# 10mm holes in 8mm mild steel



## DigitalM

Noob metalworking question from an intermediate woodworker...

I want to make some 10mm holes for bolts in some 8mm thick mild steel bar I have, for use as brackets. I've got a good pillar drill. I don't have a drill vice. Maybe I should invest in one of those. 

Should I just go at it with a 10mm drill bit or get myself a step drill like I saw in a youtube video. I won't be making holes all day long for days and days (I need to make 8 holes), but I may need to do something similar in future, I just don't need to be buying top of the range and spending a fortune without good reason. 

Any advice welcome, along with any product recommendations.


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## bourbon

The way I approach these jobs is to Put a centre punch where I need the hole, drill a smaller maybe 3mm hole Putting 3-1 oil on the flutes of the drill. Get the speed of the drill as slow as you can get it. then up the size to 6mm, plenty of oil again, then the 10mm. You will need a vice to hold it as it will have a tendency to snatch.


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## Sideways

I would pilot drill each hole with something like a 3 or possibly 4mm then push the 10mm straight through.
The 10mm has a fair sized web in the middle of the drill between the flutes. A pilot drill of about that size will make it much easier for the 10mm to go through and the pilot will also help to stop it from wandering off until the full 10mm diameter is cutting.

I've used the exact method to push 14mm holes through 10mm plate using a handheld drill.


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## Alpha-Dave

I would go centre-punch, then 4-6-10 mm standard HSS drill bits, with cutting oil. You can drill faster with the smaller bits, I would go ~1,000 rpm for 4 and 6, then closer to 500 rpm for 10 mm.

I would always use a vice for this sort of work-holding; if it grabs and swings the bar around at 500 rpm you may regret it quickly if you can’t move your hands out of the way in less than 0.12 seconds. 

Sharp drill bits are a joy to use, dull ones are a hazard; either learn to sharpen on a grindstone with a jig, or buy cheap semi-disposable ones for a fresh-edge when you need it. I probably sharpen after 20-40 holes depending on what I have been drilling.


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## Jameshow

If you don't have a vice but some scraps of 18mm plywood or MDF you can lock the piece into plywood with small offcuts all-round screwed in with small screws, you can then g clamp or bolt the ply to your pillar drill table.


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## bp122

What has been said above. 

Larger the drill bit you use, more chance of excessive heat build up, drill bit wander and a messier hole. 

Just the other day I had to drill a few 8mm holes. It is in fact quicker and easier to do it in smaller steps than to gun it with a larger bit. 

Also, easy to blunt the drill bit.

So:
1. Invest in a drill vice (worth it) or at least a drilling block
2. Use oil while cutting (use something with a long snout to reach the target area safely)
3. Do it in steps
4. Don't wear loose clothing /gloves etc
5. Debur the holes.
6. Don't forget eye protection (spiral scrap just flies off)


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## Sporky McGuffin

A drill vice is well worth having.


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## --Tom--

Without a vice clamp something to the table to butt the piece up against. Will stop it windmilling if the steel tries to catch.

4mm then 10mm will be fine, slow the speed down and use some cutting lubricant


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## pe2dave

Think of your fingers, bruised and cut (or worse) trying to hold on to some sharp metal that the drill bit grabbed?
As others, a drill vice (cheap / nasty / second hand) will reward you without you knowing it.


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## Jameshow

I'd get a couple of cobat bits too. 

Makes for a much more than effective drilling experience!


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## redhunter350

Have a look at this clamp Axminster Drill Clamps a very useful tool instead of or in addition to a vice. One of my most used tools now some 50 years old ! As far as drilling it’s pretty much all been said, either use a pilot hole or thin the point and drill straight through with a HSS 10mm drill , buy a good quality set of drills from Dormer, Ghuring or similar, not all but many of the economically priced sets will not serve you well — false economy !


