AndrewB
Well-known member
Does anyone have any good tips for keeping high-speed drill bits sharp? My drill bits quickly go blunt when used on mild steel and aluminium, and are then useless - specially with steel which they just work-harden.
How to sharpen high-speed drill bits?
- Thread starter AndrewB
- Start date
Strathglass
New member
Andrew,
There are some diy type drill sharpeners which work quite well. Even your local B&Q will sell them.
The more important thing is to use a cutting compound then the cut will be better and the drills will last much longer, especially when cutting stainless.
I use a tin of some stuff I got from a local engineering supplier when cutting steel.
For aluminium I have some parafin in a plastic bottle with a lever type spray thing at the top. It even helps prevent the swarf from sticking to the shaft of the drills.
From personal experience this his works very well as I have just finished building my mast from a 50ft extrusion and all the drills, even the hole saws are still quite sharp and still very usable.
Cheers
Iain
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There are some diy type drill sharpeners which work quite well. Even your local B&Q will sell them.
The more important thing is to use a cutting compound then the cut will be better and the drills will last much longer, especially when cutting stainless.
I use a tin of some stuff I got from a local engineering supplier when cutting steel.
For aluminium I have some parafin in a plastic bottle with a lever type spray thing at the top. It even helps prevent the swarf from sticking to the shaft of the drills.
From personal experience this his works very well as I have just finished building my mast from a 50ft extrusion and all the drills, even the hole saws are still quite sharp and still very usable.
Cheers
Iain
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ex-Gladys
Well-known member
Piece of advice given to me yonks ago, don't run them fast. This work hardens the workpiece quickly, blunting the drill double quick.
<hr width=100% size=1>Larry Botheras
Anderson 26 "Amber"
<hr width=100% size=1>Larry Botheras
Anderson 26 "Amber"
NigeCh
New member
Use the correct bits for metal
Also use an oil based cutting compound (very expensive but cheaper than having to replace bits)
High speed (wood) drills are not suitable for metals. Proper metal drills are negative camber and are only suitable for 100 - 350 rpm depending on the harndess of the metal.
It's the correct drill at the correct speed plus continual lubrication that works.
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Also use an oil based cutting compound (very expensive but cheaper than having to replace bits)
High speed (wood) drills are not suitable for metals. Proper metal drills are negative camber and are only suitable for 100 - 350 rpm depending on the harndess of the metal.
It's the correct drill at the correct speed plus continual lubrication that works.
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davehu
New member
You can either sharpen them with a special DIY unit or use a standard grinding wheel by hand but you need to know how to do it. The other points made are all correct, but when cutting Stainless it is essential to have a slow speed AND maintain a high feed load on the drill, what kills the edge is work hardening of the stainless which occurs if the drill skids on the surface of the steel rather than biting into it. If you are drilling any quantity of stainless you will need to regrind the edge periodically no matter what you do
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richardandtracy
New member
I agree with most of what's been said, but not all.
Yes, use a holder for the drill and use it on a bench grinder. Screwfix do a drill sharpening jig for about £9 - I've got one and usually can get the drills ground OK.
I tend to sharpen my drills every 100mm or so of of steel I drill through. This usually means that the drills are in pretty good condition & don't have too many problems. There are gold coloured TiAlN coated drills coming onto the domestic market. These are pretty good in that the bits last longer than the normal ones for the first use. Unfortunately, when you sharpen them, you grind off the coating and the become just the same as all the rest.
Where I differ is with the drilling feeds and speeds suggested.
The recommended cutting speed for HSS tools in mild steel is 1455 rpm for a 6mm drill. In SS (316 type) the peripheral speed drops to 728 rpm but with a feed of 0.128mm per rev. This is a heck of a feed, and is intended to avoid work hardening. I think with a hand held drill this'll feel as if your arms are being wrenched off.
For a phenomenally sophisticated feed/speed calculation tool (aimed mostly at CNC machining, but suitable for 'normal' use too), download Mike Rainey's 'ME Consultant' from http://bellsouthpwp.net/r/s/rsnmar/MEConsultantBeta1.zip. There are a few display problems with this Beta, but you may still find it useful.
Regards
Richard.
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Yes, use a holder for the drill and use it on a bench grinder. Screwfix do a drill sharpening jig for about £9 - I've got one and usually can get the drills ground OK.
