Brazing Hearth

I need a brazing hearth and after look around at what I could buy I settled on making one.

Make

brazing-hearth-001The core of this build is fire bricks for a wood stove. You can buy sheets of Vermiculite online, but I saw these on ebay and after a rough sketch with regards to size they looked just the job.

Vermiculite Villager Stove fire bricks 9″x4.5″x1″(230mmx114mmx25mm)

The fire bricks were roughly £25 for 10off which is enough to make 2 brazing hearths.

Fixings

brazing-hearth-002

I decided to use long woodscrews to fix the bricks together.

I′m a tad worried that the screws will get hot and expand, this may move the bricks apart. After more than 4 years the fixings are still working well. 

The bricks are a bit lick very soft chipboard in texture and have a tendency to flake. This means you do have to be careful drilling and tightening screws.

brazing-hearth-003Checking screw diameter to then drill hole same size as the core of the screw. As you can see from this measurement the core of the screws are just over 3mm in diameter.

Pre-drill the holes with a 3mm drill bit to try and mitigate any tendency for the screw to split the vermiculite.

brazing-hearth-004Deep threaded woodscrews go into the fire bricks really well and you can tighten the screws and they appear to get a good purchase.

brazing-hearth-0052 screws in each corner.

You can countersink each screw using a normal countersink bit that you would use for wood.

brazing-hearth-006I trimmed one of the bricks down and used this part at the top of the hearth as a trap for when I need to get a lot more heat into the work piece. I used my Record BS250 bandsaw for this with a fine wide blade – probably better to use a bit coarser blade to clear material away as the blocks are quite soft.

brazing-hearth-007The base is raised 1 brick thickness high, I did this to give strength and to allow air to circulate underneath, might be a problem with large or heavy parts. This has worked well and the hearth is still in use after more than 4 years.

The design gives a good working area and uses standard blocks. One trimmed down block is used, but you could ignore this and just go for a straight simple design.

Points of Note

When making this you just need to take some time and carefully mark and drill the holes. The blocks are soft and will not take too much force before they start to crumble.

brazing-hearth-009

Nice and simple design with a fire brick each side. The rear brick goes between the sides and is fixed to the sides with 4 screws.

This view allows you to clearly see the screws holding the base bricks.

brazing-hearth-008

Brazing Hearth in Use

The result is rather cool, now need to see how well it performs over the next couple of months and will let you know.

brazing-hearth-use-001The hearth works really well for silver soldering parts. Here you can see me using it to braze phosphor bronze bushes into steel bearing blocks.

I arranged the parts towards the back of the hearth to take advantage of the overhang. This concentrates and reflects heat back into the workpiece. This saves a lot of gas and time. thus allowing me to work with what is otherwise just a small portable torch and gas cylinder all-in-one.

The bricks themselves do get warm and so best to place the hearth on an old piece of board rather than directly on a nice workbench. The screws holding the blocks together also get very hot and so allow the hearth to cool down before moving it. The heat from the screws is likely to burn.

Price: approx £25 – you can make two hearths for this price.

Conclusion

This really worked well for a couple of silver soldering jobs. The overhang area is essential to help concentrate the heat. This feature allowed me to silver solder a 2″ diameter piece of mild steel roughly 1/2″ long with a portable torch.

Cheap to build, roughly £12.50 per hearth plus a few woodscrews.


heat treating silver steel

Heat Treating Silver Steel

A brazing hearth is really useful when it comes to heat treating larger pieces of silver steel.

The hearth reflects back a lot of the heat into the part and this concentration of heat will allow you to heat a part more readily.


silver solder test open flame heat

Silver Soldering

Silver soldering is one of the most common metal joining techniques in model engineering. Also, used extensively by jewelers. Hence there are a number of references. This page is based heavily on model engineering experience and applications.


2 thoughts on “Brazing Hearth”

  1. I’d be interested to know how you get on with your hearth. I made mine back in 2008 from thermalite building blocks which seem to take the heat well but can be a bit crumbly/dusty. The big issue with the thermalite is that it grinds the teeth off the saw but it can be cut with a hand saw with very little effort. I think the screws will be ok as long as there is enough material between them and the surface, worst case is that the joints will become slack when it gets hot.
    The lip is a good feature as it guides the heat inwards. I may use that to improve my hearth.

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