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Building A Better Bending Iron


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#1 emviolins

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Posted 05 August 2010 - 08:53 PM

After getting some great advice on bending deeply flamed violin ribstock, I tried again. I thinned my ribstock to 1.1-1.2mm and this time making sure to use plenty of force with the bending strap, my bending iron broke loose from it's plastic base.
I bought the iron off Ebay and liked it because it is made from a solid piece of aluminum. However, the heating element I knew would eventually need upgrading.
So I thought it would be fun to start a thread on rebuilding this iron from scratch. I've done some research and have found another heating cartridge from Mcmaster-Carr. I'm thinking of adding a digital tempurature control switch, but could use advice on which component(s) to buy, since Electronics is not really my cup of tea.
Should be fun and it will give me a chance to use my new camera...(Still trying to figure that out.)

#2 emviolins

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Posted 05 August 2010 - 09:13 PM

These pictures are'nt opening right, I'll try resizing them...sorry

-Ernie

#3 emviolins

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Posted 05 August 2010 - 09:13 PM

There we go...I think they are loading OK now.

Before and After...

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#4 NewNewbie

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Posted 05 August 2010 - 09:48 PM

They are loading for me, so I guess the Cyber Attack on Maestronet took a break. :)

#5 emviolins

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Posted 05 August 2010 - 10:54 PM

They are loading for me, so I guess the Cyber Attack on Maestronet took a break. :)



:)

#6 Atomino

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Posted 06 August 2010 - 12:43 AM

Well Ernie.
just check the diameter of the cartridge and start replacing it. A 250 watts one would be more than enough. I would put a Teflon layer between the "iron" and the wood and between the screws (and washers if any) inside the wooden box. I can't see a thermal probe hole. Guess the knob for controlling temperature is some kind of dimmer. Think you have to replace it even if somebody likes dimmers for the job. You can go digital, more expensive but more "professional".
Make a list of what you need and get started when you'll have all the "puzzle" pieces.

Ciao
Alberto

#7 Bill Yacey

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Posted 06 August 2010 - 01:02 AM

The temp control looks to be nothing more than a triac lamp dimmer. There isn't any feedback temperature sensing, so it's a "set by trial and error" kind of setup. If you want a thermostatic control, you could incorporate an electric frying pan cord / thermostat assembly such as this:
http://buyitnow64.st...nbeamprobe.htmlPosted Image


I would put a sealed cartridge heater inside the bore, and make sure the iron itself is grounded for safety purposes.

You could mount the iron on a teflon base as suggested, or you could use high temp phenolic or asbestos board. If you choose the asbestos, get it cut and drilled for you by someone who knows how to work with asbestos and takes the proper safety precautions. You don't want to make or breathe asbestos dust. Get rid of the plastic box; Perhaps consider a Hammond die cast aluminum boxes such as this:
http://www.hammondmf.../pdf/1590UF.pdf

"It is the mark of an instructed mind to rest satisfied with the degree of precision which the nature of the subject admits, and not to seek exactness when only an approximation of the truth is possible." - Aristotle

 


#8 Andres Sender

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Posted 06 August 2010 - 01:13 AM

Yes a project box makes a nice base:

Posted Image
The problem with the ignore feature is that if one has a sort of morbid fascination for train wrecks one can keep peeking and then the benefit is out the window.

#9 Atomino

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Posted 06 August 2010 - 01:22 AM

Yes a project box makes a nice base:


Well, can't deny that wood has his own charme too :) .

Posted Image
Alberto

#10 emviolins

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Posted 07 August 2010 - 01:30 PM

Atomino, Bill and Andres

Thanks for your interest in this thread and I hope you guys follow along with me as I progress and hopefuuly in the end I'll have as nice an iron as you.
I am totally new to bending violin ribs, but the way I see it and going from previous threads and feedback on MN...
A good bending iron must be sturdy enough to withstand excessive force when pulling with a bending strap. The iron itself should be fabricated from a solid piece of aluminum or equivalent and have the correct shape and finish. The iron should reach operating temperature quickly and have some means of controlling the temperature...SAFELY!
Obviously the one I bought was not sturdy enough and I feel it took too long to heat up.

To make it sturdy I plan to fabricate and weld a base plate to bottom of iron and then bolt this to a much heavier base.
To make it heat up quicker...a new element!
Finally a different temperature control switch :)

To begin:
Scrounging around I found a piece of 4" X 1/2" 6061-T6 aluminum bar, to make the base.

Then I marked the shape of the iron as it is now, which leads me to ask... does this shape look right?...how does one determine the shape of the iron? Should I trace out the C-Bout of a Strad since they have the tightest radius?

