JB MacDonald wrote:

I know how to find the center of a pipe, using a vee block, but my
question is how do you scribe a line from one end to the other , so the
first hole is in perfect alignment with the last hole .. take for
example a 20 foot pipe , or tubing . If we had a 20 foot layout table
fine , clamp pipe down and use a height gauge to scrib a line the length
of the pipe. if you do not have a line you could get a twist(miss
alignment) but what can a person due that does not have a 20 foot layout
table . Maybe I am being to critical

Assuming you have a drill press or drill guide that allows vertical
drilling, and assuming that you have at least a few feet of table, there
is a solution, for VHF and up anyway.

Take a small piece of plate or board and mount a rod the same diameter
as the holes you are drilling vertically from it. The accuracy here is
going to set your ultimate result. If you are off 1 degree and use the
device as a reference 10 times during the drilling, you will have a 10
degree twist, although there is a simple way to reduce that error.

Drill your first hole. Now use the device and the new hole to hold the
boom in place and slide along your table to position your drill at the
next hole. Move the device to the latest hole drilled as you run out of
table. To reduce errors from imperfect vertical on the device, rotate
it 180 degrees between each move.

I have used this method to drill 39 element holes for a 31 foot 432 beam
with almost perfect results on an 8 foot table and just a drill guide,
not a drill press. It can be used across boom diameter boundaries,
which it was in this case, with a bit of care.

tom
K0TAR

To reduce errors from imperfect vertical on the device, rotate
it 180 degrees between each move.


^ Best advice ^

Great Idea! I Just have to extend my table on the right side, keeping
my perfectly aligned Vee block clamped down . Now it sounds simple . Tnx JB

Tom Ring wrote:
JB MacDonald wrote:

I know how to find the center of a pipe, using a vee block, but my
question is how do you scribe a line from one end to the other , so
the first hole is in perfect alignment with the last hole .. take for
example a 20 foot pipe , or tubing . If we had a 20 foot layout table
fine , clamp pipe down and use a height gauge to scrib a line the length
of the pipe. if you do not have a line you could get a twist(miss
alignment) but what can a person due that does not have a 20 foot
layout table . Maybe I am being to critical

Assuming you have a drill press or drill guide that allows vertical
drilling, and assuming that you have at least a few feet of table, there
is a solution, for VHF and up anyway.

Take a small piece of plate or board and mount a rod the same diameter
as the holes you are drilling vertically from it. The accuracy here is
going to set your ultimate result. If you are off 1 degree and use the
device as a reference 10 times during the drilling, you will have a 10
degree twist, although there is a simple way to reduce that error.

Drill your first hole. Now use the device and the new hole to hold the
boom in place and slide along your table to position your drill at the
next hole. Move the device to the latest hole drilled as you run out of
table. To reduce errors from imperfect vertical on the device, rotate
it 180 degrees between each move.

I have used this method to drill 39 element holes for a 31 foot 432 beam
with almost perfect results on an 8 foot table and just a drill guide,
not a drill press. It can be used across boom diameter boundaries,
which it was in this case, with a bit of care.

tom
K0TAR

Tom Ring wrote in
:

....
the next hole. Move the device to the latest hole drilled as you run
out of table. To reduce errors from imperfect vertical on the device,

This violates an important technique of minimising measurement and layout
error, determine a datum such that you can lay everything off from that
datum, and then do just that.

the next hole. Move the device to the latest hole drilled as you run
out of table. To reduce errors from imperfect vertical on the device,
rotate it 180 degrees between each move.

This is a technique to compensate for moving the datum.

I am not saying it won't work, and I can see that you have done it to reduce
the size of accurate table needed to register the device.

Owen

Owen Duffy wrote:

Tom Ring wrote in
:

...

the next hole. Move the device to the latest hole drilled as you run
out of table. To reduce errors from imperfect vertical on the device,


This violates an important technique of minimising measurement and layout
error, determine a datum such that you can lay everything off from that
datum, and then do just that.


the next hole. Move the device to the latest hole drilled as you run
out of table. To reduce errors from imperfect vertical on the device,
rotate it 180 degrees between each move.


This is a technique to compensate for moving the datum.

I am not saying it won't work, and I can see that you have done it to reduce
the size of accurate table needed to register the device.

Owen

And yet is does work. For 39 holes in my case.

I didn't say it was highly accurate, but that by following what I did,
that it would work well enough for a long boom UHF beam DESPITE that
fact. It's also cheap and easy. Unfortunately, many of us cannot
afford the best, but need still need good results. This is one way.

If I could afford equipment like you describe, I would certainly have it
and use it, but I can't. My guess is that most of the people here are
closer to my end of the spectrum than yours. Yet another unfortunate fact.

73,
tom
K0TAR

Tom Ring wrote in
:

If I could afford equipment like you describe, I would certainly have
it and use it, but I can't. My guess is that most of the people here
are closer to my end of the spectrum than yours. Yet another
unfortunate fact.


Tom, I don't understand the reference to expensive equipment, the system I
described of placing a short close fitting rod in the first hole and
visually aligning the rod with the drill for each additional hole is very
low cost and adequately accurant.

Owen

Owen Duffy wrote:


Tom, I don't understand the reference to expensive equipment, the system I
described of placing a short close fitting rod in the first hole and
visually aligning the rod with the drill for each additional hole is very
low cost and adequately accurant.

Owen

Owen

I was refering to another of your posts -

-----------------

Wes, I agree, that is entirely practical. As far as bubble technology goes,
senstivity easily exceeds that, IIRC the plate bubble sensitivity on
theodolites is commonly around 20" (seconds) per 2mm run. By reversing such
a bubble and splitting the difference, it should be possible to achieve an
error well under 0.1mm/m slope.

Realistically, most bubbles for engineering workshop use would be more
accurate than the drilling process, so they are a quite adequate means of
registering the work.

------------------

As has been described and documented in the last few months (not here,
but in science journals), emails, and their equivalent, are sometimes
the most misunderstood things in the history of human communication.
The problem is even worse in a newsgroup, because the threads are huge,
and replies sometimes reference posts not in the current sequence, and
people receive items out of time order and often delayed.

tom
K0TAR

Owen Duffy wrote:


This is a technique to compensate for moving the datum.

I am not saying it won't work, and I can see that you have done it to reduce
the size of accurate table needed to register the device.

Owen

And the best thing about those holes is that the antenna they resulted
in set the all time gain record for a homebrew 432 yagi at Central
States.

tom
K0TAR