never thought about using a spring loaded cutter and a follower!
I will be working with round tube soon, (move into my new workshop 1st June) and was thinking about getting a metal cutting bandsaw (I had one before
and it was excellent) and some kind of tube notching device, probably the type that uses a holesaw
Then I thought, if I had a plasma cutter I could do both jobs with it. Cutting straight lines is easy enough (I had a plasma cutter before as well)
but cutting a complex shape on round tube would be tricky
I could use the tubemiter program to print out the shape onto a piece of paper which I would then cut with scissors and wrap around the tube, but
following a marked line with a plasma cutter can be tricky because the head of the cutter stops you seeing the line
What is needed it a machine that would turn the tube and as it does so, moves the head of the cutter along the required path. Probably easy enough
with cnc techniques, but can anyone think of a mechanical way of doing it?
John
I may be oversimplyfing it, but if you can't follw a line because the head obscurs it then draw the line half the thickness of the head away and
follow that?
Obviously going round a tube would mean the you would have to be at 90degrees to the cut face at all times so might be quite difficult, so how about
you make one out of larger tube and use that as a "Guide"?
Steve
Keep the plasma cutterhead still and rotate the tube with some sort of cam action to get the shape? Bit like the action of a Drill Doctor ?
quote:
Originally posted by worX
I may be oversimplyfing it, but if you can't follw a line because the head obscurs it then draw the line half the thickness of the head away and follow that?
Obviously going round a tube would mean the you would have to be at 90degrees to the cut face at all times so might be quite difficult, so how about you make one out of larger tube and use that as a "Guide"?
Steve
quote:
Originally posted by rusty nuts
Keep the plasma cutterhead still and rotate the tube with some sort of cam action to get the shape? Bit like the action of a Drill Doctor ?
Assuming you are cutting several tubes for a chassis (or similar) then if it were me, I would make a Fishmouth/Birdmouth piese out of a slightly
thicker tubing that could slide over the correct sized tube.
That way you just follow the pre made one with the head of the plasma cutter.
You could make the first one on a bench grinder or a linisher or get it cut for you and then that's your Pattern.
As for the different angles, I'm not too sure. Maybe have your "Pattern" one cut into quarters and slide the four quarters so they move
to the correct angle when cut?
quote:
Originally posted by mr henderson
quote:
Originally posted by worX
I may be oversimplyfing it, but if you can't follw a line because the head obscurs it then draw the line half the thickness of the head away and follow that?
Obviously going round a tube would mean the you would have to be at 90degrees to the cut face at all times so might be quite difficult, so how about you make one out of larger tube and use that as a "Guide"?
Steve
I'm not getting what you mean there. Do you mean a larger tube with a shaped end that would fit over the tube being cut. What about different angles?
John
[Edited on 25/5/08 by mr henderson]
you have to be careful with tube not to cut the other side while doing it .
CNC plasma can come attached with a tube cutter aswell .
best idea i can come up with is mark the the tube , then put it in a manipulator and cut by hand .
I'm not necessarily looking for a rough and ready way of cutting birds' mouths, although if it comes to it I shall have to use manual
methods, I'm more interested in finding a way of using the plasma cutter to do it.
The issue here isnt really getting the job done, it's the interestingness of designing a machine that would do it.
John
[Edited on 25/5/08 by mr henderson]
hhmmm i think ive thought of a way to do it. Ill try my best to explain.
Right if you had a chuck which you could turn by hand. On the turning end of the chuck if you have a bevel gear which turns another gear at 90
degrees. On top of the gear have an off center pin and a pushrod. Mount the plasma on the other end off this push rod in track.
SO to put it simply, as you turn the chuck this turns the pipe your cutting. It also pulls the plasma cutter down slighty and then back up. Just got
to get the gearing right which shouldnt be too hard considering its quarter turn for one up.
Hope you all follow
check this out,
http://www.kineticvehicles.com/rollbarFab.html
damn hate to say it but that looks cheaper and simpler than my idea never thought about using a spring loaded cutter and a follower!
quote:
Originally posted by mr henderson
The issue here isnt really getting the job done, it's the interestingness of designing a machine that would do it.
John
quote:
Originally posted by liam.mccaffrey
check this out,
http://www.kineticvehicles.com/rollbarFab.html
i've not read everything so this may have already come up.
What you want is to make the plasma cutter go round in a circle - then make a tube intersect that circle at an angle.
Therefore.
take a large wooden board and drill a hole in it. Make something that will rotate the plasma cutter so that it will go around the hole. Ie anything
that drops through the hole will be cut, so if a tube was pushed through the hole, held in position, the plasma cutter turned on and spun round an
inch would be removed - creating a ring or reducing the total length of the pipe.
Now make a stand to feed the tube into the hole at a different angle.
(its perfectly clear in my head, just not sure how to explain it).
just read the other link - i've posted how to cut tube to hit a flat surface, not intersect with another tube - sorry.
I like that roll-bar notcher!!! Very nifty!! Simple but clever 
quote:
Originally posted by liam.mccaffrey
check this out,
http://www.kineticvehicles.com/rollbarFab.html
quote:
Originally posted by fatfranky
quote:
Originally posted by liam.mccaffrey
check this out,
http://www.kineticvehicles.com/rollbarFab.html
Now That is ingenious
Locosting at it's best
personally im going to be using hole saws with the tubes clamped on to the vertical slide of my lathe.
i nearly got one of these before I decided on the lathe, linky