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- Nov 25, 2015
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- 9,779
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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Are all center drills the same? Frustrated here...
- Thread starter Maplehead
- Start date
To answer your specific question.
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!
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!
- Joined
- Apr 14, 2014
- Messages
- 3,534
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.
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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- Nov 25, 2015
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- 9,779
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.
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.
- Joined
- May 3, 2017
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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
Regards
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.
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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- Apr 23, 2013
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- 1,079
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.When you keep breaking cheap center drills !
Jimsehr
Last edited:
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That's why we're all here ............................to teach and help spend one and all's $$$$$$ !
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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.