Official Luthiers Forum!

I’ve run into a bridge slot cutting snag with my Bosch Colt in that the height adjustment (weakest link) no longer works properly. It worked great, until it didn’t.

What are you folks using to route the slot? I’m considering the StewMac plunge router with the Dremel, or a DeWalt palm router. My slots are 1/8”.


After some tweaking for run out, the Bosch worked great until the height adjustment went intermittent. I am very comfortable with the Bosch router. I’ve ordered a new height adjustment screw as the current one has some marginal/ flat/ a little to shiny threads. I’m not real confident that that is the problem/ solution. Anyone have tweeks or mods for improving the height adjustment?

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Measure Twice,

Karl Borum

I have the SM setup and use my dremel with an adjustable base. Has worked fine

I have a small Makita plunge router that I use for slotting my bridges. It works very well. I’m using my Dremel less and less where precision is desired. It just has too much runout. The shaft can be deflected with just a sideways push.

I have the Dewalt small router. It is a nice tool—more powerful than the Ridgid or the Makita. The only drawback is that the plunge base has a limited range of travel—it would take a longer bit than I have to cut classical guitar headstock slots. The Makita works well there. The Makita does not work well cutting truss rod slots. The added drag on the bit makes is slip sometimes, ruining the cut. For that, the Dewalt is my preferred tool.

My cordless Dremel is only a few years old, but the model has been superseded and branded batteries are no longer available. I won’t be replacing it with another Dremel. The battery and the runout issues have done it in for me.

Karl--

Have you considered getting a plunge base for the Colt? You might have to re-jig a bit, but it might help you stick with the Colt, instead of changing routers. I know some folks don't like the Colt, but I don't have problems with the several that I own.

I'm also a bit spoiled in that I have one of the Bishop Cochran router bases for the Colt, and it is YUMMY. I'm not sure you can still get those. The website still exists, and I think someone is supposed to be making them, but I remember having some trouble getting in touch with them at some point.

Hope it works out for you.

I use a Makita laminate trimmer. Helpful tip, maybe…even when I feel confident that the router bit depth won’t change by slippage in the base, I still take a piece of masking tape and tape the router and the base together. Same with my binding routers…

With my Makita, the bit slips in the collet.

Like Don, I have a Bosch Colt in a Bishop Cochran base and it's the bees knees.

I have two Colts and the height adjustment failed on one of them, but unfortunately it was the threads on the body of the router that wore out rather than the threads on the height adjustment screw. Argh.

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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

Sadly the Bishop Cochran base is no longer available following his death. I have one and if you can score a used one you will never regret it. I have a PC 310 in it so both are discontinued items and I hope they outlast me. Another six years would probably do it

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

Be sure to watch the video at the bottom of the page if you have not seen the Collins Saddle Mill before. The Mill is vacuum clamped, laser guided and its development history will be invaluable to anyone simply looking for a well performing lam trimmer.

Karl when we developed the Collins Saddle Mill our design goal was to get the slop out of the process of slotting the saddle AND to make it safe and reliable to slot a saddle AFTER the bridge has been glued to the guitar. I repeat we wanted to slot saddles when the bridge has been glued to the guitar first. It's more precise, provides you with options and there was a well known repair need for this tool in the Martin world where in the early 70's some 18's, 28's and 35's had the bridge located on the wrong position.

This mill permitted us the option of not having to remove and replace bridges on the Martins with the bridges in the wrong location. We could instead clean up the existing saddle slot, plug it with matching wood, cut the new slot where it precisely belongs and this permitted these many instruments to finally play in tune and live up to their potential.

The invasiveness of removing a bridge and any possible finish damage and subsequent repairs was completely eliminated by the process making it the best option out here for these Martins.

Dremel tools are terrible and have some of the greatest amount of runout out there. The PC 310 which was the best lam trimmer in the past 30 years or so had been discontinued.

So Dave set out on a mission to purchase every laminate trimmer available and test them all for suitability in a saddle mill. He has perhaps 100 hours of time into just the testing of everyone's laminate trimmer.

Our apprentice Link Van Cleave who is a master woodworker who had his own TV show on the West Coast took on the Bosch Colt and purchased 5 of them and tested them all for runout. He wanted at least one for his own use and ended up returning all of the the Bosch they were so bad....

Dave has a background of being a trained machinist and he wanted minimal runout.

