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Ed Shillitoe Member
Joined: 23 Mar 2007 Posts: 110 Location: Syracuse NY
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Posted: Mon Jun 10, 2013 6:42 pm Post subject: |
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Well that's too bad! But worth a try.
You are using pernambuco I suppose? I use beech for bass bows and beech bends in steam quite well. |
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Ed Shillitoe Member
Joined: 23 Mar 2007 Posts: 110 Location: Syracuse NY
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Posted: Tue Jun 11, 2013 7:49 pm Post subject: |
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Now I’m going to leave the sticks on one side for a while and get started on the screws and buttons. This picture shows the original bows that I am copying, and beneath them is a new commercial violin screw and a cello screw. I don’t really know if the screws in the old bows are original or not – the upper one in particular looks like a much more modern screw. However, it’s clear that the distance from the end of the bow to the start of the mortice is longer than in a modern bow, and that a new commercial screw will not allow the mortice to be in its correct position. So for the bows I am making I am going to use cello screws. The diameters are the same as for a modern violin screw. In fact even the cello screws are not quite long enough, but I think they are sufficiently close. If I wanted to be really authentic I could make my own screws – I have the screw cutting attachments for my lathe but I doubt if the extra work is really worth it.
There are two ways to fit the end of the screw into the button (or adjuster if you prefer). One is to make the hole in the button as small as possible, then raise barbs on the screw with a few blows of a hammer on a cold chisel. The screw is then forced into the button either by hammering or by squeezing it in a vice. This is the more traditional method. The other way is to cut a thread on the adjuster-end of the screw, then tap the equivalent thread in the adjuster and just screw the two parts together. I prefer not to use the hammer method because I am afraid of splitting the button. On the other hand it does make for a very secure fit, while a screwed in screw could unscrew sometime. But if it did you could just screw it back. So I don’t know which method is best. I have always used the threading and screwing system.
The thread that will do well on violin or cello screws is a 6-40, which is the same as the thread that the eyelet travels on. To put this thread on the screw I held the screw in a handle that was made from a piece of brass that had been drilled and tapped to that thread. Then I cut the thread on the end of the screw by forcing it bit by bit into a 6-40 die. The screw needs to be turned backward and forward to get it through, with a few drops of oil now and then. Altogether this only took a few minutes.
To make the buttons I have used a piece of mammoth ivory. This came from David Warther as a rectangular piece 2 inches long, supposedly for making 2 buttons. In fact by some careful cutting I made 3 button blanks, each 14.5 mm, which is the right size for these reproduction bows. To drill the hole for the screw I use a Sherline convertible lathe / milling machine as shown here:
This machine was recommended to me by bowmaker Josh Henry and has proven very useful. To drill the hole for the screw I put the ivory in the four jaw chuck with a drill bit in a Jacobs chuck that was mounted on the tailstock. I cut a pilot hole with a very short drill and followed up with the actual drill bit. I always use the shortest drill bits possible, or put them way into the chuck with only the smallest amount showing – this keeps the bit very stable and prevents it from wandering around on the surface before biting in and starting to cut.
I put the hole all the way through to the other end of the button with a number 37 drill. Then I changed to a quarter inch end mill and cut a recess 2 mm deep to accommodate the nipple on the stick. You have to cut the screw hole first – if you cut the recess first the mill leaves a little projecting dot in the middle and it will not be possible to get the drill to go exactly through the center of it.
After this I took the buttons out of the lathe and threaded the screw holes using a pair of 4-40 taps. I used a tapered tap to get the thread started and a bottoming tap to finish it off. The 4-40 tap leaves a thread that will be a nice tight fit for a 6-40 thread on the screw.
You can see in this picture that the threads on the outside of the bow screw do not go all the way around the end of the screw. The end is a square cross section and the threads are only on the corners. This seems to be quite good enough.
To secure the screws in the button I have always used epoxy, but this time I decided to try Loctite 262. It is very fluid and the excess is wiped up easily with a paper towel. It is a little strange however. A drop on the bench never sets – it is still liquid after several days. Apparently it only sets if it is deprived of oxygen. I tested it out by putting some on a nut and bolt which I tightened by hand – the next day I could hardly separate them with a screwdriver and wrench. I should have tested it out on ivory but didn’t think of that until too late.
