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Model Engineering in UK - Model engineering, metal crafts in UK
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Posted by Tim Leech on March 22, 2008, 6:30 pm
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On Sat, 22 Mar 2008 14:58:55 -0700 (PDT), mark
>> 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
>
>
>drill it out with one of these
>
>http://cgi.ebay.co.uk/CARBIDE-PCB-Router-CNC-NC-Chip-Breaker-1-5-mm-NEW_W0QQitemZ220215416282QQihZ012QQcategoryZ88433QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
>
>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
The risk with using a carbide drill is of breaking off the carbide
drill in the piece. If it's in too deep to smash into bits, you can
have a bigger problem than you started with.
Don't ask me how I know......
Tim
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Posted by Mark Rand on March 22, 2008, 6:04 pm
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wrote:
>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
If it were carbon steel in an aluminium head then dilute nitric acid would 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 steel
bolted to the drill press table to act as a locator, then put a pin in the
hole to locate the buggered hole with. Failing that, make a template with 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 meet the
broken screw. Then punch the broken screw out with a 1mm, or less, punch.
Finally, clean up the hole.
Mark Rand
RTFM
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Posted by Steve on March 23, 2008, 5:20 am
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> On Sat, 22 Mar 2008 18:22:04 -0000, "Steve"
> wrote:
>
>>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
>
>
> If it were carbon steel in an aluminium head then dilute nitric acid would
> 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 steel
> bolted to the drill press table to act as a locator, then put a pin in the
> hole to locate the buggered hole with. Failing that, make a template with
> 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 meet
> 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, and the hole is
one of four for holding down the exhaust manifold flange. The 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, hadn't thought that diluting it would actually
work faster! The anodising trick sounds interesting.
Not sure how to acquire smal quantities of Nitric acid locally either. Our
local chemist is nervous about selling me 500ml bottles of IsoPropyl
Alcohol, so asking for Nitric will probably give him a heart attack.
Thanks for the accumulated wisdom - back into the shed to have another go.
Steve
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Posted by David Littlewood on March 23, 2008, 7:55 am
Please log in for more thread options >
>What've got is an aluminium head machined from bar stock, and the hole
>is one of four for holding down the exhaust manifold flange. The 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, hadn't thought that diluting it would
>actually work faster! The anodising trick sounds interesting.
>
>Not sure how to acquire smal quantities of Nitric acid locally either.
>Our local chemist is nervous about selling me 500ml bottles of
>IsoPropyl Alcohol, so asking for Nitric will probably give him a heart
>attack.
>
>Thanks for the accumulated wisdom - back into the shed to have another go.
>
>Steve
>
Concentrated acid tends to "passivate" the iron unless it is heated,
which can be dangerous.
If your local pharmacist* is reluctant to sell acid (many are these
days, used to be so much easier in my youth) then I suggest you try
jewellery trade suppliers. I bought 5 litres (1 litre packages are
available but not much cheaper) of concentrated H2SO4 from H S Walsh a
couple of months ago for exactly this purpose - over the counter, as
carriage is a problem. They will take your details and expect you to say
what it's for - "pickling and etching metal" is fine, and quite truthful
in our hobby. Just treat it with reasonable reverence - it's nasty
stuff, but I prefer it to nitric or hydrochloric acids, both of which
give off highly corrosive vapours which will cause mayhem with your
tools. Wear eye protection, *always* add acid slowly to water, stirring
continuously. The reaction of H2SO4 with water is very exothermic (gets
hot) and if you add water to the top of the very dense acid a very sharp
boundary layer will heat up alarmingly and may well crack the vessel,
and much spitting is almost certain. If you get a drop on your fingers,
you probably have 10 seconds or so to wash it off before it causes
damage; if on your clothes, wash immediately at least twice in copious
amounts of water, or holes will appear fairly quickly.
*As one who studied and practised chemistry in my early career, I
dislike the way pill peddlers call themselves "chemists". Just like the
way medical practitioners have quite shamefully stolen the term
"doctor".
David
--
David Littlewood
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Posted by bigegg on March 26, 2008, 3:21 pm
Please log in for more thread options David Littlewood wrote:
>>
>> What've got is an aluminium head machined from bar stock, and the
>> hole is one of four for holding down the exhaust manifold flange. The
>> drill is a 1.5mm HSS hertel and its broken off below the top of the
>> hole (only just).
another idea - can you use it as the sacrificial anode in an
electrolytic rust removal bath (or would that eat the aluminium first?)
--
BigEgg
Hack to size. Hammer to fit. Weld to join. Grind to shape. Paint to cover.
http://www.workshop-projects.com -
Plans and free books - *Now with forum*
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>> 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