why heat treat?

[stuckinthemud]

Hi All,

I have cut a hazel stave and am going to make a small light bow for the range - a flat bow of about 30lb at 26".  I have read a lot of build-alongs on hazel self-bows and was wondering, what are the benefits of heat treating and what are the problems - it often seems to increase stress in the bow and increase the risk of crysals Do you apply heat treating to certain woods and are there others it should be totally avoided on?


Stuck
ps I don't mean treating to add reflex/deflex

[adb]

Have you read Marc's chapter on heat treating in TBB 4?

[Del the cat]

I was initially skeptical about heat treating because I didn't understand you need to go slow and get the heat right in.
I was just scorching the wood. (I ate the humble pie...  )
It will gain upto 10# draw weight, help fix bends in place that keep pulling out and improve cast.
It won't fix a badly tillered bow or magically mend chrysals.
It's a great tool in the bowyers armoury, but needs some skill, knowledge and a lot of patience.
Using it in conjunction with heat bending can achieve two results in one hit.
If you are not taking at least 30-40 minutes per limb you aren't doing it right!
Del

[Knoll]

When heat tempering the limbs, do you basically hold the gun in one spot until you've achieved desired heat application, or move gun up/down limbs to gradually build up heat?

[PEARL DRUMS]

At 30# Im not sure you will reap the benefits. But its a place to start and learn the skill.

[DarkSoul]

or move gun up/down limbs to gradually build up heat?

This!
Like Del said, you need at least half an hour per limb. Myself, I heat the bow in several section, each about a foot long. As soon as this section is very hot and caramel coloured, I move on to the next section.

[PEARL DRUMS]

I heat about 3-5" at a time clamping down each section as I go. 

[Lee Lobbestael]

I use an electric range. It heats a lager area at a time and makes it easier to achieve a uniform heat treating

[stuckinthemud]

That's a lot clearer, thanks all.

[Springbuck]

When heat tempering the limbs, do you basically hold the gun in one spot until you've achieved desired heat application, or move gun up/down limbs to gradually build up heat?

 I clamp it on a caul and hang it on supports @ 4" above my kitchen stove set to medium.  You can heat treat over a fire, BBQ, etc..  When I do use the heat gun, I keep it in one spot and move it an inch up the limb every couple minutes, so you are overlapping "spots", but everything gets 4 minutes.   Otherwise, I have dark and light spots up the limb.   Time varies with heat and thickness.   A  1/4" limb requires less time than a 12" thick limb.

[bushboy]

Yes heat treating is a great tool! Invented or reinvented by marc not sure but he has surely pioneered it thank's!the key is to have the right amount of wood to start with prior to h/t. If you start to thick most of the treated wood will be removed to achieve tiller.if you can treat and tiller with only a few scrapes it is the best