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| Flush trimming http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10101&t=17447 |
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| Author: | Andy Matthews [ Mon Jun 02, 2008 8:35 am ] |
| Post subject: | Flush trimming |
Today I received my luthiertool binding cutter jig - what a great, well made piece of kit it is  I was presuming that I'd be able to flush trim backs/tops to sides using it, but after looking at the bit surround that aint gonna happen - so I'm looking for some input from you chaps. How do you flush trim? By hand? Using a router? If you do use a router how do you combat the age old arching problems? |
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| Author: | Hesh [ Mon Jun 02, 2008 8:55 am ] |
| Post subject: | Re: Flush trimming |
Jammy buddy the Luthier Tool binding router jig is indeed a very nicely engineered tool. Congrats. Although I don't have one using a Williams jig instead here is a trick that Mario taught me that works great. Set-up your jig as you would to cut the binding channel only set it up to cut the channel .015 - .020 deep and at least the depth of the plates. This is a shallow pass and slightly beyond flush. Be sure to make climb cuts first to avoid tear-out. Once the shallow cut is made, beyond flush, you can go at the sides and true them up with a sanding block and a radiused sanding caul in the waist area. It's key to get the sides very true before cutting the final binding channel since your jig registers off the sides. The beauty of Mario's method is that once the top and back plates are taken out of play the sides are MUCH easier to true up. Now Mario uses a roto-zip bit to do this and I think that he uses a different jig too but the idea is the same, cut a shallow binding channel instead of shooting for flush and speed up your sanding of the sides. With my William's jig I add an additional step. First I use a flush cut bit, again with climb cuts, then I make the shallow pass with the binding cutting bit. |
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| Author: | Bob Long [ Mon Jun 02, 2008 9:02 am ] |
| Post subject: | Re: Flush trimming |
I do mine exactly the way Hesh described.... but for what it's worth... A flush trim bit in a router should work fine... any inaccuracies caused by the arch shouldn't matter... because your just cutting the overhang... and later you'll cut more of that away for the binding ledge.... I hope that makes sense? long |
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| Author: | Andy Matthews [ Mon Jun 02, 2008 9:06 am ] |
| Post subject: | Re: Flush trimming |
Thanks for the advice Hesh The problem I'm having is due to the small surround around the bit which seems to prevent it being used on anything with a lip like is present at this point in construction. It's difficult to describe, but I can't see a way round it.... I'll keep thinking |
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| Author: | Andy Matthews [ Mon Jun 02, 2008 9:08 am ] |
| Post subject: | Re: Flush trimming |
Bob Long wrote: A flush trim bit in a router should work fine... any inaccuracies caused by the arch shouldn't matter... because your just cutting the overhang... and later you'll cut more of that away for the binding ledge.... I hope that makes sense? long The problem arch causes in this case is that it stops the cutter trimming flush - a small amount of the top or back is still left overhanging. |
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| Author: | Dave White [ Mon Jun 02, 2008 9:15 am ] |
| Post subject: | Re: Flush trimming |
jammy wrote: Bob Long wrote: A flush trim bit in a router should work fine... any inaccuracies caused by the arch shouldn't matter... because your just cutting the overhang... and later you'll cut more of that away for the binding ledge.... I hope that makes sense? long The problem arch causes in this case is that it stops the cutter trimming flush - a small amount of the top or back is still left overhanging. Jammy, If it does that with a flush cut then won't it do the same when you cut the binding channels? Obvious thing to do is ask Luthier Tool. Failing that get out a sharp chisel and cabinet scraper. |
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| Author: | Hesh [ Mon Jun 02, 2008 9:19 am ] |
| Post subject: | Re: Flush trimming |
jammy wrote: Bob Long wrote: A flush trim bit in a router should work fine... any inaccuracies caused by the arch shouldn't matter... because your just cutting the overhang... and later you'll cut more of that away for the binding ledge.... I hope that makes sense? long The problem arch causes in this case is that it stops the cutter trimming flush - a small amount of the top or back is still left overhanging. Two possibilities here - first perhaps the roto-zip bit that Mario uses will make quick work of the overhang since this bit cuts on 3 sides. Second - when you have that small over hang left, I do too, this is when you adjust your jig to cut the shallow binding channel which will kill the over hang. BTW making an initial shallow binding channel cut makes the final cut a bit less risky because you are not removing as much material. Again, and sorry to be so stinkin redundant here I know I sound like a nag..... be sure to make climb cuts every time. |
