Pottery Kiln Fire Grate

A client brought me drawings of several ironwork projects.  One was a pottery kiln fire grate.  After some discussion, we decided to make it in two sections to make it easier to move.  Also I designed a system which would allow very easy replacement of the grate bars as they burn out.

The legs and front and back rails are at the periphery of the fire and not as likely to burn out as the grate bars.  The bars are upset on each end by peening so they can’t slip out of the rails and the rails lift off when the corner drop pins are removed.

In this case, the design is more fabricating than forging.  The rails were tack welded and the 7/8” holes for the bars were drilled.  Then the tack welds were removed.  In earlier grates I have fullered the holes.  The drop pins are forged from 5/8” round.  The shank is drawn down to 3/8” weak and the head is upset in multiple heats.  The grate bars ends are peened with the help of a vise socket buck.

Client's sketch.

Construction plans with modular design and provision for quick change of grate bars.

Peening of grate bar ends in a vise socket buck.

Making a Fire Grate

I’ve only made a few fire grates.  My clients haven’t cared much about how they will look and just wanted them simple.  That pretty well makes it a fabrication job.  They haven’t provided much opportunity for forge work and they require a site visit to study the fire box and chart the footprint, etc.  It’s the kind of job I now try to avoid, but I’m glad I learned a little from the experience I have had.

On the first grate I made I used, as I recall, 5/8” square bar and the clients turned out to be serious log burners.  The center part of the grate only lasted a couple of years.  When I built their next one I used larger stock and made the design such that replacing the center grates would be easy.  That became my standard plan.  

My approach was to measure the fire box and draw a sketch and take a couple of photos.  If there was some special feature such as a gas pipe to supply a log lighter it had to be accommodated when deciding where the feet of the fire grate would be placed on the trapezoidal shaped floor.  With the position of the feet recorded on the sketch I could return to the studio and make the two end bridges and set on a layout table just as they would sit in the fire box.  Then, I cut the front and back rails which would support the grate bars.

Then, I would decide whether a center bridge would be needed to support the rails and how many bars would be needed to fill the width with a 3” or so gap between bars and mark those positions on the front rail.  A soapstone line can be drawn on the layout table extending back along the line of each end bridge to a vanishing point.  Then, using a chalk line or a straight edge lined up to the bar positions on the front rail the corresponding positions can be marked on the back rail.

Usually, there were seven to nine bars of varying length, due tot he trapezoidal shape.  Rivets were my favorite for attaching the bars to rails.  They would allow easy removal for grate bar replacement.  In both the bridges and the grate bars the bends were done by making a shallow bandsaw kerf, heating in the coal fire and bending.

Recently I made a grate for a potters kiln using a different design which allows even easier bar replacement.   I’ll get that material together and post it soon.

Site visit sketch.

Improved sketch of foot positions.

Improved sketch of firebox with gas line pipe.

Vanishing point grate bar layout plan.

Drill hole positions for rivets marked.

A flame finial grate assembled.