Jump to content
Maestronet Forums

bow mortice cuts


Guido
 Share

Recommended Posts

Just wondering....

I have been rehairing lots of bows recently, most of low value, and the mortice cuts mostly left wanting, in particular I don't usually see pronounced angles at the front/back.

I just now have a bow with rather extreme angles (in particular the frog mortice) and also a nice curve in the sides of the head mortice (rather than just straight).

I'm wondering if these features are a general sign of quality or more readily found with one school rather than another?  

Link to comment
Share on other sites

I assume you are asking about the cuts at the ends of frog mortises.  It is unclear what you mean by "extreme angle"  and "pronounced angle."  Do you mean that the end cuts are perpendicular (or close to perpendicular) to the underslide, or do you mean that the cuts are quite far off perpendicular?

I often recut the frog mortises in cheap bows to lengthen them or to widen them or to change the angles of the end cuts.  I appreciate the time I spend recutting mortises the next time the bow comes back for rehairing.  I almost never recut head mortises.

Mortises in good bows should not be altered.

Differently shaped mortises in good bows are associated with different schools of making, but I don't know enough to know what shapes are found in what schools.

 

Link to comment
Share on other sites

22 hours ago, Brad Dorsey said:

I assume you are asking about the cuts at the ends of frog mortises.  It is unclear what you mean by "extreme angle"  and "pronounced angle."  Do you mean that the end cuts are perpendicular (or close to perpendicular) to the underslide, or do you mean that the cuts are quite far off perpendicular?

I often recut the frog mortises in cheap bows to lengthen them or to widen them or to change the angles of the end cuts.  I appreciate the time I spend recutting mortises the next time the bow comes back for rehairing.  I almost never recut head mortises.

Mortises in good bows should not be altered.

Differently shaped mortises in good bows are associated with different schools of making, but I don't know enough to know what shapes are found in what schools.

 

Thanks Brad, I should have been more clear.

What I find in many bows I have rehaired recently (mostly German trade), is that the mortices are cut at or close to 90 degree angles and the frog mortice taking the shape of a rectangle, maybe with a very subtle "undercut" at the hair exit.

I'm aware that the "textbook" mortice is supposed to look more like a parallelogram with more of an "undercut" at the hair exit to provide proper mechanics for the so-cut wedges to not come out.

The frog mortice in the bow I have just rehaired had very pronounced parallelogram shape with angles deviating from 90 degree by a lot, quite extreme, so I was wondering.

It would be interesting to learn more about differently shaped mortices and how this may be associated with different schools. Maybe someone else can chime in?

 

P.S.: I had a Bubenreuth bow with a useful stick recently that I thought worth rehairing, and found the frog mortice to be perfectly round from a drill bit, not just back and front walls with a straight section in between but the whole mortice just being one single drill hole. It's now a serviceable bow :-) 

Link to comment
Share on other sites

14 hours ago, Blank face said:

That's a feature of some better French bows.

Thanks BF, that is the sort of thing I was hoping to hear. Of course there will be exceptions and it will be the same as violins that one can't go by one feature...

Link to comment
Share on other sites

3 hours ago, Rothwein said:

Any chance of a how-to thread? 

Take 3mm or 4mm chisel and make square (or rectangle) with slight undercut at the hair exit and parallel opposite wall.

The hardest bit is to hold the frog w/o risking damage.

I have made a frog holder which supports the frog while mounted to it's stick. The adjuster is poking out a hole in the back (not visible).

1344453416_IMG_03021.JPG

Link to comment
Share on other sites

I would never do this with the frog mounted on the stick.  In addition to the danger of damaging the stick, I would find it very inconvenient, because I’m always shifting the frog around to hold it at different angles for better chisel access and to hold it up to my work light.

A frog holder is essential.  A sharper chisel makes it easier.

Link to comment
Share on other sites

9 hours ago, Rothwein said:

Any chance of a how-to thread? 

I don't think a thread is needed.

I'm sure you have noticed that some mortise shapes and sizes work better than others.  So all you have to do is take your chisel and reshape a bad mortise so that it looks like a good one.  Be careful that you don't cut through the ferrule end of the mortise into the throat.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
 Share

  • Recently Browsing   0 members

    No registered users viewing this page.



×
×
  • Create New...