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## MorrisWoodman12

Yes to most of the advice above especially as slow as possible with the 10mm bit. I'd probably pilot with a drill just a little bigger than the 10mm bit's root so I guess about 4mm: that helps keep the 10mm centred. Plus it's often easier to drill 10mm halfway through then start again from the other side. Stops the horrendous snagging as the bit comes through. 



Jameshow said:


> I'd get a couple of cobat bits too.
> 
> Makes for a much more than effective drilling experience!


But proper 5% cobalt bits not just 'cobalt' described bits as this just a coating that comes off quite quickly. Personally I would simply use a 'normal' HSS bit.
Hope this is of some help. 
Martin


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## MARK.B.

Excellent advice already given  i would add that it is easier to drill the holes in your brackets before bending to the required shape . I have a 2" scar on my left hand that was caused by a chunk of metal not held securely by a vice or clamping in place  trust me when i say it hurts A LOT, i was lucky not to have caused any permanent damage , i now have a vice and it get used every time


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## DigitalM

Thanks everyone! All very helpful. I'll get on with it!


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## Sandyn

Definitely agree, get a good sized vice which can be clamped to the drill table. Get good drills.
I normally use a centre drill to create the pilot holes. If you are drilling repeat holes in a line, centre the pilot drill on the first hole with the piece clamped in the vice, supported by a narrower bit of wood so you can drill through with the 10mm. Clamp the vice to the table, then re-check centre. In this way, it makes all the other holes already aligned in one dimension. My trusty drill chart says 600-1000 for 10mm in steel. I use cutting fluid or oil. I don't go up through the sizes. I find the possibility of drill snatch increases if you are drilling in small increments, especially with larger drills.


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## sploo

Largely just echoing others' comments, but agreed: work holding (i.e. a vice) is important (bits can "grab", and a work piece windmilling around on a drill press is really dangerous).

Don't get greedy with metal drilling; use plenty of lubricant (3-in-1 oil, or something specifically designed for the job e.g. CT-90) as it helps prolong bit life. Heat is a killer for drill bits.

Cobalt bits are great, and in smaller diameters they're not expensive.

Centre punch, then work your way up with 4-6-8-10mm bits.

You'll find that a sharp 4mm cobalt bit, with lube, will go through mild steel really easily, then the larger sizes are not too bad.


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## Sideways

This has been a popular thread so I'll risk deflecting it slightly to ask a related question.
I find when drilling larger holes into metal that working up through the sizes has a very real risk that a larger drill will grab. The bit will carve into the workpiece like a corkscrew and jam. For this reason I wouldn't drill 4,6,8,10 in turn. No need and actually more likely to cause a problem.

This is much less a problem if the work is in a vice and the job being done with a drill press but that isn't always possible or convenient. There are plenty of workpieces too big to fit in a vice or even be clamped to a drill press table. Other times when a hand drill is the only option.

The root cause is that the spiral of the drill bit is effectively a VERY coarse thread and given half a chance it will bite and try to screw itself into the previous hole. Clamped in a drill press you might be able to hold a drill back. With a hand drill or an unsecured workpiece, even a heavy or large one, you don't have enough control.

If a single pilot hole is used, around the size of the web of the bit, the chances of the large finished size drill digging in is very much less in my experience.

Has anyone else noticed the same issue ?


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## pe2dave

Sideways said:


> This has been a popular thread so I'll risk deflecting it slightly to ask a related question.
> I find when drilling larger holes into metal that working up through the sizes has a very real risk that a larger drill will grab. The bit will carve into the workpiece like a corkscrew and jam. For this reason I wouldn't drill 4,6,8,10 in turn. No need and actually more likely to cause a problem.
> 
> 
> Has anyone else noticed the same issue ?


 Yes, though I think 2mm increments might make this effect worse (especially if you have a morse taper chuck?).
Yes, pilot (4mm?) then straight in with 10, though going back from the other side sounds like solid advice.


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## Sporky McGuffin

Likewise - I think it's also down to the wrong feed rate and rpm.

Step drills don't seem to have the issue.


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## AES

@Sideways. Agree with you in part. Myself, after a centre pop mark, I'd certainly start off with a centre drill (Slocombe) chosen to be approx the same dia as the web of the 10 mm drill. (If no Slocombe, then an ordinary jobbers drill with dia as per the web of the 10 mm final drill). Personally I'd never bother with going up in steps after the first drill (such as 4-6-8) as particularly with good quality modern drills (even "just" HSS), the edges of the swarf clearance spirals are quite hard and quite sharp and will "dig in like a screw thread" exactly as you describe).

If I may, I'd also point out that the term "big" when describing a drill is entirely relative - for a watchmaker, 10 mm is gigantic, to a ship yard worker, tiny. OK, those are ridiculous examples I realise, but for the average hobby shop with a pillar drill and a decent set of drills, anything up to about 14 or 15 mm isn't SO large, especially if only drilling MS. Provided the work is held securely - when possible, a drill vice as you suggest, otherwise take other steps, like a ratchet strap or something - and provided rpm is well down and feed is firm/steady and not excessive, and providing a lubricant is used, drilling 10 mm holes into 8 mm MS plate is "easy peasy" really. I can understand a newbie having doubts when first looking at a "thick" chunk of steel and a "big" drill, but with the above caveats, no problem really.

But YES, building "your own screw thread" as you describe above while drilling sheet/plate MS (especially the thinner stuff) CAN be painful on the hands/arms until! And do NOT try it on thin sheet ali - you become the inventor of the instant rotary razor blade. DAMHIKT!


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## Sideways

Sporky McGuffin said:


> Step drills don't seem to have the issue.


That totally makes sense. Step drills - mine at least - don't have the "screw" that causes the problem. Personally I keep those for plastic and thin sheet only to ensure they always cut a very clean hole, and the steps of mine wouldn't handle 10mm plate unless I could get access from both sides.


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## Sporky McGuffin

That's a good point - I think my step drills might do 4mm at most.


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## Alpha-Dave

I think that I’m much more likely to get the drill to catch as it exits the material than any point during the main drilling, something to do with the material thinning, and the drill the screwing in to the remaining material. Therefore I often put a block of mdf or the offcut under the workpiece (but still in the vice), that’s also true for drilling thin sheet metal, but then I would prefer a hole-saw or punch depending on the hole size.

Edit: actually, the ‘worst’ catch I ever had was centre drilling a rod of ebonite (vulcanised rubber) for a pen blank; the drill’s heat softened the rubber, which caused more friction, more heat, etc and in a fraction of a second it had gone an additional couple of cm in to the blank, which the cooled and tightly held the bit. Took ages to separate the two.


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## Jameshow

Alpha-Dave said:


> I think that I’m much more likely to get the drill to catch as it exits the material than any point during the main drilling, something to do with the material thinning, and the drill the screwing in to the remaining material. Therefore I often put a block of mdf or the offcut under the workpiece (but still in the vice), that’s also true for drilling thin sheet metal, but then I would prefer a hole-saw or punch depending on the hole size.
> 
> Edit: actually, the ‘worst’ catch I ever had was centre drilling a rod of ebonite (vulcanised rubber) for a pen blank; the drill’s heat softened the rubber, which caused more friction, more heat, etc and in a fraction of a second it had gone an additional couple of cm in to the blank, which the cooled and tightly held the bit. Took ages to separate the two.


Worst material I have drilled is lead the drill went in and the lead heated and moulded around it and before I realised what was going on snap!! 
Only when I continuously pulled out did it not heat up!!!


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## Fergie 307

Always put a piece of scrap wood underneath so the drill doesn't catch on the way out. You will get a much neater exit to the hole. And an old trick for drilling large truly round holes neatly in thin metal with a normal twist drill is to place a piece of linen or similar cloth scrap over the metal and drill through it. The piece of cloth wants to be about twice the size of the eventual hole. You just place it on the surface and drill through so the cloth wraps around the end of the bit as it goes in. No idea why it works but it does.


