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Thread: Punch 12mm hole in 8-10mm steel
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21st Dec 2019, 09:07 PM #76
Hey Gazza,
A little tip for you ! Use a permanent marker to colour the end of the drill. Now you will be able to see where you are taking off metal.Best Regards:
Baron J.
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21st Dec 2019, 09:56 PM #77
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21st Dec 2019, 10:41 PM #78Most Valued Member
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Baron that whole tip was ground in two goes one each side
Gavin i donno its only a simple little machine if u put a little bit of pressure on the hand the drill stops completly i donno if this is a fail safe mode or something but i am pretty sure it should be ok with the piece being clamped down and eye protection on
What more could happen? As in the video when it spun the job the motor cut out, i know it was stupid holding the piece i get that what i didnt expect was the drill to bite just as it came thru the other side and it did but at lease the next one will be do with better practices
But honestly i dont think i need the whole kit boots, pants,gloves, face sheild, long sleeve shirt we all take risks in live for me i dont really see a hobby style drill press a hazard yes it can swin metal but the bit i was drilling was 16cm i doubt that would clean snap a 12mm bit and throw it across the room
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21st Dec 2019, 10:52 PM #79Gear expert in training
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21st Dec 2019, 11:49 PM #80Most Valued Member
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Gazza if you hold and look at your drills as BaronJ has shown in his link, from Harold Hall this will surely help. DrShBasics1.pdf, if you can print this out, I'm certain it will help you understand the geometries of a drill bit.
Looking at your pic jpg 20191221_191623. where you've gone wrong is that you've ground the back of the cutting edge into the opposite side cutting edge. If you sharpen the first 2 Facets (cutting edges), you should be able to ressurect that drill bit.
The reason when you were trying to drill, that the angle was wobbling around, it had a reverse effect on the drill bit, instead of sitting in there to drill, it was wanting to climb out.
There's no real need to reduce the WEB of the drill unless it's a large bit, possibly over 20mm, or that the drill bit has been broken up near the top and is needed to be salvaged.
I hope you can understand what I'm trying to get at.
KrynTo grow old is mandatory, growing up is optional.
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22nd Dec 2019, 12:25 AM #81
I am siding with Kyrn on this.
To my eye the cutting edge is lower than the clearance edge. It may the camera angle, but it sure looks like the grind slopes DOWN to the cutting edge with the clearance angle grind line being the highest point.
drill bit cutting edges.png
Grahame
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22nd Dec 2019, 02:08 AM #82Most Valued Member
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Thanks for noting that guys i just grabbed the bit from the shed as im usually up all hours of the night came back inside trying to take a picture and dropped it on hard tiles, game over bugger
Anyhow now i need a new one i still have i think a 14mm bit in the shed but its a cheap gold plated bit i can still use that to practice
I cant really understand that diagram above but i do understand the sharpenig process and about the rasor front cutting edges and the back cut needs to be lower or it will bind and heat up,
I see from the bot i just dropped one cutting edge had 2 grinds the other cutting edge had 4 grinds when i say grinds i mean as in 4 surfaces instead of 1 each side
I have been watching youtube and using 2 nuts together to get the 120-135 degree and both sides equally cut in width i just need practice
Also im not good with knowing my angles hence i used the two nuts but the back cut i think its called is there but it seems like it was only a few degrees and not the 10 degrees its suppose to be
Maybe i should mess around with the broken bit
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22nd Dec 2019, 02:38 AM #83
Hi Gazza, Guys,
That drill bit snapped like glass, now imagine what would have happened if it did that when it grabbed in the workpiece.
I see from the bot i just dropped one cutting edge had 2 grinds the other cutting edge had 4 grinds when i say grinds i mean as in 4 surfaces instead of 1 each side
I have been watching youtube and using 2 nuts together to get the 120-135 degree and both sides equally cut in width i just need practice
Maybe i should mess around with the broken bitBest Regards:
Baron J.
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22nd Dec 2019, 08:15 AM #84Philomath in training
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These photos were taken with a specially trained stunt drill. No grinding wheels were hurt/ turned on during this production, but it should illustrate what you are trying to do.
