Brady Watson
02-23-2008, 12:03 PM
I wanted to post some pics of one of my recent commissions - A 72" diameter brass floor inlay for Christopher Newport University in Newport News, VA. Since the design was 72" in diameter, I had to machine it in 2 equal halves. Here you see the 1st sheet of brass laid up on the Bot. It weighs approximately 640 lbs and is about 72X36" and 0.500" thick.
1638
Since the Bot wasn't really designed to handle this much weight on it's table, I used a hydraulic lift table and a 2 X 3 X 0.375" piece of steel tubing to help take the weight.
1639
After checking myself & my SBP file 47 times, I started cutting. At 1st I used a 2-flute HSS end mill and compressed air cooling, but the brass pretty much laughed at that about one foot into the cutting. I wound up using a 4-flute titanium-coated end mill to do the cutting. No cooling or lube needed. By the way, anyone who tells you something along the lines of, "Aww...brass is soft...that cuts easy!" - has obviously never machined it before! Of coarse, it depends greatly on what alloy of brass we are talking about, as they vary significantly. Compared to machining brass, aluminum is a walk in the park. This is naval brass & despite what you may think (as I did), it doesn't come 'all pretty' at this scale. (More on this later)
1640
Here's the 1st half-ring machined. In hindsight I should have finished the surface before cutting it out.
1641
...and here's the 2nd sheet - which was sitting under protective cardboard, underneath the 1st sheet. Little did I know just how much the surface would oxidize. One man's rust is another's patina...this was the 1st time I wanted to throw myself in the wood chipper...The pits were between 0.003" and 0.006" deep...which is a lot on a large piece of metal. Not even a belt sander could get out the pits...I had to use a 4" angle grinder to get them out, then...
1642
...go over the entire thing with the belt sander to flatten it out...then orbital sand from 40# all the way up to 600# paper. To answer your question, NO that isn't 'Birdseye brass'
1643
Here's the result after many long days of sanding.
1644
Getting ready to machine the 2nd half of the ring...
1645
OK...a little explanation. This is the 2nd time where I was thinking about throwing myself into a wood chipper. On the last pass of cutting out the 2nd half, the part popped up on the inside track of the arc a full 3/16" ! NOW WHAT!!!??? Luckily I have friends that are even more willful and tenacious than I am...so after a few hours of head scratching and a little welding, we made a tool to tweak the brass back down flat. The vertical stud you see is counteracting us lifting the one side of the brass about 2 feet in the air! It really took a lot of tweaking to get it flat, but in the end it all worked out...and it was a reminder as to how important good friends really are!
1646
OK...back to machining. Letters were pocketed out about 1/4" deep using a 1/4, 1/8 & 1/16" end mill and ArtCAM Pro 2008 with Area Clear Rest Machining. All tool entries were ramped into the cut on an angle to minimize shock to the cutter & spindle and stepdown values were kept very low. This was a very challenging project and I had to tweak the VR values of the tool to get it set up to satisfy the needs of cutting dense metal - without throwing the tool into Alpha mode.
1647
Here you can see the letters have been over-filled with resin. They will be sanded flat before clear coating. The brass had to be pre-heated to 100°F, filled, the resin had to cure on it's own and then post-cured @ 150° for 5 hours to reach maximum hardness and durability. You can see part of the heatbox/oven in the background.
1648
Here's a shot of both pieces at the finisher's before crating them up. Brass is funny...it looks completely different at each part you view as you walk around it.
1649
Delivery time...The big guns from WM Jordan unloaded the brass from my truck at the CNU Library, where the brass will be installed.
1650
Keith Outten and I discuss installation, while Megan takes a candid shot.
1651
Here are the 2 halves sitting in the staging area until the stone masons install them in a few weeks. I can't wait to see the final result!
1652
1653
Overall this was a challenging project, but all in all, a real pleasure to do. To see the looks on people's faces when the crates were popped open was the real reward for me. I'm flattered to have been given this opportunity to come through for CNU, and look forward to the next exciting project that heads my way.
-B
1638
Since the Bot wasn't really designed to handle this much weight on it's table, I used a hydraulic lift table and a 2 X 3 X 0.375" piece of steel tubing to help take the weight.
1639
After checking myself & my SBP file 47 times, I started cutting. At 1st I used a 2-flute HSS end mill and compressed air cooling, but the brass pretty much laughed at that about one foot into the cutting. I wound up using a 4-flute titanium-coated end mill to do the cutting. No cooling or lube needed. By the way, anyone who tells you something along the lines of, "Aww...brass is soft...that cuts easy!" - has obviously never machined it before! Of coarse, it depends greatly on what alloy of brass we are talking about, as they vary significantly. Compared to machining brass, aluminum is a walk in the park. This is naval brass & despite what you may think (as I did), it doesn't come 'all pretty' at this scale. (More on this later)
1640
Here's the 1st half-ring machined. In hindsight I should have finished the surface before cutting it out.
1641
...and here's the 2nd sheet - which was sitting under protective cardboard, underneath the 1st sheet. Little did I know just how much the surface would oxidize. One man's rust is another's patina...this was the 1st time I wanted to throw myself in the wood chipper...The pits were between 0.003" and 0.006" deep...which is a lot on a large piece of metal. Not even a belt sander could get out the pits...I had to use a 4" angle grinder to get them out, then...
1642
...go over the entire thing with the belt sander to flatten it out...then orbital sand from 40# all the way up to 600# paper. To answer your question, NO that isn't 'Birdseye brass'
1643
Here's the result after many long days of sanding.
1644
Getting ready to machine the 2nd half of the ring...
1645
OK...a little explanation. This is the 2nd time where I was thinking about throwing myself into a wood chipper. On the last pass of cutting out the 2nd half, the part popped up on the inside track of the arc a full 3/16" ! NOW WHAT!!!??? Luckily I have friends that are even more willful and tenacious than I am...so after a few hours of head scratching and a little welding, we made a tool to tweak the brass back down flat. The vertical stud you see is counteracting us lifting the one side of the brass about 2 feet in the air! It really took a lot of tweaking to get it flat, but in the end it all worked out...and it was a reminder as to how important good friends really are!
1646
OK...back to machining. Letters were pocketed out about 1/4" deep using a 1/4, 1/8 & 1/16" end mill and ArtCAM Pro 2008 with Area Clear Rest Machining. All tool entries were ramped into the cut on an angle to minimize shock to the cutter & spindle and stepdown values were kept very low. This was a very challenging project and I had to tweak the VR values of the tool to get it set up to satisfy the needs of cutting dense metal - without throwing the tool into Alpha mode.
1647
Here you can see the letters have been over-filled with resin. They will be sanded flat before clear coating. The brass had to be pre-heated to 100°F, filled, the resin had to cure on it's own and then post-cured @ 150° for 5 hours to reach maximum hardness and durability. You can see part of the heatbox/oven in the background.
1648
Here's a shot of both pieces at the finisher's before crating them up. Brass is funny...it looks completely different at each part you view as you walk around it.
1649
Delivery time...The big guns from WM Jordan unloaded the brass from my truck at the CNU Library, where the brass will be installed.
1650
Keith Outten and I discuss installation, while Megan takes a candid shot.
1651
Here are the 2 halves sitting in the staging area until the stone masons install them in a few weeks. I can't wait to see the final result!
1652
1653
Overall this was a challenging project, but all in all, a real pleasure to do. To see the looks on people's faces when the crates were popped open was the real reward for me. I'm flattered to have been given this opportunity to come through for CNU, and look forward to the next exciting project that heads my way.
-B