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Re: [ATM] Cutting large-diameter PVC
I'd draw the circumference by tracing the edge of non stretchy ribbon
wrapped around the tube, taking care that the ribbon was lying flat. This
should give you an accurate line.
Cutting this pipe with a table type circular saw could get very exciting on
short notice. To do this safely, you probably want a helper, a large
sawtable, and a very large crosscut sled or similar arrangement so that the
tube won't get misaligned w/r/t the blade in mid cut. (leading to damaged
tube, stalled saw, and/or tube flying across room, depending on the power of
your saw.) You would then need to make several passes to cut the whole
circumference.
A hand held circular saw/skilsaw could work freehand, and I'm sure people do
it, but they are braver than I. If you could come up with a way of putting
a more or less circular "fence" around the tube so that the edge of the saw
sole opposite the blade was touching/bearing on the fence, and the sawblade
was on the waste side of the cutting line, it might just work, esp. if you
clamped the tube to a bench so it could not move. This way, at least the
saw won't twist in the kerf and ruin the work. You would have to unclamp,
rotate, clamp, and cut several times, but, if your fence was
circumferential, "straight", and did not move, you could work to quite close
tolerances, I would think. I'm thinking of something like a very long
hoseclamp (eg used for flexible heating ducts) with little blocks of wood
between it and the tube, or much larger pieces with an inner circumference
cut with a jigsaw or bandsaw. Aligning these would take time, but would be
doable. Using a female pipe fitting cut into sections might work out well,
if you can get one for this size.
If I were doing it, I'd have to make the sled, and I'd likely decide to use
a coarse tooth hack saw or even a wood saw, if I did not have a jig saw or
Sawzall to use. It'd be faster than making the sled.
Unless you spend the time making a good sled that really holds the work
still, you are going to end up rasping/filing/sanding to the line in any
case. If you do not have one, renting a belt sander for an hour or two
could make this easier. Also, many woodworkers have bandsaws that will cut
up to 12 inches, although you would want to smooth the cut afterwards.
Good luck,
Rod
----- Original Message -----
From: "Kevin MIchael Zabbo" <chaosopher23@yahoo.com>
To: <atm@atmlist.net>
Sent: Friday, October 19, 2007 5:37 AM
Subject: [ATM] Cutting large-diameter PVC
>I have acquired, for free, two lengths of 10" PVC
> pipe. One look at them and free may have been too
> high a price, but there is enough pipe to make the
> tube for my 8" Newtonian, as long as I tie the tubes
> together. That part has been figured out. However -
> (don't ya love this part of the emails?)
>
> The tubes themselves have badly out-of-square ends.
> While I have experience cutting large diameter stuff,
> I do not have access to much more than a circular saw,
> which does a wonderfully fast job at cutting PVC with
> a nice, sharp fine-tooth blade. While not a smooth
> finish, it is fast and clean enough to rasp away.
>
> Is there an easy way to cut this stuff square, so I
> don't spend a whole day rasping away at it to get it
> to within the 1mm squareness that's good enough for a
> telescope? Remember now, a circular saw is what I'm
> going to use. I'm too lazy to go at it with some sort
> of hand saw.
>
> Many thanks,
> Transplanted Yankee, Seeker of the Darkness
> Kevin
>
> I published my first novel! You can get it here, from the publisher!
> http://www.publishamerica.com/greetingcardpro/pickup.asp?CardSentID=126045&rID=48283
>
>
>
> Their search stringbox is on the right side about halfway down.
>
> search using my name: kevin michael zabbo
> and it will take you right to my book page.
>
> The title is anna's blood, which also takes you there.
>
> Please order your copy soon! I love you!
>
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