"Boulder blaster" commercial or self made.

[Assembler]

Anyone drill a 3/4" hole first then a larger hole next in the same spot?

 

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[BlasterJ]

Anyone drill a 3/4" hole first then a larger hole next in the same spot?

I have made that work with SDS+ drills and smaller holes. It might work on bigger SDS Max holes, but it definitely won't work with a pneumatic or large gas drill unless you buy an expensive reaming bit.

The problem is that you are only engaging the very tips of the cutting edges and the carbide just can't take all of that force pounding on such a small point of contact.

You can do the opposite - drill, say a 1.5" hole and then make it deeper with a 1.25" drill.

 

[Assembler]

I have made that work with SDS+ drills and smaller holes. It might work on bigger SDS Max holes, but it definitely won't work with a pneumatic or large gas drill unless you buy an expensive reaming bit.

The problem is that you are only engaging the very tips of the cutting edges and the carbide just can't take all of that force pounding on such a small point of contact.

You can do the opposite - drill, say a 1.5" hole and then make it deeper with a 1.25" drill.

Yep that make sense as all of the carbide should be in contact with the rock.

Drilling a 2" hole first then a small 3/4" hole is what I would like to try.

 

[Assembler]

Looks like machining work needs to be done for a boring bar setup for the end of the lathe. I may be able to use different bar stock to fit inside of the lathe end and then weld off of it. Right now it is not high on the list of things to do as a impact mill is.

 

[BlasterJ]

Looks like machining work needs to be done for a boring bar setup for the end of the lathe. I may be able to use different bar stock to fit inside of the lathe end and then weld off of it. Right now it is not high on the list of things to do as a impact mill is.

So one thing to keep in mind is that you don't want your finished device to be possibly considered a "short barreled shotgun" by definition. The commercial unit uses a nail gun blank and the larger cartridge is getting set off by the water pressure effect.

 

[Assembler]

So one thing to keep in mind is that you don't want your finished device to be possibly considered a "short barreled shotgun" by definition. The commercial unit uses a nail gun blank and the larger cartridge is getting set off by the water pressure effect.

Correct no short barrel as the Mossberg barrel is 24" long and the real machining is for a 2" o.d. thick sleeve that is on the outside of the shotgun barrel. There is also machining of the receiver / firing pin assembly. Having a longer barrel equals more effective energy going into the rock due to the fact that far more powder is being burned and not and not going out the barrel.

This will take some time as a fair amount of "Tooling" has to be acquired first......lol.

 

[Assembler]

Found a place that a lot of hobbyist go to for tooling and it is not so scary in fact when you compare to a commercial cannon and the charge loads is a fraction of the costs. Will have to break down and get some tooling first......lol.

I even got motivated enough to go to a estate sale to pick up a quality shot shell re-loader - all metal etc. so I can do 3" shells now.

 

[Assembler]

Still will have to lay out a pattern for the receiver / firing pin.
If the first receiver has some issues may have to machine a second one.

 

[N-Lionberger]

Still will have to lay out a pattern for the receiver / firing pin.
If the first receiver has some issues may have to machine a second one.

So you’re boring out a tube to sleeve a mossberg barrel? If you’re wrong about this it might make a pipe bomb.

 

[Assembler]

So you’re boring out a tube to sleeve a mossberg barrel? If you’re wrong about this it might make a pipe bomb.

This is not for everyone. The shotgun barrel is way to thin by itself.

One needs to look at some math and books about this. The typical shotgun barrel can not take very much pressure as there are a number of stories about shotguns failing due to different issues.

One has to be willing to accurately measure for metal movement / stress. One has to be willing to reload with safety in mind as well. One has to be willing to take a number of precautions in using this as well.

 

[Assembler]

One also needs to start with very light load and work there way to a heaver load looking for any and all issues.

 

[Assembler]

There are charts for the amount of metal movement before metal fatigue and failure will take place. The goal is to be well below this level at all times. One needs to measure for this on a regular basis. If the first barrel starts to wear out then one must be willing to make a new one. Most people will not blast that much.

 

[RTR]

On "White Water" their blasting big boulders underwater .Have you seen it ?

 

[Assembler]

On "White Water" their blasting big boulders underwater .Have you seen it ?

No not yet. Will try to take a look. Thanks for the heads up tip.

 

[alloy_II]

Feathers and wedges.

 

[RTR]

No not yet. Will try to take a look. Thanks for the heads up tip.

What their using works great on granite boulders ,not so great on shale boulders.

 

[Assembler]

Feathers and wedges.

Great how to there. I have seen china men splinting boulders that where around 18' in size with nothing but pins and a large hammer after drilling the holes for the pins.

 

[alloy_II]

Looks like machining work needs to be done for a boring bar setup for the end of the lathe. I may be able to use different bar stock to fit inside of the lathe end and then weld off of it. Right now it is not high on the list of things to do as a impact mill is.

I don't think your Atlas lathe has a large enough pass through spindle bore hole for this project.

 

[Assembler]

I don't think your Atlas lathe has a large enough pass through spindle bore hole for this project.

Correct the bore is to small. One can still machine shorter sleeves and weld them together as this is the plan here. The goal of the baster is to generate enough gas pressure to be useful.

I may look into a larger lathe and just pay for someone to machine it.

 

[alloy_II]

Correct the bore is to small. One can still machine shorter sleeves and weld them together as this is the plan here. The goal of the baster is to generate enough gas pressure to be useful.

I may look into a larger lathe and just pay for someone to machine it.

I would cast the barrel ( home foundry ) style then have the bore machined to finalize the project.

Casting metal at home is easy to do, for this project I would use the lost foam method, making the core to keep the barrel hollowed out. See video below.

For the beginner I would recommend using a core box sand like Petrobond which uses oil for the binder while green sand uses water, if the moisture content isn't correct you cold have a steam explosion.

For this reason I've never considered myself apt at using green sand.

What is Petrobond sand?​

– Petrobond is a formulated bonding agent, bonding sand with oil instead of water. – Less gas is formed permitting use of finer sands with lower permeability. Petrobond gives a finer finish. – Petrobond produces near die cast quality casting with green sand practice.