Drill Doctor is Mangling my Drill Bits

[rusty_ratchet]

I've been using my Drill Doctor 750x for the past year with great results. I've only sharpened 118 degree HSS bits and recently bought some secondhand bits that appear to be black and gold Norseman bits (135 degree split points). I've followed the instructions for 135 degree split points and the Drill doctor is mangling my bits. In particular, I am having problems with negative relief. I've tried increasing the angle of the alignment chuck and this does not help.

Any suggestions?

Thanks!

 

[fatboyf150]

Sub'd I have the same problem.

 

[Koobs]

I have found that with these type of bits, the second step takes a light hand. The relief cut takes two hands, and a good ear. You barely hit it with the wheel on both sides, keeping the sound the same for both. Takes some practice. Good luck!

 

[plinker]

I had a similar problem with drill bit's. Ended up being they were not aligned in the chuck properly. The finger's that grab the bit when setting the depth need to hit the flute of the bit.

 

[davewo]

I have the 750x and my results are all over the place. It sharpens evenly, but rake is unpredictable. I really feel like somrthing must have worn out. I gave up and just take them into work and use a "real" sharpener now.

 

[rusty_ratchet]

Thanks for the replies. My problem with negative relief was solved by going to the negative (-) side of 118 degrees, not the positive (+) side as indicated in the manual. I am unable to split the point and my results aren't great overall, but getting towards acceptable.

 

[uart]

Thanks for the replies. My problem with negative relief was solved by going to the negative (-) side of 118 degrees, not the positive (+) side as indicated in the manual. I am unable to split the point and my results aren't great overall, but getting towards acceptable.

So does that mean that you've just resharpened them to regular 118 degree non split point rusty?

 

[rusty_ratchet]

So does that mean that you've just resharpened them to regular 118 degree non split point rusty?

No, they are 135 degree, non split point. I align the bit two notches to the NEGATIVE (-) side of 118, then put them in the "sharpening hole" (or whatever that thing is called) set at 135.

The manual states that if you have negative relief you should go to the plus (+) side in the alignment port, but that doesn't work for me. Having said that, my bits are sharpened at 135 degrees with no negative relief, but the "cutting" part of the bit (look at the 135 degree part of the bit, then rotate the bit 90 degrees) has way to sharp a cutting angle. This is to say that when I get rid of the negative relief the angle isn't nearly as blunt as it should be. This makes me wonder how well the bits will cut tough material and how well they will hold an edge.

I've tried following the manual for splitting the point and various experiments and haven't been able to get it to come out right.

This whole thing makes me wonder if I should't just resharpen by bits for 118 when they need to be resharpened. Definitely better results that way.

 

[dnschmidt]

Of all the tools I own this is the most useless I've ever had. I can sharpen a drill quite well using a belt sander or grinder. Why I'm able to do a better job freehanded than this tool does using a dedicated jig is one of life's greatest mysteries. A completely useless tool. The reason it's useless is that it doesn't produce enough of relief for the cutting edge which is PRETTY DAMN IMPORTANT since that's what does the cutting. A drill bit without relief is a center punch.

 

[uart]

Having said that, my bits are sharpened at 135 degrees with no negative relief, but the "cutting" part of the bit (look at the 135 degree part of the bit, then rotate the bit 90 degrees) has way to sharp a cutting angle.

OK I see. So after you've corrected for the negative relief you're now getting too much relief angle.

I'm not sure what the procedure for splitting the point is on the DD, but from your pictures it kind of looks as though when it tried to grind back trailing edge to split the point, it was somehow also nicking the leading edge on the other side in the process. What I'm trying to say is, this might be a completely separate thing to the true relief angle you're sharpening to (like more of an artefact of the splitting point process somehow going wrong).

Now that you're not splitting the point, can you take look at the angle of the chisel edge. This is often a good indicator of how much relief angle you've got. If you look straight on at the end of the bit and align the two cutting edges so that they're vertical, roughly what angle does the chisel point make with the horizontal? I believe it should be somewhere about 30 to 45 degrees past the horizontal.

 

[rusty_ratchet]

Trying to split the point is definitely causing damage, but I don't think it is causing negative/too much positive relief problems.

I took a look at the chisel edge and it is about 40 degrees give or take. I am pretty sure that part is ok, it is everything else. I hope it is just me and not a limitation of the DD.