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twist drill preservation


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here are some proven tips from me on longevity of twist drills

When you purchase a brand new drill take an Arkansaw stone or some light sand paper and gently stone the face of the drill or the lip when these drills are ground new they have microscopic slivers that tear into large imperfections when drilling.

Try if possible to drill into another piece of steel when drilling through a piece { NO NOT INTO YOUR DRILL PRESS TABLE OR YOUR VISE } and don't completely drill through that piece either.

One of the most detrimental things that happens to a drill is when you drill through is that little thin section right before the drill breaks through gets so hot it anneals the hardened drill , were blacksmiths we know that right.

Be sure you have the correct speed for drilling , a slower speed is always better than a higher speed, if you have doubts.

Keep good pressure on drill ,

Another dulling factor is a drill that dwells

If you are using cutting oils this even worsens the dulling process. If you are not pushing the drill, think of the honing process, that is what you are doing honig the cutting edge away. A couple drops of oil is all that is needed at entry.

A properly dressed twist drill in a blacksmith shop, for what blacksmiths usually cut, will never need replacing just minor touchups. i have dressed drills on the job and drilled thousands of holes in mild steel with out any maintenance .

if there is any interest in this subject i will expand

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A dwelling drill is one you are not applying enough pressure to in order to get it to bite. It will sit and grind (hone) itself until the tip is a round slag ball if you keep at it long enough. Even with good coolant, you have to keep steady presser on the bit.
I use cutting oil for coolant, with out it I will always burn up the tip on a drill long before I will with it. The drill press I am using is a 16 speed floor standing one and set on the lowest speed always. I use Marvel Mystery Oil and apply a squirt at the start then at the first hint of smoking afterwards.

Edited by NateDJ
Read the first post wrong first trip arround.
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wood is fine try using a very tight grain wood or even "nova ply"
i understand you can not always back your work up like drilling pipe or
on site eye beams , etc
but here is a grind that will minimise drill pulling when drill goes thru
and it lends itself for longer lasting , takes a slight more physical energy
but worth the expense for the results , recommended grind for brass also

grind the positive rake on the drill to nuetral rather than positive
rather than grind till you understand function , use a sharpening stone at first
a few swipes on the face is all you need
be careful not to wrap around to the margin of the drill
i will try to generate better pics on my cad system

drilling principles is one of the most important aspects of machining and
sometimes blacksmithing however somethings are overlooked

will expand


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  • 1 month later...

I realise this an old thread and I'm a newbie but I would love to work out how to sharpen twist bits. I know I can put an edge on just about anything else. By hand or with a gadget.
*VIDEO* Carl demonstrating the Spyderco Tri-angle Knife sharpener
But Twist bits, never.
When Grandad passed I picked up his collection of British twist bits. Rusted up so they have been in oil for near on 9years. But I still don't knoew how to sharpen them properly.

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Hi handy little book that you can get from bolt shops called
"Engineers Black Book 2nd edition"
It show different angles, lip clearance, for different types of material the 2nd edition comes with a drill point sharpening gauge.
book has heaps of handy imformation. There is a trouble shooting section also. See how you go

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  • 2 months later...

try this..wrap tape around the flutes..say 2 inches back..wrap it straight.now put your thumb at the end of tape.twist and roll the bit..now flip it and grab the tape on the other side...right at the same tape end...keeps the flutes square to each other...twist and roll.
and keep your feet planted..think of yourself as a machine.flowing motion.

Edited by fix
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The following bits come from heavy manufacturing useing Twist drils from 1/8" to 4".

A properly MACHINE fed twist drill will outlast a hand fed drill every time. So if you have a drill press with feed, look at the speeds and feeds chart in whatever manual you use and use the feed.

A properly sharped, and fed drill, with the correct speed, lubricated, will always outperform a hand fed, or dry or overspeed drill.

Take the time to look at the speed and feed charts and you will probably discover that most mordern drill press's of the "16 speed offshore type" may not turn slow enough for a drill of the rated size. A 5/8" HSS drill in a forging of mild steel should be turned at 366 RPM as a starting point. A feed of 0.004 to 0.007 is per rev is recommended. Cutting compound is reccomended. (Above from the Cleveland Twist Drill Co)

Waiting for the coolant to smoke may let the drill get hot enough to "Check" or micro crack.
With good practice flood coolant is used.

