Official Luthiers Forum!
http://www.luthiersforum.com/forum/

Neck Flatness
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=21763		 Page 1 of 1
Author:  Ken C [ Thu Apr 02, 2009 8:52 pm ]
Post subject:  Neck Flatness
Working on the neck fit of my SJ last night and noticed that the flat deck of the neck (where the fingerboard will be glued) has a slight upwards bow to it. I got the 5 piece mahogany neck from Chris at Hanalei Moon and am wondering if I should flatten the neck, or if this bit of an arch was intentionally built in. A few passes over the jointer could flatten it up, but I don't want to mess with it if this arch is intended.

Thanks,

Ken
Author:  the Padma [ Thu Apr 02, 2009 9:53 pm ]
Post subject:  Re: Neck Flatness
If me brain recalls, this "slight upwards bow" is called compensation in the neck...some do and some don't.

If it is true compensation, the neck will be dead flat from about the 5th to the end but will bend up slightly towards the nut. Usually used on classical builds with out truss rods.

Well thats how I remember it.


the
Padma
Author:  Jim Watts [ Thu Apr 02, 2009 9:56 pm ]
Post subject:  Re: Neck Flatness
Ken, I'd flatten it. You want to start with a straight neck otherwise you'll have fits when you go to level the frets. Also if your using something like Titebond you'll introduce more back bow.
Author:  woody b [ Fri Apr 03, 2009 5:20 am ]
Post subject:  Re: Neck Flatness
I can't think of any reason not to level it.
Author:  Mattia Valente [ Fri Apr 03, 2009 6:30 am ]
Post subject:  Re: Neck Flatness
Level it.
Author:  Ken C [ Fri Apr 03, 2009 7:36 am ]
Post subject:  Re: Neck Flatness
The jury has spoken. I'll level it when I get back in the shop.

Thanks.

Ken
Author:  Michael Dale Payne [ Fri Apr 03, 2009 8:59 am ]
Post subject:  Re: Neck Flatness
Sounds to me as if the neck cuped on you due to an RH change at some time or another since built. I use HM necks often never had this issue. Just to be clear here don't sand or plane it to level or any means that removes material. To do so would shallow up the truss rod slot at both ends leading to your truss rod not fitting. This would force you to reslot the depth of the truss rod slot and thin out the neck at the nut end. Maybe too much. I would heat it to about 120F on a blanket then clamp it down to a true flat surface like a cast iron table saw's extention and let it stay ther for several days.
Author:  Ken C [ Fri Apr 03, 2009 10:22 am ]
Post subject:  Re: Neck Flatness
Michael, the bow isn't very much. I'd probably only have to take 1/32" off around the center. The heel and the neck where the truss rod adjusts wouldn't be touched. I have about 1/8" clearance between the truss rod and the fingerboard bed.

Ken
Author:  Michael Dale Payne [ Fri Apr 03, 2009 10:29 am ]
Post subject:  Re: Neck Flatness
Ken C wrote:
Michael, the bow isn't very much. I'd probably only have to take 1/32" off around the center. The heel and the neck where the truss rod adjusts wouldn't be touched. I have about 1/8" clearance between the truss rod and the fingerboard bed.

Ken


On a HM neck? I have never gotten one from Chris with a truss rod slot deper than just a couple thousants deeper than the Allied double acting truss rod that he supplies with his necks. Now you may have had Chris build to your specs and not provide a truss rod or provide a differnt one. but I just would be sure you are measureing the slot depth / rod depth at the nut ends t be sure first.
Author:  John How [ Fri Apr 03, 2009 11:33 am ]
Post subject:  Re: Neck Flatness
Also keep in mind that if this neck is already at finished size, if you take any material of the nut end, you will lengthen the neck.
Author:  Ken C [ Fri Apr 03, 2009 11:50 am ]
Post subject:  Re: Neck Flatness
Thanks Michael, I may have overestimated, but the gap is definately more than a few thousandths. I'm not at home, so I don't have the exact measurements, but I took the filler piece out above the truss rod when I was fitting the neck, and I recall it being fairly thick, more than 0.06". I'll make sure before I start messing with it.

John, your point taking care not to lengthen the neck is good. I am already cautious about that.

Thanks!
Author:  woody b [ Fri Apr 03, 2009 1:18 pm ]
Post subject:  Re: Neck Flatness
If you lengthen it just take a little off the face of the peghead to get it back right. Make the headstock overlay a little thicker to make up for the thickness then.
Author:  Michael Dale Payne [ Fri Apr 03, 2009 1:27 pm ]
Post subject:  Re: Neck Flatness
woody b wrote:
If you lengthen it just take a little off the face of the peghead to get it back right. Make the headstock overlay a little thicker to make up for the thickness then.


aaaaaaaa no! Easier to remove thickness at the heel cheek but I guess it can be done at the peghead if you account for it in the veneer plate.

but this all seems like a lot of work that a little heat and calmping will solve.
Author:  Ken C [ Fri Apr 03, 2009 11:08 pm ]
Post subject:  Re: Neck Flatness
To close the loop. I checked my truss rod groove this evening, and I had plenty of thickness to work with. So I put a strip of masking tape at the nut end and another at the heel end to give me a little margin and made a couple of passes of the fingerboard bed over the jointer. I then laid the fingerboard on the neck and marked each side of the nut and ran the peghead a couple of times over the jointer to get the fingerboard bed back to the correct length as pointed out by John How. Finally I pulled the tape and made a couple of passes of the neck over some 150 grit stuck to some glass and wallah! I have a perfectly flat fingerboard bed with plenty of room to still glue in my truss rod spacer. All was done in about 20 minutes. Very easy fix. Initially, I just wasn't sure it was all that necessary, but now that it is done, I am glad I did it. The neck bed and angle to the body are perfecto!!

That's all I had time to do as we ran off to Ann Arbor this evening for dinner and to see the Chris Smither show at The Ark. Chris was fantastic as usual.

Thanks again for the advice.

Ken
Page 1 of 1 All times are UTC - 5 hours
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/