This drill could do with a regrind as I notice there is a chip out of it but that will happen once it is late enough not to disturb the neighbours.
firstly the geometry you are trying to achieve -
The first photo shows the relief as the drill slopes away from the cutting edge. You don't need much - just enough so that as the drill does not rub and can bite into the material being drilled. Too much and the edge becomes weak. (Second photo) Both cutting edges should be around the same length. If they are not the drill may tend to cut oversize as the cutting forces balance out. The chisel point where the two ground surfaces meet should be well defined as that scrapes away material at the bottom of the hole for the cutting edges to more efficiently cut. That is why a pilot drill only needs to be that big - you are just making life easier for that chisel point.
P1040713.JPG P1040714.JPG
If you want to show your results, these two views are the critical ones.
The action to achieve this is simple but can take practice. First photo - the bit is positioned on the wheel so that the edge is parallel with the wheel surface. Some people like to position this 'above' the wheel centreline, as it helps put the relief on the grind but as long as you are not below you will get a result. You are sharpening the bit by rotating it but you are also swinging it to the side. The second photo shows the drill swung away (blue axis) from the original position (red axis). Light cuts - if you go too hard, the chances are that you produce a non-symmetric grind as well as blue the drill. As John says, use some texta or similar to mark the end before grinding, especially if it is chipped/ damaged. That way you will know when you have full clean up.
P1040711.JPG P1040712.JPG
The sideways movement is not much; all you are doing is putting that relief in there as you grind. I learnt this method from watching a Darex M5 drill sharpener work. If you don't swing to one side, the shape you get is still conical but there is no relief, so harder to drill the hole.
The tips are the most critical - they are moving at the fastest speed and are less well supported. The drill have used for the photos with that small chip would not cut properly and in a worst case situation, rub, over heat and possibly further degrade the bit and/ or ruin the hole. If you are drilling a work hardening material (SS for example) with a blunt or damaged bit, the rubbing is enough to harden it up so that very quickly, not even a properly sharpened bit will salvage the hole.
Any further grinding (Point splitting, web thinning) is 'nice to have' stuff - the operations I've outlined above will give you an 'off hand' sharpened bit. Not as accurate as a jig sharpened bit, but enough to work. I would suggest practicing with a bit between 6 and 8mm until you are consistant.
Further observation - if your drills snap like that just from being dropped, I would suggest the head treatment is not quite right.
MichaelLast edited by Michael G; 22nd Dec 2019 at 08:17 AM. Reason: spelling
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22nd Dec 2019, 08:18 AM #85Most Valued Member
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Absolutely DONOT wear gloves whilst using a bench grinder, gloves and rotating machines don’t mix regardless of how tightly they fit.
https://m.youtube.com/watch?v=r8oORR6jyh8
This will help explain some of the science and geometry behind grinding a drill bit, before you roll your eyes it’s reasonably entertaining also..
With regard to your drill press, check the pulleys are tight on the shafts, the belt is tight on the pulleys, the chuck is tight on the taper (I had to Loctite mine). Might also pay to take the belt off and see if the bearings in the motor and the head have any slop. Those drills are built to a price, there is definitely no clutch or over torque safety on them.
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22nd Dec 2019, 10:18 AM #86Gear expert in training
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Never ever wear gloves near spinning things
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22nd Dec 2019, 04:57 PM #87Most Valued Member
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Thanks for all the help, i will be buying either the milwakee helix drill bit set or the sutton drill bit set but i need to be careful as that bit i dropped last night and snapped was a $23 sutton drill bit
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22nd Dec 2019, 06:17 PM #88Most Valued Member
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Are there any problems using hex drill bits on a lathe and drill press? https://www.tradetools.com/product-r...oaApbGEALw_wcB
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22nd Dec 2019, 08:38 PM #89
Hi Guys,
In hindsight, It was probably not a good idea to suggest that Gazza used gloves, particularly in view of his inexperience. I do occasionally wear gloves, usually those vinyl ones. They will rip very easily.Best Regards:
Baron J.
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22nd Dec 2019, 10:27 PM #90Most Valued Member
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The hex drills are aimed at lazy tradies that just want to use a 1/4 impact for everything. Technically nothing to stop you using them, the hex will provide a non slip engagement in the chuck, but you pay a premium for it over regular twist drills. You are also at reduced shank at much smaller sizes to a much smaller reduction size. Reduced shank in twist drills is generally only a reduction to 3/8 to accommodate a 3/8 chuck or to 1/2 in sizes bigger than 13mm or 1/2” again to allow larger drills in a smaller chuck. They’ll work for you, but if I were considering the purchase I probably wouldn’t.
TLDR yes they will work, but there are better options.
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