Once the screws were set inside the buttons I rounded off the buttons in the lathe, holding the screws in the four-jaw chuck and using a live center in the tailstock. Once each button was round I turned it around with the button in the tailstock and made the face square.
The buttons are oversize at this point, but they are completely round and the screws are exactly in the center. These operations are quite standard machining procedures and not particularly difficult if you have a lathe. The dimensions of everything are a bizarre mixture of inches, millimeters, and numbers. It would be much easier to use the metric system all the time.
Last edited by Ed Shillitoe on Tue Jun 11, 2013 9:28 pm; edited 2 times in total |
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Mat Roop Senior Member
Joined: 24 Mar 2007 Posts: 911 Location: Wyoming Ontario
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Posted: Tue Jun 11, 2013 8:41 pm Post subject: |
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fabulous information Ed... thanks for taking the time to post!
Cheers, Mat |
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Ed Shillitoe Member
Joined: 23 Mar 2007 Posts: 110 Location: Syracuse NY
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Posted: Thu Jun 20, 2013 8:23 pm Post subject: |
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Back to the sticks. They did rotate quite a bit when they were cambered, so before making the screw holes I planed them down at the handle end using the alignment block as before. I don’t worry about the octagons being perfect, as long as the sides of the sticks are vertical and the top and bottom are at right angles to the head. I then make the screw holes and the mortice in three steps. First I drill the outer screw hole. I put a dot with a pen on the end of the stick as close to the center as I can. I do it by eye, then measure to see if it is centered – if not then I make a bigger dot that is centered.
I drill the hole on the Sherline lathe, holding the stick in a vice that came from the little lathe that I used for many years – a Unimat model 1. The Sherline does have a vice but it is big and hard to adjust so I put the Unimat vice on a little platform and it works well. To get the stick to the right height I just try different wood scraps under it until the little black dot lines up with a drill bit. I use a very short drill to get the hole started – as with making the button – so that it can not wander around the end-grain surface before starting to cut. After the pilot dimple is made and seems to be in the center I take out the little drill bit and replace it with a number 31 drill bit. I set it so that just a little bit of the bit is showing outside the chuck and drill a bit with that bit. Then I extend the bit a bit and drill another bit. It’s a bit slow to do it this way, but it makes for a hole that goes just where I want it. The actual size of the bits are tested on a scrap of wood before I make the real hole. I make the hole long enough to extend into where the mortice will start.
Next I rough out the mortice. To do this I set the Sherline machine into the milling configuration which takes a minute or so.
Then I use a 4mm end mill to drill down into the end of the stick in the middle of where the mortice will be. I make the mortice quite short, since it can be extended to its full length later on, when I see exactly where the frog will sit and travel. I file down the eyelet that came with the screw to its minimum size, then cut the mortice only just wide and deep enough to hold it. Later on, the mortice might get a little bigger, so I keep it as small as I can at this stage.
Now I return the Sherline to its lathe configuration and drill out the far screw hole. Here is the view of the mortice with the drill bit cutting the far hole. It would have been quicker to drill the near hole and far hole all at the same time, but I have found that if I cut the mortice after the near hole, then I can see if the near hole is lined up as well as it should be. If it is not, I can adjust the position of the far hole so that the screw is lined up correctly anyway. Really, this extra step could probably be missed out but I don’t like to take the risk of having the screw off center. The far hole was drilled with a number 43 drill.
Now both bows have the screw holes drilled in the right place and the mortices roughed out. I go over the mortices with a couple of chisels to smooth out the sides and bottoms so that the eyelets will travel smoothly from one end to the other when the button is turned.
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Ed Shillitoe Member
Joined: 23 Mar 2007 Posts: 110 Location: Syracuse NY
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Posted: Sun Jun 23, 2013 7:59 pm Post subject: |
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The frogs are going to be made from the same batch of mammoth ivory. I got some pieces from the same supplier but in large enough pieces for violin frogs. They came pretty much square, but just to be sure I put each one in the Sherline machine and milled the top and bottom surfaces to as to make them perfectly flat, parallel, and at 90 degrees to the sides.
