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I’m making a bow – would anyone like to watch?
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ctviolin
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Joined: 07 May 2009
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Location: Roswell

PostPosted: Thu Jul 11, 2013 9:35 am    Post subject: Reply with quote

wm_crash wrote:

You can't believe the amount of progress that happens in my planning and vision, unfortunately I can't take photos to show you folks Smile
cheers,
wm_crash, the friendly hooligan



Yes, I believe I can understand the amount of progress that happens in that regard perfectly!

I'm with you on that one, 100%, wm...
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Ed Shillitoe
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Location: Syracuse NY

PostPosted: Sun Jul 14, 2013 8:13 pm    Post subject: Reply with quote

Craig: It did take a little practice to get the octagons reasonable. I see from my notes (and my box of mistakes!) that my first two bows were far too thin and asymmetrical and I didn't finish them. Then the next three seemed fairly good but I decided to make them round which obviously covers up some mistakes quite well. Then on the fourth one the octagonal faces seemed quite good so I left it octagonal. Of course my opinion of 'quite good' would not have passed muster in the Hill workshop! But as I think I said before, the real trick is to make the sticks square at all points - with each of the four faces the same width and at 90 degrees, and then making the octagon is just a matter of carefully planing off the corners with the longest plane possible. If you can make scrolls like the one you just showed then a bow stick won't be any problem!

And on another matter - I tested out the red Loctite on some scraps and it does hold a metal screw into a piece of ivory quite well. On the other hand it has no effect at all on holding a metal screw into a piece of ebony - the best thing for that is hardware store 5 minute epoxy. And the epoxy also works on ivory so there is really no need for red Loctite in a bow shop.
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Ed Shillitoe
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PostPosted: Sat Feb 01, 2014 6:43 pm    Post subject: Reply with quote

These transitional bows have been delayed for a long time while I worked on some other projects. But I’m finally getting back to them.
I’ve picked one to finish and I’ll just save the other until I need it. The one I picked has developed a slight bend to the right while it was waiting, but less than one millimeter. The head has enough extra thickness that I can plane that off and it will be completely straight again.

I finished the fitting of the frog to the stick, planing down the facets while keeping the frog lined up with the head. Every so often I tightened up the eyelet a half turn. Toward the end I marked the place to plane the stick by blackening the underside of the frog with oil pastel, and then planing away just the parts of the stick that had picked up some black.



Finishing the rest of the stick has meant planing it square in cross section while keeping the thickness the same at each point as the originals that I am copying. Then to make the stick an octagon I have been planing off the corners of the square. At the same time I am keeping an eye on the weight – the originals have sticks of 35 and 41 grams. And at the same time as all that I am checking the tension of the stick. I am doing that using the setup shown here. It is a simple bench to place the stick on, with a screw that can be adjusted to be exactly one centimeter from the stick at the most outcurved part. Then I press on the stick with a spring gauge until it touches the screw. The reading on the gauge shows the tension on the stick. One of the original bows has a high tension of 700 grams and the other is 1,200 grams which is very strong.





So, when the dimensions, the weight and the tension are all simultaneously the same as the originals, the stick will be finished! In reality they can’t all be right at the same time so there have to be some small compromises.
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whatwasithinking
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PostPosted: Sun Feb 02, 2014 11:31 am    Post subject: Reply with quote

Ed,

Your attention to faithful reproduction of the originals is impressive! Do you have continuing access to the originals, or did you measure them once and give them back?

And could you explain your method of measuring tension? I'm using a Stroup gauge, with a dial indicator and a two-pound weight, but your method looks simpler. It appears that you move the stick a fixed distance and measure force, is that correct?

Bob
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Ed Shillitoe
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PostPosted: Sun Feb 02, 2014 12:13 pm    Post subject: Reply with quote

Hi Bob:

I do have the original bows to hand. Back in the 1970's there was very little interest in old bows, and even on a graduate student stipend I was able to build up a small collection of them.

The tension method does indeed measure the force needed to straighten the stick by a set distance. It's derived from the Bolander method (page 64 in his book) where he presses down on the stick with a scale and I did it that way for many years. Now I find its easier to turn the stick horizontally and press on it with a spring gauge. The distance of a centimeter is entirely arbitrary, but it works for me.

Interestingly, pretty much all bows are in the range of 500 gram to 1000 gram - Tubbs, Hills, French, German, Glasser, carbon fiber, $13 Chinese bows - they all fit in the same tension range. Tubbs tend to be the weakest, but otherwise they all overlap a lot.

I find the most important thing is not to let the stick get too weak. If it seems weak while still octagonal then it should not be made round as that will take off another hundred grams or so of tension. If it is really weak then it is time to throw it away and start again with a new piece of wood. Measuring tension is useful when evaluating alternate woods or new batches of pernambuco.

