Drill bit angle for drilling blanks?

[Russknan]

Thanks to Christmas and the LOML, I am faced with an unexpected conundrum. I am now the proud owner of a Drill Doctor 750X bit sharpener. (Making Tim The Tool Man noises!) And I'm ready to take on a couple of bits (10.5 and 12.5 mm) that have had me holding my breath each time I use them because they are so dull. But now I have the ability to choose whether to grind them at 118 or 135 degrees. And I can even split the points! Easily in over my head here. Any suggestions? Different choice for wood vs acrylic? TIA. Russ

 

[flyitfast]

Russ, you asked the right questions! I have been wondering the same thing.
Hope you get some good answers.
I'll be listening.
gordon

 

[watch_art]

The instruction manual describes the angles, what they're for, and how they'll cut. I keep most of mine at 118-125ish or so, for a nice moderate (not aggressive) cut and flat bottomed holes. If flat holes aren't important, then you can go a bit more aggressive. Play with the angle of the front thingy, low down makes an pointy bit, high up makes a flat bit.

 

[comben001]

Habitually 118 degrees is the norm. I got a Drill Doctor for my birthday in November and I have re-sharpened every drill bit I have ( about 4 complete sets + about 20 large drill bits!!! ) You will love it ! I don't think I will have to buy another drill bit for a long while... I love it when a product does exactly as stated in the advertising...

 

[Lenny]

Someone please correct me if I'm wrong ...

180 degrees minus 60 degrees (assuming you use a 60 degree center bit to start your hole) leaves 120 degrees = the ideal drill angle.

I very much prefer them over brad points for drilling pen blanks for that reason alone.

 

[Daniel]

I found 118 works the best for blanks. I can no longer recal what the steeper angle is for but it tends to split blanks. I do remember that. I keep the DR. plugged in right next to the drill press at all time. no excuse to nit hav a sharp bit. once you get it down sharpening takes only a minute.

 

[frank123]

My drill doctor only grinds at the standard 118 degrees, so that is what I use and have never found a problem on anything I've drilled with it.

(Got my DD almost new off of craigslist for 10 bucks so the single grinding angle wasn't a consideration)

An aside: One big plus to my precision drilling from the DD was the ability to make a spotting drill out of old or broken drill bits. Ideally, the spotter should be a degree or thereabouts less than the drill angle to present exact center for first contact but I've found that using the same degree as the bit works well and givers much more precision starts than a 60% center drill will. Starting drilling from the center instead of the edge of the spotting hole eliminates the tendency for a drill bit to wander a very tiny bit on start.

 

[skiprat]

Someone please correct me if I'm wrong ...

180 degrees minus 60 degrees (assuming you use a 60 degree center bit to start your hole) leaves 120 degrees = the ideal drill angle.

I very much prefer them over brad points for drilling pen blanks for that reason alone.

A centre drill is 60 deg incuded angle and a drill bit is approx 120 deg included angle.
Contrary to popular belief, centre drills weren't made so a drill bit would match. They were made so that a lathe centre would match. :wink:

Edit; Here's a pic that shows that a normal centre drill matches with 60 deg lathe centre, but not with a drill bit.
Centre drills ( originally called Slocombe drills ) also come with curved - rounded, cutting edges for ball ended drive centres.
A 60 deg centre drill should not be used if the tailstock centre is going to be offset to do taper turning.

As far as drill angles go, I make all of mine about 120 deg. But if I'm going to drill a lot of plastic sheet, then I might sharpen it to look almost as sharp as a pencil. :wink:

 

[Lenny]

Thanks Skip!

 

[Russknan]

Wow! That was fast! I appreciate the advice. One more thing, though, should I put a "split point" on my bits, or just leave them in standard configuration (terminology escapes me)? Russ

 

[Chasper]

I use 118 and split points.
Make sure the adjustment that sets the angle at 118 is screwed down tight, it will loosen after several bits have been sharpened.

