# Are all center drills the same? Frustrated here...



## Maplehead (Nov 28, 2021)

Hi All
I'm getting pretty frustrated. When I had my old 100 pound LMS mill I could bang out a bunch of my brass guitar bridges. I wanted my guitar parts to be steel so I took the plunge and upgraded my mill to my 1000 pound Grizzly G0678 mill and my 36 pound lathe to my 1100 pound M1112 lathe. I have yet to make a complete set of guitar parts for one guitar. Regarding my steel bridges, I'm always breaking center drills in them. It drives me nuts. I go dog slow so as not to force the bit in, and I'm always brushing away the chips so as not to allow them to interfere with the drills cutting. My RPM's are around 350 but I've tried other speeds. I'm drilling into mild steel. My center drills come from Harbor Freight. Are they inferior? As you all know, once you break anything HSS into mild steel then the piece usually becomes trash. I have 62 holes I need to drill in my bridge. 48 of them end up getting tapped with a #6-40. I bought a Tapmatic for that that works awesome, but getting to the tapping point is the issue now. Any advice is appreciated.


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## jcp (Nov 28, 2021)

I would suggest more speed....a lot more....and get some higher quality drills.


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## Maplehead (Nov 28, 2021)

jcp said:


> I would suggest more speed....a lot more....and get some higher quality drills.


Do you have any suggestions for better center drills?


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## mmcmdl (Nov 28, 2021)

How about using a spotting drill ? KEOs center drills are good .


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## Maplehead (Nov 28, 2021)

Never heard of a spotting drill. Will investigate.


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## mmcmdl (Nov 28, 2021)

Maplehead said:


> Never heard of a spotting drill. Will investigate.


They don't break and provide a true start to a hole .


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## jcp (Nov 28, 2021)

Spotting drills are are actually the correct tool for what you're doing.


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## Maplehead (Nov 28, 2021)

jcp said:


> Spotting drills are are actually the correct tool for what you're doing.


When would one use a spotting drill compared to a center drill, and visa-versa?


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## mmcmdl (Nov 28, 2021)

Maplehead said:


> When would one use a spotting drill compared to a center drill, and visa-versa?


When you keep breaking cheap center drills !


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## compact8 (Nov 28, 2021)

That's very odd ......  I have broken small-diameter drills ( talking about around 1 mm ) but never any center drills. I have got some really crappy center drills but they just refused to go into the metal instead of breaking.  This is just wild guess but is it possible that the run out of the spindle or the tip of the center drill is excessive ? This is the run out of my crappy center drills but still they do not break :


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## mmcmdl (Nov 28, 2021)

Center drills are made for the use of turning a shaft between centers with the small tip providing clearance for the center point . Hence the 60 degree angle . A spotting drill is a much more rigid tool vs. the CD . Pretty darn tough to break one if at all possible .


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## jcp (Nov 28, 2021)

Most of the center drills I've broken have been while doing 'gummy' steels (1018 etc.) with not enough rpm and too much pressure.


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## compact8 (Nov 28, 2021)

Maplehead said:


> When would one use a spotting drill compared to a center drill, and visa-versa?


I just learned this recently. Spotting drill is used for starting a hole and center drill is more for drilling a hole to accomodate the tailstock center of lathes. Spotting drills have a much more pointed tip so it has lower tendency to wander.  The angle of the tip is also optimized to minimize the wandering of the drill used after it.


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## jcp (Nov 28, 2021)

I suppose the terminology is confusing. Reading 'center drill' leads one to thinking 'centering a hole for a drill' when in fact it means 'drilling a hole for using a center' (live or dead).


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## Maplehead (Nov 28, 2021)

compact8 said:


> That's very odd ......  I have broken small-diameter drills ( talking about around 1 mm ) but never any center drills. I have got some really crappy center drills but they just refused to go into the metal instead of breaking.  This is just wild guess but is it possible that the run out of the spindle or the tip of the center drill is excessive ? This is the run out of my crappy center drills but still they do not break :


I've never checked that but it looks like I'm going to switch to the spotting drill.