I tend to sharpen my drills every 100mm or so of of steel I drill through. This usually means that the drills are in pretty good condition & don't have too many problems. There are gold coloured TiAlN coated drills coming onto the domestic market. These are pretty good in that the bits last longer than the normal ones for the first use. Unfortunately, when you sharpen them, you grind off the coating and the become just the same as all the rest.
Where I differ is with the drilling feeds and speeds suggested.
The recommended cutting speed for HSS tools in mild steel is 1455 rpm for a 6mm drill. In SS (316 type) the peripheral speed drops to 728 rpm but with a feed of 0.128mm per rev. This is a heck of a feed, and is intended to avoid work hardening. I think with a hand held drill this'll feel as if your arms are being wrenched off.
For a phenomenally sophisticated feed/speed calculation tool (aimed mostly at CNC machining, but suitable for 'normal' use too), download Mike Rainey's 'ME Consultant' from http://bellsouthpwp.net/r/s/rsnmar/MEConsultantBeta1.zip. There are a few display problems with this Beta, but you may still find it useful.
Regards
Richard.
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sailorman
Well-known member
it sounds that for a start u may have cheapo bits.
buy good quality ones run with some lubricant.
u can use a propriatry sharpening device but rty to get an engineer or similar to show u "free-hand" its not difficult just a Knack.
keep sharp & slow spd
<hr width=100% size=1><P ID="edit"><FONT SIZE=-1>Edited by sailorman on 17/11/2003 18:05 (server time).</FONT></P>
buy good quality ones run with some lubricant.
u can use a propriatry sharpening device but rty to get an engineer or similar to show u "free-hand" its not difficult just a Knack.
keep sharp & slow spd
<hr width=100% size=1><P ID="edit"><FONT SIZE=-1>Edited by sailorman on 17/11/2003 18:05 (server time).</FONT></P>
TheBoatman
New member
Buy good quality drills not the stuff you get in B&Q go to an engineers suppliers.
As for cutting speeds, to say fast or slow is not good enough every material has its optimum cutting speed, although slower is better than faster. Unfortunately with any h/held drill you can't control the speed properly.I've forgotten most of the cutting speeds now but for ordinary free cutting mild steel it's 60 feet/min. So in modern terms thats 18,000mm/min divided by curcum of drill (6mm D = 18mm C)
18,000 div by 18 = 1000 rpm.
For stainless its 20 feet /min
or 330 rpm for same size drill.
You might like to invest in an engineers pocket companion, fits in your top pocket and is packed full of cutting speeds drill sizes/conversions, metric threads, british threads tapping drill sizes etc.
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As for cutting speeds, to say fast or slow is not good enough every material has its optimum cutting speed, although slower is better than faster. Unfortunately with any h/held drill you can't control the speed properly.I've forgotten most of the cutting speeds now but for ordinary free cutting mild steel it's 60 feet/min. So in modern terms thats 18,000mm/min divided by curcum of drill (6mm D = 18mm C)
18,000 div by 18 = 1000 rpm.
For stainless its 20 feet /min
or 330 rpm for same size drill.
You might like to invest in an engineers pocket companion, fits in your top pocket and is packed full of cutting speeds drill sizes/conversions, metric threads, british threads tapping drill sizes etc.
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ArthurWood
New member
Are they so expensive that you can't buy a new one?
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mldpt
Member
One thing that doesnt seem to have been mentioned as well as lubricating while drilling a drill should allways be kept cool while grinding a tin of water handy and keep dipping the drill when grinding will stop it blueing and tempering.
Mike
<hr width=100% size=1>www.sailingforfun.co.uk
Mike
<hr width=100% size=1>www.sailingforfun.co.uk
richardandtracy
New member
HSS drills retain their heat treatment up to dull red heat - hence their name, high speed drilling gets them red hot. You'll only get real problems with HSS drills if they get so hot they start to spark - I did that once and managed to friction weld a drill in a hole. Was I peeved!
The older carbon steels loose their tempering at temperatures above 250C, well below red heat, and the idea of a water bath is valid for them.
Regards
Richard.
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The older carbon steels loose their tempering at temperatures above 250C, well below red heat, and the idea of a water bath is valid for them.
Regards
Richard.
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Avocet
Well-known member
I take it you're using them with a hand drill? If so, (especially "in-situ" it will be almost impossible to get enough force on the drill to feed thebit correctly. Even with lubricant mine do the same. In a pillar drill it's a completely different story. I think feed force is the single most important factor (although lubrication and cooling are important too). Modern electric drills always seem to turn far too fast and just make everything too hot!
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