Sharpened drillbits not cutting vol 2

[Ttrees]

Hello folks, I was intending to make some washers from this lawnmower blade.
I know the answer is likely two things that come to mind, heat treating it to anneal it, or
buying a carbide bit, but I'm wondering how I got this far using some cobalts up to 12mm,
and some various Silverline's/Lidl's to do the rest.

I've been watching all the engineering boyo's I could find about sharpening drill bits
and I haven't seen them discuss hard metals using HSS in detail.
From some old engineering pages on google, I see that the angle of the drill is less acute for harder steels, so have been aiming to replicate that.

As you can see a low grind compared to the grind for usual mild steel

Fair enough the edge does look gone on this bit below, but not the case for them all.
I have watched so many of the same videos, and tried finding one of the Lyle grinder
which demonstrated a grind which looked like it has positive sweeping on the end compared to the bit underneath.

Another question or something worth a remark, again couldn't find out the video where I watched it from... was a quick remark about the web pointing toward the cutting edge.
From that comment I get the idea that seems that I could be rubbing on the heel
I can't find a video nor article demonstrating freehand grinding for hard steels.
From one of the engineer folk on youtube, someone mentioned a turn needed for the big drills
This leads me to think is this the reason.

I must inspect the bits that I ground to do the job this far, and see if the chisel points are less flatter looking.
Not that I've used the chisel points as a lot of bits were used, but I have been grinding lower and lower for the last ones.
Has this affected geometry, and I need to twist the bit to counter the chisel from ending up like so...
and hopefully end up with a tip with more of an upwards angle, which might also be the key to not bottoming out on the heel?

Any comments welcome
Thanks for reading
Tom

 

[J-G]

First thing that I see is that the 'web' has not been thinned. With drills that size I would consider that imperative. This is what would make the 'chisel points less flat looking'.

I don't drill 'Hard materials' so can't offer other advice.

 

[kenledger]

For actually sharpening drills there is no substitute for practice. When i went into the toolroom i was given a 1/2 drill that was flat on the end and told 'sharpen it'. Took about an hour and a half before it was grudgingly accepted lol. Small drills are harder to sharpen (bloody impossible for me now!)

Cutting back the web as J-G says is good but you should not drill a large hole straight out. Start with a small drill working up to the size you want. Make sure you have enough material to drill out, don't try to say drill from 10mm to an 11mm theres a good chance it will grab.

And always clamp your work piece, i see you a relying on a bit of wood to stop the work piece from spinning if it grabs, not a good idea.
The size of drills your using will just swing that lawn mower blade around causing a lot of damage.

 

[J-G]

For actually sharpening drills there is no substitute for practice

I'll at least second that !
Like Kenledger, I also learned to sharpen drills during my apprenticeship as a tool-maker (1956 - 1962). I still sharpen drills as small as 1mm Ø by hand & eye !

 

[paulrbarnard]

I'll at least second that !
Like Kenledger, I also learned to sharpen drills during my apprenticeship as a tool-maker (1956 - 1962). I still sharpen drills as small as 1mm Ø by hand & eye !

Drill and tool sharpening by hand were 1st year apprentice tasks when I did mine in 76. I did a 3mm only a couple of days ago. Not sure I could manage 1mm

Edit: I tell a lie it was a 3.3mm I was tapping a 4mm thread...

 

[kenledger]

I'll at least second that !
Like Kenledger, I also learned to sharpen drills during my apprenticeship as a tool-maker (1956 - 1962). I still sharpen drills as small as 1mm Ø by hand & eye !

I went into the toolroom in 1968, started in in sheet metal in 66. After tool room went into the drawing office. I was happiest in the tool room though, i learnt so much in there.

 

[Ttrees]

Thanks for your suggestions folks
It appears that I could have been misleading, I didn't start with those big drills.
Brand new cobalt was finding things difficult, some needing work before use.
I have no bother cutting holes in mild steel, and small stainless holes,
and the web is not in contact with the material for the rest of the way.

I don't have any mild steel to do the job and test if it's cutting a larger hole well.
That would have taken some questions out of the equation for me.

Yes indeed
The work is solid, and the quill cannot lift the lawnmower blade over the clamped down timber as the drill is just over the work (the table needs lowering if wanting to swap drills)
And it's definitely not a grabby material that might climb up a drill.

Understandably drilling tool steel is not a common thing that was done in manufacture,
but I thought I'd be able to find something on the matter.
Difficult to even find info on split points, but at least some stuff exists on that matter.