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## Maplehead (Nov 28, 2021)

I did a qucik search on Amazon for Keo spotting drills and most are at 90 degrees. Considering most "jobber" drill bits are at 60 degrees, a 90 degree spotting drill would be incorrect. So that's odd. I am basing this off of this article I just read.








						Spot Drilling: the First Step to Precision Drilling - In The Loupe
					

In high precision machining, drilling a hole exactly where it is needed is a challenge. The challenge comes with choosing the right spot drill for your job.




					www.harveyperformance.com


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## mmcmdl (Nov 28, 2021)

Can you imagine using a center drill vs a spotting drill on a cnc mill drilling thousands of holes ? The center drill must get that small point down into the stock which takes lots of time and it's also very weak . A spotting drill will plunge to the desired depth in seconds and create a true start for the drill . I realize we aren't production guys , but using the right tool for the job is why we're all here .


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## mmcmdl (Nov 28, 2021)

Spotting drills come in different angles MH . I got a bucket full of them down the basement .  What you googled is not a spotting drill either . I'll get some pics and load them here .


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## compact8 (Nov 28, 2021)

Maplehead said:


> I did a qucik search on Amazon for Keo spotting drills and most are at 90 degrees. Considering most "jobber" drill bits are at 60 degrees, a 90 degree spotting drill would be incorrect. So that's odd. I am basing this off of this article I just read.
> 
> 
> 
> ...


Common jobber drills have a tip angle of 118 degrees, not 60. You will need spotting drills with slightly larger tip angle. All those I have got are of 120 degree type.  The 90 degree type is designed to do spotting and chamfering at the same time at the expense of less spotting accuracy. Although they are much more common, I don't use them.


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## Maplehead (Nov 28, 2021)

mmcmdl said:


> Spotting drills come in different angles MH . I got a bucket full of them down the basement .  What you googled is not a spotting drill either . I'll get some pics and load them here .


Considering my tap drill is a #33 at .113" in diameter, can you recommend a spot drill for me to use? More precisely, can you link me to one on Amazon or eBay?


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## mmcmdl (Nov 28, 2021)

Maplehead said:


> Considering my tap drill is a #33 at .113" in diameter, can you recommend a spot drill for me to use? More precisely, can you link me to one on Amazon or eBay?


I'll post a few pics . I have quite a few 1/4" up to 1" spotters , but they are a common tool .


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## mmcmdl (Nov 28, 2021)

Small spotting drills . They come in single or double lip with all different angles . I also use them for easy deburring of small holes and use them over a CD whenever I can .


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## Maplehead (Nov 28, 2021)

Would this one be good for my need?


			Amazon.com


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## mmcmdl (Nov 28, 2021)

I would go with the 1/4" , but that's just me .


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## Maplehead (Nov 28, 2021)

mmcmdl said:


> I would go with the 1/4" , but that's just me .


Ok, cool. In the meantime would either one of these bits get me through today? The one on the left looks like a good angle but more likely to break while the one on the right has a much sharper angle.


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## mmcmdl (Nov 28, 2021)

C sinks , so no . Better off using a larger center drill and just spotting the hole with it . No need to bury that point .


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## Maplehead (Nov 28, 2021)

mmcmdl said:


> C sinks , so no . Better off using a larger center drill and just spotting the hole with it . No need to bury that point .


Got it


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## Bob Korves (Nov 28, 2021)

Another issue, which may or may not be an active factor here, is having as rigid a setup as possible.  When doing cuts, have all axes of the machine and other tooling locked down snug, except for the single moving axis for making the cut.  Yes, even on smaller cuts with smaller tools.  It is a habit, when ingrained into your mind, becomes automatic and quick, and many problems go away by doing so...


