MAN vs. MACHINE OR IS PLEK BETTER THAN HAND FRET WORK?

MAN vs. MACHINE

OR

IS PLEK BETTER THAN HAND FRET WORK?

BY

BRIAN HOWARD

www.brianhowardguitars.com

PLEASE NOTE THE PHOTOS THAT ACCOMPANIED THIS ARTICLE WERE APPARENTLY LOST BY PHOTOBUCKET.COM!

 I APOLOGIZE AS THE VISUALS MADE THE CASE...... BUT THE WORDS ARE STILL VALID AND IF I CAN RESTORE THESE PHOTOS I WILL. UNTIL THEN LET THIS BE A WARNING ABOUT CLOUD STORAGE OF YOUR IMPORTANT DOCUMENTS ETC!

   As with all new technology, the price and size of CNC equipment has dropped considerably over the years and is now turning up in small one man shops and maybe even your local guitar store. This article will examine the work of one of these high tech wonders and compare it to good old fashioned hand work done by a skilled professional. In the course of this I will also be explaining a bit about my fretwork techniques and the tools I use. This story starts off with an existing out of state client who bought a backup for his Spector 5 string bass. The original recently had its frets leveled and crowned on a PLEK machine by a shop local to him. The used one he found that was essentially the same instrument was drop shipped here for a go over and wound up getting a level, crown & polish on the frets while here. Upon comparing the two he was amazed at the difference…….My work felt better, played cleaner and did it with better action. Now the other one has been sent in for an L, C &P as well. So I am using this opportunity to show that the old ways are every bit as good, even better than the newest toy.

   To begin I have removed the strings and have the bass on my bench. I typically do my fret leveling with the instrument lying at an angle up across my repair vise as shown. The laws are in a V shape to support the neck. More on the reasoning for this later….  

  The first thing I need to do is make the neck straight. For this I used a steel straightedge and 3 small high strength magnets. The magnets have been specially selected solely for this purpose as they all measure the exact same thickness. They are place so they rest between frets at each end of the fretboard and one in the center. The first picture shows how much back-bow the neck has after the strings have been removed. The straightedge actually rocks on the neck. The exact amount of neck arch would be half of the dimension measured under this magnet at the end of the board.     The next picture shows the center magnet after I have backed off the truss rod. If all is perfect the truss rod should be completely slack when the neck is straight. That is my case here, but not the case on every job. Regardless of truss rod tension, the fretboard must be straight if you want to do precise fretwork. One thing to watch out for here is finger wear on the fretboard. Make sure none of your magnets are over a finger divot! I also check the surface of the board at each edge as well as down the center to asses for twist. If twist is found one has to pick the happiest medium and a more in depth assessment that includes any fret wear should be done.

  Now the instrument can be masked off to protect it while the work is done. I have also marked all the frets with a red marker to better show the leveling work as it progresses, typically I omit this. The following procedures should be done immediately from start to finish to be absolutely sure the wood of the neck has not moved at all in reaction to environmental variables.

  For leveling I use simple beams. They are made from carpenter’s levels. One edge has been machined and lapped perfectly true. The I-beam shape makes them very sturdy so they do not flex or twist while being used. It is paramount to have a working beam that is no more than 1 fret space shorter than your entire fretboard. If you cannot work the entire surface of all the frets at once you will never be perfectly level. I have an 18” for guitars and am using my 24” here for this bass.

  The true side is lined with pieces of self stick sandpaper, 320 grit. This is no time to save a few pennies on supplies, do not use cheap abrasives! I use Norton but any high quality name brand should be good. The thing here is abrasive granule size……the more uniform your abrasives the better the work. Also, change out the paper way before you think you need to. As the paper cuts the fret it also wears, so to keep the beam from developing any small “low” spots due to abrasive wear keep it fresh. The key here is to keep each variable as small as possible so they don’t stack up and ruin the job. The difference between a good fret job and a spectacular one is less than .001”!

  I place the instrument over my vice so that the vise supports in the center of the neck, the headstock floating in the air and the bottom of the guitar resting on my bench. By only supporting the neck in the middle it is free to float perfectly straight and any undue pressure while working will cause a see-saw effect to ensure you do not use to much force. Gravity also helps clear away debris from the fret surface to keep the cut as clean as possible.

