If you are planning Q1 capital spending for a tool room, job shop, or a heat treat department, the right oven furnace choice matters. Temperature headroom, insulation, door ergonomics, burner style, controls, utilities, and workload fit all pull in different directions. This guide compares three proven families from Charles A. Hones, Inc. FireBox‑IS, FireBox‑HT, and Fiber‑Box. You will see where each model slots into common processes. You will also get a short worksheet to size your chamber and match your quench plan.
Operating temperatures and where each model fits
- FireBox‑IS, rated to 2,000°F. A dense firebrick stack. Excellent for hardening, normalizing, preheat, and many carburizing setups with boxes or stop off compounds. A strong generalist for tool steels and carbon steels.
- FireBox‑HT, rated to 2,150°F. A hybrid insulation stack, 4‑1/2 inches firebrick plus 2 inches block insulation. When you want more temperature headroom, faster recovery, and tighter control around critical points for high alloy or air hardening steels, HT is reliable.
- Fiber‑Box, rated to 2,200°F. A fiber and firebrick combination, with firebrick in the combustion chamber and door seal and fiber on the sides and rear. Heats fast, recovers quickly, and holds high setpoints with less mass. Ideal for tool steel hardening cycles, glass and enamel work that benefit from quick response, and high mix job shops.
What temperature do you heat treat steel? Typical austenitizing ranges are 1,475 to 1,900°F depending on the grade. Tempers run 300 to 1,100°F. Carburizing often holds 1,600 to 1,750°F. All three families cover these requirements. Choose higher rated models if you want margin for process development or heavy loads that pull heat from the chamber.
Insulation stacks and heat profile
A dense firebrick wall stores heat and delivers stable soak conditions. It is slower to heat up, but steady. FireBox‑IS uses thick firebrick throughout for durability and uniformity on long soaks.
A hybrid wall blends brick where flame contact and sealing matter, and fiber where quick response helps. FireBox‑HT and Fiber‑Box use this approach in different ratios. The result is faster heat up, better turn around between loads, and lower gas consumption on many duty cycles.
For carburizing with boxes, the greater thermal mass of FireBox‑IS can help stabilize the box environment. For frequent open door cycles and short runs, Fiber‑Box has the edge.
Door styles and ergonomics
Standard builds include counterbalanced guillotine doors with robust seals. Doors open cleanly, reduce radiant spill, and protect operators. Air‑operated doors are available on request for production work or when you want hands‑free loading. That option pairs well with roll‑out quench tanks when you need consistent time from furnace to quenchant.
Burners, utilities, and controls
Charles A. Hones furnaces use Venturi style gas firing that often runs at low gas pressure without blowers. Spark ignition or digital ignition packages are standard. A digital PID controller manages temperature. High limit protection and flame safety devices are included.
How do industrial furnaces get so hot? Efficient combustion, proper primary air mixing, and the right refractory lining. Venturi burners entrain air at the mixer, then combust in a tuned chamber. The insulation keeps heat in; the controller cycles firing to hold setpoint. For many users, this natural draft method delivers the needed temperature without the complexity of blowers.
Pros and cons, natural draft Venturi vs. powered burners:
- Natural draft Venturi systems
- Pros, simple gas train, low electrical demand, fewer moving parts, quiet, reliable at low to moderate firing rates, good for a wide range of heat treating ovens.
- Cons, less control over excess air at extreme capacities, chimney and room conditions influence draft, limited turndown compared to a fully modulating, forced draft package.
- Powered burners
- Pros, tighter combustion control, high turndown, better compensation for varying loads and chamber backpressure, useful in very large chambers or specialty atmospheres.
- Cons, higher initial cost, more components to maintain, higher electrical requirements, potential noise.
Most tool room ovens in this size range run well with Venturi systems. If you need a forced draft package, discuss powered options and controls during the spec review.
Workload sizes and chamber selection
FireBox‑IS offers twelve standard sizes from 18 x 24 x 10 inches up to 30 x 84 x 16 inches working space. One example handles 24 x 48 x 14 inches and up to 300 pounds. FireBox‑HT lists six compact to mid sizes, such as the 1414S at 14 x 14 x 8 inches and the 1818L. Fiber‑Box covers comparable footprints, with fiber construction improving ramp and recovery for the same chamber volume.
Map your largest part to internal width, depth, and height. Leave clearance for circulation and safe handling. For fixtures and carburizing boxes, account for box walls and lids. If you plan a quench pull straight out of the door, confirm hearth height and door travel.
