curious1

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Everything posted by curious1

  1. Those look sweet. I think you’ve convinced me to use delrin.
  2. I had imagined to chuck up the peg like this: the shaft can go in a three jaw chuck at the live end and I would make a small block off wood with a hole drilled in it slightly smaller than the pip on the head of the peg. The pip self centers in the hole on one side and the dead center goes in the hole on the other side. I’m pretty sure I could finish off the details of the collar if it was in the form of a plain ring glued in place on the peg. the pegs are very beautifully turned from fabulous wood so I don’t think I can bring myself to fix them w krazy glue (there are a couple worse than the one pictured).
  3. Thank you everyone for the suggestions. this method seems the most sensible and workmanlike.
  4. Hi! I have some very nice boxwood pegs with damaged ebony collars that I would like to replace. How difficult is it to turn them and where can I find out how to do it? Can I turn the new collars off the pegs and then just slide them on or must they be turned in place?
  5. I think that can be fairly described as ‘crushing it’.
  6. Very similar to the Stradivari peg. Very fine structure to the medullary rays and tight pore structure. My guess is some type of fruitwood. Pear, cherry, ive never seen plum (Meyer suggestion)?
  7. This is a peg in the old style from a Stefano Scarampella.
  8. Probably purfled after the top is glued to the ribs to which the neck is already joined but before the fingerboard goes on. The purfling goes past the neck but doesn’t join up.
  9. Agreed. The joint gives it strength while the glue should just hold the joint in place.
  10. Hi Edi, there’s not much to discuss. It either fits or it doesn’t. If one has trouble making it fit err to making it tighter at the bottom (at the button) and tighter at the front (ribs). There is not really any meaningful difference between the two neck settings styles as relates to the sides of the mortice
  11. As I am comfortable with this joint’s similarity in three views with a dove’s tail, I will ignore the pedantry. It’s the trapezoidal shape that makes it a dovetail.
  12. Additionally, most necks fail at the bottom of the mortice first and then the back of the mortice gives way. And while it is true that the back of the neck heel is mostly in compression that is only true only up until the bottom of the mortice fails. Also, the geometry of the <90 degrees is strongest for lateral stability also.
  13. I’ve been meaning to post this for awhile to the 158degree neck angle discussion but it is now closed. So, new thread. This is the reason, to my mind, setting the bottom of the mortice deeper than the top makes the joint stronger. No doubt the engineers will correct my errors. in the 90degree option the neck rotates around point A (the top of the neck mortice). For the neck joint to fail the glue must break in tension at the back of the mortice and the bottom must break in shear. As the neck rotates the bottom of the joint opens and encourages this type of failure. in the <90degree option the neck again rotates around point A but now the bottom of the neck is forced into compression against the the bottom of the mortice. This greatly reduces the likelihood of failure in shear. Additionally the back of the mortice would need to fail in shear (C) AND in tension. The small lip at the top of the ‘neck’ illustrated below indicates that the neck would need to slip upward to escape the mortice. The back of the neck heel is longer than the mortice at 90 degrees. (The hypotenuse of a 90 degree triangle is longer than its base). Compression under load is the principal structural feature of the dovetail joint.
  14. As Don said, arch height does not seem to affect cross grain stiffness much but as the arch is lowered the plate will need to be left thicker to maintain longitudinal stiffness. A thicker plate will increase cross grain stiffness in relation to longitudinal stiffness. The relational difference between M2 and M5 leads to all sorts of secondary effects in the transition range and bridge hill and the ensuing tonal differences. Lower arches sound different generally because the cross grain bending is relatively stiffer.
  15. Maybe it doesn’t really matter. And it’s a strong possibility I’m wrong about the whole thing. Necks aren’t the only things that fail.
  16. The <90 degree mortise is stronger because the back of the mortise (and the neck heel) is longer than the front of the mortise. The shape of the joint provides resistance to the shearing force along the button. The neck must slide upwards as well as outwards to fail (this can be seen in the video by observing the change in position of the small red dot at the top of the ‘mortise’).
  17. Here is a visualization of the 90 degree mortise and why it is more likely to fail. Because the back and the front of the mortise are the same length there is no resistance to the shear force along the button. As the neck hinges at the top of the mortise the joint opens providing no resistance to the shearing force of the failing joint.
  18. I guess you are right in normal playing playing conditions. Under abnormal playing conditions though, like when the neck joint fails, collapsing the fingerboard onto the top and shearing the neck away from the button, it switches to being in tension.
  19. A mortise of less than 90 degrees decreases the risk of failure of the joint in tension while increasing the shearing force. That is a trade off I’ll take any day of the week.
  20. Cutting the mortise 90 degrees to the button actually makes the joinery weaker. Just as the sides of the mortise form a dovetail (in two directions) so should the bottom of the mortise form a dovetail (the bottom should be deeper than the top). Dovetails are keyed joints that when stressed become tighter. A 90 degree mortise is an ‘open’ joint. Because the back of the neck heel and the vertical depth of the mortise are the same it is easy to break open this join. When on the other hand the mortise is less than 90 degrees it is ‘closed’ joint. The back of the neck heel is longer than the depth of the mortise. It will be harder for the joint to open because the bottom of the joint will tighten when strain is put on it.
  21. I would worry about leaving a top 4.5mm+ in the center especially if the top is heavy (historical precedence is not with you here. Most old violins are ~3mm in the center). Personally, I would sacrifice some of the cross grain stiffness (thickness in the center) to lower the plate’s weight.
  22. The only true confirmation of M5 would be by vibrating the plate and observing the modal pattern. M5 without bass bar: