stuart little
Established Member
That's my way of looking at it, never wear rings, watches, or ties when using ANY machine, including the likes of hand drills!
Large drill bits - why so long?
- Thread starter GrahamRounce
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Having drilled tens of thousands of holes in metal on a lathe I can tell you that high speed vibration when drilling (assuming everything is being held tightly) is caused by a blunt drill usually one lip being blunt and the other sharp.
I have used gun drills over 3 feet long with no noticeable vibration.
If you start "off centre" the drill will wobble but it won't "vibrate".
Vibration is indicative of "chatter" and chatter comes when two hard things collide and one of the hard things doesn't cut the other hard thing.
You can centre drill and go straight for a 12mm drill. Its not the kindest thing to do to the drill and in very hard materials (like 316L) it will significantly shorten drill life.
But you can do it and there won't be any vibration.
Ideally you'd want to clear the chisel area of the 12mm drill by piloting with a 1/8th drill initially.
I dunk the first inch or so of all my drills in cutting grease before starting to cut.
A proper suds system would be nice but its messy and I only use mine as an absolutely last resort for difficult to machine materials.
I have used gun drills over 3 feet long with no noticeable vibration.
If you start "off centre" the drill will wobble but it won't "vibrate".
Vibration is indicative of "chatter" and chatter comes when two hard things collide and one of the hard things doesn't cut the other hard thing.
You can centre drill and go straight for a 12mm drill. Its not the kindest thing to do to the drill and in very hard materials (like 316L) it will significantly shorten drill life.
But you can do it and there won't be any vibration.
Ideally you'd want to clear the chisel area of the 12mm drill by piloting with a 1/8th drill initially.
I dunk the first inch or so of all my drills in cutting grease before starting to cut.
A proper suds system would be nice but its messy and I only use mine as an absolutely last resort for difficult to machine materials.
I'm a big fan of cutting edge, I think he does some of the best machining videos on YouTube currently. He has said before - he works to a appropriate to the industry he's working in. No, the centre hole wasn't concentric but it was for the top of an overgrown bottle jack to sit in. It didn't NEED to be concentric, so he didn't waste time making it so. Obviously if it was a critical part he'd spend the time. The man is in business to get parts out of the door quickly, not chase thousandths for something that's going to get battered by a ham fisted mechanic next week.
As mentioned by others "blacksmiths drills" drill speed is the key, plenty of info on net and youtube, as too coolant lube and workpiec firmly held.
Surprised no one has mentioned the most obvious reason why stepping up through multiple sizes of drill is not a good practice. If you do this all the cutting is being done by a very narrow portion of the cutting surface, around the outer perimeter. This will cause it to overheat very quickly, affecting the accuracy of the hole, and drastically reducing the life of the bit.
Official word on the subject:
https://www.hse.gov.uk/engineering/lathes.htm
I am posting it for information only.
Please could you advise what the key feature of a blacksmith's drill is that makes it suitable.
To assist your thought process, please peruse these two offerings and be specific in your reply of the differences:
https://www.cutwel.co.uk/13mm-hss-s...th-s-drill-08610-series-presto-0861013-0-12-2
https://www.cutwel.co.uk/hole-makin...lack-oxide-finish-hss-jobber-drill-d1105-yg-1
Ttrees
Iroko loco!
Since the heading is sorta on topic, might as well ask how easy it is to find extra long bits,
or if someone can tell me what the correct terminology for these is?
Great for testing allsorts and whatnot.
Cheers
Tom
or if someone can tell me what the correct terminology for these is?
Great for testing allsorts and whatnot.
Cheers
Tom
As I said, mentioned by others blacksmiths drills though you made no comment on! The op stated "I've searched for shorter, stubbier ones" which to me indicates they want a smaller drill bit, the blacksmiths drill meets their criteria for job in hand.
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Ttrees
Iroko loco!
Liddle do have blacksmiths drills up to quite a large diameter,
sold frequently, and probably often left over nearing discount, like in my local.
Not found issue with the few packs of them.
Great value I've got from them, aswell as a box of Sliverline ones.
sold frequently, and probably often left over nearing discount, like in my local.
Not found issue with the few packs of them.
Great value I've got from them, aswell as a box of Sliverline ones.
guineafowl21
Established Member
My thoughts too - blacksmith drills are shorter, which is what the OP was searching for.
I wouldn't think a blacksmith's bit and a Jacob's chuck any shorter than a MT bit.
UK drills one company that does long bits, there are many others.
Long series or extra long series.... Be prepared to pay through the nose if you want larger sizes....
I use the emery strip , just making sure it's long enough that your hands are nowhere near the chuck. Also often stick a piece to a length of old smooth belt, old car timing belts work well for this as well. Held as you describe.
For internal work just cut a slot in a piece of bar to take the end of a strip and then wrap it round the bar, making sure you wrap it in the correct direction so when it meets the work of is being pulled in the same direction it is wound. Or if you are rich buy ready made drums of an appropriate size 
I think the issue is that people seem to find anything involving fairly big machines sexy for some reason. As Deema says lots of things wrong with the way he has done that, certainly not a good example.
J-G
Established Member
I suspect that most of the negative comments (certainly from me!) come from the fact that he takes particular care of protecting the outside of the billet so as to preserve its integrity but makes no reference to the fact that the concentricity it really quite secondary. Had he mentioned it, I would probably not have been quite so scathing.
Im in the camp of do it properly to the best of your ability all of the time, it’s then second nature and requires no thought. Practice makes perfect. There are a number of reasons why you always check concentricity, the most important for ground stock is that if it isn’t concentric then it’s not held by the jaws securely and you don’t want that large heavy lump of steel coming at you. He faced the stock after drilling, that’s just lack of experience / knowledge and thought. He should have faced then drilled, just changed the sequence around of what he did. Things like that indicate a lack of training, knowledge and or experience.
I’d suggest watching mrpete222 on uTube for a better approach to machining.
I’d suggest watching mrpete222 on uTube for a better approach to machining.
Another point was his use of the belt sander, quite apart from the way he used the thin strip of emery, which made me wince. Very basic principle that when you bring a rotating tool like a grinder into contact with a rotating workpiece, they should be travelling in opposite directions. So he should have had the machine running in reverse when using that tool. Some may view that as pedantic, but it is just an example of sloppy/lazy practice, nothing to do with "getting the job out of the door".
