Back Grafts

I have 4 ukes that are just about ready to close up except for one thing. I need to attach those pesty back grafts. This is probably the part I dread the most in the building process (even more that finishing). You can only machine them so small and thick without them coming apart and when sanding them by hand it is very easy to break them which usually happens right about the time I’m getting close to being finished with the piece. How do the rest of you deal with making and preparing your back grafts? Here is a pic showing how small I prefer them to be.

I've done one "after the fact" by using a straight edge and my laminate trimmer (or did I use my foredom with the StewMac base?). Eitherway, I did it before the grafts and bracing went on.

Since then, I do it during the glue up. . .

Sorry, I know this was of absolutely no help to you at this stage. You're where I was, sort of, during my first one. At this stage, treat it like an "inlay", and you should be fine. Probably need to make a jig/spacers to elevate it off the bench (I would do a piece of ply, and run in across the table saw three times (okay, more than that), to make slots for the grafts and bracing. Make the ply longer than the back so you have some extra to clamp a straightedge to.

Aaron

Aaron seems to be talking about the decorative strip down the centre on the outside. You seem to talking about the reinforcing strip on the inside. If it's on the inside, it's normally glued on before the braces (I do it on the radius dish in the go-bar deck) then profiled and notched where the braces cross it. I think Pete's done a couple of videos that cover it.

Dave Higham said:

Aaron seems to be talking about the decorative strip down the centre on the outside. You seem to talking about the reinforcing strip on the inside. If it's on the inside, it's normally glued on before the braces (I do it on the radius dish in the go-bar deck) then profiled and notched where the braces cross it. I think Pete's done a couple of videos that cover it.

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Oops, you're right. From the looks of the pic, I thought it was already glued. I guess I read the term "graft" and related it to an end graft. Of course, I should have know since I used the term "graft" in describing what Dom is talking about.

I usually thin the piece of Spruce down to where I need it on the thickness sander, and cut it into strips on the table saw afterwards. Then go at it by hand on the edge of the bench to round it over.

Okay, now that I'm on topic, I hope that helped. . .

Aaron

Whenever I go to Elderly, I peek inside of soundholes. It seems to me that most uke builders don't include the reinforcing strip down the center, which makes me question its usefulness.

I guess I will have to do a video for you Dom since I culled a lot of my early stuff last year (back up to 80 videos again...) - they are so easy to do! Glad you are building again - you have had a haiatus no?

Kekani said:

Oops, you're right. From the looks of the pic, I thought it was already glued. I guess I read the term "graft" and related it to an end graft. Of course, I should have know since I used the term "graft" in describing what Dom is talking about.

I usually thin the piece of Spruce down to where I need it on the thickness sander, and cut it into strips on the table saw afterwards. Then go at it by hand on the edge of the bench to round it over.

Okay, now that I'm on topic, I hope that helped. . .

Aaron

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Thanks Aaron. I got home late last night after a night out with my wife and I wasn't sure what you were saying. Wasn't sure if it was from the alcohol I consumed or what. So I decided I better just crash and revisit this thread in the morning.

I have been using the small grafts that come from Hanalima and thinning them more by hand etc. I've haven't built enough ukes at any one time where I really thought about preparing them from a spruce plate. I think I have a piece I can work with.

Matt Clara said:

Whenever I go to Elderly, I peek inside of soundholes. It seems to me that most uke builders don't include the reinforcing strip down the center, which makes me question its usefulness.

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Matt, I don't know what ukes you are looking in but I would guess that more ukes that have 2 piece backs will have the back grafts than those that don't.

Pete Howlett said:

I guess I will have to do a video for you Dom since I culled a lot of my early stuff last year (back up to 80 videos again...) - they are so easy to do! Glad you are building again - you have had a haiatus no?

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Pete, I would love to see your video. I've been enjoying your most recent ones in the batch build series. The day job, gigging with the rock band and attending and playing at more of the uke fests etc. kept me out of the shop for ALL of 2009. I'm trying to change that a bit right now. Two of the seven I have in progress were started two years ago when I built the spruce top tenor. So I sort of have my own batch build going on at the moment.

You have too many gifts Dom. I don't think you'll 'like' the vid as it has a shop tool that I made that I find totally indispensible when doing this stuff. It's so obvious you'll kick yourself when you see it!

Pete Howlett said:

You have too many gifts Dom. I don't think you'll 'like' the vid as it has a shop tool that I made that I find totally indispensible when doing this stuff. It's so obvious you'll kick yourself when you see it!

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I stand ready to kick myself Pete. Always room for another shop made tool.

Dom, for some reason I've had no problem ripple the strips against the grain, and then reducing them down to thickness on my home-made drum sander. I'm surprised by your troubles in this area. I have my own troubles, i.e. finding a quick way to marry the joint between the body and neck using the barrel bolt method... ernie..

I use 1/64" model aircraft plywood - a strip about 3/8" wide.

Ernie, I think my problem lies in the fact that I want the grafts to be "very" thin. As Dave indicates he is using the 1/64" ply material. I'm not trying to go that thin but taking the pieces that come in the bridge patch kits at Hanalima (which is what I've been using to date for my grafts) which start out at .080 - .085. I want them down to at least .070 and in sanding them against the grain by hand is a pain and one slip up and the little boogers break. I've seen production ukes with big hunks of wood as back grafts and I'm trying to keep things as light as possible.