 

[walshjp17]

In the Latest Issue of Woodturning Design, Kurt Hurtzog has an article addressing this exact issue (among others). The article starts on page 17. The answer, according to Kurt (a PMG member) is "it doesn't matter". To quote him, "It almost doesn't matter what type of drill bit you use to drill holes, providing the bit is sharp, you have a good starting location, and exercise the proper speeds and feeds for the material."

BTW, the article called "It Doesn't Matter" contains some really good advice and answers many perplexing questions.

 

[jttheclockman]

In the Latest Issue of Woodturning Design, Kurt Hurtzog has an article addressing this exact issue (among others). The article starts on page 17. The answer, according to Kurt (a PMG member) is "it doesn't matter". To quote him, "It almost doesn't matter what type of drill bit you use to drill holes, providing the bit is sharp, you have a good starting location, and exercise the proper speeds and feeds for the material."

BTW, the article called "It Doesn't Matter" contains some really good advice and answers many perplexing questions.

I read that article and to me there was some questionable advice in there in my opinion. When something starts out as saying "it almost doesn't matter" makes me wonder abit. I definetly would not use a brad point bit on a segmented blank especially one with metal in it. ( just an example)

 

[watch_art]

what bit would you use on a segmented blank with metal in it?

 

[flyitfast]

As usual, there are always several folks out there that provide the advice that makes the rest of us better.
Thanks to Russ for asking and to all that responded with very logical answers.
Maybe I'll start the new year out with consistently sharper drill bits
I hope someone can explain the question on segmented blanks with metal in them - that's where I'm headed next.
Thanks all.
gordon

 

[jttheclockman]

what bit would you use on a segmented blank with metal in it?

I use the standard twist drill bits for the fact they are designed to cut metal and do not have that flute that can catch on edges of any glue joint. You want a 110 to 120 degree angle. Those steeper angle bits are too aggressive for pen turning in my opinion.

 

[KBs Pensnmore]

Split point bits are normally used on larger diameter drill bits or on drilling stainless steels.
Kryn

 

[mikespenturningz]

Isn't the lower number more aggressive than an higher number on the angle of the drill? Maybe I am confused?

 

[jttheclockman]

Drill bit info

Drill bit - Wikipedia, the free encyclopedia

 

[leehljp]

what bit would you use on a segmented blank with metal in it?

This is NOT related to drill bit angle or split tip, but to segments, especially with metal in it. Since the subject is mentioned in your post, here is tip I learned from Eagle a long time ago: Wrap a layer of string (or two, or several layers of thread) real tight around the unturned blank and CA it until it is totally soaked. Let it set to cure, then drill. Nothing like added strength to assist drilling in difficult and sensitive material.

Also, if you can, turn the segmented blank in a chuck to get it basically rounded using very light touches, then wrap with thread/string and CA.

 

[watch_art]

what bit would you use on a segmented blank with metal in it?

This is NOT related to drill bit angle or split tip, but to segments, especially with metal in it. Since the subject is mentioned in your post, here is tip I learned from Eagle a long time ago: Wrap a layer of string (or two, or several layers of thread) real tight around the unturned blank and CA it until it is totally soaked. Let it set to cure, then drill. Nothing like added strength to assist drilling in difficult and sensitive material.

Also, if you can, turn the segmented blank in a chuck to get it basically rounded using very light touches, then wrap with thread/string and CA.

Gauze should work too, right? I've got some wood blanks with metal bits in them and don't want them to explode. I've got only one chance so don't want to goof it up.
Thanks!

 

[SteveG]

"Gauze should work too, right?"

I have no experience with this...my response is simply from reasoning on the idea, FWIW. The strength from thread wrap plus CA works because of the tensile strength of the tightly wrapped thread augmented by the structure provided by CA. Gauze may not provide the tensile strength because of being woven. The individual threads of the gauze sort of "zig-zag", even if you attempt a tight wrap. I would go with the string or thread approach.
Steve