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Model Engineering in UK - Model engineering, metal crafts in UK
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Posted by Steve on March 22, 2008, 2:22 pm
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I've managed, through nothing but carelessness, to break a 1.5mm drill bit
in the cylinder head of the little glow motor I'm (still) making. Only one
hole left to complete and I broke the soddin' bit into the head. I've been
dripping sulphuric acid into the hole for the past couple of days, without
seemingly much progress.
Any better ideas for getting the broken bit out? Is there anything better
than H2SO4 to do this job?
I can bodge it , but rather not without trying.
Steve
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Posted by Dave Baker on March 22, 2008, 2:29 pm
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> I've managed, through nothing but carelessness, to break a 1.5mm drill
> bit in the cylinder head of the little glow motor I'm (still) making.
> Only one hole left to complete and I broke the soddin' bit into the head.
> I've been dripping sulphuric acid into the hole for the past couple of
> days, without seemingly much progress.
>
> Any better ideas for getting the broken bit out? Is there anything better
> than H2SO4 to do this job?
>
> I can bodge it , but rather not without trying.
Other than getting it burned out by EDM machining there's no easy way.
--
Dave Baker
Puma Race Engines
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Posted by Cliff Coggin on March 22, 2008, 2:46 pm
Please log in for more thread options
> I've managed, through nothing but carelessness, to break a 1.5mm drill
> bit in the cylinder head of the little glow motor I'm (still) making.
> Only one hole left to complete and I broke the soddin' bit into the head.
> I've been dripping sulphuric acid into the hole for the past couple of
> days, without seemingly much progress.
>
> Any better ideas for getting the broken bit out? Is there anything better
> than H2SO4 to do this job?
>
> I can bodge it , but rather not without trying.
>
> Steve
The head isn't brass by some remote chance is it? Potassium alum will
dissolve steel in a couple of days without affecting brass. If it is any
other metal I can't help.
Cliff Coggin.
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Posted by David Littlewood on March 22, 2008, 3:32 pm
Please log in for more thread options >I've managed, through nothing but carelessness, to break a 1.5mm
>drill bit in the cylinder head of the little glow motor I'm (still)
>making. Only one hole left to complete and I broke the soddin' bit
>into the head. I've been dripping sulphuric acid into the hole for
>the past couple of days, without seemingly much progress.
>
>Any better ideas for getting the broken bit out? Is there anything
>better than H2SO4 to do this job?
>
>I can bodge it , but rather not without trying.
>
>Steve
It *will* dissolve, but takes time. Warming the metal helps, as does
prodding it with a stick as often as you can be bothered. Also, you need
to change the acid fairly frequently as the volume of acid down the hole
is completely inadequate to dissolve that much steel. Don't use
concentrated acid, it will actually be very slow to react; something
like 20-30% concentrated acid to water (add acid to water, slowly and
with stirring) will be best.
If the block is aluminium I do not recommend complete immersion, as
sulphuric acid may cause pitting - I know it did on mine when I had to
do this a few weeks ago
David
--
David Littlewood
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Posted by mark on March 22, 2008, 5:58 pm
Please log in for more thread options > I've managed, =A0through nothing but carelessness, =A0to break a 1.5mm dri=
ll bit
> in the cylinder head of the little glow motor I'm (still) making. =A0 Only=
one
> hole left to complete and I broke the soddin' bit into the head. =A0 I've =
been
> dripping sulphuric acid into the hole for the past couple of days, =A0with=
out
> seemingly much progress.
>
> Any better ideas for getting the broken bit out? =A0Is there anything bett=
er
> than H2SO4 to do this job?
>
> I can bodge it , =A0but rather not without trying.
>
> Steve
drill it out with one of these
http://cgi.ebay.co.uk/CARBIDE-PCB-Router-CNC-NC-Chip-Breaker-1-5-mm-NEW_W0QQ=
itemZ220215416282QQihZ012QQcategoryZ88433QQssPageNameZWDVWQQrdZ1QQcmdZViewIt=
em
this has been done before ...by myself with these ...they do work .
dont put too much pressure on them ...and they just chew away at
it .........may take a few mins .
all the best.mark
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> bit in the cylinder head of the little glow motor I'm (still) making.
> Only one hole left to complete and I broke the soddin' bit into the head.
> I've been dripping sulphuric acid into the hole for the past couple of
> days, without seemingly much progress.
>
> Any better ideas for getting the broken bit out? Is there anything better
> than H2SO4 to do this job?
>
> I can bodge it , but rather not without trying.