From: "Dwight K. Elvey" 
To: atm{at}shore.net
Reply-To: "Dwight K. Elvey" 


Hi Shawn
 The worst of it is that you are more likely to jam or
break a bit that is vibrating. When drilling, it is best to drill most of
the hole with the final size, good lubrication and the right speed.
 I used to do the stepping through the sizes thing
until a machinist friend pointed out my nasty looking holes. He showed me
the right way. It is still best to drill a pilot hole, just don't drill it
so large that it causes the drill to vibrate. Like most things, a little is
a good thing but too much is worse( now, where is my beer ).
 Of course, if an exact size is needed, you want
to drill slightly undersized and use a reamer bit to make it the exact
right size. Most of us home folks don't have a nice set of reamers handy so
we need to depend on a good drill. They make variable sized reamers but
these require a test piece to play with to get the sizes right. It is
better to buy the right sized fixed reamer if you need it. I've never seen
these at hardware stores but any machine shop supply will have them. Dwight


>From: "McHatten, Shawn" 
>
>Hey Dwight
>       Hmmm? Interesting. I was wondering about that when you said it before.
I
was always taught to move up through the sizes as Bill mentioned below.
Especially for larger sizes in metal (above 3/8in). I kinda remember
something about it was to save the larger bits from wearing as fast but
can't honestly tell you why or where I heard it.
>       However I have definitely noticed the vibration and 3 or 5 sided hole
that you talk about. I've had to drill a number of 1/2in holes in 1/4in
truck frame using a portable hand drill. Started with 1/8 moved to 3/8 and
then 1/2. The vibration is noticeable on the 1/2in.
>       Have you ever heard of "moving through the bit sizes"
before or do you
know where it started? Anyone else heard of this? And is the pilot hole just for
guidance. It definitely seems to make the larger holes drill faster with a guide
hole (1/8in). Maybe the wedge on the larger bits are just too big to start
the hole properly?
>
>Thanks
>Shawn
>
>-----Original Message-----
>From: Dwight K. Elvey [mailto:dwightk.elvey{at}amd.com]
>Sent: Thursday, April 17, 2003 1:31 PM
>To: atm{at}shore.net
>Subject: Re: ATM drilling aluminum
>
>
>>From: "William Thornley" 
>>
>>Hi Eric,
>>
>>You'll find aluminium soft enough to mark your drilling point with the push
>>of a sharp scriber(easier to line up your markings) . Centre punch this with
>>a centre punch and hammer. That will get your first drill right where you
>>want it. Hammer across the drilling point (hold the centre punch at an
>>angle) if you missed slightly, to bring the drilling point back to your mark
>>and repunch.
>>
>>Next, start with a small drill 2-3mm (1/16"-1/8").
Increase in increments of
>>3 or 4 drill sizes between drilling until you reach your wanted size. That
>>way you will ensure your final hole is dead centre.
>
>Hi
> As I stated in my previous post it is best to not step the
>drill sizes. If the hole is a large percentage of the drill
>size you intend to end up with, the dill will virbrate.
>This often makes a hole with three or 5 lobes as the drill
>steps around the hole. It is better to make only a small
>pilot hole about the size of the wedge part of the final drill
>size you intend to have.
>Dwight
>
>>
>>Hope this helps
>>
>>Regards,
>>
>>Bill Thornley
>>Sydney, Aus.
>>
>>>Eric wrote:
>>>Thanks, everyone, for your input on this.  Think I'll get a
drill >press :)
>>>
>>>Regards,
>>>Eric
>>>
>>>
>>
>>
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>
>
>

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