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Posted by Suzy on January 8, 2008, 1:32 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?
>
> BugBear
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
Plus, I would add, as they are so cheap buy yourself a drill-press. It will
revolutionise (ouch!) all your work. And if you've got away without before
ALWAYS wear safety spectacles especially now that drilling is nearer eye
level.
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Posted by bugbear on January 9, 2008, 4:52 am
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Suzy wrote:
>> 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
>
> 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
>
> Plus, I would add, as they are so cheap buy yourself a drill-press. It will
> revolutionise (ouch!) all your work. And if you've got away without before
> ALWAYS wear safety spectacles especially now that drilling is nearer eye
> level.
Actually, I am desperately short of workshop space, the issue
with a drill press is not cost, but space. I also strongly prefer
(just as a personal quirk) not using electric tools.
http://i48.photobucket.com/albums/f234/bugbear33/workshop.jpg
I may try and buy something like this:
http://homepage.mac.com/galoot_9/gpimages/post_drill.jpg
BugBear
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Posted by Trevor Jones on January 9, 2008, 8:21 am
Please log in for more thread options bugbear wrote:
>
> Actually, I am desperately short of workshop space, the issue
> with a drill press is not cost, but space. I also strongly prefer
> (just as a personal quirk) not using electric tools.
>
> http://i48.photobucket.com/albums/f234/bugbear33/workshop.jpg
>
> I may try and buy something like this:
>
> http://homepage.mac.com/galoot_9/gpimages/post_drill.jpg
>
> BugBear
Take a look at the Cole Drill, as well, then. At least, know what one
looks like, so as to recognise it as the bargain it is, if you see one
at a car boot sale.
They take up little space, and will drill holes that would make many
other drills give up. Portable, too! :-)
Lesse.... http://www.dogpatch.com/bobp/shop/cole_drill.jpg
Cheers
Trevor Jones
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Posted by bugbear on January 9, 2008, 9:41 am
Please log in for more thread options Trevor Jones wrote:
>
> Take a look at the Cole Drill, as well, then. At least, know what one
> looks like, so as to recognise it as the bargain it is, if you see one
> at a car boot sale.
>
> They take up little space, and will drill holes that would make many
> other drills give up. Portable, too! :-)
>
> Lesse.... http://www.dogpatch.com/bobp/shop/cole_drill.jpg
Duly Noted ;-)
BugBear
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Posted by Allan Waterfall on January 9, 2008, 12:17 pm
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Just drill the hole first and mark the outer circle afterwards using a
paper template if you're only making a knob.
Allan
--
Allan Waterfall
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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?
>
> BugBear