To save you the gory details there was a clear winner in our tests the DeWalt and that is the one that he designed his saddle mill around. These mills were produced in our shop, we built and sold about 20 of them and they went all over the world. When we stopped selling them because we did not want to be in that business favoring to do our repair work they were selling for around $4,500 each. We no longer produce them but receive inquiries every month or so usually from people who have no idea that this is a serious tool with a serious price tag....

Our mill and the ones we shipped had runout of around 0.001" and that was what we were looking to find AND deliver.

The DeWalts were upgraded with chucks from "Precise Bits" and we are the ones who turned the OLF onto who Precise Bits is and what they do.

Of all the lam trimmers that we bought, tested and returned the five that Link in California tested were by far the sloppiest out there. They averaged out of the box around 0.005" of runout which is way too sloppy for a saddle mill. To be more precise we measured runout at the tip of the bit that was doing the work. So our runout measurement is what the work piece will see meaning the resulting saddle slot. 0.005" slop in a saddle slot is unacceptable and enough of a gap that the saddle might rock and the gap could be seen with the human eye easily.

Now to level the playing field professional standards for how a saddle fits need to be defined and discussed here because YMMV is in play. A proper saddle should fill the slot in a gapless manner, not rock, no gaps, full, flat bottom contact with a flat bottom on the saddle and the bridge installed on the guitar. The ends of the saddle should have zero gaps as well and the curvature of the ends needs to be precise, eloquent and fit perfectly. That's how we make our saddles.

If there is a UST (under saddle transducer) the saddle needs to be capable of moving up and down with only finger force but never, never loose and capable of leaning. The saddle can fit more snugly if there is no UST.

So our standards were and remain very high for this function which must be considered when evaluating how one may get to this point.

Lastly the DeWalt also had a good history, big company behind it and it was well made in other respects too so we went with it and purchased over 20 of them and they never let us down. Our mills have been in the wild now for 10 years or so with zero failures or complaints about the DeWalt Lam trimmer we shipped installed in them.

With all this said do yourself a favor and join the professional luthiers who pretty much all universally agree that Dremel tools when it comes to precision are..... well they are just not all that....

Big Box store lam trimmers can be all over the map too in our experience and the most popular one we discovered was one of the worst for precision.



https://youtu.be/d3tmkLVEAQo?si=vc9_YMCkiL9UuD2s

Not wanting to be argumentative. but regarding run out, do we not fit the saddle to the slot?
If a slot is 0.005" oversize, would we not just make the saddle a little wider?

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Hesh, did Dave happen to test the Foredom tool with its handpiece? I want something small and manipulatable like the Dremel but without the runout.

Hi Colin and that's not argumentative at all. Good question.

So what if "we" are no longer involved? Part of building serviceable instruments is controlling tolerances so that the plethora of after market things that folks invariably wish to do or add may work as billed. We also want the next person servicing the instrument to be in a position to do great work too and that means a starting point that is not hack work.

The classical crowd not so much but today's steel string player may want to add a Tusq saddle that is billed as a drop in fit... or a pick-up that has a UST that benefits from being in the center of the saddle slot and not having one edge not in contact with the saddle bottom.

A huge and all too common problem with poorly cut saddle slots is a bottom that is not level. The pick-up with a UST will have balance problems when this happens.

Some food for thought. Preslotted bridges glued to a domed top.... so is the slot bottom still level? No.... the bridge will flex ever so slightly and more so over time creating balance issues for pick-ups.

If the slot is cut with the bridge glued to the guitar top the slot can be perfectly flat in the bottom when the bridge is glued to a curved surface.

The Martin community can purchase bone, after market Martin saddles that are an excellent, drop in fit because of the close tolerances that both the saddles and the slots are crafted to.

I agree with you that fitting a saddle can be done and we do that anyway but we want to make the saddle smaller to fit. If it needs to be bigger to fit we need a new saddle, again....

I have three Suhr guitars in my current collection. Suhr is like Fender only on steroids and I would also offer the comparison of Toyota (Fender) to Lexus (Toyota with tighter tolerances) as well. When I wanted my butterscotch Blonde Suhr Tele to have a one piece "black guard" like the famous Teles in the beginning of it all I could order one from Suhr that was made specifically for my Tele. They are all CNC and record what they make and ship. So they squirted one out, a black guard that fit so perfectly it was virtually gapless around the neck pocket. Impressive!