Ed
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whatwasithinking
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PostPosted: Mon Feb 03, 2014 12:18 pm    Post subject: Reply with quote

It looks like 1200g equals a bit less than 300 using Stroup's method. Very stiff indeed! I've measured some carbon bows that are stiffer, but not many wood bows seem to be that stiff. I'll be curious to see how the bloodwood stick dimensions turn out, to produce similar results. Is it relatively stiff wood?
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seammc
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PostPosted: Fri Feb 07, 2014 11:17 pm    Post subject: measuring the deflexion Reply with quote

2 scales one under the tip the other under the frog and push down the center ... the sum of the two scales should be the same
Jim
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whatwasithinking
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PostPosted: Fri Feb 07, 2014 11:57 pm    Post subject: Reply with quote

Very clever! How do you measure the 1cm deflection?
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seammc
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PostPosted: Sat Feb 08, 2014 11:49 am    Post subject: 1cm deflection in ed's approach Reply with quote

I misunderstood the question ..Sorry... \hence an edit\

I think Ed has rendered a super clue

For my use only, I just deflect the bow to straight, ( that would be a playing tension .. kind of) reason being there are all sorts of woods and tapers (and spines) and looking to get a standard result ... In using a different wood the arch will be different and the deflection so grams will be the only common denominator ...I didn't have spring scale and now I do. ..So 2 scales are out

My apologies for the confusion on my part .. dial indicator will measure 1 cm with the right fixture.... still overkill

Ed's approach is probably way better than mine

Jim
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Ed Shillitoe
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PostPosted: Fri Feb 28, 2014 9:13 pm    Post subject: Reply with quote

So, back to the frog. I milled out the trench in the mill and cut a preliminary mortice with a 4mm mill bit. Then I shaped the silhouette by outlining it from the template and sanding away the rest of the outline with a large disc sander and a small oscillating drum sander.






I finished the mortice and the shape at the front with a combination of small chisels, hand files and a high speed dentist’s drill.






I hacked off some of the sides of the frog with a hacksaw






Then rounded the sides with a sanding drum in the lathe. For bass bows I usually use a template for the curve of the sides, but for this small frog I just did it by eye.






To finish the button I put it in the lathe chuck and turned down a collar, being careful not to leave a sharp edge. With a silver button the edge strength is better, but with ivory a piece could easily break off.






To make the octagons I put the button into a scrap of wood that has a screw hole through the center and 8 flat surfaces.






The wooden holder is then held in the mill vice and the first flat surface is milled. The holder is then turned 90 degrees and another surface is milled. Then so on and so on until the octagon is done.






I hand-sanded the frog and button with finer and finer grits of silicon carbide paper, and then buffed them on a wheel with white rouge. Emory cake, which I use for ebony, also works fine except I found that the mammoth ivory has some microscopic splits which are quite invisible until you polish with emory. Then they become all too visible and have to be bleached and sanded out.






I left the front of the frog relatively square, which is a feature of the mid 18th century bow frogs.
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whatwasithinking
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PostPosted: Sat Mar 01, 2014 6:43 pm    Post subject: Reply with quote

Ed,

What a nice looking frog and button! You're giving me milling-machine envy. I'm thinking your frogs get done faster than mine. May I ask where you found the dental drill? Is it a two-hole, or four-hole drill? I'd been thinking about looking for a four-hole setup, with the chip blower feature. They're not expensive from China, although I guess there might be shipping restrictions.
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Ed Shillitoe
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PostPosted: Sat Mar 01, 2014 9:40 pm    Post subject: Reply with quote

Thanks Bob. You do need a milling machine - I think only the real hardcore historically-accurate enthusiasts do without them these days. I find that the Sherline convertible lathe/mill works fine for violin bows. For bass bows its just about big enough. I use it to drive buffing wheels and sanding drums so its quite versatile.

The dental drill is very optional but kind of fun. I got the drill and the control unit off e-bay from China. The unit is in some kind of case that was clearly used for something else at some time but the internal components seem new. The handpiece is 4-hole but I don't know what the importance of that is. I chose it because it has a laser light aimed at the burr, which comes on when the drill is running. That is well worth having. I don't bother with the water cooling and don't use the air syringe either. I got a local air compressor. Its certainly handy for cutting mortices in ebony and ivory and especially for getting out the lumps of epoxy glue that hold the hair in some new student bows. I don't know anything that works as well for that particular task. I imagine it would work well for cutting up pegs that are stuck in violins to get them out piece meal, but I've not tried that yet. Josh recommends them for cutting out an eyelet from the inside of a frog mortice.
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Ed Shillitoe
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PostPosted: Sun Mar 23, 2014 11:31 am    Post subject: Reply with quote

These are the jigs I use to cut the nipple on the end of the sticks. The larger one is for bass bows and the other is for violin bows.



They are held in the tool holder of the lathe and the little circular saw is put in the chuck. Then I turn on the lathe and put the bow stick onto the screw of the jig. I hold the bow in my right hand and turn it slowly while advancing it into the saw blade by turning the cross feed screw of the lathe with my left hand. This produces the nipple in about half a minute





There are other ways to do this but this seems to be the most simple, as long as you have a lathe.

Now the bow goes to the hairing bench to get some hair temporarily to see how it looks when it is tightened up. This one still had a small bend to the right so I heated it up and got it straight again. The camber was not perfect so while it was tightened I went back to the stick with the scraper planes and improved it.

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seammc
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PostPosted: Sun Mar 23, 2014 12:16 pm    Post subject: Most impressive Reply with quote

The frog is beautiful

I do wish that I could keep my work area as neat and organized as pictured, however tomorrow or next week, in the same area, I may be repairing an automobile or fabricating a snow plow repair..... Or some such...

Jim
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Ed Shillitoe
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PostPosted: Sun Mar 23, 2014 9:01 pm    Post subject: Reply with quote

Thank you Jim. It's certainly easier to keep things organized if you only do one thing. If I was fixing snow plows on the same bench I don't think it would look so neat!

Ed
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