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Bending with a pipe
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Author:  bcombs510 [ Mon Sep 28, 2020 5:48 pm ]
Post subject:  Bending with a pipe
Hello,

Recently I joined a few other OLF folks at Dean’s luthier garage sale. It was a great time. :)

Anyway, I picked up two really nice bending irons. These were hand made by Dean and have a digital controller. There are two sizes of iron which works out great since the smaller one I can use for ukes.

Until now I’ve bent everything in a bending machine. I want to learn bending by hand. I have some questions:

1) I have seen the iron oriented both horizontal and vertical. Which do you prefer? Does it matter?

2) I have seen a table being added when the iron is oriented vertically. Does that help with keeping the side from skewing? Do you recommend it?

3) Any tips on marking up the wood that help? Do you mark up just the waist or do you mark the entry and exit of the primary curves?

4) Any procedure tips? Temp recommendations, etc...?

5) Any recommended you tube videos to watch?

Thanks for any pointers. I’m laid up with a back injury at the moment so just researching for now.

Brad


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Author:  Colin North [ Mon Sep 28, 2020 6:32 pm ]
Post subject:  Re: Bending with a pipe
1) I have seen the iron oriented both horizontal and vertical. Which do you prefer? Does it matter?
VERTICAL
2) I have seen a table being added when the iron is oriented vertically. Does that help with keeping the side from skewing? Do you recommend it?
YES. YES
3) Any tips on marking up the wood that help? Do you mark up just the waist or do you mark the entry and exit of the primary curves?
JUST THE WAIST IF NON CUTAWAY, entry and exit of the primary curves for florentine cutaway
4) Any procedure tips? Temp recommendations, etc...?
BACKING SLAT. 235 degrees on my iron
5) Any recommended you tube videos to watch?
anything sensible on youtube, esp I like https://www.youtube.com/watch?v=VxpCEyXQ6o0

Sorry to hear about your back, get well soon!
Author:  Brad Goodman [ Mon Sep 28, 2020 6:38 pm ]
Post subject:  Re: Bending with a pipe
Hi Brad,
I’ve only bent with a pipe and here’s what I can tell you.
I prefer to have the pipe horizontal.
I make a string and put a knot for the waist, for the tail and for the heel.I mark the waist and start there then I do the upper bout then I do the lower bout
I’ve bend pretty hot just short of scorching the wood.
There are some videos of me on YouTube bending the sides and bindings.

It takes me approximately 45 minutes to bend each side.


Here's the video:
https://www.youtube.com/watch?v=q5T-Zek_DAQ


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Author:  jfmckenna [ Mon Sep 28, 2020 8:10 pm ]
Post subject:  Re: Bending with a pipe
I like it horizontal too. I've seen people bend vertical and thought to my self... Huuuuh? But then they might think horizontal is barbaric. To each their own. Find out what works for ya.

I've tried all kinds of methods. Waist first, top first, lower bout first, and so on and find that it really makes no difference. In the end I am always fussing to get the waist right. I tend to like starting at the top, head block, first and then move along. I have a piece of plywood with the tracing drawn out to constantly keep an eye on the bend. Once I get it right I strike a line on the side down to the tracing with a pencil and use that as a fulcrum of sorts to continue the bend. Once you get something right you want to keep it.

When you make a bend the wood is still really hot so hold it in position past where you want it to be till it cools and it will spring back to what you want, if not do it again.

I can bend a side in about 15 minutes now. Some people get it right away but it was something I had struggled with.

Incidentally I had recently bought a side bender to bend some expensive BRW and I hate the thing.
Author:  Clay S. [ Mon Sep 28, 2020 8:25 pm ]
Post subject:  Re: Bending with a pipe
A good pair of heat resistant gloves can let you work a little closer to the pipe until you get the hang of it.
https://www.ebay.com/itm/932-F-Heat-Res ... SwbtVZO6oZ
A good pair of asbestos welding gloves would work if you can find them.
Author:  doncaparker [ Mon Sep 28, 2020 9:41 pm ]
Post subject:  Re: Bending with a pipe
Brad—

I had a great time at Dean’s, as well. I think we have the beginnings of a regional luthiers group. Sorry your back is still giving you trouble.

Here are some responses from a hot pipe enthusiast (but nowhere near a learned authority).


1) I have seen the iron oriented both horizontal and vertical. Which do you prefer? Does it matter?

I have done both, and I prefer vertical. Both are fine. You might want to experiment and see what you like.

2) I have seen a table being added when the iron is oriented vertically. Does that help with keeping the side from skewing? Do you recommend it?

I’ve never tried it. I don’t really have trouble keeping the sides square.

3) Any tips on marking up the wood that help? Do you mark up just the waist or do you mark the entry and exit of the primary curves?

I put masking tape inside one side of the body mold from end to end, and mark where the waist and each center line are. I then transfer the tape to the flat side and transfer the marks. I don’t mark anything else. I might look into it and see if I think it helps.

4) Any procedure tips? Temp recommendations, etc...?

