Kinda long first impression
Just thought I'd share some thoughts since I recently picked up a 500X.
I've been looking at getting a Drill Doctor for quite some time, and read a few reviews, and never dropped the coin, because I couldn't find a 500 or 750 for sale up here (only the 350). The 500X and 750X are essentially the same beast now. There is an added level of adjustment available with the 750. But if you are in need of this you probably sharpen your bits by hand. The 500X can sharpen bits over 1/2" as mentioned with an accessory chuck.
Granted having the skills to REALLY sharpen a bit by hand would be cool. Personally I'd rather invest that time in learning how to weld. Besides it would still require me to purchase a grinder that I don't currently have any other use for anyway.
The newest generation of DD designated by the 'X' have some simple improvements that reduce the operator error that caused poor results in the past. The set up, and acquiring the cutting and relief angles, and the actual sharpening, is a no-brainer.
I found the most difficult part was in 'deciphering' the anatomy of a drill bit based on the relief drawings that they provide. This is an important skill, so closely compare your old bits, to a sharpened bit, and the diagrams. Starting with a mid to large sized bit will definitely help the learning process.
Some problems with small and large bits were mentioned in earlier posts.
The smallest bit that is easily sharpened is 1/8. Smaller than that will require a very quick and gentle touch, and as mentioned splitting them is basically impossible. That said I don't see much of a need to split such small bits anyway. Fitting the smaller bits into the chuck requires an easy extra step not worth describing here, but rest assured it is very easy. All said considering the low cost and the regularity with which I break bits of this size, many of mine will likely be replaced with new bits from the store.
Large bits have the challenge of being, well, large. If you find yourself sharpening large bits a lot, or find yourself in a particular rush, a coarser grit, user replaceable grinding wheel is available. I'd bet the time replacing the wheel would be close to that of the extra grinding, but I can definitely see the value and might invest in one myself.
Easily the biggest immediate challenge that I noticed has also be mentioned, and that was the seeming ambiguity associated with splitting the points. That definitely hasn't been addressed as well as it could be, and is in my opinion a simple design flaw. Unlike the other processes that are well defined by notches, and clicks, and the like, splitting a point requires a 'finer' touch and multiple visual checks.
Ok, looking back at all that I wrote, it may not seem like I'm really selling the tool. Honestly, I think this thing rocks. The few challenges that do exist are truly miniscule and I overcame them within half a dozen or so attempts.
Being able to sharpen a bit in a minute or so, changing a dull 118 degree, standard bit into a sharp 135 degree, split point in literally about a minute is amazing!
Sharpening my good $60 bits alone will pay off the costs in only a couple of sharpenings. The average home diy guy drilling into drywall and plywood might not really see the value in the tool, but guys like us using larger bits and drilling into various metals, I think the DD is nearly invaluable.
