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Hello id be interested to hear opinions on the pros and cons of either method,thanks.

If you slot the bridge for the saddle off of the guitar you have to glue the bridge on in the exact position or you may not be able to intonate it properly. Slotting the saddle with the bridge on the guitar allows you to put the slot exactly where it needs to be. I've done both but do my bridges on the the guitar now. If you can locate the bridge with sufficient accuracy I don't think it makes a big difference on a new build.

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Steve Smith
"Music is what feelings sound like"

What Steve said. Lots of guitars have been built with pre slotted bridges that were positioned very nearly..... in the right place.....

One major, iconic manufacturer mislocated the bridges on thousands of guitars in the 70's and in time many of them have been fixed (under warranty). Since intonation could not be set well or accurately players who only played cowboy chords may have never noticed. Others had issues.

Below is a link to our video page and if you scroll down you will find a video for the "Collin's Saddle Mill." Dave designed this saddle mill over ten years time and we do sell these. Two OLFers have them along with Elderly instruments in Michigan.

Does a builder need a saddle mill? Nope, I didn't but it does add a level of accuracy that if you are really looking for superb intonation can be appreciated.

In the repair world bridges are made not bought.... This means that we have to slot them too. It's WAY easier and MUCH more accurate to slot an unslotted bridge on the guitar with a saddle mill than it is without one.

Additionally you know those USTs? Under saddle transducers. How do you install one on a through saddle instrument? You don't unless you have a saddle mill to mill a special pocket for the UST.

Lastly glue your flat bridge on a domed top guitar and what happens to the bottom of the pre slotted saddle slot? It's no longer flat. If you have a saddle mill you can flatten it out so that not only the saddle makes complete contract for maximum vibrational transfer but UST's will have any pressure points equalized for better equalization or balance.

Saddle mills permit us to optimize the set-up and resulting sound from many instruments.

http://www.annarborguitars.com/styled-4/index.html

Of course, Hesh is the man for this, but I can say that if you don't need the Collin's saddle mill just yet, but still want something to use, the SM saddle routing jig coupled with a Dewalt 611 and 3/32 end mills from Burchett Quality Tool (thanks again to John Hall for this great resource) has been a very stable setup for me. You need the 1/8 chuck adapter for the Dewalt, but it is much much more solid than a dremel. Good luck!

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When you measure for the saddle slot you are going to do it the same way weather it's on or off the bridge so frankly I don't see what the difference is. Unless I'm mistaken. The way I do it is to rout out the slot and make the bridge then place it exactly where I want it to be which is typically .1in longer then the scale length. Then I mark the bridge location, finish the guitar, and glue the bridge on.

So I would imagine that if the bridge was already glued on then you would mark a point that is exactly where you want the saddle to be which would be about .1in longer then the scale length and then rout it out... Right?

I guess one advantage of doing it after would be if you place faux saddle pieces in position to get exact intonation on both E strings then just rout out the angle? IDK But personally I don't want a router anywhere near my finished top so I do it before

For me, the pucker factor of getting a pre-slotted bridge located properly is nothing compared to what it would be for slotting the bridge on the guitar. Positioning a pre-slotted bridge exactly where it's supposed to go for proper intonation is no problem. Also, it's a whole lot easier to recover from "stuff" happens events with the bridge off the guitar. Routing the saddle slot is the first thing I do after thicknessing and squaring up the bridge blank, so if stuff happens, it's no big deal in terms of time and worked invested to that point. And I agree about not wanting a router near the finish.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

On the guitar. Three messy saddle slots with a Dremel and I stepped up. This makes the job as easy as falling of a log........... My first job with the saddle mill was my #3D-18 I was taking to the Ann Arbor guitar fretting and setup class last Spring. I used a .250 bit to clean out the old slot completely, had a great piece of matching Macassar Ebony glued it in with HHG, and after carefully measuring and positioning the mill routed a beautiful .250 saddle slot. Not a real big deal glued in a nice filler HHG and routed a perfect 3/32 slot with a snazzy 5 degree back angle and we were off to the races, or was it Michigan:)

That sure gets the TAS going

_________________
Steve Smith
"Music is what feelings sound like"

With a sweet mill like that - on the guitar work is easy and much lower risk.

I do all mine off the guitar.... But I also shape the bottom of the bridge to match the top dome.

Without a mill like that - one slip or mishap with a router would ruin a bridge and maybe also the top...

Then - you just adjust your intonation on the saddle as per usual.