Now I know you are not advocating doing work that is .... just good enough or will pass the SLO (saddle like object) smell test. Nor should we be or at least I'm not here to support doing anything less than great work.

So yes we can make a sloppy saddle that is not uniform in it's dimensions to support an imperfect, sloppy saddle slot but now I have a question for you.

Why would anyone ever want to do substandard work in the first place?

Karl is asking us for what we believe to be the best tool of this type so of course I'm motivated to reply by the quality of the results of what I recommend. Unlike likely anyone else here on the OLF my crew actually tested every lam trimmer on the market exhaustively including multiple samples.

So if I were a Karl and I received reply that was beyond "this is what I use and it works for me" I might appreciate what I just read from this Hesh guy. I'm sure Karl does too I got a Christmas card from him last year, thanks again Karl.

Anyway there is more too such as how uniform the slot is from one end to the other, how straight it is, how sharp is the transition from the bottom to the sides in the slot that might prevent the saddle from fully seating.

Long ago on this forum Mario shared with us that he ships his incredible guitars with two saddles, a winter and summer saddle accounting for the rise and fall of the top dome seasonally. Mario would have to make two saddles that are imperfect for every guitar if he was not working to a level of high precision.

Foredom is more of a Dremel like tool with hand piece and not a laminate trimmer which is what we wanted, the lam trimmer for our mill. I'm admittedly guessing but I would expect the Foredom like the one we have and use for other things to be more precise than a Dremel but it is no match power and precision for a lam trimmer that has been carefully sourced, tested and augmented with aftermarket collet.

I suppose a saddle mill could be built around a Foredom, we wanted to go with lam trimmers.

Thanks. Just trying to get some knowledge for another application (inlay). I use the Makita plunge trimmer in my saddle slotting jig (not as nice as the one in the video, but it works).

I had a “Well, duh!” moment and did a search for runout on the Foredom handpiece. Foredom itself specifies it on its website: .003”. Too big for me. I’ll stick with the routers for the detail inlay stuff. I was just looking for something smaller and easier to manipulate. (Each of my routers measures less than .001” runout. I got lucky with my purchases.)

Thanks for the help fellas. Lots of options.

A year ago, I ordered and installed one of those Precision collets for the Bosch Colt after reading about it here on OLF. Interestingly, Precision stated that the Bosch Colt was so bad, they wouldn't guarantee or accept returns of their collet for that router. The collet was a VERY good purchase none-the-less. If only the depth adjustment wasn't a POS.....

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Measure Twice,

Karl Borum

That's interesting that Precise Bits singles out Bosch Colt as being awful, that was what we independently found too. I've been arguing with the woodworkers on the forum for years that we found the Bosch Colt to be one of the least desirable lam trimmers for precision and the plunge implementation.

Wanted to mention one more thing.

We often get complaints from people with acoustic pick-ups with a UST, under saddle transducer that the guitar doesn't sound balanced when plugged in. These are not ones that we had worked on or installed the pick-up.

We tell them in advance, setting expectations is everything.... that in our experience UST balance problem are often because the saddle slot and/or the saddle are not flat and properly fit. So we take in the instrument and mill the saddle slot bottom with our Collins Saddle Mill making it perfectly flat even though the bridge is glued on a guitar top with a dome.

Next we flatten the saddle and/or make a new one depending on the fit using a surface plate for perfect (relatively speaking) flatness on the saddle bottom.

In combination the two actions, flat saddle bottom and slot bottom result in the balance being restored to sound just as ****** as the guitar sounded from the factory with that pick-up in the first place....

Seems to work nearly every time so the point here for those who care about the details and known realities of where some of our stuff may not work so well is that the saddle fit, quality, flatness as well as the saddle slot can make or break how well a guitar is to gig with when amplified. It also affects the acoustic tone as well for those of us nuts enough to actually hear it.

Many of us when building will chase a hifi capability where we want to capture and amplify as much of the desirable tone of the instrument as possible. We shave tiny slivers off largely inconsequential little finger braces to chase a tone as we tap away and check our spectrum analyzer for results.

You can throw a lot of that tone that you gain through careful voicing right out the door by not paying attention to and understanding the physics of how a properly fit saddle interacts with the bridge and the guitar top.