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

can you go electric and have no exhaust? A quick Google search turned this
up.

http://www.icscuttingtools.com/Electric.htm

Karl

Just wrap a rag around the trigger area, where the exhaust ports are.
JR
Dweller in the cellar


On 29 May 2009 20:23:58 +0100, Richard Smith
wrote:

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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Would a needle scaler do the job?
http://metalworking.mscdirect.com/CG...PMPXNO=2876452


--
Stupendous Man,
Defender of Freedom, Advocate of Liberty

"Stupendous Man" writes:

Would a needle scaler do the job?
http://metalworking.mscdirect.com/CG...PMPXNO=2876452


--
Stupendous Man,
Defender of Freedom, Advocate of Liberty

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

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?


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.

"Stupendous Man" writes:

The stuff is a precision stainless steel casting - we mustn't
tool-mark it. ...


..., or even try using a plastic bit in a conventional
chattergun. One could be turned from Delrin pretty quickly.

Sorry - would you explain that for me - a "chattergun"? Maybe I can
then visualise this plastic bit which would fit this tool -- Rich S

Sorry - would you explain that for me - a "chattergun"? Maybe I can
then visualise this plastic bit which would fit this tool -- Rich S

Sure. Visual--
http://www.tubemachine.com/1/images/...r%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.

On 30 May 2009 23:55:24 +0100, Richard Smith
wrote:

"Stupendous Man" writes:

The stuff is a precision stainless steel casting - we mustn't
tool-mark it. ...


..., or even try using a plastic bit in a conventional
chattergun. One could be turned from Delrin pretty quickly.

Sorry - would you explain that for me - a "chattergun"? Maybe I can
then visualise this plastic bit which would fit this tool -- Rich S

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 --

Bruce L. Bergman writes:

On 30 May 2009 23:55:24 +0100, Richard Smith
wrote:

"Stupendous Man" writes:

The stuff is a precision stainless steel casting - we mustn't
tool-mark it. ...


..., or even try using a plastic bit in a conventional
chattergun. One could be turned from Delrin pretty quickly.

Sorry - would you explain that for me - a "chattergun"? Maybe I can
then visualise this plastic bit which would fit this tool -- Rich S

If I was designing something like that, Prototype Number One would
take a standard pointed air-chisel bit. Cut off the point right where
...

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