The depth of each facet on the finished bow will be around 3mm and the width will be 4mm. I suppose with a little bit of mathematics, knowing that the width of the stick will be 9 mm, it would be possible to calculate the depth of the facets. But in fact I just took a rough measurement from the bows that I am copying. I marked the center lines on the frog blanks, and the depth of the facets, with a pencil in a pair of dividers. Usually I use a marking gauge which scribes a line that is more accurate, but my gauge fell apart as I was starting and I didn’t want to wait until I get a new one. I then used a 4mm end cutting mill bit to cut a groove 3mm deep along the center line. It took numerous passes to get the groove deep enough – you can not cut much ivory in a single pass.
Then, without adjusting the left-right setting of the vice, I drilled the hole for the eyelet at the appropriate point. As with all holes, I used a very short drill to mark a dimple and then checked that it was exactly in the center of the groove. Then I changed it for a number 35 drill and drilled the actual hole. Again, the hole was done in stages, with just a little bit of the drill bit showing out of the chuck for the first couple of mm, then using the whole length of the bit to extend it.
To cut the angled facets on the bottom of the frogs I used a ¾ inch 90 degree countersink bit. Quite by chance the flat end of this bit has a diameter of 4mm, and so to make the facets I just lowered the bit onto the frogs a little at a time for each pass of the tool. I think I was able to cut about a tenth of a millimeter with each pass, and so it took some time to get the facets done. But everything looked fine at the end.
Getting the eyelets into the holes is just a matter of holding them firmly and screwing them in. The holes are not pre-tapped. It is the same with a frog made of ebony. The fit has to be pretty tight. The best way to get a good grip on an eyelet is to use parallel-jaw jewelers’ pliers as in the picture – it was Lynn Hanning who showed me this. Some bow makers use a regular pair of pliers with the ends filed down so as to hold the eyelet firmly.
At this point I put the frogs loosely on the sticks and tightened up the eyelets bit by bit to see what kind of a fit I am getting.
They both look quite good for this stage, and I will be able to plane down the handle ends of the sticks while tightening up the eyelets a turn at a time, so as to get a good fit on the sticks.
To help keep the sticks straight and the frogs in line, it helps to tighten up the sticks using a wire in place of the hair. For this I have drilled a hole in the heads and frogs in the place where the mortices will go, and put a piece of brass rod in the holes.
For wire I am using an old cello string. When one of the bows is tightened up it is easily seen that the stick curves a little to the left. This can be corrected by planing away more on the left as it is thinned down, or by twisting the frog a little to the left by planing more of the facets on that side.
When I pluck the cello string when the bow is at a medium tension it gives a clear A-flat. I suppose a little calculation would allow that to be translated into the tension of the bow which is an important consideration to players. But as with the width of the facets, I don’t really know how to do that.
And here is my marking gauge. Can anyone suggest what type of new one I should get?
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Cliff Green Member
Joined: 01 Apr 2007 Posts: 111 Location: Amissville, Virginia
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Posted: Mon Jun 24, 2013 8:56 pm Post subject: |
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Fascinating Ed. I'll have to give bows a try. My favorite marking gauge is Tite-Mark. I've been using one for 10 years or so. They seem to have gotten a lot more expensive. Their advantage is that the base of the quide plate is threaded into a cylinder that has 2 thumb screws. This allows you set the cylinder on the marking shaft with one screw and make micro adjustments of the guide plate securing with the second screw. They used to be sold by Woodcraft and Japan Woodworker but I can only find them at Lie Nielsen and Highland Hardware. |
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Ed Shillitoe Member
Joined: 23 Mar 2007 Posts: 110 Location: Syracuse NY
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Posted: Tue Jun 25, 2013 8:40 am Post subject: |
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Thank you Cliff.
