Monday, January 31, 2011

Fire Pit Project

I spotted a professionally made fire pit while wandering around Fredericksburg, Texas.  It looked like a great addition to our patio and a fun welding project for me.  Below is a picture of the final product, complete with a swing away grill and foot-rest/guard.  The only thing left to do is to get it to the patio... need a couple of friends to help carry it!  I had a great time creating it.  It pushed my beginner level welding skills and forced me to learn some new tricks.

To start with I had to find the rounded tube piece that makes up the body of the fire pit.  Typically, a  "tank head" is used.  A tank head is the end of a compressed gas or liquid tank.  They can be purchased new, but have more character and cost less if recycled from a scrap yard. Here's the tank head I salvaged locally.  Note the jagged edge on the rim and small pipe sticking out of the bottom.  These had to be corrected/removed.

The first step was to clean up the rim of the tank head.  It had been rough cut with an oxyacetylene torch to get it down to a size that could be handled as it was removed from it's prior home.  Whoever did it was not concerned with the final product.  After some careful measurements and drawing out a guide line I trimmed down the rim with my Hobart plasma cutter.  I'm still amazed at how well plasma cutters work.  The cut was amazingly clean and fast.

Next step required a couple minutes with an angle grinder.  The plasma cutter did such a neat job that very little grinding was needed.

Next up were the legs.  I decided to keep it simple and follow the "3 points make a plane theory".  The pit was going to have three legs making it more forgiving on the measurement and fabrication side of things.  The plan was to have the three legs attach towards the bottom edge of the tank head and come down at an angle. Each leg would have a quarter inch thick plate steel "pad" to keep it from sinking into the ground or damaging a patio's surface.  Click the picture above to watch a video of me cutting the 1 1/2" 14 gauge steel tubing to make the legs.  Oh, and yes this is my custom built chop saw and cutting grate table. You can see more by visiting my previous post.

Here I am rounding the edges of the pads with the Hobart plasma cutter.  Click the picture to watch the video.

I followed the measure twice, cut once rule and still goofed it up.  The legs should be further under the tank head.  Had to go back to the saw and try it again.  Luckily I didn't have to fabricate new legs.  Note the rounded pads on the tips of the legs.

After re-cutting the top of the legs they fit into their intended spots.  This picture was taken after the legs were carefully positioned and tack welded in place.   I surprised myself in that there was less than a quarter inch variance on any two measurements taken from edge of the rim to the ground (Beginners Luck!).

Now for the swing away grill.  I wanted the edge of the grill to closely follow the curve of the pit.  Having never bent this type of material I wasn't quite sure how to proceed.  I ended up bending the band around the pit and clamping it as I went.  A quick cut with a cutoff wheel on the grinder and I had a complete loop.  One tack weld and the clamps could be removed.

I finished up the weld that held the two ends of the band together and added a half inch rod across the middle making sure that one end of the rod rested on the joint.

Using a large nut and bolt as a pivot point I was able to create the swing away feature.  With the nut welded to the pit and the bolt welded to the loop you can remove the grill or adjust the height by spinning it around.

Another first for me was bending the 5/8" rod to make the foot rest/guard.   Most of the recommendations I found online involved equipment that I didn't have access to.  I settled on doing it the old fashioned way.  I took a 10' section of rod and laid it across the mouth of a piece of channel steel (see above).  By striking the rod between the edges of the channel with a hammer and slowly moving the rod I was able to slowly bend it into a circle.  It was a challenge to make sure it was only bending in one direction.

This picture shows the rod after I cut it to the proper length, worked it into a circle and clamped the ends together.  A quick tack weld and I was able to take it to the welding table for further adjustments.  One hour and one sore back and I had a nearly perfect circle.

Using short pieces of the same rod I attached the foot-rest/guard to the pit.  This picture shows three attachment points.  The final version had a total of six.

Another view showing the swing away grill screwed on. 

Last thing to fabricate was the grill to fit inside the band.  I laid the band on top a piece of expanded metal, traced the outline and cut it out with the plasma cutter.  I left it a fraction of an inch wider than needed so I would have room for error and ensure a tight fit.  There were several places that I had to use the grinder to get it to fit.  I used my stick welder and a 7014 rod to tack the grill in place.

I used an twisted knot wire brush on an angle grinder to remove the rust, paint and welding crud off the pit.  A light sanding and cleanup and the pit was ready for paint.  I used Rustoleum's flat black, high heat spray paint. It took three cans to apply two coats.

Here's the finished product waiting to be taken to the patio.  I kind-of forgot about the weight.  It's easy to slide across the concrete floor in the garage, but not so easy to get across gravel paths. I'm really happy with the way it turned out and had a great time building it.

Friday, January 21, 2011

Darth Vader Approved?

I recently added a Hobart Airforce 700i plasma cutter to my shop.  Hobart really didn't provide much guidance as to what type of eye protection is required or even recommended when using the 40 amp unit.  This being a hobby, me being inexperienced and after some of the lessons learned via the school of hard knocks I tend to err on the side of caution. I submitted several messages on the Hobart online forum and eventually got the recommendation to use "eye protection with a minimum of #5 lens shade".  I already knew that much and had been using my #5 shade goggles from my oxyacetylene torch when running the plasma cutter.  Most of the time the torch handle blocks the arc light. It's only when you cut at angles or are forced into an odd position are you exposed to more light and potential for sparks and other debris flying back at you.  I also found that I commonly went back and forth from plasma cutter to grinder requiring me to switch to a clear face shield so I could see what I was doing.   I wanted additional protection for my face while using the plasma cutter plus make it as easy as possible to go from cutting to grinding.  Preferably without changing safety shields.