Like Brad Goodman, I think it is best to bend very hot, and just pull the wood off the iron and re-wet it if it gets too hot. This is one of the advantages of hot pipe bending. Heat on/off in an instant, and you can always add water. Looked at from the other side: you will constantly struggle to bend the wood if the iron is not hot enough.

I like to bend the waist first, upper body second, lower bout last.

For the waist, I like to heat as much wood as possible by placing the side on the flattest part of the iron, rocking it, letting it get flexible, then sliding it to a tighter curve on the iron to finish the bend.

A bending strap really helps avoid blowouts on the outside of the bend.

Remember to remove the side from the iron and hold it in compression in the shape you want for a few moments, so it will cool in the shape you want.

I like soft, well fitting leather gloves, like deerskin. Better touch feedback if the gloves fit well. These are great for overall hand protection in the shop.

5) Any recommended you tube videos to watch?

Richard Howell, Nigel Forster.

Good luck!
Author:  J De Rocher [ Tue Sep 29, 2020 12:49 am ]
Post subject:  Re: Bending with a pipe
1) I have seen the iron oriented both horizontal and vertical. Which do you prefer? Does it matter?

I like having the pipe clamped to my bench top vertically. In that orientation, I'm looking down on the edge of the side against the pipe so the shape and progress of the bending is very easy to see. It also places the pipe closer to my head so it's easier to hear what's going on and it puts it at a good height and position to really lean into it if needed.

2) I have seen a table being added when the iron is oriented vertically. Does that help with keeping the side from skewing? Do you recommend it?

I haven't seen that, but I haven't needed something like that to keep the sides straight.

3) Any tips on marking up the wood that help? Do you mark up just the waist or do you mark the entry and exit of the primary curves?

I mark the locations of the centers of the bends for the upper bout, waist, and lower bout (both on the insides and outsides of the sides) and those marks line up with corresponding marks on the body mold to help keep everything aligned during bending. I always start by bending the waist. My rationale is that the waist is the tightest bend on my non-cutaway instruments and if a side is going to crack or break, I think it's more likely to happen there. I feel like it's best to find out right away if a side is going to be problematic by doing the tightest bend first before much time is invested in bending the side. I haven't broken a side yet (knock on wood) aside from one of the practice sides I bought from LMI when I first started.

Attachment:
Sides marked for bending.jpg


4) Any procedure tips? Temp recommendations, etc...?

I'm copy/pasting some of an an edited reply I made to a similar previous thread.

Taking advantage of the flatish side of the bendng iron to pre-warm the wood and then sliding it over the tighter radius part to make a bend is really effective.

I thickness the sides to 0.080" and for particularly tight bend areas like the tip of a Ventian cutaway I go down to about 0.075".

For water application, I spritz the specific area that's going to be bent right before going to the bending iron. Most of the time, I only spritz the side that goes against the iron. I re-spritz as the wood drys out. Some woods can benefit in the tight bends from a bit of additional spritzing on the outside surface. Based on my experience with curly koa and curly maple, I don't spritz curly woods on the outside of a bend since that can weaken the fibers at the tops of the curls (where there's lots of runout) which can lead to them lifting and causing a crack.

Temperature: I have the standard bending iron sold by StewMac and LMI. For most woods, I have it set at 6 on the dial which corresponds to about 380 degrees (measured with a surface thermometer). For woods that put up more resistance to bending, I set it at 6 1/2 which is about 420 degrees and keep the wood moving. It actually takes a while for the hot pipe to get fully up to temperature so having a thermometer of some type to make sure you are where you expect to be when you start bending is helpful.

Pre-treating the wood with SuperSoft II to make it more receptive to bending can make a significant difference, in my experience. Others have success using Windex for this.

If a side wants to spring back, bending the offending section to the target shape and then immediately clamping it in the mold and letting it cool has taken care of it.

One thing that works really well for me when doing the tight bends is shown in the photo below. Using two blocks positioned close together on either side of the location of the bend allows you to really concentrate the bending force in a small area and makes it easier to end up with tight bends. I use this method routinely and it helps a lot, for me. The pipe has to be firmly clamped to the bench because this approach can require a lot of pressure for some woods, but it works. It's also useful if it turns out that there is a weak spot right next to where a tight bend needs to go because you can isolate the bending action to just the area next to the weak spot so the side doesn't break. It also works for highly figured woods that don't want to make smooth bends but want to bend as facets instead. The flats of the facets can be made to bend this way.

Attachment:
Tight bends using blocks.jpg
Author:  doncaparker [ Tue Sep 29, 2020 7:41 am ]
Post subject:  Re: Bending with a pipe
A supplement to my above post:

I agree with J about the water. Spritz the area you want to bend, but not the other parts of the side. You can always spritz more, as needed. I use distilled water.
Author:  Ruby50 [ Tue Sep 29, 2020 8:48 am ]
Post subject:  Re: Bending with a pipe
A couple of you have mentioned a strap - how wide? how long? what material? a source?

