Building a bandsaw on the cheap from mostly scrap wood

[footfootfoot]

Wine bottle corks

[lumberjim]

.

[Griff]

split and whittle

[footfootfoot]

He needs a lathe...

[glatt]

Tinkered with the band saw for several hours today, but nothing to show for it.

The table is made of particle board, and I had cut through the plastic laminate top and bottom to make it the right size. This left an exposed particle board edge. That stuff can suck up moisture and start crumbling like nobody's business. So I found an old partial can of oil based varnish and sealed the cut edges of the particle board.

I made new tabs to go on the top cover, but didn't install them yet. It was a rare moment of clarity. The saw has a bit of a vibration to it, so I wanted to figure out what was vibrating and fix it before locking in on a cover size. You can see the motor shaking a bit too as the frame shakes.

I read in that Bandsaw book Foot recommended that you should align the wheels so they are co-planer and not rely on the crowned wheels so much to align the saw blade. So I got out my straight edge to fine tune that. I figured I might need to shim the wheels with some washers to get them perfectly lined up. When I lined the straight edge up with the bottom wheel, the top wheel was a full 9mm out of alignment further back. WTF? I have no idea how that happened. Did I measure the shaft wrong? Is it a metric thing with the layers of the frame? I don't know, but I do know that I need to fix it before I finish the cover. It's going to mess with the cover a lot to move that top wheel 9 mm forward.

I took the blade off the saw and ran just the powered bottom wheel. The vibrations were still there. I took the bottom wheel off and ran just the motor. No vibrations. So I got out my dial indicator and measured the pulley on the powered wheel. As I slowly rotate it, the needle goes 5 thousandths in one direction and then 15 thousandths in the other. The pulley is 20 thousands out of round. I wonder if that's enough to cause those vibrations? I bet it is. So I'm attempting to turn the pulley again to get it nice and round. I think when I turned it before, my chisel was just riding up the hump and then down into the hollow. I hold it fast to the tool rest more this time as I turn the bottom of the pulley.

So the saw is basically completely disassembled right now as I try to tweak this stuff.

[footfootfoot]

Originally Posted by glatt

Tinkered with the band saw for several hours today, but nothing to show for it.

The table is made of particle board, and I had cut through the plastic laminate top and bottom to make it the right size. This left an exposed particle board edge. That stuff can suck up moisture and start crumbling like nobody's business. So I found an old partial can of oil based varnish and sealed the cut edges of the particle board.

I made new tabs to go on the top cover, but didn't install them yet. It was a rare moment of clarity. The saw has a bit of a vibration to it, so I wanted to figure out what was vibrating and fix it before locking in on a cover size. You can see the motor shaking a bit too as the frame shakes.

I read in that Bandsaw book Foot recommended that you should align the wheels so they are co-planer and not rely on the crowned wheels so much to align the saw blade. So I got out my straight edge to fine tune that. I figured I might need to shim the wheels with some washers to get them perfectly lined up. When I lined the straight edge up with the bottom wheel, the top wheel was a full 9mm out of alignment further back. WTF? I have no idea how that happened. Did I measure the shaft wrong? Is it a metric thing with the layers of the frame? I don't know, but I do know that I need to fix it before I finish the cover. It's going to mess with the cover a lot to move that top wheel 9 mm forward.

I took the blade off the saw and ran just the powered bottom wheel. The vibrations were still there. I took the bottom wheel off and ran just the motor. No vibrations. So I got out my dial indicator and measured the pulley on the powered wheel. As I slowly rotate it, the needle goes 5 thousandths in one direction and then 15 thousandths in the other. The pulley is 20 thousands out of round. I wonder if that's enough to cause those vibrations? I bet it is. So I'm attempting to turn the pulley again to get it nice and round. I think when I turned it before, my chisel was just riding up the hump and then down into the hollow. I hold it fast to the tool rest more this time as I turn the bottom of the pulley.

So the saw is basically completely disassembled right now as I try to tweak this stuff.

Even in the best of situations, it's an iterative process. It's worth the effort IMO. You inspired me to tackle my store-bought saw and for the first time in 10 years the thing cuts like it is supposed to. Duginske's book is great.

[xoxoxoBruce]

Originally Posted by footfootfoot

He needs a lathe...

Yes...

[glatt]

I figured out my misalignment problem. This vertical peice was built exactly according to the plans in metric. But apparently it was supposed to be as wide as those two 3/4 inch boards underneath it. I guess metric lumber is thinner than the US lumber I used.


So I just need to cut a 9mm thick shim to go in there. And things should line up.

Although maybe that will mess up the blade guide fit. I need to ponder this.

[footfootfoot]

It happens to the best of us, at least your bandsaw didn't go plowing through the atmosphere, continuing out beyond Mars and now could be orbiting the sun...

This article begs to be re-written, Onion style, with Glatt exchanged for NASA and bandsaw for rocket and Mrs; Glatt as the JPL Admin. Bu I'm too tired right now.

http://edition.cnn.com/TECH/space/99...ars.metric.02/

CNN) -- NASA lost a $125 million Mars orbiter because a Lockheed Martin engineering team used English units of measurement while the agency's team used the more conventional metric system for a key spacecraft operation, according to a review finding released Thursday.

The units mismatch prevented navigation information from transferring between the Mars Climate Orbiter spacecraft team in at Lockheed Martin in Denver and the flight team at NASA's Jet Propulsion Laboratory in Pasadena, California.