Here is shape of iron now:

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#11 Bill Yacey

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Posted 07 August 2010 - 01:57 PM

If you are going to directly bolt the iron to that base, it's going to get just as hot as the iron. There really isn't any need to heat the base. To get around this, you need some sort of thermal insulator between the iron and the base.

When I made my Iron, I made the curve radii slightly tighter than any I would encounter on a violin. You need to over bend the ribs slightly as they tend to spring back slightly after the bending process.

"It is the mark of an instructed mind to rest satisfied with the degree of precision which the nature of the subject admits, and not to seek exactness when only an approximation of the truth is possible." - Aristotle

 


#12 emviolins

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Posted 07 August 2010 - 02:21 PM

[quote name='Bill Yacey' date='Aug 7 2010, 02:57 PM' post='475304']
If you are going to directly bolt the iron to that base, it's going to get just as hot as the iron. There really isn't any need to heat the base. To get around this, you need some sort of thermal insulator between the iron and the base.



Bill
Yes. this is one of the questions I was going to ask you when I got to that stage. The plan is to heliarc base to iron and then bolt to a stable base. I did take note of your previous suggestion of using high temp phenolic or asbestos board and I did notice Atomino's use of some kind of insulator on his iron. Is that Teflon Atomino? I would like to stay away from using asbestos tho...would McMaster-Carr be a good source for purchasing the insulator material?
I have emailed the original maker of this bending iron, and asked what grade of aluminum he uses on these irons. I know different grades of Aluminum have different welding properties. Hopefully the two will be a good match. Would you be willing to post a top view shape of your iron. I find all the different shapes on some of the commercial ones interesting.

#13 Andres Sender

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Posted 07 August 2010 - 03:02 PM

Welding is overkill. You can use bolts to hold it down and even help with isolation. I used PTFE washers on mine to help isolate the threaded rod from the box. I think something like that with a wood base is fine. The Ibex irons just have a sheet of something between the iron and the wood. I just used the project box as a time saver.

There is such a thing as too much mass. Mine is solid and it heats slowly and if you overheat it it takes a long time to cool down.

Mine is made to a shape that would allow me to make a small Andrea Amati if I wanted to.
The problem with the ignore feature is that if one has a sort of morbid fascination for train wrecks one can keep peeking and then the benefit is out the window.

#14 emviolins

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Posted 07 August 2010 - 06:10 PM

Welding is overkill. You can use bolts to hold it down and even help with isolation. I used PTFE washers on mine to help isolate the threaded rod from the box. I think something like that with a wood base is fine. The Ibex irons just have a sheet of something between the iron and the wood. I just used the project box as a time saver.

There is such a thing as too much mass. Mine is solid and it heats slowly and if you overheat it it takes a long time to cool down.

Mine is made to a shape that would allow me to make a small Andrea Amati if I wanted to.




Andres
Glad you replied because I would like to ask you a few questions about your iron. You did a very nice job on it. I did read your two threads on it.
If I understand correctly, you drilled and tapped four holes into the bottom of your iron? Can you tell me what size threaded rod or bolts you used?
Are the rods attached to the project box or do they extend through the box and into the wooden baseplate? I don't remember what material your project box is made from...is it one of the aluminum ones?
I'm not familiar with PTFE washers, what are they and where do you buy them? I'm also interested in knowing what type/size element you used in your iron. If I remember correctly, I think you said that you got it from McMaster. From what I understand 250watt is sufficient.
Too me welding a baseplate is much simpler than drilling and tapping holes, since I was a welder in my former occupation.
My design will basically look the same as Atominos iron.
I think CB Fiddler posted pictures of a disassembled Ibex iron showing the piece of insulation you referred to. It looked like it burned through to the wood.
I have a good idea as to a base which might seem overkill too, but I want to avoid something breaking or bending when I excert alot pressure on the strap, and not worry about being sent reeling.
Please continue to watch this post and offer advice, as I do appreciate your expertise on this subject. I'm still kinda wondering about whether or not I have the right shape.

-Ernie

#15 Atomino

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Posted 07 August 2010 - 06:30 PM

Yes, I think you don't need to weld a base. As it gets hot as the iron, you risk to scorch your hands while bending close to the box. If I should make another one, I would surely build it without a base. The pushing effort in bending violin and viola ribs is minimal, two M6 screws threaded in the iron will do just fine. I tried with PTFE but got melted over 140°C. Teflon stands until 250°C and I'm happy with it. Don't forget to insulate both the iron and the screws/washers, whatever material you chose for the box.
A 500 Watt cartridge heats up my brass "iron" in no time. Guess you can pick one between 150 and 250 Watts. Look for Watlow Firerod heating cartridges on Ebay.
Shape is ok. Bending correctly is a matter of adjusting the rib on the iron, you just have to do it getting accustomed to the available curves.