I I think it largely depends on how nice a slot you expect/want. The precision required to mill a perfect slot is the same on or off the guitar and it is no small thing. A good router, a collet with no run out, A high quality bit, minimized bit extension, and a slide mechanism completely free of play are some of the ingredients either way.
A small bit requires multiple passes to get full depth. Many systems fail at this task and leave steps in the slot.
If your not sure your method will do it every time, it's probably best to slot off the instrument. If you have confidence it will come out every time, there is no reason not to do it on the instrument.
If you can cut a slot within a half thousandth of the bit size your doing well.
Repair pretty much necessitates being able to do it on the instrument. If your just building, you can afford a little more risk.

I cut the slot on the guitar. I made a simple jig out of scraps of plywood and MCP that I can clamp to the guitar body. It does take a little time to set up (10 -15 minutes) but I don't slot that many bridges in a year. I use a PC trimmer with a square base, 1/8th inch Stew Mac collet and dental burr type bits. For non - through saddles I hand plunge the router. The Collins mill looks like a nice machine, but for what I do I could never justify the expense.

Out of necessity, I've had to recut slots ON the instrument (not mine). Since I don't do repairs (they were for a friend), I made a quick jig out of scrap wood, and threw it away.

Out of design process, I slot OFF the instrument. This vid may be long, so just peek at the actual saddle slot cutting. This works for straight slots obviously, but may give some ideas for a modified version for angled (horizontally) slots.

Hi aaron , are you using 1/8in bit for the initial slot and 1/4in for the secondary slot on the uke bridge ?? Looks easy to make . thanks for posting

Yes.

Someday I'll get Trevor's book- he has jig designs in them that lock the router in a track, uses rails, is adjustable, etc. There's so much more that can be easily done with this, but my primary focus is accomplished- getting the 7 degree angle for the saddle slot.

The KMG bridge setter from kencierp works well, but it only works for a single scale length.

http://www.cncguitarproducts.com/kmg-br ... ckage.html

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I'm not a luthier.
I'm just a guy who builds guitars in his basement.
It's better than playing golf.

I just watched the cutting part of Aaron's video and saw the orientation of the plunge mechanism is not typical. The direction the router tends to rack is parallel with the slot.
This strikes me as a detail that could make a big difference If your using a plunge base.
Most use a plunge rig with a hand on either side of the slot. Any racking will tend to throw the bit to the side.

Beautiful shop David!!! That space has great karma!

I take it by racking you mean movement or "tipping" of the router causing inaccuracies in the slot?
I also take it that since the DW611 used in this jig runs parallel, the orientation is a good thing? I never thought about it, but if the base was round, I'd probably use Trevor's method and mount it on a rail of sort for ONLY lateral movement.

Don't get me wrong, if I don't keep the router against the fence, the slots becomes crooked. BUT, its not that difficult to keep it against the fence.

I never thought about it either until I saw your video Aaron.
I'm referring to the slop in the plunge bushings. Most plunge basses wobble pretty badly during the plunge or when they lock on one post and the raising spring moves the other side up. I think your atypical orientation of the router might negate some of that slop. The motion would tend to be along the slot like a pendulum.
I purchased a Festool plunge router years ago, hoping it would have precise enough bushings to be a dedicated bridge slotting tool. I found the same slop as in any other plunge router and bailed.

Here's a photo of a brand new relatively expensive instrument. The bridge rout had a significant step in it. Instead of shaving the step off, a saddle .009!" undersized was used so it would sit down in the slot. Come on now. If your name's on the label............................

Even a rigid $100,000+ CNC can cut a poor slot when the feed speed is pushed too far or someone tries to get just ten more out before changing a dull bit. There's often a tell- tail offset to the plunge hole at one end.

And no more pictures of Collins mills! I have to keep wiping the corners of my mouth every time one is posted.

Ah, I get it. To be honest, I never noticed that there ISN'T a step.

Yes. Unfortunately, when you use the standard fence arrangement, all the router makes I have will rack perpendicular to the slot. The DeWalt plunge bases seem to be among the best for least racking, but they still will if you give them a chance. There may be makes available with the rails oriented in the perpendicular direction.

The way I get around this is to use a smaller bit than the slot width, then take a light full depth cut off each face of the slot. With the anti-backlash screw mechanism I have on my rig I can make that adjustment at full plunge with the bit spinning, so no steps or width variation in the slot.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

I always got that little ridge when I used my PC310 and lowered it in it's standard base with the threaded ring. Now I have the Bishop Cochran base and it routes a perfect slot.

I route on the guitar for repairs but off the guitar for new builds.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

It seemed counter intuitive at the time, but I finally achieved a perfect slot every time by making a base for my Dewalt that tilts down square to the bit. Shimming the inside of the casting so it registers only on three points keeps a consistent position at different depth settings.
I wasn't sure it would work but it does, every time.

Trevor, moving the travel sideways without lash sounds impressive. With the proliferation of 3D printers and home made CNC's I noticed no-lash lead screws are all over Ebay now. I was thinking of picking one up for a height adjustment. Care to share a photo of your rig?