Mortise depth?

[polkat]

I've read a lot of info on this forum about how deep to cut the mortise and am wondering if I've been doing it wrong all along. I carve my necks so that the length from the back of the nut to the end is 136mm. The heel (and by this I mean the flat part of the back of the neck that butts up against the flat back of the mortise cut) I cut at 87 degrees to the fingerboard mounting surface. I then cut the mortise 4mm deep overall, which I may adjust later depending on arch heigth. . But I have read here that some cut the mortise so that it is deeper in the block at the bottom of the cut then at the top by several millimeters. Sort of an angled cut in reference to the centerlines of the block. I assume this is to get the right neck angle without further adjustment like I sometimes do.

Does anyone have an actual diagram of this cut? And how does one relate it to different arch heights?

Like this?

[MANFIO]

"But I have read here that some cut the mortise so that it is deeper in the block at the bottom of the cut then at the top by several millimeters." Yes, that's it, it's about 2 or 3 milimeters deeper in the bottom region, it will make the mortise stronger.

[barnesviolins]

If I cut the heel at 87 degrees, leave a 6mm or so shelf, set the neck extension at 28.5mm (I always set a new neck at least 1mm higher) and cut the top of the mortise into the inside black of the perfling, it always seems to come out deeper at the bottom than the top.

With 87 degrees at the heel and 27.5-28.5 extension, is your mortise depth coming out equidistant at the top and bottom?

Dorian

[matthew tucker]

I've often wondered why violin mortices seem so shallow. What's the down-side of a deeper mortise, say up to 10mm? The up side, it would seem to me, is a stronger neck joint.

[Andres Sender]

I imagine it's because a properly-made normal joint works fine, so if the joint is deeper you create unnecessary difficulties for later modification or restoration with no appreciable benefit. It would be kind of like using strong glue to put on the top.

[Brad Dorsey]

I think you don't have to worry about mortise depth, because if you do everything else right the mortise depth will be correct by definition. By "everything else right," I mean make a standard arching height and make the neck with the correct length (13.6 cm from the narrow end of the fingerboard to the wide end of the neck) and with the correct angle at the end (Courtnall & Johnson say 85 degrees, but 87 is probably acceptable.). Now if you cut the mortise so the neck length from the end of the fingerboard to the top edge is 13 cm and the fingerboard height projected to the bridge position is 27 mm, the mortise is automatically the correct depth. If you made the mortise depth any different, the neck mensure or the fingerboard projection (or both) would be incorrect. It normally ends up that the mortise is deeper at the back than at the top, but there's no need to measure it.

[polkat]

Thanks guys. Brad, that makes sense. As I said, I often have to adjust the mortise to get the right fingerboard projection, so I guess that I was doing it right after all (just didn't see it). It's not always 2.5mm deeper at the back, but it is recut from my starting 4mm overall.

Sorry guys, I think I asked a question that didn't need asking.

[saintjohnbarleycorn]

polkat, thanks for asking the question, the information is useful to me and maybe some others on the site.

[NewNewbie]

The angle that is cut on the neck varies with each maker, some

leave it at 90* , and others 87* , while some go with 85*.

 I've even seen some people advocate 86.5*, so each will have

to carve a different mortise.  

Some also go with a length of 137 mm instead of 136 mm , so they

too will have to cut a different mortise.

I've heard some people claim that a *well* cut mortise does not

even need any glue to work.

All should end up with the same or close to the same; string

length, and string angle in the end.

What is the best? I don't know.  Michael and company seem to

be in the 87* camp if I recall correctly.

[COB3]

I believe they only meant that a well-fitted neck will hold significant weight without glue (see David Rubio's website), but no one would claim that a properly fitted neck did not need the glue to resist the tension of the strings. Was that what you meant?

I believe that the angle over the strings should be around 158 degrees-- but I have heard other numbers, never off by more than a degree, as being "proper". Same on the angle of the heel-- I have seen 83, 85 and 87 advocated-- 83 seems too sharp, to me-- 87 seems a little too close to square-- I settled on 85, but I would bet there are many who would swear it was wrong....

There is most likely a range within which most anything will work. For some things that range is very narrow. But observation tells me that the numbers you are concerned with have some working latitude.

All good violins are NOT exactly the same, but they kinda look that way, to the untrained eye. I saw a photo of the David Fulton collection recently-- not a very detailed photo, as it was a news item, and included 10 violins (all set up with boxwood fittings) and three violas. The violins in the picture were less than an inch tall (corpus), so most detail was lost, but what impressed me is that they all looked exactly alike at that distance.

I'd like to see that collection up close--evidently it is not far away from here. I would like to see what differences and similarities are observable at close range. The "Lord Wilton" is in that collection, as well as the "King Joseph". It seems that the differences are very slight, but that they matter.

[Darren Molnar]

Is their a standard heel angle for double bass? I've seen the upper

block at an angle on some in addition to the heel. What would it be

assuming that the block was not at an angle? or if it was?