[TheForge] Lamps and pipe slitting.

[theforge@mailman.qth.net]

In a message dated 1/1/2002 5:54:09 AM Pacific Standard Time, 
theforge-request@mailman.qth.net writes:

<< Anyone have any other wonderful ideas for pipe >>

Ralph, 

Just finishing up a book called "Advanced Metal Working Techniques with Peter 
Renzetti". Here's how he handled the pipe slitting for some 6' torchieres. 
Thought you might find it of interest. Might be a bit difficult to understand 
without some diagrams. If you want them, let me know off line. 

And all too obviously, I am sure, this is an underhanded way of promoting 
this book.

Will you be coming down to Gichner's this year? 

Don Plummer

The columns for the torchieres are about 6 feet in height and each of the 
total torchieres are 7-1/2’ high. They consist of 4 1-1/4" naval bronze tubes 
setin a square with four 6' filets filling in the spaces between the tubes. 
Each tube is 72” long and that means each of those thin filets must be 72” 
long also. Here’s the technique I used to get those filets. 
    
The filets are segments of stainless steel tubing that are half the size of 
the larger tubes. That is they are cut from stainless tubing that is 3/4” ID. 
The photo to the right shows the simple device that will work well for this 
application. This is a piece of plate aluminum that is probably about 3” 
thick. This piece will be subsequently clamped in a milling machine or 
something similar. For your own application choose the aluminum stock 
according to how you will be clamping it. Then drill a hole exactly the 
outside diameter of the tubing you from which you will be cutting a segment. 
Make it near an appropriate edge because you will want to cut a slot in it 
that will allow a slitting saw to run through this channel. In this instance 
I used a slitting saw with a 4” blade that is 1/16” thick. This fits on an 
arbor on the milling machine that is on a vertical shaft. Saw is cutting 
horizontally. Also, you will need to drill a small hole through which you 
will later insert a guide pin. Note this at the top of the aluminum block. 

It is very important that everything be rigid. That’s part of the beauty of 
the Bridgeport milling machine is you can lock all the tables and keep 
everything very positive.  It needs to be solid cause you are always pushing 
everything. Feed to the saw needs to be very positive and you need to control 
that feed rate into the saw. It actually takes quite a bit of effort to push 
this through the blade. RPM of blade is important and it needs to be 
controlled to prevent bounce. You also need to have fluid because stainless 
can be difficult to cut as it is a resistant material. It is very abrasive 
and plastic so need something to keep it from gumming up, must be lubricated. 

Also, controlling of the movement of the rod being cut into the blade is 
worth some consideration as there is considerable resistance from the blade 
revolving against the tube. Thought should be given as to how this will be 
handled AND controlled. In this case I used a simple device that is much like 
the doohickey used on the piston of a storm or screen door to hold it open. A 
similar device is used on the newer caulking guns.  I fixed a lever to the 
top of the Bridgeport table and attached a cable to a tab of metal drilled 
larger than the tubing and with a slight bend to it.  When I pulled against 
the lever it would lock and pull into saw. The other way it could slide 
easily for repositioning. This gave me more mechanical advantage and allowed 
me to pull it through with little effort and a more positive feed. Obviously 
one could accomplish the same effect with a rack and pinion, a mechanical 
feed, or something more automated. But this worked quite well for the limited 
number we had to to.

One of the basics of metalworking is that you gotta figure out how to do 
things. And one of the best ways to do that is to apply other experiences 
from your life. One must constantly think about what you are doing and how 
can it be done better, faster, cheaper, safer. Part of my theory of 
relativity. 

Once your jig is appropriately made we can begin cutting the filets. Mount 
the jig in your milling machine or whatever you are going to use to make this 
initial cut. I use a milling machine because I have one. With a little 
imagination I am sure you could come up with some alternative device that 
would perform the same function cleanly and safely. This will be a form of 
conventional cutting. That is, the blade will rotate toward you as you push 
the tubing into the jig. Set it’s depth to cut cleanly through the walls of 
the tubing. We ran our first 6 foot segment through and it cut a slot from 
one end to the other.  The 3-5’ diameter of the blade will keep the first cut 
straight and longitudinal. 

Now to cut out the segment. Remember I mentioned a paragraph ago about the 
guide pin. Well, you will have to now insert a metal pin in that guide hole. 
It will be used to follow the slot just cut. It must be positioned so that it 
will give you a segment filet that is the correct width for your application. 
Now run the tubing through again and you should have your filet. 

If you used a slitting saw as suggested you should have a filet that is 
without burr. An abrasive disk or alternative blade may introduce a burr that 
could complicate the subsequent fitting and soldering. Slitting saws have no 
offest in the teeth and they cut very smoothly. I was able to get three 
segments per 3/4” stainless tubing.  We needed four of these per torchiere or 
sixteen in total. Once the jig was in place and correctly positioned this 
task did not take long at all. And every filet was exactly the same. But we 
did have to cut about 100 feet of the filets in total.