Process mapping, which furnace excels at what
- Hardening, tool steels and carbon steels: FireBox‑HT and Fiber‑Box for response and headroom. FireBox‑IS if you favor thermal mass and long soaks.
- Tempering: All families handle temper ranges easily. If tempering is a large share of work, consider separate temper ovens to free capacity.
- Carburizing: FireBox‑IS works well with pack boxes and stable long soaks. Fiber‑Box is also viable where fast heat up reduces cycle time before the soak.
- Preheat and staging: Any model performs. Choose Fiber‑Box for frequent door cycles and short dwell jobs.
- Glass and enamel work: Fiber‑Box for fast response and high peak temperatures up to 2,200°F. Stable sealing at the door helps with atmosphere control around the work.
A quick worksheet to right‑size your furnace
Use the prompts below before you request a quote.
- Part size and fixture allowance
- Largest part L x W x H:
- Fixture or box allowance (inches on all sides):
- Required clearances for handling (inches):
- Throughput and duty cycle
- Pieces per hour or per shift:
- Typical load weight:
- Number of door opens per hour:
- Preferred ramp time to setpoint:
- Soak time at temperature:
- Quench strategy
- Quench medium (oil, polymer, water, air):
- Quench location (roll‑out tank, adjacent tank, remote):
- Required door to quench time:
- Desired air‑operated door or manual:
- Utilities and site constraints
- Fuel (natural gas or propane):
- Available gas pressure:
- Electrical supply for controls (120V standard):
- Venting path and stack details:
- Controls and safety
- Digital PID setpoint profiles needed:
- High limit setpoint:
- Flame safety requirements and interlocks:
What equipment is used for heat treatment?
A quick worksheet to right‑size your furnace
Common equipment includes heat treating ovens, salt bath furnaces, quench tanks, fixtures and baskets, temperature controllers, and gas trains with safety shutoff. Charles A. Hones builds the oven furnaces, salt baths, and quench tanks that cover most in‑house needs. If you are exploring broader categories, browse our heat treating equipment lineup to see standard packages and options.
What are the four types of furnaces?
In industrial use, you will see gas fired box furnaces, electric box furnaces, salt bath furnaces, and atmosphere furnaces that use sealed or semi sealed designs. Within gas fired designs, natural draft Venturi packages are common, and powered burner systems serve larger or specialty chambers. For metal melting, separate melters exist, distinct from heat treat ovens.
What are the five main types of heat treatment?
- Annealing
- Normalizing
- Hardening
- Tempering
- Case hardening, including carburizing and carbonitriding
Your temperature window, soak time, and quench medium determine the furnace build and options you should choose.
Which type of furnace is best for heat treatment?
For general tool steel and carbon steel work in job shops, a gas fired box furnace with digital PID control is a practical answer. Within the Charles A. Hones line, pick FireBox‑HT or Fiber‑Box if you value ramp speed and headroom. Choose FireBox‑IS if you want brick mass and steady, even soaks. The best choice aligns with your heaviest load, the number of daily cycles, and your quench plan.
Options that increase throughput and consistency
- Air‑operated doors. Improve repeatability on time to quench and reduce operator strain.
- Roll‑out quench tanks. Mount on tracks in front of the door to shorten path and time from furnace to quenchant.
- Silicon carbide hearth plates. Included on Fiber‑Box. Durable and stable.
- Spark ignition packages and flame safeguards. Standard on most models. Confirm in your quote.
Budget notes and lifecycle cost
A FireBox‑HT in a compact size can be an economical way to add high temperature capacity. FireBox‑IS covers larger chambers with heavy loads. Fiber‑Box delivers energy savings when cycles start and stop all day. Natural draft firing keeps electric consumption low and maintenance simple. Forced draft can be specified when your loading or process needs it.
Ready for a spec review and quote?
Charles A. Hones, Inc. has designed and built gas fired ovens and furnace burners in New York since 1911. Every unit is manufactured in the USA. Send your worksheet and questions to info@charlesahones.com or call 315‑623‑2124. If you are comparing models or planning a custom size, ask for a review of your part mix, daily cycle plan, and utilities. We will help you choose the right heat treatment furnace and options for Q1.
Internal resources you may find useful:
- Explore our heat treating ovens and related gear here, heat treating equipment.
- For specialty burner packages and guidance, see process burners.
- If you need a full oven family overview, visit industrial furnace supplier.