Results 1 to 12 of 12
Thread: Drill Doctor Design Problem
10-29-2007, 11:15 PM #1
I have noticed my DD 750X does a fairly decent job on larger drills but is terrible on small bits under ~1/4". Got to checking things over, and it's apparent that the "indexing" sheet metal tabs are to blame. Their purpose is to align the bit in the chuck by rotating the loose bit in the chuck until the smallest diameter [at a point slightly behind the tip] is along the horizontal plane. The plastic chuck is then tightened.
Problem is that different diameter bits are grabbed at different distances from the tip--fat bits are grabbed further back. Assuming the same helix angle [?], the bits will be ground differently.
I've been grinding everything to 135 deg., and noticed that if I use the 118 deg. indexing mark for smaller bits they come out much better--when ground at 135 deg. Bits down around 3/16" actually need to be set to ~110 deg. or less, but there is no way to do it except to slightly rotate the bit by hand before tightening the chuck.
10-29-2007, 11:29 PM #2
That is a good observation . Don't know if I'd call that a design flaw , or just a fine tuning requirement .
I have the same unit ( I think ) and I tried to sharpen the small drill on the end of a center drill . If you look at a CD you will see it has No helix or twist . So I turned the chuck to the full left , Max clearence position , and now I have dozens of center drills that cut great !
10-29-2007, 11:58 PM #3
Don should ban drill doctor threads, much like he bans chi com lathe and chi com mill threads. Every drill dr thread ends up being 50 posts of opinions.
FWIW, I did notice the same thing as Benesesso, and finally decided,"this is crazy", gave the thing away to somebody, and cut my losses.
10-29-2007, 11:58 PM #4
That is one of the main issues with the DD.
As you point out, the positioning can change, although the helix also tends to change, in that there are more "turns per inch" on small than large drills. That compensates the effect, which is apparently what they count on.
Problem I have is that a lot of drills I have are not "standard" helix angles. Lots of ex McDonnell stuff, and old toolmaker's goodies.
The DD is made for the "average home guy" with hardware store drills. So it does not aline by the actual edge, but by the "inferred position" from a spot up the flutes a way. If your drill isn't like that, they can't help you, and you have to figure it out yourself.
The loosey-goosey plastic collets are no help in that..........
I finally decided it was too much trouble, so I have been hand-sharpening. Starting to get decent at it now...... But it stinks to do for small drills
Have you ever gotten a good split point with the DD? I always get a small untouched square area at the absolute point, never can get a true split.
10-30-2007, 12:15 AM #5
>"Have you ever gotten a good split point with the DD?"<
No. I don't even try anymore. I can sharpen larger bits by hand too, but not the smaller ones--too hard to see.
10-30-2007, 05:11 PM #6
the 750x has a different splitting method than the older 1/2" DD that I'd used in the past and it's horrible in comparison.
I've been on the hunt for a professional drill grinder at a steal of a price for some time now - but I haven't been successful yet.
Like others I can do ok with hand sharpening a larger drill, but we do lots of stuff in the #7 and smaller range, a solid carbide #29 is a real treat!
10-30-2007, 05:18 PM #7
For certain common bits, over a range of a bit under 1/4 up to about 1/2 or a little more, my 750 does a competent no-brainer just-get-a-bunch-done-with-minimal-hassle effort. And with a very few exceptions, they all cut quite nicely for essentially no effort.
Over 1/2, MUCH more easily done by hand in my experience. Though if the point is completely burnt, the DD750 large collet will let me rough by hand and then use the DD to get it even/ballanced far easier/faster that I could by hand; then I always touch up by hand.
For sub 1/4, the DD can be a pain but I sometimes use it anyway if I'm already doing a box of dulls. Depends on how small. I've got a Christen that I use for my "needs to be on the money" bits (as far as a drill goes anyway), but the DD bits work ok for most "just punch a starter hole" needs.
And finally, I find the split-point to be finicky to say the least, it defintely requires a bit of "feel". But generally I do use it on roughly 1/3 to 1/2 my drills of a given size, dependent on size ranges indicated above. I can split a big point easily enough by hand, but on the smaller stuff, the DD works ok, though not so easy to keep them even.
10-30-2007, 05:25 PM #8
Try holding very small drills against a vertically held India stone. Get the drill at the same angle it was when new, and only needs the edge touched up a bit,unless it has been screwed up and ground wrong already.Then,it takes more eyeball gauge. Move the stone up and down,slowly rotating the drill as you approach the cutting edge. I wear 4X close up glasses and can sharpen a #80 this way. it gives you a much better view of the end of the drill,and is slow,which helps acuracy. Lately,I found one of those little Meteor drill grinders. It is for small drills,and has a built in eye loupe. Once I had to keep resharpening a #80 bit with it on a long job until the flutes were almost used up. You can accurately regrind drills,including large ones,by chucking them in a lathe and grinding the correct point on them with the toolpost grinder.THEN,carefully back the cutting edges off and grind up close to the cutting edge,but leave a little bit. Stone this last part with an India stone until the cutting edge is actually reached. Then,the 2 flutes will be equal. Of course,you need a true chuck,or collets for smaller drills,to do an accurate job.
10-30-2007, 09:04 PM #9
God bless anyone who can hand sharpen any drill bit. What is great about being to hand sharpen any bit no matter the diameter is you actually know what is necessary configuration to drill a hole. I hand sharpen drils. Been doing it for many years. I also have a Black Diamond drill grinder which I am absolutely in love with. Even it has it's nuances. I though know what a drill bit looks like. As I age, I use an Optivisor when free handing any thing less than 3/16. John
10-30-2007, 10:38 PM #10
I got the drill doc 750 for work, got tired of the clowns in the grinding room. I have ground some of the 1/2 in. drills we use for balancing parts and they came out good.
The guys in the grinding room split the points by hand and can't do it well enough.
The Drill Doc 750 did a nice job of it. Its not the best in the world but for the money it does the job.
We generaly get about 5000 holes out of a drill before we resharpen and the size has to hold.
10-30-2007, 11:16 PM #11
>"We generaly get about 5000 holes out of a drill before we resharpen and the size has to hold."<
Are you drilling soft aluminum or plastic?
I finally got to drill my first holes using my Gorton 1-22. Had to drill a couple of 1/4" thick angles with a 5/8" bit. Used a 1/4" bit for a pilot hole, then slipped in the 5/8" after I sharpened it with the DD. Running at 65 RPM was like watching a slow-motion movie, with 2 nice long chips twirling up until I backed out and cut them.
What a difference from using my 5/8" capacity Taiwanese 16 speed drill press, which can't drill a hole bigger than ~3/8" without slipping the V-belts. One of these days I'm actually going to mill something.
11-05-2007, 02:06 AM #12I've been grinding everything to 135 deg., and noticed that if I use the 118 deg. indexing mark for smaller bits they come out much better--when ground at 135 deg. Bits down around 3/16" actually need to be set to ~110 deg. or less, but there is no way to do it except to slightly rotate the bit by hand before tightening the chuck.
Another tip is to spray the drill holder(s) and cam surfaces with silicone spray to make them easier to rotate and reduce wear. I also wiped the grit off between bits to further reduce wear.