Drill Bits - Need some help and advice

[oldtimer 66]

LD1 correct. The shearing forces for aluminum are less than steel but the SFM is much much higher thus the CI per minute is higher thus more HP is required. On a high silicon content aluminum material even carbides have a difficult time staying sharp. Thus a lot of times diamond type cutters are used. When synthetic type diamond tooling is used the SFM can go from say 400 /500 SFM to 1500 / 2000 SFM or even higher depending upon the machine HP and a bunch of other factors. There was a comment on coated drills that after you re-sharpen it the first time the coating is gone and the drill is just the same as a regular drill then and or something to that affect. When you sharpen a drill you are sharpening it by creating new clearance on the back side of the cutting edge. If the coating is removed in that area it does not effect the face of the cutting edge that still has the coating on it. You sharpen a drill by creating clearance behind the cutting edge. The gold coat/ titanium nitride/ creates a slippery surface for the shearing of the material at the cutting edge. Less friction, less heat, less HP. My last comment is on web thickness of drills. Now this refers to jobber length drills but the rule of thumb here is that the drill is only good for approx. 1/3 of the flute length. After that the web gets to thick and the drill does not perform properly and should be replaced. That's all I have from my memory and not the internet. LOL. Later.

 

[oldtimer 66]

One other thing. Standard drill points are 118 degrees nothing else. If it 135 degrees or something else it's not standard. Later.

 

[Sodo]

You're not likely to soften HSS by grinding. You can silver solder it to a boring bar (red hot) and it will still be hard when it cools. Carbon steel is a different story.

Interesting. So High Speed Steel is not a carbon steel? I suppose if a drill bit could lose its strength due to loss of heat-treat then the microscopic cutting edge would soften almost immediately.

So I have wasted time worrying for no reason about heat coloration when sharpening, for many years?

 

[Shield Arc]

Here is a cheap and easy way to check the proper angle of a drill bit. Most of us here have two of these.

 

[LD1]

I dont fuss too much about getting the angle perfect. Just make sure they are equal so both edges cut. I have actually ground some bits to 80 degrees in a pinch when I didnt have or couldnt find a countersink for a FHCS

 

[Mark @ Everlast]

Are you planning to get a full index or just source a few at a time? I've found a few relatively inexpensive bits that work well. First, I bought a small index of Bosch bits. These worked well and lasted very well. They were coated, but the steel itself was very good. I only had a issue with them snapping. I've also found a local hardware store that sells a bunch of bits that are branded "Ivy Classic". They have a whole tool line including bits. They've got them in HSS, Moly, coated and even true cobalt. I've found that they are relatively long lived, especially the cobalt. I've also had good luck with the Norse (?) bits from Fastenal. Work well, good to resharp too. I've also had good luck with Nitro brand drill bits. In fact I do like them as what I've drilled with them they seem to last and last.

 

[cadman1970]

I bought a Dayton set about 20 years ago and a few years ago a drill doctor to sharpen them. I have had very good service with them. Now as for lubrication and Kenny suggests I asked my brother who is a machinist and he said your wasting your time putting oil on the tip it is gone as soon as you cut, we use cutting oil to cool because of the speed we cut. If your drilling a big hole through thick metal you could use water to cool the work and make less of a mess as with the oil. We used to drill 5/8 mild steel at work on cutting edges for snow plows the guys would always use oil and we had a mess. I did about 10 cutting edges one shift used 1 drill bit and no oil just kept sweeping up the cuttings, made sure to run the drill press at a slower speed and not apply to much pressure and the bit lasted for over 80 holes with no problem. Patience is a virtue, some rush and use dull bits.

 

[the old grind]

Other than too little stressed IMO about dunking/swirling when hot I liked the video very much, as well as OT66's obviously very 'experienced' post #41. :thumbsup: (makes me miss my last job, hopping from CNC to manual to snag grinders)

Brazing/soldering carbide tips (sintered tungsten micro-particle makeup, btw) to a drill's body isn't like heating to extremes what wants to hold a lasting edge once sharpened. Carbide (now the cutting edge) can take much more heat, .. as when drilling out a broken HSS drill, tap, reamer, or SAE grade 8 bolt that HSS barely scratches. Blue chips are usually more desirable than blue HSS.

Sodo, ordinary 'carbon steel' drills (rough & black, super cheapo) are for wood. If any goes to mush on the first hole in steel, mark the box 'wood only' and put 'em with the woodworking stuff. btw, +1 on using water vs oil when drilling steel. Lube & hydro oils, nope. ATF, maybe. Bacon grease is still considered among the best ever for drilling & tapping if you uh .. don't mind the aroma. (mmm .. baaaacon ..) tog

 

[FredH]

I have had pretty decent results just using the H.F. bit sets for up to 1/2" and also good results with thir larger bit set , ( forget the name of them ) . Up to 1/2" , I can resharpen on my drill doctor . The bigger ones , I take to my Bro as he has a bigger model Drill Doctor . For Bigger holes , usually use the Bi-metal hole cutters or just the plasma cutter if a really big hole . I only have a H.F. Bench drill press , so am limited on speed also .