After a little Internet research, I found a combination face shield/drop down shade lens made by Hypertherm titled, "Hypertherm Multi-Purpose Plasma Cutting Operator Face Shield".  I was able to get past the long-winded name and see that it might actually work.  The clear lense provides protection to your face from sparks or other debris from the grinder and a flip down #6 shade lens for use with the plasma cutter.

I ordered one from Baker's Gas & Welding Supplies, who by-the-way has great customer support.  I accidentally ordered the #8 shade model instead of the #6.  A quick call Baker's fixed the problem and confirmed the order.  The correct shield arrived on time as promised.  An initial inspection showed it to be a quality product.  It's both well made and well designed.

The shield is comfortable and not as bulky as the cheaper generic clear one I use for grinding.  The lens itself is of better quality and doesn't fog up or scratch as easily as the generic model.  I gave it a quick run through while using a grinder and found it to be very comfortable.  You almost don't notice the #6 shade protruding from the top of the shield.

Next I tried it out with the plasma cutter.  I had some initial problems.  The #6 shade, while only one increment darker than my #5 goggles, made it much harder to see the workpiece prior to starting an arc.  The distance between the shade and my face allowed light to enter from behind, causing a reflection, and further obstructing my view.   Even indoors it was impossible for me to accurately see what I was doing if I had sunlight from a door or window coming from behind me.  I eventually was able to set up my cutting table in such a position to keep most light sources in front, allowing me the visibility I need to accurately use the cutter. 

I'm wondering if this shield is designed for more powerful cutters that cast a brighter arc.  It's well made, provides great protection and works for grinding applications, but only work with my plasma cutter if I'm using it at the high end of it's 40amp range and I'm able to position myself without light sources behind me.

Friday, January 14, 2011

Fun Stuff While Learning To Weld

Here are some of the projects that I've used to test out equipment, figure out how things work and try out tips and techniques that I've only read about.  You can't be timid, diving in and getting your hands dirty is the only way to learn. I'm finding it takes patience and tons of practice to grasp these skills.

I used this fish to practice heating and bending items with the oxyacetylene torch and tacking light gauge metal with the stick welder.   This was before I had a plasma cutter so I cut the sheet metal with a grinder/cutoff wheel.  What a difference the plasma cutter makes.  Cuts are cleaner, can be much more complex and are exponentially quicker to make.

Here's a knight-in-armor guy I put together using the oxyacetylene torch.  I had fun adding pieces of rod, bending them into place and trimming off the excess using a pair of bolt cutters.  The torch gave me great flexibility and allowed me to be creative on-the-fly and not have to have every piece planned and pre-cut.

Different angle of the same guy.  I made the helmet out of one inch thin wall tubing.  The details were cut using a grinder/cutoff wheel.  The shield was made from thin flat steel cut to length and welded together using the torch.

After getting tired of practicing welding different angels on scrap metal so I came up with the idea of building a cube out of  quarter inch plate steel.  I forced myself to make all the welds with the cube in place (without rotating it to an easier angle).   Some of the verticals were a real challange for me.  Had to play around with the amperage and weld speed before I found the right combo. I ended up giving the grinder a real workout.  Had to build up and grind down many area to get a "perfect cube" with sharp edges.

Eventually I had a clean cube so, now what?  I hadn't really thought through what I was going to use it for once finished.  I ended up adding casters to the bottom mounted on heavy gauge angle iron, painting the whole thing safety blue and using it as a small patio table.  It's perfect size to roll up next to a chair or lounger and hold a drink.  It's also probably one of the sturdiest patio tables around.  The weakest component, the casters, are rated to 1,000 lbs. a piece.  So  if need be my new table can support a mid-size sedan.  You just never know when when that could come in handy.

I called this one "Man Riding Meteor".  This may have been my first "real" creation ever.  I used the oxyacetylene cutting torch to carve out the base from quarter inch steel.  I left the edges intentionally jagged to look like a flame trail or meteor flying through the air.  The head and feet are made from chain links and the body is quarter inch steel rod.  I used a oxyacetylene torch to weld everything together.

A view of my shop (the wife calls it our garage).  The major tools are a Victor oxyacetylene setup, Hobart stick welder, Hobart plasma cutter, Dewalt chop saw and Ingersoll Rand air compressor.  I built the tables and racks from scratch.  The third table/rack with the bender on it is still in works.  I plan on using it hold all my scrap material in the lower half and have the top free for a vise and the light material bender.  I'm going to have to devise a way to have drop-down legs secure it from rolling around while bending or prying.

This one is kind of the ugly duckling.  It doesn't seem to have too many admirers.   I created it while playing with scrap to practice different weld angles angles and material thicknesses.  The top is held to the base with an old truck water pump.  It can swivel a full 360 degrees.  Many of the other pieces move or spin.  This was a great learning experience for me.  Great to experiment with different welding rods, amperage settings and materials.  Also presented my with an opportunity to be a touch more precise with the cutting torch.  I removed small nipples from the top of the water pump without damaging or marking the rest of the piece.  I'm guessing that this one will eventually find it's way back into the scrap pile.