hard ground. The tool I use is my electric jack hammer. The title says "demolition breaker" and that's the correct name, but most people I know use the term jack hammer.

Above is a shot of a Makita Demolitions Breaker. It draws 1300W and weighs about 19 kilo with a point in it. Not the sort of thing the average home renovator would buy, but definitely a hire tool that can save a lot of hard work.

[edit] Safety

Wear your safety gear when using these tools. Minimum of-

Good boots.
Gloves.
Ear protection.

Depending on the material you are digging - breaking,

Eye protection from flying chips.
Dust masks, especially with concrete in a confined place.
Stout clothing is always a good idea for this sort of work.

It is a real pain wearing all this safety gear, and many times I see guys working without it because it is more comfortable that way. Don't do it. Apart from the obvious benefit of saving you from serious injury, safety gear saves you from heaps of minor irritations during the working day.

I know from personal experience that if I don't wear my ear muffs, or ear plugs when using a noisy machine, I will feel far more tired at the end of the day, and probably have a headache as well. Nothing to do with the work, just the noise. (I also know that the main reason I have to wear headphones listening to music now at age 65 is mainly because I didn't bother at age 25.)

[edit] Types of Bits

The breaker at the right is as big as they go, it uses standard air tool bits that are 1 1/4" dia.
The Makita above uses standard 1" dia. bits.
The standard non proprietary bits, must save the hire companies a lot of cash.
You can get point bits, used for hard concrete and rock.
Chisel bits, used again for hard concrete and rock, but tend to promote splitting is some materials, allowing you to break off larger pieces.
Spade bits are wider and are used for softer materials, in fact the larger ones with a curved face are often called clay spades.
If you are hiring one ALWAYS get at least one spare bit. When breaking up concrete I like to get two points and a chisel.
Make sure the bits are sharp. They don't wear down quickly, but the do get gradually more inefficient as they wear.

[edit] Freeing a Stuck Bit

Lets say that you are breaking up some concrete and you make a common first timers mistake of trying to break off too big a lump. You rattle away for 5 minutes. Nothing happens except that you have the bit jammed rock solid.

So you turn the release pin.
lift the machine off the embedded bit.
Put in your spare one.
Then proceed to break up the concrete around your stuck bit, freeing it.
No sweat. Easy as pie.

[edit] General Use

These machine work hard so try to help them by following these pointers.

Try to get power from a 15 amp outlet.
Use a good 15 amp lead.
Use the shortest lead possible.
Break up and clean up as you go along. It gives the machine a rest now and again and a clean work area is a safer work area.

If you are starting to break up a section of concrete or dig a hole in rock, be aware that it is always easier to split of a bit at an edge. If it is very hard, do only a small bit at a time, until you create an edge.

If you are starting off in the middle of a slab, chip away breaking out small bits in a small area. What you are trying to do is get through to the earth below. This is the hard bit. When you have got through, It will get a lot easier. Always split into the hole and work back from it.

Most people when first using a jack hammer only do half a job. The illustration below shows a slab of concrete about to be broken up.

In example "A" the operator has given it a rattle close to the edge and split a lump of concrete off. Good so far, then the novice usually pulls the bit out and splits a bit more off close by. I've seen large areas done like this and then the guys start struggling with a pick and shovel to get it out of the ground

What you should do after each bite is use the jack hammer as a crow bar to lever up and loosen the concrete (or rock or clay etc.) as in sketch "B". This makes it a lot easier to shovel out of the way.

This levering the broken stuff up also makes it easier to get at any mesh or reo bar in there. Cut your reo with bolt cutters, or maybe an angle grinder with a cutting disk in it.

I am right handed so I tend to favour that side, so if I have broken out a chunk and then want to move over a bit, I lean into the machine with my right hip and thigh and I push the weight of the machine about with the top of my thigh, taking the weight partly off my hands arms and shoulders.

Working with these machines is a bit like article writing. "It's a tough job but somebody's gotta do it".