Thanks

Ed M
Author:  jshelton [ Tue Sep 29, 2020 9:23 am ]
Post subject:  Re: Bending with a pipe
I use a piece of cotton material (old bed sheet) dipped in water and lay it on the side where it contacts the iron (vertical) to provide steam and prevent scorching. My iron is homemade from a piece of 8" aluminum irrigation pipe hammered to an oval shape. It's heated with a propane torch. I flip some water on the iron and when it pops it's time to bend. Been doing it that way for over 50 years.
Author:  doncaparker [ Tue Sep 29, 2020 9:58 am ]
Post subject:  Re: Bending with a pipe
Links to bending straps:

https://www.lmii.com/bending-heating/25 ... steel.html

https://luthiers-bench.com/products/ben ... 9651370823

https://www.stewmac.com/luthier-tools-a ... strap.html
Author:  bcombs510 [ Sat Oct 03, 2020 4:59 pm ]
Post subject:  Re: Bending with a pipe
Thanks, all!

I was actually able to hobble downstairs to the shop for a couple hours today, first time since Labor Day weekend! :)

I was excited to try out the bending iron. My intention was to bend binding for a ukulele fretboard. The shape is in the pic below. My thought was to just take a single length of binding and make the bend in the middle.

I first cut the purfling ledge around the fretboard using the SM binding cutting bit, and glued in the purfling separately. I then thinned the binding, which is ebony, to .060 and tried to bend this shape. I snapped two pieces so I stopped. They both splintered on the outside side of the bend and then snapped.

Should I expect to be able to bend this shape? I see all kinds of tight binding on mandos, etc... I expected I could bend this shape in a single piece.

Image

Brad


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Author:  Mark Mc [ Sat Oct 03, 2020 5:20 pm ]
Post subject:  Re: Bending with a pipe
That is a tight bend, and ebony can be a cranky timber for bending. In ebony it is difficult to discern the grain direction. Some pieces just snap because of short/cross grain while another similar looking piece might be OK. I often throw a few failed ones away before getting a good one. There are a few other tricks to try. Going thinner will increase your chance of success. Try Supersoft II or other stuff (fabric softener) to precondition the wood. Use a thin metallic strip to support the back side as you bend (I use galvanised steel flashing). If it splinters but doesn’t completely snap it might be usable because ebony patches and fills pretty invisibly with dust and CA. If all fails, would black plastic binding be so terrible? Nobody would know except you....... [uncle]
Author:  doncaparker [ Sat Oct 03, 2020 5:35 pm ]
Post subject:  Re: Bending with a pipe
Brad--

Everything Mark said, but let me add this: Maybe you should first practice by bending some binding from a cheaper species, one where it is easier to see the grain. That way, you can get a feel for the process without breaking a lot of binding you care about, then try the ebony after you have your sea legs.

I do think a strap can help.

Also, with the binding, and the tight bend, you might be tempted to use that skinnier bending iron you bought. Keep in mind that, while the skinnier iron will help you get a tighter bend, it is hard to start the bend on a skinnier iron, because there is nothing close to a flat spot on a skinnier iron. The more you touch the iron only tangentially, the harder it is to heat as much of the strip as you want to in order to get the bend to happen. This might sound crazy, but you might want to fire up both irons, start the bend on the larger iron, then only use the smaller iron to make an existing bend (one obtained on the larger iron) tighter. Just an idea. Good luck!
Author:  SteveSmith [ Sat Oct 03, 2020 5:39 pm ]
Post subject:  Re: Bending with a pipe
I've bent a fair amount of ebony bindings on the pipe. Ebony is funny wood, some of it will bend ok, some just seems to be brittle and splits.
Author:  J De Rocher [ Sat Oct 03, 2020 6:10 pm ]
Post subject:  Re: Bending with a pipe
Like Mark and Steve, I've found bending ebony binding to be finicky and can vary a lot from one piece to another, but I have been able to do fairly tight bends with it. Sometimes it takes breaking one or two pieces before getting an intact tight bend.

I've done testing of bending of troublesome binding both before and after treating it with SuperSoft II and it definitely helps. In one case it made binding that simply would not bend without snapping, bend nicely.

That said, the radius on the treble side right by the highest fret slot looks to be very tight. I looked back through my plans and the smallest radius I've done for ebony binding was 2" for binding that was 0.080" thick. If you have ebony binding pieces from different sources or purchases to choose from, you might try sampling to see if one set of ebony bindings is more cooperative. Otherwise, you may need to go thinner than 0.060" and/or use SSII to get that really tight bend.

Did either of the hot pipes you got come with rings like the ones in the photo below? I put those on my hot pipe when bending binding spaced apart so the the binding just fits between them. That way, the binding is being heated from the edges as well as the wide face that's against the pipe itself. I haven't done actual testing with and without the rings, but I think they probably help.

Attachment:
Hot pipe rings.jpg
Author:  DennisK [ Sun Oct 04, 2020 8:50 am ]
Post subject:  Re: Bending with a pipe
bcombs510 wrote:
Should I expect to be able to bend this shape? I see all kinds of tight binding on mandos, etc... I expected I could bend this shape in a single piece.

Image

Probably not. Walnut could do it, but ebony is too stiff and brittle. African blackwood is a little easier, but still probably wouldn't do it. I'd recommend either switching to plastic, or cut the end piece from a 1/4" thick board, glue it on, sand it flat to the fretboard edges, glue the straight strips, and then some more sanding.
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