My drill doctor stays set up on the work bench , simply walk over and drop the bit into the chuck , semi tighten and drop into the unit to set the depth . Depth set , tighten chuck , and usually 3 to 5 turns bit is sharp . My better half works for the company ( Darex ) now in Ashland . Some of the perks of Her position ( Quality Control ) , is they load Her up with various tools they have in production so She knows how they work . Knife / Tool sharpener is pretty cool . I have not used any of them , But if a 58 y.o. Woman can figure figure them out , can't be all that difficult . Something I did learn is that the Drill doctors are more accurate than people give them credit for . On all models during production , units get tested for accuracy by actually using the unit with various size bits and checking the bits under a microscope and other testing eqiupment , ( this I never knew , figured parts were just thrown into a hunk of plastic and boxed up ) . This is NOT a AD or a Sells pitch for anybody to buy any model of a D.D. , Just my experience and what I have learned fro Better Half who works there .

Fred H.

 

[Big Barn]

I have had pretty decent results just using the H.F. bit sets for up to 1/2" and also good results with thir larger bit set , ( forget the name of them ) . Up to 1/2" , I can resharpen on my drill doctor . The bigger ones , I take to my Bro as he has a bigger model Drill Doctor . For Bigger holes , usually use the Bi-metal hole cutters or just the plasma cutter if a really big hole . I only have a H.F. Bench drill press , so am limited on speed also . My drill doctor stays set up on the work bench , simply walk over and drop the bit into the chuck , semi tighten and drop into the unit to set the depth . Depth set , tighten chuck , and usually 3 to 5 turns bit is sharp . My better half works for the company ( Darex ) now in Ashland . Some of the perks of Her position ( Quality Control ) , is they load Her up with various tools they have in production so She knows how they work . Knife / Tool sharpener is pretty cool . I have not used any of them , But if a 58 y.o. Woman can figure figure them out , can't be all that difficult . Something I did learn is that the Drill doctors are more accurate than people give them credit for . On all models during production , units get tested for accuracy by actually using the unit with various size bits and checking the bits under a microscope and other testing eqiupment , ( this I never knew , figured parts were just thrown into a hunk of plastic and boxed up ) . This is NOT a AD or a Sells pitch for anybody to buy any model of a D.D. , Just my experience and what I have learned fro Better Half who works there . Fred H.

Fred. I've had a Drill Doctor now for about 15 years and had no idea Darex was the manufacturer. Maybe your wife should bring one of these home to check out....

XT3000 Drill Sharpener and Grinder - XT3000 Manual - Drill Sharpeners and Grinders. Terry

 

[FredH]

Fred. I've had a Drill Doctor for now for about 15 years and had no idea Darex was the manufacturer. Maybe your wife should bring one of these home to check out....

XT3000 Drill Sharpener and Grinder - XT3000 Manual - Drill Sharpeners and Grinders.



Terry

Yea , I Already Tried That !!!!:thumbsup: She won't even Ask .

Fred H.

 

[Big Barn]

Yea , I Already Tried That !!!!:thumbsup: She won't even Ask . Fred H.

I'm currently bidding on one locally but bidding is already up to $1350 with 3 days to go.

Terry

 

[dragoneggs]

Here is a cheap and easy way to check the proper angle of a drill bit. Most of us here have two of these.

Ha ha... Pretty close with that shop tool... only 2 degrees off. Can't say I have ever measured anything with my nuts though.

 

[Mace Canute]

You're not likely to soften HSS by grinding. You can silver solder it to a boring bar (red hot) and it will still be hard when it cools. Carbon steel is a different story.

Hardening is speed dependent. If you heat a soft carbon steel above the Curie point fast cooling will make it hard. If you reheat that same steel above the Curie point and then very slowly cool it, it will be soft again. HSS will become soft when it is heated to high temperatures but the speed that it cools at in air is sufficient to make it hard but it does not become as hard again as it was in it's preheated state. You might start at 67-70rc and then end up at 58-60rc which is still hard enough to be a good cutting edge.

 

[Sodo]

Ha ha... Pretty close with that shop tool... only 2 degrees off. Can't say I have ever measured anything with my nuts though.

Yeah nobody will know the units but you can usually count with them. For example the number of degrees off. Or you could count the number of people who know the angle is wrong.

 

[the old grind]

Adherence to the 118^ drill point is to avoid being sued by Apple (TM) for patent infringement.

They invented the 120^ angle too ...

 

[dragoneggs]

Yeah nobody will know the units but you can usually count with them. For example the number of degrees off. Or you could count the number of people who know the angle is wrong.

Typically I measure the degrees by the size of the nuts.

 

[oldtimer 66]

Quench and temper is all I know. Never heard of a tool steel that would go to 67/ 70. Stratified yes uniform no. M4 vacuum melt degassed best 62/64. Carbide yes on a different scale..

 

[Mace Canute]

Quench and temper is all I know. Never heard of a tool steel that would go to 67/ 70. Stratified yes uniform no. M4 vacuum melt degassed best 62/64. Carbide yes on a different scale..

The M40 series and T15 can be hardened to 70rc according to Machinery's Handbook 29th Edition.

 

[cormier]

Here is what i use to get me in the ballpark. mild steel 80sfm x 4 = 320 rpm for a 1 " drill. So just divide it from their. if 1" =320rpm then 1/2" = 640rpm and 1/4" = 1280rpm and so on. For Stainless steel i cut the speed by 1/2 and aluminum i go about 25% faster This gets me in the ballpark and i dont burn up my drill bits.