Ciao
Alberto

#16 emviolins

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Posted 07 August 2010 - 06:54 PM

Yes, I think you don't need to weld a base. As it gets hot as the iron, you risk to scorch your hands while bending close to the box. If I should make another one, I would surely build it without a base. The pushing effort in bending violin and viola ribs is minimal, two M6 screws threaded in the iron will do just fine. I tried with PTFE but got melted over 140°C. Teflon stands until 250°C and I'm happy with it. Don't forget to insulate both the iron and the screws/washers, whatever material you chose for the box.
A 500 Watt cartridge heats up my brass "iron" in no time. Guess you can pick one between 150 and 250 Watts. Look for Watlow Firerod heating cartridges on Ebay.
Shape is ok. Bending correctly is a matter of adjusting the rib on the iron, you just have to do it getting accustomed to the available curves.

Ciao




Atomino

Thank you for your thoughts on the baseplate burning your hands. Perhaps a smaller baseplate is called for. The Ibex iron is bolted at the base and I never heard of anyone mentioning getting burned. I will give it some more thought and perhaps use bolts instead of a baseplate.

My iron has a 3/4" hole drilled in it and McMaster sells a 3/4" diameter element, but it is 500W, which I thought was too much. Today at the local hardware store I found 3/4" bronze bushings that I could use to reduce the hole diameter to 5/8". McMaster does sell 250W heater cartridge in a 5/8" diameter. This type of cartridge has to be in direct contact with the iron. No? What I mean is...it has to fit tight, correct?
Hopefully the bronze bushings would withstand the heat. I have never worked with bronze before.
I will also look into the Watlow Firerod heating cartridges on Ebay. Also where did you buy the teflon?

Ciao to you my friend

#17 Andres Sender

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Posted 07 August 2010 - 07:36 PM

Hi Ernie, thanks for the comments.

If I understand correctly, you drilled and tapped four holes into the bottom of your iron? Can you tell me what size threaded rod or bolts you used?

10-32 stainless

Are the rods attached to the project box or do they extend through the box and into the wooden baseplate? I don't remember what material your project box is made from...is it one of the aluminum ones?

Rods just attach to the project box, which is aluminum. I think the weakest spot in my design is the small screw size that fits into the bottom of the project box. I used longer ones going through the wood from below to hold the box to the wood, SS for added strength so I'm not too worried that the thing will give way.

I'm not familiar with PTFE washers, what are they and where do you buy them? I'm also interested in knowing what type/size element you used in your iron. If I remember correctly, I think you said that you got it from McMaster. From what I understand 250watt is sufficient.

PTFE is the generic, Teflon is the brand. Or at least that's what I thought until I read Atomino's post. At any rate according to the specs at McMaster it's a good insulator. I got the washers from McMaster, along with the 250 watt iron which is plenty.

Too me welding a baseplate is much simpler than drilling and tapping holes, since I was a welder in my former occupation.

If you have a drill press drilling and tapping is a cinch.

I think CB Fiddler posted pictures of a disassembled Ibex iron showing the piece of insulation you referred to. It looked like it burned through to the wood.

Yes that was an eye-opener, but I still think the principle is sound--i.e. the way Atomino has it seems fine.
The problem with the ignore feature is that if one has a sort of morbid fascination for train wrecks one can keep peeking and then the benefit is out the window.

#18 Andres Sender

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Posted 07 August 2010 - 07:41 PM

Just be sure not to use oil-soaked bearings as bushings. I think in a pinch you could wrap the cartridge in aluminum flashing or sheet aluminum to make a tight fit. Or just use the 500 watt element if you can find a switch that is compatible, and keep the setting lowwww. :)
The problem with the ignore feature is that if one has a sort of morbid fascination for train wrecks one can keep peeking and then the benefit is out the window.

#19 emviolins

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Posted 07 August 2010 - 07:48 PM

Just be sure not to use oil-soaked bearings as bushings. I think in a pinch you could wrap the cartridge in aluminum flashing or sheet aluminum to make a tight fit. Or just use the 500 watt element if you can find a switch that is compatible, and keep the setting lowwww. :)



Andres

These bushings were listed as bronze bearings and they feel very oily. They will not work?
They cost 4.00 a piece, so I hope so. I do like the alum. flashing idea. Thanks.

#20 Andres Sender

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Posted 07 August 2010 - 08:00 PM

http://en.wikipedia.org/wiki/Oilite
The problem with the ignore feature is that if one has a sort of morbid fascination for train wrecks one can keep peeking and then the benefit is out the window.




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