rear-exhausting air chisel

Hi all
Need your expert help on tools - air tools
We (in a lost-wax foundry) use a small air chisel for knocking out ceramic shell from castings - when we can't use a big brutal knock-out
machine. Problem is - exhausts forward as per most chiselling type air tools - and as this tool is only used in entrant shapes, this results in everything release erupting back as a fountain of grit and dust all over the operator.
So, contrary to most air chisel use where exhaust direct forward blows dust away (a bonus), in this case we need the tool to exhaust to the rear - preferably up a short pipe taped back along the incoming air-line to keep things really steady around the work area and avoid exhaust blowing up the operator's sleeve, etc.
This chisel is about the size and shape of a die-grinder (yes, I know that's a rotary tool).
Anyone got any help they can offer?
Thanks in advance
Richard Smith
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can you go electric and have no exhaust? A quick Google search turned this up.
http://www.icscuttingtools.com/Electric.htm
Karl
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Just wrap a rag around the trigger area, where the exhaust ports are. JR Dweller in the cellar
wrote:

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Good point - don't know the answer to that!
Some of the job which is causing us the biggest problem will be coming through next week - I'll try it. It could indeed be the answer. Glad I asked. And we have plenty of needle descalers around to borrow. Looks like I'll be dropping by the welding section again.
The stuff is a precision stainless steel casting - we mustn't tool-mark it. Reckon will look for a needle descaler where the needles are very rounded-end (as opposed to sharp - there's some of those around too). How could I really make that so - smooth and round the ends? Could I dance the needles on a piece of fine grinding wheel, for instance? Then burnish on thick hard plate?
We do have a reducing valve where the tool plugs in - we can turn down the power to no more than necessary.
Thanks very very much for this suggestion
And thanks to the other contributors.
The rag around the front of the current air chisel is doable for this one particularly problematic job. Electric tools - they tend to be big, noisy, vibratory and not last long, but yes an SDS drill with rotation-stop and a blunted chisel could also get us out of this squeeze.
Rich S
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I don't know what the needles look like new, they tend to get pretty rounded thru use, just using it for a while against a rock ought to smooth them for final polishing on a 3m scotchbrite wheel. Since all you want to do is bust a ceramic coating, air pressure could be set very low, or even try using a plastic bit in a conventional chattergun. One could be turned from Delrin pretty quickly. Another solution with no damage might be an ultrasonic device.
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Sorry - would you explain that for me - a "chattergun"? Maybe I can then visualise this plastic bit which would fit this tool -- Rich S
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Sure. Visual--
http://www.tubemachine.com/1/images/imga/190air%20hammer.jpg
Just use a straight shank bit, or cut off a formed one, and insert into a plastic end cap. I'm not a plastics guy, so i don't know what type would last longest.
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wrote:

If I was designing something like that, Prototype Number One would take a standard pointed air-chisel bit. Cut off the point right where the shank goes straight.
Cut a section of 1/2" Black Pipe about two inches long, drill and tap three or more holes on the front half for grub-screws - Drill three or four larger holes (1/4" - 3/8") on the back half of the pipe. Ream out the inside of the pipe with a twist drill to knock off the weld seam ridge.
Weld the back half of the pipe to the shank of the chisel, with the two pieces overlapped a half inch or so. Then crank up the amps another notch and puddle weld through the big holes on the side of the pipe to the tip of the chisel shank, to spread the stresses around.
Get several chunks of 1/2" or 5/8" OD (whatever fits your pipe or tubing ID) in Nylon and Delrin rod to see which one lasts longest. Check with plastics suppliers, they might have a Fiberglass filled plastic available that will be stiffer.
Cut off 4" chunks of the plastic rod, and sharpen one end into a blunt pencil tip, or whatever shape you need to knock off the investment plaster. Chck the straight cut end into your pipe & chisel socket and secure with grub screws. Then chuck the chisel tip into the air gun.
Use it for a while, see what works and what doesn't. Then take the lessons you've learned and make the next prototype. When you don't need to change it again, now you can go into production.
--<< Bruce >>--
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Hi everyone
The needle-descaler seems promising. Removes ceramic with very little dust generated. Is forward exhausting but that exhaust is at very low velocity and the length of the needles away from where the action is.
Borrowed needle-gun with most rounded needles. And turned down air pressure at reducing valve until burnishing surface of 316 stainless castings but not tool-marking. And still shifts ceramic shell at a goodly rate. This stuff we have to shift isn't conventional ceramic shell but some refractory cement poured into recess in shell to reinforce it. So a bit harder. But hopefully... Will see in a couple of days when next lot of this job comes through.
Thanks again all.
Richard S
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