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## DAT510 (Nov 28, 2021)

Stefan Gotteswinter has a great youtube video on Center and Sotting drills.


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## woodchucker (Nov 28, 2021)

Maplehead said:


> When would one use a spotting drill compared to a center drill, and visa-versa?


A center drill is meant for a CENTER on a lathe. that's what it's original intention was. Many use it to drill a spot... but like everyone has suggested a spotting drill is a better option.  A spotting drill has a single or slightly more or less twist. So it's stout. it's mean to give the drill point a landing to keep it in this spot. they make different angles.

I'll bet your speed is too low, and with a bigger mill you don't have the feel you had before.  speed is your friend on the small point.
But with a spotting drill you can get by with the same speed as your drill bit.


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## woodchucker (Nov 28, 2021)

compact8 said:


> That's very odd ......  I have broken small-diameter drills ( talking about around 1 mm ) but never any center drills. I have got some really crappy center drills but they just refused to go into the metal instead of breaking.  This is just wild guess but is it possible that the run out of the spindle or the tip of the center drill is excessive ? This is the run out of my crappy center drills but still they do not break :


that's not a lot of runnout. it's a drill bit.. it's in a drill chuck... not an accurate tool.


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## B2 (Nov 28, 2021)

To answer your specific question.


Maplehead said:


> My center drills come from Harbor Freight. Are they inferior?



Yes, almost every drill bit I have purchased at HF is low quality. Maybe there are some good ones, but I have not found them. They work ok for a while in wood! I sometimes buy a set when I need to drill in plaster for hanging a picture etc and I know that they will not last long anyway.  For drill bits, I start out looking at Grainger.  This is partly because there is a store near me and I just place an order and then go pick it up the next day or when ever they let me know the parts have arrived.

WRT to Center drills. Yes, they can vary considerable.  I have purchased some from AliExpress which are fine and some which do not even have the point in the center!  I have even gotten some where the shaft is bent! (true for drill bits too).  After a while any of them will get dull. 

I have used Center drills to make lots of starter holes in steel in one pass.  Just as with any drill bit and the work material there is an optimum speed (RPM) and an optimum plunge rate.  Just as with smaller drill bits the speed for small center drill bits needs to be much higher than for the larger bits.  I typically run a bit for a #6 hole at ~2000RMP or so.  It is not that for small bits you "can" run faster RPM, but that you "should".    The exact speed depends upon material and plunge. (There are some tables on the internet that can provide some RPM guidance for drilling in to various materials and bit size.)  I also use thread cutting oil to cool.  I choose the center drill speed to be about the same as I would for the bit I am going to use for the tap.  The key to determine if you are at the right speed and plunge rate is to observe the material coming off.  On a lathe we tend to avoid spirals as they tend to grab and become a hazard, but I find that for drilling when I get a nice spiral of material then this is about the optimum speed for limiting tool wear.  Too slow and they tend to grab, bend and break the bit, but too fast and little cutting occurs and you just rub the tool edge against the work ..... generating excessive heat at the tool cutting edge making it dull fast.   Again use lubricant both for the cutting edge cooling and for the sides of the bit going into the hole to reduce friction and grabbing. 

By the way, for a two fluted drill bit that is sharpened correctly you should get two simultaneous spirals ...  when the cutting rates are adjusted right.  However, many cheaper drill bits, or self sharpened drill bits, have one cutting edge which is more aggressive (sharper or sticking out farther) and so only one flute is actually cutting!!!!   Anyway, always lubricate, especially for steel, but also for sticky materials like Al or brass!


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## projectnut (Nov 28, 2021)

The debate of center drills vs spot drills has raged on since Christ was in Sunday School.  In a production situation where time is money I would give the edge to spot drills for anything except lathe work.  In a prototype, repair shop, or in the hobby world to me their interchangeable.  The prototype shop I worked in used center drills exclusively.  In essence the boss was too cheap to buy both styles, so center drills were the only option.

