JiayouyAdjustable Guitar Nut & Bridge Sander Luthier Tool for Electric Acoustic Guitar Bass Silver

This worked really well for me. For less than $40, it's not a precision tool. One wheel is 0.002" (0.05mm) higher than the rest, resulting in a very minor wobble. Close enough for me, a hobbyist! The wheels and bottom of the sled are not perfectly flush. The wheels extend 0.02" (0.5mm) more than the sled, which means you'll have 0.02" of saddle or nut showing once you're done sanding. Not a big deal once you know this measurement (could be different for you). I just add an additional 0.02" to the amount of saddle hanging out. Having zero experience, it did what I needed...way better than doing it by hand.

I have two of these here in front of me. One is the replacement and the other is the first one I purchased last week. Both of these Bridge/Nut sanders have the ability to rock side to side. One has .003" clearance between a wheel and a granite surface. The other one has an .008" clearance between a wheel and the granite surface. This is where the rocking motion comes from. This device is a poorly made copy from China. The replacement tool is jamming within the clamping mechanism. It's totally unusable. Also both of these tools are not using parallel clamping action to hold the bridge or saddle. So with unequal clamping grip and the rocking of the body... I would not recommend purchasing this product from this seller. I can't vouch for his other China copies of professional tools. But avoid... don't even think of buying this item from this seller if you are serious about the sound quality of your musical instruments. The original producer of this particular tool is from Italy and has "Made in Italy" stamped into the side. The company logo of theirs is also stamped next to the "Made in Italy" wording. These two I have here have no logo or country of origin stamped into the side. Can't say I blame them for not claiming such shoddy machining.

This product is used to ensure the creation of a flat, 'square' bottom on guitar nuts and saddles. This is important to the transfer of energy/vibration from strings to the wood of the guitar and is accomplished by having as much of the saddle or nut in contact with the wood as is possible.Like some of the other reviewers, I was concerned about the potential for lack of quality and accuracy. But given the price point, I figured with a few mods it might be acceptable.As expected, when received the unit's quality was ok though imprecise. After all, it's a knockoff of an Italian brand-name product. If this were being used for precise machining purposes it would be unacceptable. But for its purpose, 'very close' is usually good enough.As you can see in the attached pictures, while sitting on its wheels (after adjustments) there is a .012" / .305mm gap between the tool and the aluminum tooling plate (the plate is milled to .0005 accuracy for flatness, which though not perfect, is good enough for non-machining purposes). The tolerance is the same on both ends and in the center.When you adjust the saddle of a guitar, the change in string height at the 12th fret is half of the amount of the change in the saddle height. So, assuming your saddle measurement was off (high) by .305mm, at the 12th fret the string would be raised by only ~.15 mm. Less than a quarter of a millimeter is not going to affect your playing much. And since the saddle height RAISED the string by .1525mm, lack of precision in the tool isn't going to be the cause of any buzzing. If anything, the tool will give me an extra .15mm in string height to avoid buzzing.Of course, if the lack of precision bothers you, you can use the adjustment screws to lower the saddle and take off an additional .305mm of bone material (good luck making that adjustment accurately)... The knurled nuts on the top of the tool have 10 marks radiating from the hole that measure movement of the nut up or down in .10mm increments. So, for a .305 adjustment you'd have to turn the knob 1/3 of an increment. No way to be more precise than that I'm aware of.As for the tool 'adjustments' mentioned above, I did 3 things:1. LEVEL THE TOOL - (Picture 3) Like others, my unit 'rocked' on the flat plate when received indicating that all 4 wheels were not level with each other. Given that the machining of the tool was imprecise I used that fact to 'solve' this problem. I loosened all 4 wheels with an Allen wrench which allowed the tool to sit flat on the plate. Then while pressing down on the body of the tool, I tightened each wheel again, but just enough to stop each wheel from wobbling and hold them in place. As expected, this evened out the wheels and lowered the gap between the plate and the tool bottom.Note, however, that if you re-tighten the wheels as tight as you can you'll likely ensure that any manufactured imprecision in placement of the bolt holes will again cause the unit to start rocking. By making this adjustment, I'll probably have to do it again as the wheel bolts loosen with use, but it's a small inconvenience. At least it stopped rocking, and the gap was reduced (originally the gap was .635mm).2. REMOVE PLAY FROM MEASUREMENT BOLTS - (Last picture) The two top knurled knobs are used to push the nut or saddle down on each side to your desired depth. Then the side bolts are tightened to clamp the material in place. This adjustment allows you to position the saddle or nut so you can sand away excess bone/plastic material off the bottom to whatever height you wish. The side bolts came with compression springs to keep the bolt under some tension, but the top bolts had no spring tensioners and were somewhat loose. I feared that while sanding they might move, allowing me to sand more than I intended and ruin a good bone blank. I got a couple of 0.8 x 9.5 x 20mm compression springs and slipped the bolts in the springs before screwing them back in place. Problem solved.3. MARK THE TOOL - (Last picture) As mentioned, the knurled knobs at the top allow you to adjust the depth of the bolts, and the radiating marks give you some guidelines to measure how much the saddle will move (.10mm for each mark x 10 marks, so 1 full turn = 1mm). Unfortunately, the knurled knobs had no markings to indicate how far you've moved the knob. So, I got a Permanent Ink Sharpie and made some vertical marks on each knob myself.Next, the purpose of the 4 wheels is to show you when you have sanded down far enough. As you sand, when the wheels start to move, you are within (in my case .012") of having removed sufficient material. However, I noticed that there really is no easy way to determine when the wheels start moving because everything is shiny. So, I made several marks across each wheel so I can watch them for movement as I sand. When the marks start moving, I'm done.I also used the Permanent Marker to write the amount of gap between the bottom of the tool and the tooling plate on each end of the tool. I did this mainly because my memory is somewhat craptastic, and if I ever lose my mind and start worrying about a .15mm tolerance, I won't have to break out the feeler gauges again...

I'm a professional guitar repair tech. My luthier mentor showed me one of these tools and I knew I had to get it. I put it to work yesterday and I think it will pay for itself just in time saved in less than a week.

Other reviews reported that the bolts that tighten the clamp were to short, I found if you just flip the tightening nuts over you have plenty of additional space to hold bigger nuts. This is nicely machined, the bearings run smooth.All bearings are dead flat with the bottom. I have no experience with the $200+ Stewart Macdonald tool, but cannot believe that it could be any better. Maybe the Stewart Macdonald comes with instructions, this did not. But certainly cannot see how anybody would need instructions.

The finish is poor but the tolerance is somewhat acceptable. It wobbles very little on flat granit but not on sanding paper so I guess it is good enough.The biggest problem is that the adjustment screws move way too easily, and can move while you sand and ruin the line. They lack the tensions spring the two tightening screws have.The solution is easy, grab an empty soap/shampoo bottle that has a pump. Cut out the plastic and get the spring out, and use wire cutters to cut the spring in half.I wouldn't bother with marking the lines. When flushed, the saddle sticks out 0.25mm, which a saddle ruler can show, so lets say you want to bring the saddle down by 1mm, just measure 1.25mm and file away. Note that 0.25mm was what I measured - it may vary, so better try a blank you don't care about, sand until its "done" and measure how much is still sticking out.On a whole - it is a mediocre tool, over priced, but functional and for the minor adjustments at home it is fine, and it costs less than having a luthier doing the adjustment. It is not rocket science, if you can change nylon strings, this should be easy. If I were a professional or if money is no object, I'd get the higher end, made in Italy version, from stewmac , but that is 4x the price.