Lockheed Martin helped build, develop and operate the spacecraft for NASA. Its engineers provided navigation commands for Climate Orbiter's thrusters in English units although NASA has been using the metric system predominantly since at least 1990.

No one is pointing fingers at Lockheed Martin, said Tom Gavin, the JPL administrator to whom all project managers report.

"This is an end-to-end process problem," he said. "A single error like this should not have caused the loss of Climate Orbiter. Something went wrong in our system processes in checks and balances that we have that should have caught this and fixed it."

The finding came from an internal review panel at JPL that reported the cause to Gavin on Wednesday. The group included about 10 navigation specialists, many of whom recently retired from JPL.

"They have been looking at this since Friday morning following the loss," Gavin said.

The navigation mishap killed the mission on a day when engineers had expected to celebrate the craft's entry into Mars' orbit.

After a 286-day journey, the probe fired its engine on September 23 to push itself into orbit.

The engine fired but the spacecraft came within 60 km (36 miles) of the planet -- about 100 km closer than planned and about 25 km (15 miles) beneath the level at which the it could function properly, mission members said.

The latest findings show that the spacecraft's propulsion system overheated and was disabled as Climate Orbiter dipped deeply into the atmosphere, JPL spokesman Frank O'Donnell said.

That probably stopped the engine from completing its burn, so Climate Orbiter likely plowed through the atmosphere, continued out beyond Mars and now could be orbiting the sun, he said.

Climate Orbiter was to relay data from an upcoming partner mission called Mars Polar Lander, scheduled to set down on Mars in December. Now mission planners are working out how to relay its data via its own radio and another orbiter now circling the red planet.

Climate Orbiter and Polar Lander were designed to help scientists understand Mars' water history and the potential for life in the planet's past. There is strong evidence that Mars was once awash with water, but scientists have no clear answers to where the water went and what drove it away.

NASA has convened two panels to look into what led to the loss of the orbiter, including the internal peer review panel that released the Thursday finding. NASA also plans to form a third board -- an independent review panel -- to look into the accident.


Metric system used by NASA for many years

A NASA document came out several years ago, when the Cassini mission to Saturn was under development, establishing the metric system for all units of measurement, Gavin said.

The metric system is used for the Polar Lander mission, as well as upcoming missions to Mars, he said.

That review panel's findings now are being studied by a second group -- a special review board headed up by John Casani, which will search for the processes that failed to find the metric to English mismatch. Casani retired from JPL two months ago from the position of chief engineer for the Lab.

"We're going to look at how was the data transferred," Gavin said. "How did it originally get into system in English units? How was it transferred? When we were doing navigation and Doppler (distance and speed) checks, how come we didn't find it?"

"People make errors," Gavin said. "The problem here was not the error. It was the failure of us to look at it end-to-end and find it. It's unfair to rely on any one person."

[glatt]

I even bought a metric tape measure and used metric units every time I measured anything.

The plans said that US dimensional lumber could be used for the frame, but I wish I had bought a thickness planer and run the boards through to make them all the standard metric thickness when I started this thing because this is the third time I have run into an issue with the frame being thicker than the plans called for and it caused a problem.

At least it's in my basement where I can fix it. If it was on Mars, I would be out of luck.

[footfootfoot]

And stationary rather than travelling at 24,000 KPH

[glatt]

I spent all weekend taking it apart and tweaking it.

The biggest improvement in eliminating vibrations was re-balancing the wheels. It's possible there was moisture in them from the glue up and as the glue dried and the wood around the glue dried, the balancing I did before had to be tweaked a little. Although it's also possible that I just did a shoddy job last time.

Also, a big improvement was that the pulley on the drive wheel was 20 thousands of an inch out of round. So I spun that wheel up again and very carefully used a chisel to get the pulley groove round. I could feel the chisel wanting to rock back and forth with the pulley as the wheel rotated each time, so I really held it tightly against the tool rest and just eased it ever so slightly against the pulley to nibble gently away at the higher side as it came around. I could hear a bit of a pulsating cutting sound as it only nibbled away at the high side. Once the sound became constant cutting, I stopped. When I measured it again, it was 5 thousandths out of round.


Then I turned my attention to getting the wheels lined up better. And I started taking pictures.

To get the top wheel directly over the bottom wheel, I needed to pull it forward by 8-9 mm.

So I started by removing the brackets that hold the entire top wheel assembly in place. Fortunately they are just screwed on. No glue.



Then I cut two shims 8 mm thick.



I glued the shims to the uprights.



And clamped them to dry

[glatt]

Maybe this was another metric vs. USA issue, or maybe it's just a bad detail in the plans, but the notch I cut in the table support to make room for the lower powered wheel isn't long enough to pull the wheel forward and remove it from the shaft. To remove the lower wheel, you have to take the table off. So after removing the table to get the wheel off, I chopped the notch a little to make getting the wheel off easier in the future.



And here's is the top wheel reassembled after putting that shim in.



I don't have enough hands to hold a long straight edge and take a picture at the same time, but this picture is supposed to show that the top and bottom wheel are coplaner now. Yay.



With the top wheel pulled forward, the blade guard made out of the oil can doesn't fit around the wheel any more. So I have to make a bigger one. Fortunately, I have another one of those big olive oil cans in my junk pile. This time, I plan to use the English side of the can.

[glatt]

It will be as wide as this blue tape.

I didn't get a shot of the completed guard yet. But it's done and installed.



The saw blade is tracking well now, and the vibrations are much improved.

Now I have to work on the cover again.

[Griff]

Bravo!