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## AES

Fergie 307 said:


> Always put a piece of scrap wood underneath so the drill doesn't catch on the way out. You will get a much neater exit to the hole. And an old trick for drilling large truly round holes neatly in thin metal with a normal twist drill is to place a piece of linen or similar cloth scrap over the metal and drill through it. The piece of cloth wants to be about twice the size of the eventual hole. You just place it on the surface and drill through so the cloth wraps around the end of the bit as it goes in. No idea why it works but it does.




Well that's a new one on me, thanks. I must try it sometime.


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## Sideways

Alpha-Dave said:


> Edit: actually, the ‘worst’ catch I ever had was centre drilling a rod of ebonite (vulcanised rubber) for a pen blank...


Me too.
I melted a brand new drill into one of my first ever acrylic blanks. I didn't even try to separate them !
Lesson learnt


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## Jameshow

Fergie 307 said:


> Always put a piece of scrap wood underneath so the drill doesn't catch on the way out. You will get a much neater exit to the hole. And an old trick for drilling large truly round holes neatly in thin metal with a normal twist drill is to place a piece of linen or similar cloth scrap over the metal and drill through it. The piece of cloth wants to be about twice the size of the eventual hole. You just place it on the surface and drill through so the cloth wraps around the end of the bit as it goes in. No idea why it works but it does.


I've sandwiched thin metal between two sheets of plywood and drilled through both!


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## AES

Jameshow said:


> I've sandwiched thin metal between two sheets of plywood and drilled through both!



Yup, that works well too (and ditto BTW, for cutting out thin sheet metal on the scroll saw).


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## baldkev

Invest in some quality bits. Ive got bosch cobalt which are ok, and some very good irwin titanium bits. Also have some metabo hss ( not good )


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## Beanwood

I asked almost exactly this quetion on a mig-welding forum 

Mine was actually drilling a 7mm blind hole in an arbor press ram, so I could cut an 8mm screw thread.

In summary - drop your drill speed right down (500 RPM?). Drill a small pilot hole (3-4mm sounds right) UNLESS you're using a good quality split point drill bit. It seems (And I tried it in order to prove it to myself) split point drill bits don't really like a pilot hole.

I also bought some CT-90, and honestly - it was worth the money in my view.


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## Fergie 307

Sideways said:


> That totally makes sense. Step drills - mine at least - don't have the "screw" that causes the problem. Personally I keep those for plastic and thin sheet only to ensure they always cut a very clean hole, and the steps of mine wouldn't handle 10mm plate unless I could get access from both sides.





Sideways said:


> This has been a popular thread so I'll risk deflecting it slightly to ask a related question.
> I find when drilling larger holes into metal that working up through the sizes has a very real risk that a larger drill will grab. The bit will carve into the workpiece like a corkscrew and jam. For this reason I wouldn't drill 4,6,8,10 in turn. No need and actually more likely to cause a problem.
> 
> This is much less a problem if the work is in a vice and the job being done with a drill press but that isn't always possible or convenient. There are plenty of workpieces too big to fit in a vice or even be clamped to a drill press table. Other times when a hand drill is the only option.
> 
> The root cause is that the spiral of the drill bit is effectively a VERY coarse thread and given half a chance it will bite and try to screw itself into the previous hole. Clamped in a drill press you might be able to hold a drill back. With a hand drill or an unsecured workpiece, even a heavy or large one, you don't have enough control.
> 
> If a single pilot hole is used, around the size of the web of the bit, the chances of the large finished size drill digging in is very much less in my experience.
> 
> Has anyone else noticed the same issue ?


I think the problem is if you go from say 8 to 10 mm then all the cutting is being done at the very edge of the flute, this then becomes very hot, more likely to jam and ultimately blunts the drill. As a rule of thumb I would never drill the pilot hole more than half the size of the bit you intend to use to finish the hole, and probably a bit less of the material is very thick. So in this case I would agree with 4mm as probably the ideal size.