I've seen the ad for those gauges and they are indeed quite expensive. Also they seem to use a sharp wheel instead of a point. Do you think the wheel would leave a good line on something hard such as ebony or ivory? The screw adjustment looks good though. |
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Chet Bishop Super Member
Joined: 23 Mar 2007 Posts: 678 Location: Forest Grove, Oregon
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Posted: Tue Jun 25, 2013 9:46 am Post subject: |
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I got one of these from Rockler, and it works very well. Mine is not calibrated-- I have to use a ruler to set the depth, but he wheel is very sharp, and works quite well so long as you don't go the wrong direction and unscrew the connector. (I nearly lost the cutter that way, once).
http://www.rockler.com/product.cfm?page=21921
The one pictured here seems to be nicer than the one I have. _________________ Chet Bishop
https://bluefiddles.com
https://fivestringfiddles.com |
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Cliff Green Member
Joined: 01 Apr 2007 Posts: 111 Location: Amissville, Virginia
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Posted: Tue Jun 25, 2013 10:18 am Post subject: |
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Ed
The wheel on the Tite Mark gauge works very well on ebony and other hard materials. I use mine for initial layout of saddles and nuts. I think it works better than a point since it doesn't chatter. When I want something this extravagant I usually plant it on my wife's gift list since I get a surprise, sort of, and something more useful than her unguided attempts.
If you can get past the price, I'm sure you will love it and be hard pressed to revert to another model. |
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whatwasithinking Member
Joined: 26 Jan 2013 Posts: 230 Location: Washington State
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Posted: Tue Jun 25, 2013 10:25 am Post subject: |
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Could you enlighten me regarding the use of this tool? Would this replace the sharp edges of my calipers for marking frogs, etc? I see that the one Chet mentions is described as useful as a depth gauge, but lacks calibration. I'd love a better depth gauge, but is this a good solution? Thanks. |
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Ed Shillitoe Member
Joined: 23 Mar 2007 Posts: 110 Location: Syracuse NY
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Posted: Wed Jun 26, 2013 9:06 am Post subject: |
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I only use the marking gauge for the frogs, but I need it there for marking center lines and for the sides of the trench. The screw-adjustable one with a wheel is looking quite good, but over $50 seems a lot more than I would like to spend. I think the last one cost about $5 from the hardware store - but it broke which I suppose tells me something. For milling to a particular depth I do use a gauge but it's not essential because on the Sherline metric model you turn the wheels one turn per millimeter and get to a particular depth without a marked line. Thanks for all the suggestions - I'll be thinking about this while I continue on with a pencil! |
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whatwasithinking Member
Joined: 26 Jan 2013 Posts: 230 Location: Washington State
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Posted: Wed Jun 26, 2013 2:59 pm Post subject: |
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Okay, I now understand how you're using this. Seems very handy. I see that Lee Valley sells the Veritas Metric Micro Adjust version for $41.50. People seem to like them pretty well. After making do with just my calipers, this might make life a lot easier. |
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ctviolin Super Member
Joined: 07 May 2009 Posts: 961 Location: Roswell
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Posted: Wed Jul 10, 2013 2:48 pm Post subject: |
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Ok, I'll admit - I've been in the background working on both a violin and a bow.
The jig I had thought up for bow making, was a total disaster - as I went ahead, I slowly figured out that the process made the jig useless - so, at least my understanding has gone foreward a teeny tiny bit...
I did ruin both of my rosewood bow blanks (so what - rosewood I have no lack of - the pernambuco blanks I have not touched yet, as, until I prove to myself that I can do adequately well on rosewood - it gets left in the "blank" stage.
Sorry about not posting more, but I've been fairly busy, exercising my jaws needlessly, in the "other" section...
Anyone else (other than Ed, that is <G>) making progress thus far? _________________ Look,
Listen,
Learn. |
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ctviolin Super Member
Joined: 07 May 2009 Posts: 961 Location: Roswell
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Posted: Wed Jul 10, 2013 2:53 pm Post subject: |
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I've got to add Ed, that you're abilities simply seem to bypass my abilities (or, lack there of) completely...
How long did it take you to be able to adequately cut the blank to size with the facets intact, and with the diameter of the stick with an appropriate dwindle?
(gulp!) _________________ Look,
Listen,
Learn. |
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wm_crash Member
Joined: 24 Feb 2013 Posts: 140 Location: Wilmington, DE - USA
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Posted: Wed Jul 10, 2013 8:41 pm Post subject: |
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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
cheers,
wm_crash, the friendly hooligan
ctviolin wrote: | Anyone else (other than Ed, that is <G>) making progress thus far? |
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