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Wayne02
03-07-2011, 08:36 PM
I've been reading through the old threads on the drill doctor and only found one that referenced the model 750SP. It's not listed on the DD website and there are few google hits.

I take it this must be the prehistoric model?

Anybody know what the differences are between the 750SP and the 750X? Looks like both can do the larger drill sizes.

Thanks

mc_n_g
03-07-2011, 09:43 PM
The SP is the older model. At one point in time moons ago there was recall on the older model because the chuck would bind. They gave a very nice upgrade option for the new model (basically a little more than shipping). I cannot speak for the upgrade now. I turned in my old one for the new model, a 500X (1/2" capacity).
I can say that my old one did bind when the chuck was turned. The turning is a major part of the sharpening process. It worked but would bind. The newer model I have had no problems with. The process is one that takes a light hand and pay attention to the sound and feedback when looking at the drill.
If you do a lot of metal working and use certain size drills all the time and wear them down then I would say yes to it. Yes you can shapen a drill with your hand but there is no way in he!! you are going to have even cutting lips on the drill tip. For wood I would say do not bother but metal working is a different story.
You will see stories of people complaining about it and it does not work...blah...blah. I have never had a problem with it not doing a proper job. Is it as good as a professional drill bit grinder....no. I can easily see a difference in drill bits I have sharpened and the amount of cutting pressure required in a lathe, mill or drill press. The chips come out different, not as much heat and the finish is better.
Larger drills will take a little more time to sharpen than the smaller drill bits. The surface are the wheel has to grind is larger and therefore the overall process will be slower. Biggest thing to both models is read the instructions, use light pressure, turn at a steady rate and adjust settings based upon what the drill point looks like when completed.

J Tiers
03-07-2011, 10:23 PM
I have a 500, which DD upgraded to a 750 due to severe problems with it, which they could not cure, nor even offer a suggestion on.

I was extremely happy for about 50 or 75 drills of all sizes. Obviously I knew how to operate it, etc. Loved it, and sharpened up a lot of drills.

The grind is a bit odd, but functional in general.

Since then it has gone rapidly into the crapper.... it has been useful ONLY for the larger sizes, from perhaps 5/16" and up. Smaller drills come out with very uneven lips, and the more-than-occasional reverse relief.

This is because, not of binding, but of extreme looseness, the end of the drill will move over 1/16" (1.5mm) with the parts assembled and drill in a collet in the tube. perhaps they over-corrected on the binding issue. Obviously if the drill tip is not located accurately within 1/4 or 1/3 of the entire diameter, there is going to be a problem. And indeed there is.

And also due to an apparent defect in the alignment "jaws", which although visibly OK, fail miserably to set the smaller drills in correct alinement, despite using the 'trick" needed to counteract the loose collet jaws (slight un-tightening movement).

DD could not offer any suggestion as to the looseness or the jaws, they did not appear to understand their own machine, unfortunately, and mostly suggested I upgrade at full pop. For obvious reasons I have not done that......

The 750 is probably the best type, if only because you can sharpen the larger sizes, which are less likely to suffer from the problems listed above.

Don't bother with it on anything at or under 0.25 inch or maybe a bit larger.

And don't pay a lot...... I paid a bit over a hundred bucks new, which on the basis of buying new drills vs sharpening has basically paid off, even though I never plan to use the machine again, ever.