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Posted by bugbear on January 7, 2008, 10:57 am
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over the holiday I had cause to make a 1/4" whitworth knob.
1" diameter, 1/4" thick, 1/4 whit hole in the middle.
Simple enough job, but I only had some 1" x 1/4" Alu flatstock
(actually an old shelf bracket!!).
I cut off a slice, centre popped, marked a circle,
and attempted to drill the tap hole for 1/4"
I was off the mark by 1.5mm
As a "proof of concept" I then hacksawed the square
piece octagonal (remove corners) and filed to a good
circle. The hole (of course) was still off centre.
At this point I should point out that I am a woodworker
with a few files and a hacksaw. I don't have a lathe,
or even a drill press.
It's all hand work.
What techniques could I use to get an accurately placed
hole?
BugBear
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Posted by Norman Billingham on January 7, 2008, 12:07 pm
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> over the holiday I had cause to make a 1/4" whitworth knob.
> 1" diameter, 1/4" thick, 1/4 whit hole in the middle.
>
> Simple enough job, but I only had some 1" x 1/4" Alu flatstock
> (actually an old shelf bracket!!).
>
> I cut off a slice, centre popped, marked a circle,
> and attempted to drill the tap hole for 1/4"
>
> I was off the mark by 1.5mm
>
> As a "proof of concept" I then hacksawed the square
> piece octagonal (remove corners) and filed to a good
> circle. The hole (of course) was still off centre.
>
> At this point I should point out that I am a woodworker
> with a few files and a hacksaw. I don't have a lathe,
> or even a drill press.
>
> It's all hand work.
>
> What techniques could I use to get an accurately placed
> hole?
Give yourself a chance by not trying to drill the tapping size hole in one
go. Either buy a 1/8" stub drill or (better) a BS3 centre drill. Either
gives you a short stiff drill which will locate much better in your centre
pop and give a start for the bigger drill.
You can drill aluminium with wood drills - if you had a brad point wood
drill of the right size (1/4 BSW = 5.3mm) that would work too - what you
need is a positive centre location.
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Posted by Austin Shackles on January 7, 2008, 3:43 pm
Please log in for more thread options On or around Mon, 07 Jan 2008 15:57:18 +0000, bugbear
>over the holiday I had cause to make a 1/4" whitworth knob.
>1" diameter, 1/4" thick, 1/4 whit hole in the middle.
>
>Simple enough job, but I only had some 1" x 1/4" Alu flatstock
>(actually an old shelf bracket!!).
>
>I cut off a slice, centre popped, marked a circle,
>and attempted to drill the tap hole for 1/4"
>
I assume you got your centre punch in the middle, by the expedient of
drawing diagonals on the square bit first?
--
Austin Shackles. www.ddol-las.net my opinions are just that
Travel The Galaxy! Meet Fascinating Life Forms...
------------------------------------------------
>> http://www.schlockmercenary.com/ << ...and Kill them.
a webcartoon by Howard Tayler; I like it, maybe you will too!
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Posted by bugbear on January 8, 2008, 5:16 am
Please log in for more thread options Austin Shackles wrote:
> On or around Mon, 07 Jan 2008 15:57:18 +0000, bugbear
>
>> over the holiday I had cause to make a 1/4" whitworth knob.
>> 1" diameter, 1/4" thick, 1/4 whit hole in the middle.
>>
>> Simple enough job, but I only had some 1" x 1/4" Alu flatstock
>> (actually an old shelf bracket!!).
>>
>> I cut off a slice, centre popped, marked a circle,
>> and attempted to drill the tap hole for 1/4"
>>
>
> I assume you got your centre punch in the middle, by the expedient of
> drawing diagonals on the square bit first?
Yes, and I even marked a 7mm circle (as well as the outer 25mm circle
for the final shape of the knob) from the centre "dot".
So I can see and measure my error quite well :-(
BugBear
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Posted by MikeH_QB on January 8, 2008, 5:52 am
Please log in for more thread options > over the holiday I had cause to make a 1/4" whitworth knob.
> 1" diameter, 1/4" thick, 1/4 whit hole in the middle.
>
> Simple enough job, but I only had some 1" x 1/4" Alu flatstock
> (actually an old shelf bracket!!).
>
> I cut off a slice, centre popped, marked a circle,
> and attempted to drill the tap hole for 1/4"
>
> I was off the mark by 1.5mm
>
> As a "proof of concept" I then hacksawed the square
> piece octagonal (remove corners) and filed to a good
> circle. The hole (of course) was still off centre.
>
> At this point I should point out that I am a woodworker
> with a few files and a hacksaw. I don't have a lathe,
> or even a drill press.
>
> It's all hand work.
>
> What techniques could I use to get an accurately placed
> hole?
>
> =A0 =A0BugBear
As Norman B suggested, if you 'center popped' first it will only be
quite a shallow indentation, use a small drill first (like 1/8") as
that will locate in the mark. Then use the 1/4" tapping drill.
Alu is obviously quite soft, so a 'big' drill will tend to grab into
the metal only approximately where u first place it - hence (probably)
your 1.5mm error.
Mike
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> 1" diameter, 1/4" thick, 1/4 whit hole in the middle.
>
> Simple enough job, but I only had some 1" x 1/4" Alu flatstock
> (actually an old shelf bracket!!).
>
> I cut off a slice, centre popped, marked a circle,
> and attempted to drill the tap hole for 1/4"
>
> I was off the mark by 1.5mm
>
> As a "proof of concept" I then hacksawed the square
> piece octagonal (remove corners) and filed to a good
> circle. The hole (of course) was still off centre.
>
> At this point I should point out that I am a woodworker
> with a few files and a hacksaw. I don't have a lathe,
> or even a drill press.
>
> It's all hand work.
>
> What techniques could I use to get an accurately placed
> hole?