Once you learn how to use them in different materials you're unlikely to break them.  With a bit of experience it's easy to tell when they're at the end of their useful life.  It's that last time when you're in a hurry to finish a job, have only a few holes left to spot, and you already know you're pressing your luck that one breaks.

To your original question "Are all center drills the same?" the answer is a resounding *NO.  *As mmcmdl mentioned in his first post on the subject KEO is an excellent brand.  I'm sure there are others, but I have always stuck with KEO over the years.  I tend to buy them by the box to minimize per unit price.

As a side note a few years ago I couldn't find KEO #2s by the box.  I was in a hurry and ordered a box of "imports" hoping they would be acceptable quality.  They were a disappointment to say the least.  I could have carved a better hole faster with a pocket knife.  They were absolute junk.  No amount of speed or different feed rates made one iota of difference.  I would stick with the known name brands.  They may be slightly more expensive, but as always you get what you pay for.


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## woodchucker (Nov 28, 2021)

I would not rely on the HF bits.
I have a set of their titanium coated 80degree from about 1999... I believe they were drill pro back then Not warrior.
The have been good. I got the step drills.. they were horrible, had to return 2 times to get a set that cut. And they are ok. Got taper of the same type, they don't cut.
One good little bit is the double ended 1/8 they are stout because of their small size..

The rest of my drill bits are all American made, high quality. There's a big difference in some.
My centering drills are mostly american made.. I have a small set I got from CDCO, and they have been good. 
There is a diff in quality... And sometimes even an American made can be crap... The USA made is generally better steel, but sometimes QA lets one get by.

you need a spotting drill for what you are doing.


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## tjb (Nov 28, 2021)

Are you sure the table and head are indicated perpendicular to each other?  Do you have the same problem or evidence of binding with larger size drill bits?  Buying 'new' is no guarantee that all axes are accurately indicated.  I ran into that issue with my new lathe a couple of years ago.

Regards


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## Maplehead (Nov 28, 2021)

On thing I learned today after researching spot drills is that all I need is just that v shaped hole. With the center drills I was bringing the entire tip all the way down into the part until I was getting a bit of chamfering from the main body of the center drill. I thought the chamfering was the part that helps guide the drill bit. I could have avoided a lot of aggrevation by just using the v shaped tip of the center drill and going in no further. Well now I know.


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## Maplehead (Nov 28, 2021)

tjb said:


> Are you sure the table and head are indicated perpendicular to each other?  Do you have the same problem or evidence of binding with larger size drill bits?  Buying 'new' is no guarantee that all axes are accurately indicated.  I ran into that issue with my new lathe a couple of years ago.
> 
> Regards


Yup, my mill is pretty well dialed in. The only issue I have with the G0678 is that I don't like the slippage I can get when using the gib tightener for the quill when I use the fine downfeed. I use the z-axis crank for the knee now for fine feeding - another tricked learned here thank you.


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## Jimsehr (Nov 28, 2021)

mmcmdl said:


> When you keep breaking cheap center drills !


You can use a spotting drill to do two things at once. The sturdy spotting can be used in place of a center drill and you can also chamfer the hole you are tapping at the same time.
Jimsehr


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## mmcmdl (Nov 30, 2021)

Maplehead said:


> On thing I learned today after researching spot drills is that all I need is just that v shaped hole. With the center drills I was bringing the entire tip all the way down into the part until I was getting a bit of chamfering from the main body of the center drill. I thought the chamfering was the part that helps guide the drill bit. I could have avoided a lot of aggrevation by just using the v shaped tip of the center drill and going in no further. Well now I know.


That's why we're all here ............................to teach and help spend one and all's $$$$$$ !


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## NC Rick (Nov 30, 2021)

I took out a brand new 1/4” carbide spot drill last week and without thinking left the mill at the speed it was on to spot a hole in a bracket I was making out of hot rolled 1018. The point grabbed and broke before my eyes.  I was sad and it taught me a lesson.  HSS likely better for most of my use.