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## Fergie 307

AES said:


> Well that's a new one on me, thanks. I must try it sometime.


 found this video of a guy demonstrating it.


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## Jameshow

baldkev said:


> Invest in some quality bits. Ive got bosch cobalt which are ok, and some very good irwin titanium bits. Also have some metabo hss ( not good )


I got 100 bits for £10 off eBay - never again!!!


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## emlclcy

i had lots of 10mm holes to drill in the top of a welding table i made so i hired a mag drill. it has a magnetic base and uses special cutters that drill the hole in one go with oil fed down the middle of the cutter. i was so impressed with it i bought it and have used it many times since


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## MorrisWoodman12

Jameshow said:


> I got 100 bits for £10 off eBay - never again!!!


I was drilling stainless steel. Knew it would be hard going so bought a pack of drills from Homebase.  Never again. Some of them even had the rake on the bit ground the wrong way. 
Have drilled SS several times successfully since, just gone slow with plenty of cutting fluid.
Buy good, buy once.
Martin


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## MorrisWoodman12

Fergie 307 said:


> found this video of a guy demonstrating it.



How can that ever work?


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## AES

Fergie 307 said:


> found this video of a guy demonstrating it.





Well, I've watched it now. Seems to work very well, though I've no idea how/why. Must try it myself sometime (I actually do have a similar job coming up soon, will let you all know how I get on). Thanks.


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## redhunter350

Yep oldest struck in the book works every time, we used a small piece of fine emery cloth, also works if you are getting chatter with a countersink. Why ???? No idea it just does


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## Jameshow

MorrisWoodman12 said:


> I was drilling stainless steel. Knew it would be hard going so bought a pack of drills from Homebase.  Never again. Some of them even had the rake on the bit ground the wrong way.
> Have drilled SS several times successfully since, just gone slow with plenty of cutting fluid.
> Buy good, buy once.
> Martin


I was drilling bolt holes for a camper van 8mm each X 20?? 

I then went to 4/8mm cobat drill bits - fantastic!!


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## Alpha-Dave

Fergie 307 said:


> found this video of a guy demonstrating it.




Isn’t the problem that he’s drilling into the support structure of the vice? Second time around he has removed enough of the jaw to let the drill pass through.


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## Fergie 307

If you have ever tried drilling a hole that size in thin sheet with a normal drill bit, you tend to get a very irregular hole, often much worse than in the first example in the video. The cloth trick gives you neat round holes every time. No idea why it works, seems completely counter intuitive, but it does. I was shown this years ago by my dad.


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## Threadedpipe

not read all the replies before but after drilling literally thousands of holes in steel over the years use a dot punch then either use a 4mm then 8 and finally 10mm drill bits or 5mm then 10mm if 3 bits is too much work 
drill bits on steel don't waste your time on cheap drills I would use dormer and only dormer tried the cheap ones they are not worth it don't see big brand and think must be good i.e. Bosch drills in my eyes have a special place to be stored - the rubbish bin if you get resistance don't keep pushing let the drill do the work


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## Limey Lurker

I, too, have drilled many, many holes, in every common metal. I can't imagine an occasion where I'd have used a pilot hole to drill a 10mm hole in 8mm mild steel. I served an apprenticeship as a toolmaker.


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## Fergie 307

I think to be fair it's about speed, if you have a good pillar drill that will go down to a suitably slow speed, then I agree a pilot hole is quite unnecessary. The video I posted is a good example, clearly a fairly heavy duty machine with auto feed, and running at something like 100rpm, although he is using a pilot hole, probably owing to the fact that the material is pretty thin. But I think most people on here are probably using kit designed primarily for woodworking, so may have 500 or so rpm as their slowest speed, in which case a pilot hole is a good idea. You could of course use a cordless to give a slower speed, but might not have the torque for the job.


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## pe2dave

Threadedpipe said:


> not read all the replies before but after drilling literally thousands of holes in steel over the years


 I do wonder if that's the difference? For every hole in steel, I drill 100 in wood. I'm on my second box of
?cheap? drills (apart from replacing tiny ones I break through my fault) and they work fine.
Were I to drill lots, in steel, I guess I'd invest in better drill bits.


