Thermometer for bending blanket

[jeffhigh]

I've been bending by hand with an Ibex iron, but have now got a blanket.
What do you use for temperature measurement and where in the bending sandwich do you put it?
Thanks

[Dominic]

Jeff, I have a meat probe which is OK but I doubt the accuracy of the number I am seeing due to gaps around the probe end. I use slat, wood wrapped in wet paper, slat, blanket slat. I stick a probe into the wood layer at the waist. I am sure I am not getting the correct absolute temp but relatively my method works.

I really like the look of the new LMI control box. Has computer controlled dial in heat for more accurate wood heating for different woods. A thin wire probe goes in with the wood layer and has good contact with the wood and the blanket above. I also like the cantilevered bending machine body but I wouldn’t buy one. Simple enough to make. I thought it would be good to mount one flush to the wall above a bench out the way. Then loading and unloading sides from the side is simple.
Good luck
Dom

[jeffhigh]

Thanks Dom
Do you pull out the thermometer befoer cranking down the waist caul?

[Dominic]

Yes, but I pull it out before cranking it down. Its a thin metal tubebut is too thick to fit in the wood layer without getting crushed. I really use it to check that the blanket is working. The variable knob on my temp set box is a bit dodgy and sometimes it does not heat up properly. You can get those surface discs but they will sit on the outside of your stack and again not give you any idea what temp the wood is at. I would be great if I could find something that could be taped onto the wood and left there during heating and bending and would give accurate temp of the wood.
If anyone knows of such a device let us know.
Cheers
Dom

[Allen]

I use to use the thermometer. Have a couple from Dick Smith. But honestly, after bending a dozen sets using it, I noted the time it took to get to temperature and now just go by the clock. For me it's 2 minutes to heat. Bend in 30 seconds. Turn off blanket. Let cool and then cycle through the same times again.

[Bob Connor]

I do it much the same as you do Al.

Last time I used the thermometer was showing Pete Williams (forum member) what the heat is doing.

when I was using the thermometer I was starting the bend at 110 degrees.

Most of the problems I've seen with bending sides is having them too thick.

I don't have that problem any more as I'm laminating my sides and bending them at .040".

Don't even have to bother spritzing them.

Regards

[auscab]

I don't have that problem any more as I'm laminating my sides and bending them at .040".

Don't even have to bother spritzing them.

Regards

Bob,
when you do it this way , aren't you going through twice as much timber to get it down to .040" ?
and why not stack .6 mm veneers ?

[Bob Connor]

Yeah. twice as much timber but the guitars sound twice as good

I now buy low grade timber specifically for the internal side.

[brian64]

Bob, if you're not using veneers, how are you getting to .040" in your laminations? Are you laminating thicker pieces and then thicknessing? What's the difference in end result between what you're doing and laminating veneers?

Thanks,

Brian.

[Graham Long]

Hi,
Going back to the original question about temperature measurement. I've been using simple thermocouples, they are as simple as twisting two wires together. Very slight gauge, with Teflon insulation so they can be put into the foil wrap or under the slats so you get the actual temperature of the wood.
Cheers
Graham

[Bob Connor]

Bob, if you're not using veneers, how are you getting to .040" in your laminations? Are you laminating thicker pieces and then thicknessing? What's the difference in end result between what you're doing and laminating veneers?

Thanks,

Brian.

I run them through the drum sander until I get them to the required thickness Brian.

There's probably no difference to using multiple laminations.

I have spoken to a veneer mill about doing me up a heap of sides at .040 and there's no problem having that done.

I resaw a lot of my own wood so there is never any shortage of sides with knots and other imperfections that are still perfectly good to use for the internal facing laminate.

Regards

[brian64]

Thanks for the reply Bob. How many layers do you have in your laminations? Are they all parallel grained, or do you have a cross-grained layer?

Thanks,

Brian.

[jeffhigh]

Hi,
Going back to the original question about temperature measurement. I've been using simple thermocouples, they are as simple as twisting two wires together. Very slight gauge, with Teflon insulation so they can be put into the foil wrap or under the slats so you get the actual temperature of the wood.
Cheers
Graham

That sounds interesting Graham.
Any details on your setup, I know bugger all about thermocouples?

[Bob Connor]

Thanks for the reply Bob. How many layers do you have in your laminations? Are they all parallel grained, or do you have a cross-grained layer?

Thanks,

Brian.

Only the two layers Brian and they are both quarter sawn with the same grain orientation.

Only reason is that is the wood I have available. I don't think the grain orientation would make that much difference in this situation. I glue them with Titebond. The American builders I know use epoxy but I try and avoid it wherever possible due to it's sensitizing properties.

[Graham Long]

A thermocouple is basically a joint between two dissimilar metal that produces a small voltage (emf). This voltage is proportional to temperature.
The ones I use look like thin speaker wire (figure 8 type flex) but have teflon insulation so they can with stand much higher temps before melting. I strip the outer insulation to leave the two inner cores with about 60-70mm of insulation and then they are stripped and joined together. This end is then put into the sandwich of slats timber and heating blanket. I've been putting it in the center of the lower, but it can go anywhere as the heating blanket should heat evenly over its length.

I have a temperature controller set up which turns the blanket on and off to achieve the set temperature. But the thermocouple can be read with hand held meter.
I started using the controller after cooking a set of sides.
Hope this explains it
Cheers
Graham

[jeffhigh]

Thanks Chuckie