  The first thing I do is set the beam down and gently slide it up and down the neck as I work across. One quick very light pass…. This will show the current condition of the fret crowns. It will show any play wear, dings etc as they will light up. If the machine and its operator did their job correctly we should see a crisp, even width matte silver line down the center of each fret. That is not what I found…..This picture is of frets 9,10,11&12. Notice the low spot on 11. This may be .0015” low which is more than enough to be noticeable to some players and especially important for all those who crave the lowest possible action.

  Here we see another similar low spot on fret 4. The entire fret plane is spotty all within about a .002-.003” tolerance. Maybe fine for production guitars, maybe? Definitely not going to be the best playing axe ever though……

  Now that I can see what is going on with the plane of the frets I start to work. One has to be very gentle with the pressure used with the sanding beam. If there is any appreciable fret wear it is usually toward the center of the board in the “Sweet spot”. So if too much pressure is applied the beam can actually push the neck to conform to fret contact…..when we remove the beam it would then flex back to true and our frets almost as unlevel as when we started but giving the impression we had done a great job.

  Small light strokes up and down while briskly moving from the bass to the treble side and back. The goal is to remove material evenly on both sides of the fretboard so you don’t wind up with frets taller on one end that the other. Stopping every few seconds to check progress, brush away debris and asses the condition of the sandpaper.

  As work progresses we can see how bad it really is. In this picture we can get an idea how unlevel some frets really are. You can see the fret crown getting wider and flatter where I have cut it down yet some low spots remain. This is nowhere near what play wear would look like but for a guitar with a fresh fret job it is not so good.

  When you reach a point that there is at least a small break across the top of each fret your frets are now level. Nowhere near playable but level.

  Now I must restore the crowns on all the frets. I do this with a diamond file made just for this purpose. The goal here is to file down the frets until there is just a barely visible break across the top from leveling. I am looking for about .020 or a little less across the top of the fret after this operation. This picture shows the widest flat I will accept after crowning.

  Next I will polish the frets to a mirror shine. This process begins with maroon Scotchbrite. I rub out all the frets until they are an even dull grey with no evident tool marks from the previous two operations. This is followed by a rub down with light grey Scotchbrite. You will see the surface brighten and any missed tool marks will pop out. They are addressed at this time. Then I run the frets across my buffer on a buff that I reserve just for this purpose.

  The masking tape can be pulled and the fretboard cleaned with lemon oil and here is what it looks like. The lemon oil makes the frets look a little duller in the photo than they actually are.

NOTES & THOUGHTS

  One thing that struck me as odd about this instrument and the fretwork that was done prior was the nut slots. Part of running a guitar through a PLEK machine or most any fret level job for that matter is re-cutting the nut slots. These hadn’t been touched since birth the way it looks.

  As it looked by how much material I removed from frets 1-3 the PLEK operator was really trying to maximize fret height after the job. Too much so in my opinion at least for the tool he was using. This would also explain the low spots seen on my initial rub assessment and the poor quality of the work.

  Let me explain why. A PLEK machine is a computerized wonder and capable of very precise work. Its pitfall is it is a complex machine with lots of moving parts. Every one of these moving parts will have clearance or “play” so it can move and function freely. When taking a heavy cut all the play is taken out of the system and for the most part things go well. A light cut on the other hand allows the machine to wander around in its range of tolerance. And that would be the play of each moving joint added up. So, say we have 5 joints on the machine, each with .0007” play. That adds up to a final variation in work of .0035”. More than enough to prevent good action on the instrument.   One must also always question how well maintained a machine like this is at a local shop. Large factories have maintenance programs and care for their investments well. But a small shop must keep an expensive piece of equipment running all day to pay for itself……Doubtful someone comes in at night and does a PM. And it may not even get re-calibrated on a regular basis so until someone complains about the quality of the work its piety much push the start button and go.

  On the other hand, hand work is no guarantee of accuracy in and of itself. As I mentioned I have my own tolerance stack to worry about. Like the trueness of my beam & the uniformity of my abrasive materials. I also must concern myself with technique and not distorting the neck by using too much pressure and a myriad of other details.  But I do demonstrate that a man is still capable of outperforming a machine in accuracy.