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## AES

pe2dave said:


> I do wonder if that's the difference? For every hole in steel, I drill 100 in wood. I'm on my second box of
> ?cheap? drills (apart from replacing tiny ones I break through my fault) and they work fine.
> Were I to drill lots, in steel, I guess I'd invest in better drill bits.




I do sympathise with you mate. My own experience is that it's just not true that all cheapo no name twist drills are rubbish. Some definitely are, some definitely are a LONG way from being rubbish - in fact just as good as the big names - sometimes!

And that's why I sympathise, because when buying no name cheapos, unless there are obvious visible defects (say in the grinding) there's just no way to tell without buying and trying. Some even "look" just as good/better than the big names!

Over the years when buying drill sets (I mainly buy one offs for special sizes or replacements now), I reckon I've ended up with sets with about 50% complete rubbish and about 50% acceptable to good. A couple of cheapo sets had several good and several rubbish drills in the same set.

If there is a way to sort the wheat from the chaff, I don't know it.


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## pe2dave

AES said:


> If there is a way to sort the wheat from the chaff, I don't know it.




<grin/> Drill lots and lots and lots of holes in steel?
(Sorry, couldn't resist).

There must be a median way with drills for 'ordinary' use. 
My ?? 40 yo set has no name, Marked HSS DIN 338, description in 3 languages. 1-10mm by 0.5mm.
Still in use - I bet there are some in there I've not used!


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## Fergie 307

I agree that you can't beat really good quality ones, especially in very small sizes where cheap ones are often not properly formed, however for day to day use I have been very surprised by the quality of the sets from Aldi, the ones they do in a folding plastic case. Both wood and metal bits have been very good, and seem to be very accurately ground. I have drilled loads of holes with the metal working ones in both steel and aluminium, and haven't had to sharpen one yet.


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## hairy

I' didn't know the dead bit on the point of a drill is called the web.
Does the size of this vary much, so a smaller web allows a bigger step in drill sizes as you go up to the required size?


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## AES

hairy said:


> I' didn't know the dead bit on the point of a drill is called the web.
> Does the size of this vary much, so a smaller web allows a bigger step in drill sizes as you go up to the required size?




I'm not sure if there's a proper "formula" or not (there probably is), but YES, the size of the web is smaller on a "small" drill than it is on a "big" drill. Obvious really! It's in the grinding angles. Purely from "idly looking" I'd say web size is directly proportional to drill dia - about 10 or 15% at a guess. But I'm sure someone better informed than me will be along in a minute to confirm - or to ridicule!


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## AES

Fergie 307 said:


> I agree that you can't beat really good quality ones, especially in very small sizes where cheap ones are often not properly formed, however for day to day use I have been very surprised by the quality of the sets from Aldi, the ones they do in a folding plastic case. Both wood and metal bits have been very good, and seem to be very accurately ground. I have drilled loads of holes with the metal working ones in both steel and aluminium, and haven't had to sharpen one yet.




And other "non-professional" suppliers too, such as my local DIY Emporium - but only sometimes! Again, I'm back to "have a look, if it looks OK, try it" - and it's pot luck if they're any good or not. But Yes, for me, the 2 Aldi sets I've tried are at least "OK".


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## hawkeyefxr

As have been said basically, safety. The bit about clothes is especially important nit just about grabbing the work piece but loose clothing. Swarf can grab ahold of cloths and pull you in.You will not stop that drill!


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## hairy

I was more wondering if different brands, or drills aimed at different materials, would have bigger or smaller webs? So a posher drill has a smaller web for any given size?


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## AES

Again no doubt somebody will correct me if necessary, but AFAIK hairy, "general" twist drills (e.g. not for glass drilling, masonry drilling, or wood drilling to think of 3 examples off the cuff) are indeed just that - general purpose/general materials drills. As said, that's only my own take, no doubt someone knows better.