Installing the graft as one piece, as was mentioned above, might be a viable option also.

Ernie - make a simple horizontal borer using a pair of drawer slides and a corded hand held electric drill. I am sure I made a video of this last year. To hold the drill I use my Zyliss useless drill stand mount thingy - see Zyliss thread. Total accuracy! I'll video it when I do my batch of necks next week!

Dominator said:

I have been using the small grafts that come from Hanalima and thinning them more by hand etc. I've haven't built enough ukes at any one time where I really thought about preparing them from a spruce plate. I think I have a piece I can work with.

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Truth be told, I use the offcuts from my Spruce tops. More truth be told, I thinned a top too much, and got a slew from that piece.

The most difficult part for me is slicing them on the table saw. Its a pain because I usually have a rip blade installed, so I have to change it out to crosscut (I hate changing blades, except when I clean them, which is very often - I know, doesn't make sense). Actually, the PITA part is actually cutting it because it blows out so easily at that thickness (or should I say thinness?). So, I do the doublestack and tape method (with "whole" pieces of Spruce, not offcuts), and use two pushblocks.

Pete, please follow up with a link when you do that vid. I'm right behind Dom ready to kick myself as well. . .

Matt Clara said:

Whenever I go to Elderly, I peek inside of soundholes. It seems to me that most uke builders don't include the reinforcing strip down the center, which makes me question its usefulness.

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Not sure what instruments you're looking at, but most, if not all of the instruments I see have back grafts. I've seen some with the grain going in the same direction, but at least its there. I've seen a few factory instruments without back grafts, but never a "builder's" instrument.

Aaron

I'll take a couple sheets wood and glue them together to make one sheet about 12" X 12" or so. Similar to making a top or back. Then I sand it to about .060" This sheet gets ripped into 1/2" wide strips (cross grain) using the same sled as I cut my kerfings with. They are also cut with the same blade, a thin kerfed laminate cutting blade. Finally I put a bevel on the sides of the strip on my horizontal belt sander. I glue the strip to the back as one whole piece and hold them down with go-bars. If you have your braces ready and get them in within about ten minutes or so it is easy to notch and remove the little pieces of wood required. Pretty simple.

Pete Howlett said:

Ernie - make a simple horizontal borer using a pair of drawer slides and a corded hand held electric drill. I am sure I made a video of this last year. To hold the drill I use my Zyliss useless drill stand mount thingy - see Zyliss thread. Total accuracy! I'll video it when I do my batch of necks next week!

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Thanks Pete, this is the hardest area of the build for me. Looking forward to the batch necks video on this problem area... thanks, ernie..

I've a feeling that this subject is getting into the realms of, as the French would say, 'why make it simple, when you can make it complicated'?
When you make an instrument, (normally) you've got the offcuts from the front or back (and in fact the back makes more sense) from which you can make a cross-grain strip (or strips) to use for the back graft.
Leave them (or it) at full thickness and glue it (them) onto the back. There are various methods of doing this; clamping a straight edge onto the back and pushing the strip(s) up to it, putting 2 or 3 layers of masking tape on the back on either side of the strip(s), etc.
Once glued, put a couple of layers of masking tape on either side to protect the back and,using a block plane, plane the strip down to the thickness you want (personally, I can't see why you'd want to go less than 1/16") and round the edges over to form a convex surface (not necessary, it just looks nicer). In fact, Pete has one of those miniature Chinese planes and he's ground the blade to a convex shape just for doing that. That's fine but for lesser mortals like you and me (you're not included Chuck) a block plane and a small sanding block will work just as well but take 3 minutes longer! That's all there is to it.
I don't quite understand Chuck's 'If you have your braces ready and get them in within about ten minutes or so it is easy to notch and remove the little pieces of wood required.' I like fish glue, and leave the back graft to glue overnight, then I cut the notches for the braces. If I used Titebond Original, I'd give it an hour before taking off the go-bars and cutting the notches for the braces.

Edit. I can't make any sense at all of Pete's or Ernie's posts. I've a feeling that they are (or perhaps I am) in the wrong thread! ???

Edit 2. Apologies... I've just read through the whole thread again and realised that Ernie's and Pete's posts were slightly off-topic.

Dave Higham said:

Edit. I can't make any sense at all of Pete's or Ernie's posts. I've a feeling that they are (or perhaps I am) in the wrong thread! ???

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I was speaking of problem area's I have, as opposed to back grafts. Mine was neck to body joint. Pete simply responded to that comment... ernie..

Dominator said:

Matt, I don't know what ukes you are looking in but I would guess that more ukes that have 2 piece backs will have the back grafts than those that don't.

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Thats a good point--I'll have to double check for which ones have single piece backs.

Sorry if I wasn't clear. I have my braces radiiused, sanded and ready to go before i glue the back graft on. Once I glue it in place I'll wait about ten minutes. That allows enough time for the glue to set enough so that the graft won't move, but I can still easily "pop" out the little notched pieces that I've cut with a chisel to allow for the braces since the glue isn't fully cured yet. It takes me about ten minutes to glue the bracing and back graft on.