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Posted by mark on March 23, 2008, 8:02 am
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> > On Sat, 22 Mar 2008 18:22:04 -0000, "Steve"
> > wrote:
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> >>I've managed, =A0through nothing but carelessness, =A0to break a 1.5mm d=
rill
> >>bit
> >>in the cylinder head of the little glow motor I'm (still) making. =A0 On=
ly
> >>one
> >>hole left to complete and I broke the soddin' bit into the head. =A0 I'v=
e
> >>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? =A0Is there anything be=
tter
> >>than H2SO4 to do this job?
>
> >>I can bodge it , =A0but rather not without trying.
>
> >>Steve
>
> > If it were carbon steel in an aluminium head then dilute nitric acid wou=
ld
> > get
> > the steel out without harming the aluminium. HSS is, I think, more work.=
> > Can
> > check tomorrow.
>
> > Is the hole for a head mounting screw? If so, how about:-
>
> > Is the drill broken off flush? if not then drill 1.5mm into a bit of ste=
el
> > bolted to the drill press table to act as a locator, then put a pin in t=
he
> > hole to locate the buggered hole with. Failing that, make a template wit=
h
> > the
> > hole locations out of a bit of scrap and screw that to the underside of
> > the
> > head with some of the existing holes.
>
> > Once you've done that, carefully drill from the other side until you mee=
t
> > the
> > broken screw. Then punch the broken screw out with a 1mm, or less, punch=
.
> > Finally, clean up the hole.
>
> > Mark Rand
> > RTFM
>
> What've got is an aluminium head machined from bar stock, =A0and the hole =
is
> one of four for holding down the exhaust manifold flange. =A0The drill is =
a
> 1.5mm HSS hertel and its broken off below the top of the hole (only just).=
>
> I can't get at the hole from the other side.
>
> I'm using conc sulphuric, =A0hadn't thought that diluting it would actuall=
y
> work faster! =A0 The anodising trick sounds interesting.
>
> Not sure how to acquire smal quantities of Nitric acid locally either. =A0=
Our
> local chemist is nervous about selling me 500ml bottles of IsoPropyl
> Alcohol, =A0so asking for Nitric will probably give him a heart attack.
>
> Thanks for the accumulated wisdom - back into the shed to have another go.=
>
> Steve- Hide quoted text -
>
> - Show quoted text -
some windscreen washer winter additives are 100 percent isopropyl
so dont go wasteing your money at the chemist .when 1 litre of the
stuff can be bought for =A31.29
all the best.mark
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