Of course in Cast iron, the practice is usually dry. In stainless, the use of coolant is required, and feed MUST be maintained to prevent workhardening of the material.

For small shop use, in non-production, coolant is usually pretty messy and a bother, and unless really needed, I use a stick lube. Does not get rank, leak or freeze and works fairly well.

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  • 1 month later...

I relize this is an old thread but, the subject is still an important one so I'll lend my hand and see if I can help.
Describing the drill sharpening prosses in writen words is not easy and I am not able to supply pictures at this time but, here goes.
First you need to dress your grinding wheel so it is flat and square. The star wheel dressers work better than the dressing sticks.
Next you will need to have a secure place to rest your right hand so, the tool rest of your grinder must be in good shape.
As far as I know everybody supports the drill with the right hand and does the motion with the left. I have never seen any one do it differantly in the nearly 30 years I have been a machineist.
Be sure to have a container of clean water at hand so as to constantly cool the drill as you grind.

When you sharpen a drill you must put the same angel on bothe flutes and they must be the same length or the drill will cut over size or not at all.
The area behind the "cutting edge" must fall away so that no part of it is higher than the lips (cutting edge)

The motion of the left hand is what does the grinding correctly. It is not impossible to learn and once masterd will never be forgoten but, it is nearly impossible to describe without a demonsrtation.
Take up a new, unused drill in the right hand between the thumb and for finger and hold it in front of you so the lips are parallel to you (pointing to the left and right) with about a 1/2-3/4 " sticking out from your fingers.
Now bring it to the face of the grinding wheel (leave it TURNED OFF for now) and see how the shank has to be swung to the left and the drill has to be turned so that the cutting lips are parallel to the wheel face and parallel to the tool rest. If your toolrest is bent then you must hold the drill inline with the axis of the grinder spindle.
This is the starting position.

The drill pivots on the fingers of the right hand and is swung in two directions at once by the left hand so that the heel is made lower than the front edge.
The left hand will guide the shank of the drill in a downward arc and a clockwise arc at the same time in order to achieve this. This is as seen from above and back a step from the ginder.
So now with your drill in hand practice this movment untill you can match the profile of the factory fresh point before turning on the grinder.
Remember that the point must be sharpend evenly on bothe sides and the same angel on bothe sides.
Once you get into the grinding position stay that way untill you are done, don' t stop to admire your work or you will forget wich flute you started on or if you ground the same number of times on bothe.
I always take 3 passes on each side so I know I have taken an equel amount from bothe sides and count to myself "123 flip 456" and so on, watching carefully to keep the same angel on bothe sides as I flip from one side to the next.
If you wait untill your drill is really dull or damaged befor you re-sharpen you will have a much more difficult time of it and the drilling will go much slower. If you try to push even a slightly dull drill through stainless and it starts to "squeel" you must stop and re-sharpen or you will end up getting the work hot and it will "work harden" so that you will never get an ordinary drill through it.

When the drill is sharpend CORRECTLY it will give off two identicall chips from bothe flutes and the hole should just catch the drill and keep it from falling through (size on size)
A couple of common mistakes when begining the grind are to "dwell" or hesitate slightly at the lip and cause it to always be below the heel. If this happens then the heel will touch the work befor the cutting edge and prevent it from cutting.
Also, be sure to take only as much off the heel as needed for clearance. Swinging too far around or makeing too much of a downward arc will cause you to run into the other cutting edge around the back side and ruin your drill.
Practice makes perfect. When I was first taught how to sharpen drills my old shop master handed me a coffe can full of dull and broken drills and took me to the grinder and described and demonstraighted on a handfull of drills and then tested each one untill it would "catch" in the same hole it had just drilled. He then watched me do a few and made some corrections to me and, then I spent the next two days sharpening and re-pointing drills (there were two more full cans in the tool crib)
Again, catch the drill befor it gets too dull. Then it may only need a quick touch up and back to work instead of a more difficault sharpening job that might be better to just replace the drill untill you have the time to devote to it.

As Ptree says above, the stick wax works very well and is safe for use around little kids or pets. Lard oil works well too but, hardends up after it gets hot so clean it off when you're done.

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