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| Author: | Andy Matthews [ Mon Jun 02, 2008 9:20 am ] |
| Post subject: | Re: Flush trimming |
I meant using a flush cut bit in the router with it's standard base. I've thought of way to describe the issue I'm having... The plastic surround around the bit could be thought to be the infeed/outfeed tables on a surface planer (on a tiny scale) When you adjust the cutter to the position which would flush trim, everything lines up dead on - infeed, cutter, outfeed. So no material is removed! |
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| Author: | Richard Wilson [ Mon Jun 02, 2008 9:34 am ] |
| Post subject: | Re: Flush trimming |
I flush trim with a standard 1/2" flush bit that you can get at any hardware store on a regular trimmer with no jigs or modified bases etc. I went this way because I got sick of having to change bits the whole time on my binding jig, so I just bought another trimmer and keep it with a flush bit the whole time (comes in handy in many tasks around the shop). Of course the buying another trimmer part is just for lazy people like me... The arch has no detrimental effect on the cutting and without bulky jigs in the way I can get the job done in no time (sounds like an infomercial...). There is normally a small ledge left which is gone in no time once I start sanding. |
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| Author: | Terence Kennedy [ Mon Jun 02, 2008 11:28 am ] |
| Post subject: | Re: Flush trimming |
I do pretty much like Todd for the overhang. Trim with a hardware store flush cutting bit. Take the residual down a little more freehand with a robosander on the drill press, and block sand flush. Then stick in the vise and true up the sides with a 3/4" sanding block and a firm circular block for the waist. It goes pretty fast. I have a Rotozip but it would scare me to turn it loose on a guitar. But then again I never tried. Terry |
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| Author: | Hesh [ Mon Jun 02, 2008 1:41 pm ] |
| Post subject: | Re: Flush trimming |
Another possibility where you can just use the laminate trimmer freehand is to make a donut and use double sided tape to stick it to the base. The donut pictured is MDF with some shellac on it and it was angled into a wedge shape and a mark is placed on the thinnest side. The exact angle that I made mine I am forgetting but it was derived back when I made it by calculating the dome of the top (in my case 25') and the dome of the back (15') and using something in the middle so that one donut would work fairly well for either the top or back. Prior to using the donut the bearings on the flush cut bit rode on the side with the lower edge pressing into the side more and this created a crease in softer woods like Mahogany. Once I started using the donut the bearing rides more flat on the sides and the crease is gone. Best of all the slight overhang that resulted prior is gone now and the cut is mostly flush. The mark is so that as you go around the guitar turn the laminate trimmer so that the mark is always pointing in the general direction of the center of the dome. Again, climb cuts are a good idea. Cheap and easy to make, works well. Attachment: DSC01526.jpg Attachment: DSC01527.jpg
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| Author: | Andy Matthews [ Mon Jun 02, 2008 2:07 pm ] |
| Post subject: | Re: Flush trimming |
Flush cutting bit in the lam trimmer it is! Thanks chaps. I've been thinking about this this afternoon and came up with a similar idea to you Hesh. I used to use a lam trimmer with a tilting base when I was learning, but my new Bosch doesn't have that option so I'll sort out a wedge of some description to minimize the overhang. Also ordered a luverly down-shear trimming bit too 
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| Author: | Jody [ Mon Jun 02, 2008 3:32 pm ] |
| Post subject: | Re: Flush trimming |
use a round over bit . Jody |
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| Author: | ChuckH [ Mon Jun 02, 2008 4:12 pm ] |
| Post subject: | Re: Flush trimming |
Howdy Jammy, This is a timely thread cause I'm right at this point also. Jody, what's your theory on using a round over bit? I have a a couple flush cuts but not a round over. Is it similar to a quarter round bit? |
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| Author: | Jody [ Mon Jun 02, 2008 7:07 pm ] |
| Post subject: | Re: Flush trimming |
right chuck, its the way Frank Finocchio showed me to do it , flush cuts never cut flush , a small round over will cut the sides flush and give a nice turn on the top edge,just make sure you set the depth so you dont cut the ledge, some round over bits will cut a ledge. and be sure your bit is sharp, i just did mine and got a little pull out on the lower bout, looking at the cut now ![[headinwall]](./images/smilies/headbangwalluf8.gif "Mad") ,the bit wasnt sharp, Jody
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