And BTW, "standard length", "standard material", "standard dia/steps" twist drills are often called "jobbers twist drills". I presume/guess the name is a clue


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## Fergie 307

hairy said:


> I was more wondering if different brands, or drills aimed at different materials, would have bigger or smaller webs? So a posher drill has a smaller web for any given size?


Never really thought about this issue but it seems to me that this will be determined entirely by the angle and back relief used to grind the tip. The issue I have found with the cheap micro drills you can buy is that if you look at the tip they are often a right mess. If you get a dormer drill in say 0.5mm and look at it under magnification it is as perfectly formed as one say 10mm. I would love to know how they grind ones that small. But you pay for it, the last time I bought some they were about £5 each. I use these small sizes in watchmaking. I also have a set of Mikuni carburettor jet drills, again tiny but perfectly formed, and also an eye watering price when I bought them many years ago. If you buy some really cheap and nasty jobber type bits you can sometimes find that the tips aren't even on centre, which makes them essentially useless. Overall I would say if you buy something like a dormer then you know it's going to be good. If you buy cheap then you take pot luck, some will surprise you and be very good, some will be dreadful. But the difference in price is so great you can certainly see why people are tempted by the cheap ones.


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## TRITON

"I want to drill some holes in a bit of metal".

Now we're 3 pages in to a bun fight


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## AES

TRITON said:


> "I want to drill some holes in a bit of metal".
> 
> Now we're 3 pages in to a bun fight




I can't see any sign of a bun fight. What have I missed, please do tell.


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## TRITON

AES said:


> I can't see any sign of a bun fight. What have I missed, please do tell.


You've missed nothing, just seemed that way with the thread going on so long. I must be too used to how long threads go


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## jonn

Fergie 307 said:


> Never really thought about this issue but it seems to me that this will be determined entirely by the angle and back relief used to grind the tip. The issue I have found with the cheap micro drills you can buy is that if you look at the tip they are often a right mess. If you get a dormer drill in say 0.5mm and look at it under magnification it is as perfectly formed as one say 10mm. I would love to know how they grind ones that small. But you pay for it, the last time I bought some they were about £5 each. I use these small sizes in watchmaking. I also have a set of Mikuni carburettor jet drills, again tiny but perfectly formed, and also an eye watering price when I bought them many years ago. If you buy some really cheap and nasty jobber type bits you can sometimes find that the tips aren't even on centre, which makes them essentially useless. Overall I would say if you buy something like a dormer then you know it's going to be good. If you buy cheap then you take pot luck, some will surprise you and be very good, some will be dreadful. But the difference in price is so great you can certainly see why people are tempted by the cheap ones.


If you want to find the quality of drill bits, get a Tormek DBS-22. With poor drill bits they just disappear while grinding, whereas with quality bits you get superb usability in both wood and metal. Also found some 12 to 25 mm Chinese bits with reduced shank which cut very well, also in steel.


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## J-G

For some reason I've yet to determine this Forum got deleted from my normally 'Open' set so I'm having to 'catch up' from early January -  

Lots of excellent advice has naturally already been provided but some auxiliary questions have not been (IMO) adequately addressed. AES particularly asked about the 'Web' - - Yes, as far as Jobber drills are concerned, there is a corelation between the drill diameter and web thickness but no one has mentioned that it has long been good engineering practice to 'thin' the web as part of the sharpening process.

It's all very well buying sets of drills on 'price' and expecting even the cheapest to be 'ready for use' out of the box. Sharpening drills is labour intensive, (read costly) even using sophisticated machinery so 'Chinesium' drills are more likely to be left just as they come off the machine with little or no 'relief'.

The only drills that I don't sharpen by hand from new are very small solid carbide drills (0.3mm through to 6mm by 0.1mm increments) and anything above a 5mm 'Jobber' I will always thin the web.

I haven't looked at any but I'm sure there will be many YouTube Videos describing the web thining process.


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