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How do you make a counterbore?
- Thread starter alexmin
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- Mar 12, 2006
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I tend to run my clearance holes tighter than standard, plus screw head sizes vary by type (pan,button,socket, etc). If you're using pan, you'll often find the standard counterbores are too small.
I get a good drill, the proper size I want to clear the head and have it ground by a tool grinder into a piloted counterbore.
This allows me the flexibility to run whatever clearance holes I want with whatever head size.
It costs usually about $20 per drill to do this, though the last time I had it done I had 2 done for #2 panheads for $20 and they were perfect.
Some guys grind quick and dirty counterbores by hand out of drill bits. This will work in a pinch, but I find precision cutting tools are usually a good idea if you want precision, repeatable results.
I get a good drill, the proper size I want to clear the head and have it ground by a tool grinder into a piloted counterbore.
This allows me the flexibility to run whatever clearance holes I want with whatever head size.
It costs usually about $20 per drill to do this, though the last time I had it done I had 2 done for #2 panheads for $20 and they were perfect.
Some guys grind quick and dirty counterbores by hand out of drill bits. This will work in a pinch, but I find precision cutting tools are usually a good idea if you want precision, repeatable results.
Take a drill bit, cut it in half, insert in variable speed drill and hold the tip laterally against a grindstone while drilling to grind the pilot point. Hold the drill at an angle to get the countersunk angle and then afterward grind the cutting edge by hand.
I'm going to get a flood of posts about how dangerous it is, but, if you dont have other tools it will work and wont be any more dangerous than drilling a hole in the wall to put up grannies mirror.
I'm going to get a flood of posts about how dangerous it is, but, if you dont have other tools it will work and wont be any more dangerous than drilling a hole in the wall to put up grannies mirror.
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- Mar 12, 2006
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- 2,264
Not sure it's too dangerous, but if you're building folders and want a pilot that's +/-.001 and a flat bottom on the bore thats, well, flat ...you'll need a really steady hand.
(A tool grinder will also usually sharpen the 'blades' on the flat when doing a counterbore from a drill. This is nice because your cutting with the flat of your counterbore in your mammoth, pearl or carbon fiber, not scraping it out. I find it's more effortless to cut and easier to control depth that way.)
(A tool grinder will also usually sharpen the 'blades' on the flat when doing a counterbore from a drill. This is nice because your cutting with the flat of your counterbore in your mammoth, pearl or carbon fiber, not scraping it out. I find it's more effortless to cut and easier to control depth that way.)
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Alexmin, try saw and tool sharpening services in the yellow pages. My work place does them all the time. $20 sounds about right, getting two done at once saves on setting up time which gets passed on to you. Specify how tight you want your tolerances and you should have no problems.
Langchop, do it all the time mate. My motto is "I'm a knifemaker, I can do anything"
peter
Langchop, do it all the time mate. My motto is "I'm a knifemaker, I can do anything"
peter
- Joined
- Jul 28, 2003
- Messages
- 1,617
Find a new source for counterbores. Check ebay, Try Enco, J&L industrial supply, Production tool supply. google on counterbore. You don't need the high buck Brown and Sharp you just need HSS counterbores. The small sizes you need shouldn't cost more than $4 or $5 each.
Not sure it's too dangerous, but if you're building folders and want a pilot that's +/-.001 and a flat bottom on the bore thats, well, flat ...you'll need a really steady hand.
QUOTE]
very true J.. If i wanted accuracy I just pay
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- Feb 17, 2007
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We all do things that have danger to them, we work with extremely sharp metal, various power tools, a lot of exposed rotating equipment. I mean look at just buffers, drill presses and belt grinders. I think that true safety is looking at what could possibly go wrong and minimizing the risk of that occurring and then doing as much as possible to minimize the damage that occurs if something occurs in spite of our safety measures. Most of safety starts with a intelligent mind focusing and looking at the possibilities. I have worked with very dangerous equipment all my life. In my youth my reflexes saved me several times. As I have aged I have learned that that is a poor system and depend on my brain way more although it is not foolproof, it sure helps.
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Buffing a knife blade is probably one of the most dangerous things I can think of (that knifemakers do regularly).
- Joined
- Dec 23, 2006
- Messages
- 84
To make a counterbore:
Take correct dia. drill, grind the end as flat as possible on a bench/belt grinder.
use a straightedge of some kind to check for evenness by holding it against the end up toward a light/bright surface. It is important to have the end as even as possible, otherwise one edge will cut more than the other, causing problems such as oversize holes, offset, rough finish etc.
Once the end is perfectly flat, use the edge of the grinding stone to cut a shallow "V" groove across the web of the drill, perpendicular to the cutting edges. The web is the solid center of the drill, look it up if you're not sure.
The final step is to grind a slight angle from each cutting edge back across the lands of the drill (google "drill bit nomenclature" to see diagrams) to give the bit some lip clearance. Be sure not to grind the angle exactly from the cutting edge, leave a few thousandths of an inch, so that that you don't alter the straightness of your cutting edges. This clearance, as well as the v grove across the web, give the bit the necessary clearance to enable it to go through material, otherwise there will be rubbing and overheating. If you notice the bit not cutting and/or getting too hot, this is probably why.
I've made these counterbores in diameters as small as 1/4", but I'm sure you could go smaller with patience and a steady hand. Saves money too!
Take correct dia. drill, grind the end as flat as possible on a bench/belt grinder.
use a straightedge of some kind to check for evenness by holding it against the end up toward a light/bright surface. It is important to have the end as even as possible, otherwise one edge will cut more than the other, causing problems such as oversize holes, offset, rough finish etc.
Once the end is perfectly flat, use the edge of the grinding stone to cut a shallow "V" groove across the web of the drill, perpendicular to the cutting edges. The web is the solid center of the drill, look it up if you're not sure.
The final step is to grind a slight angle from each cutting edge back across the lands of the drill (google "drill bit nomenclature" to see diagrams) to give the bit some lip clearance. Be sure not to grind the angle exactly from the cutting edge, leave a few thousandths of an inch, so that that you don't alter the straightness of your cutting edges. This clearance, as well as the v grove across the web, give the bit the necessary clearance to enable it to go through material, otherwise there will be rubbing and overheating. If you notice the bit not cutting and/or getting too hot, this is probably why.
I've made these counterbores in diameters as small as 1/4", but I'm sure you could go smaller with patience and a steady hand. Saves money too!
howiesatwork
Gold Member
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- Jun 16, 2004
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- 2,466
Got pics to go with the description, Mike?
Alex,
As far as I am aware, I have only ever seen drillbit sharpening apparatus that regrind the cutting edge for a normal type of drill. Their purpose is to get the correct 'approach angle' (sorry i dont know the real name for this) of the drillbit tip and the correct cutting edge angle. You could probably play around with the adjustments to try and cut a counterbore, but obviously it depends on the sharpener.
Lang
As far as I am aware, I have only ever seen drillbit sharpening apparatus that regrind the cutting edge for a normal type of drill. Their purpose is to get the correct 'approach angle' (sorry i dont know the real name for this) of the drillbit tip and the correct cutting edge angle. You could probably play around with the adjustments to try and cut a counterbore, but obviously it depends on the sharpener.
Lang