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## Larry42 (Nov 30, 2021)

Take a look @ Stefan Gotteswinter's video on center drilling. Excellent description of how and why. 
About the "runout" on the tip of a center drill, I think what is being indicated is the back clearance not runout.


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## RJSakowski (Nov 30, 2021)

With apologies to the 40 preceding posts regarding possible redundancy, here are my observations. 

If there is runout in either the center drill or the setup, a center drill will orbit around the true spindle axis.  If you push forcibly, it will start off the true spindle axis as play in the spindle allows.  When the main cutting edge contacts the work , it will tend to run true and snap the tip.  With the larger center drills, they just carve a new spot but smaller ones will break the tip.  I was using 0000 and 00000 center drills with tips of .015" and .010" and breaking them regularly.  A solution is to make light first contact and allow the center drill to find the true spindle axis.  Once it has done so, as evidenced by the lack of wobble in the tip, you can proceed with the main cut.

If the broken tip leaves a stub, the tip can be reground to make a spotting drill

As to brand, all my larger center drills are house brand from Travers or MSC. with the exception of two Malcus No. 7's picked up at a hamfest.  The 0000 and 00000 were purchased from Small Parts Inc. , no longer in business, and of unknown brand but likely to be German made.

Edit: corrected tip size of 0000 and 00000 center drills.


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## woodchucker (Nov 30, 2021)

RJSakowski said:


> With apologies to the 40 preceding posts regarding possible redundancy, here are my observations.
> 
> If there is runout in either the center drill or the setup, a center drill will orbit around the true spindle axis.  If you push forcibly, it will start off the true spindle axis as play in the spindle allows.  When the main cutting edge contacts the work , it will tend to run true and snap the tip.  With the larger center drills, they just carve a new spot but smaller ones will break the tip.  I was using 0000 and 00000 center drills with tips of .010" and .005" and breaking them regularly.  A solution is to make light first contact and allow the center drill to find the true spindle axis.  Once it has done so, as evidenced by the lack of wobble in the tip, you can proceed with the main cut.
> 
> ...


I haven't ordered from small parts in years, but I just looked them up, they are still in business according to the website.


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## RJSakowski (Nov 30, 2021)

woodchucker said:


> I haven't ordered from small parts in years, but I just looked them up, they are still in business according to the website.


The name/brand still exists but it isn't the same company.  Amazon took them over when they went out of business.  I ordered quite a bit from them around fifteen years ago and they were the go-to place for things like hypodermic tubing and small diameter stainless rod as well as precision tools.  For the benefit pf those unfamiliar with SPI, here is their 2002 catalog.  Nine pages in their index alone.  Pick any material/part/tool at random and see what Amazon offers. http://bahrnet.dyndns.org:2980/webshare/BahrZ/Small Parts Inc 2002 Catalog 22.pdf


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## Jimsehr (Nov 30, 2021)

I think a spotting drill is just a very short stiff drill with no flutes. And you can grind any starting point on it you want. The more the point is split the less it wants to run out. I grind my own and it only takes a few minutes to do so. And broken center drills work great to make spotting drills. I can’t see why drills are made with a 118 point . Why not a 120 point ?  I mostly use split point drills and if I don’t have a split point drill I grind it too a split point. And I grind 118 point drills to split point . And 99 percent of my drills start out as Harbor Freight drills. I buy them planning to sharpen them before I use them. This is for a home machine shop where most of us use the easy to cut materials like 12l14 and the like. When most of what I drilled was tough stainless or Inconel and that type material then I shopped for the better high priced drills and carbide drills.
 Jimsehr


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## woodchucker (Nov 30, 2021)

Jimsehr said:


> I think a spotting drill is just a very short stiff drill with no flutes. And you can grind any starting point on it you want. The more the point is split the less it wants to run out. I grind my own and it only takes a few minutes to do so. And broken center drills work great to make spotting drills. I can’t see why drills are made with a 118 point . Why not a 120 point ?  I mostly use split point drills and if I don’t have a split point drill I grind it too a split point. And I grind 118 point drills to split point . And 99 percent of my drills start out as Harbor Freight drills. I buy them planning to sharpen them before I use them. This is for a home machine shop where most of us use the easy to cut materials like 12l14 and the like. When most of what I drilled was tough stainless or Inconel and that type material then I shopped for the better high priced drills and carbide drills.
> Jimsehr


I have a friend he's been a machinist for over 50 years, says he doesn't like split points... Not sure why, I don't remember what he told me..


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## mmcmdl (Nov 30, 2021)

woodchucker said:


> I have a friend he's been a machinist for over 50 years, says he doesn't like split points... Not sure why, I don't remember what he told me..


One reason , they are harder to re-sharpen correctly by hand .


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## wachuko (Nov 30, 2021)

Learned something new... now I need to buy some spotting drill bits...  I have been using (and some times breaking) my center drill bits for everything...


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## Maplehead (Nov 30, 2021)

wachuko said:


> Learned something new... now I need to buy some spotting drill bits...  I have been using (and some times breaking) my center drill bits for everything...


That's why this is a great site. Donate when you can.


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## Jimsehr (Nov 30, 2021)

mmcmdl said:


> One reason , they are harder to re-sharpen correctly by hand .


It’s hard to sharpen any drill . Even with a drill grinding machine. Till you learn how. 
All most all  the newest fancy drills that I’ve seen have a split point.
I have been hand grinding drills since 1953 . That is getting close to 70 years. 

Jimsehr


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## compact8 (Dec 1, 2021)

Interesting. Just found that all the drill bits I purchased recently from a vendor are split-point type. Will try to use them without spotting drills and see how the accuracy is like ......


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## Jimsehr (Dec 1, 2021)

compact8 said:


> Interesting. Just found that all the drill bits I purchased recently from a vendor are split-point type. Will try to use them without spotting drills and see how the accuracy is like ......


I think you should still start a hole with a spotting drill. Because they are short and stiff they don’t want to walk when they start drilling.
Jimsehr


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## compact8 (Dec 1, 2021)

Jimsehr said:


> I think you should still start a hole with a spotting drill. Because they are short and stiff they don’t want to walk when they start drilling.
> Jimsehr


Sure. I just want to test it but just found that it's no longer needed because someone has already done it :






Now I got a new problem with these 135 degree drills in hand - I don't have any suitable spotting drills for them because the angle of the spotting drill must be bigger than 135, say 140 but they are very expensive.  I will make sure that the drills I buy in the future will be 118 degrees, not 135.


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## woodchucker (Dec 1, 2021)

compact8 said:


> Sure. I just want to test it but just found that it's no longer needed because someone has already done it :
> 
> 
> 
> ...


You only need one spotting drill.


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## compact8 (Dec 1, 2021)

woodchucker said:


> You only need one spotting drill.


Yes I realized it now because all it needs is just one tiny dent to accomodate the chisel point of the drill bit but I keep wondering why they make spotting drills of different sizes.   I have got three in my tool box : 6 mm,  3 mm , 1.5 mm. The latter two will probably sit there to collect dust.


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## woodchucker (Dec 1, 2021)

compact8 said:


> Yes I realized it now because all it needs is just one tiny dent to accomodate the chisel point of the drill bit but I keep wondering why they make spotting drills of different sizes.   I have got three in my tool box : 6 mm,  3 mm , 1.5 mm. The latter two will probably sit there to collect dust.


I don't know.. to make more money?


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## Jimsehr (Dec 1, 2021)

compact8 said:


> Sure. I just want to test it but just found that it's no longer needed because someone has already done it :
> 
> 
> 
> ...


Just grind spotting drill to degree you want.
Jimsehr


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