I'm still left scratching my head why am I not able to get any further along.
I seen Tubalcaine has an instagram account, I might see if he touches on that if I can get logged in to that bloomin glitchy place.

Thanks
Tom

 

[ptturner]

Hi Tom

I take it you mean the flymo blade is cobalt steel not the drill? I think the problem is your relief angle on the drill is not steep enough so you are 'rubbing' the metal. Im not critical on angles myself prefering to roll the drill to achieve the cutting and clearence angle in one per side.

You might like to get hold of tubal cains book on drilling and tapping in the workshop practice series, it explains a lot of common problems.

However getting the man himself on social media even better!

Jon

 

[Rorschach]

The chisel point is too wide and it looks like the drills don't have enough relief angle.

 

[Ttrees]

Thanks for your input Ptturner
I was going to update this today or tomorrow
I should clarify the cobalt drills are probably the next level up from HSS, but they only go to 13mm from my supplier.
The ones photographed were mostly sold by silverline as 'blacksmiths drills'
probably HSS, I don't know, good value for about 20 quid for a box of them.
I bought some inbetweens to make a set up.
That lawnmower blade seemed to be too tough for the bits, so I got some stainless instead and made some washers from that.
I ended up going back to somewhat of a traditional grind again, as it seemed to be easier on the 2hp (I think) motor.
A few of those cobalts needed sharpening before use before, so I cannot say that their brilliant, but seem to keep an edge better than the HSS.
I reckon I didn't have enough relief as you say, and it seems that this is more difficult to do with a lower angle for harder steels.
Especially if you don't have a wheel dresser to do that final bit.
Using a more apt grind for mild steel again
It seems tough going for my drill, even on the stainless as I have no bother getting a cut turning the chuck by hand with these bigger drills.

I might have another shot at the lawnmower blade again to see, but might use the belt sander to see if it gives a better edge/can achieve more clearance easier than on the grinding wheel.

Rorschach
That brings the question I asked again
Is the chisel point critical geometry wise, although its not being in contact with the work
Does it always indicate that I don't have enough relief on the bit.
Does it look alright in that regard?
The view of the bit from the top was to show the wear on the lips, and the profile.
I can do the split point if necessary, but I can drill incrementally for these harder metals.

Hard to find a good video on drilling hard steels, been watching folks since, with no results apart from folks using carbide drills.

Thanks for reading
Tom

 

[redhunter350]

Tom, regarding your last summary: -
The chisel point is of no consequence when you have already drilled a pilot hole - the point of you larger drill is not cutting ! Point thinking is only beneficial if you have a thick web and are drilling into solid material.
Relief - your grinds look pretty good in the photos but I think a little and I do mean a little more relief may help. Too much relief weakens the cutting edge.
As far as the Blacksmiths drills are concerned they are totally unsuitable for drilling harder or tougher materials, OK for mild steel or none ferrous materials. They are plain carbon steel and even for MS you need to run them much slower than HSS. Incidentally Cobalt drills are HSS but with the added element of Cobalt to the alloy which improves performance.
The lawn mower blade will probably be close to the same hardness as your Blacksmiths drills so the drills will fail particularly as they heat up and loose hardness, this does not happen with HSS.
The included angle for grinding harder materials will not make a huge difference, a little but not so much and defiantly not enough to solve your problem.

Hope this helps
John

 

[Ttrees]

Hello folks
Not got the chance on seeing if the bits manage to cut that steel yet.
I had a look at these silverline ones again, and they are definitely titled HSS.
I think I paid about 20 quid for the box of them new.
The edges last for about two minutes, so not much point in showing you better photos of the drills again.
I believe I've read somewhere that you're not meant to quench these in water, so I wasn't doing that until recently, as I think I misread that advice, seeing that it is the norm as with chisels and whatnot.

I might revisit this again, and see what the matter is.
I'll make sure to either have a grindstone dresser or lug over the belt sander to get some more precision involved.
I might have some more stainless to drill, so will compare if I do.

As said I could get small chips turning by hand, but couldn't manage without peck/stick/spank chuck and repeat.
Maybe I could do with some new belts, I don't know,
they seem to be good enough for what I need, no cracks and still are round, but seem too long for some settings, I had to select a faster speed for any torque.
Still quite usable for the meanwhile, I don't need such performance normally.

Was reluctant to go digging for a silly plane that I made
Took the hacksaw and cutting disc to it afterwards, and concentrically turned two squares of stainless down on the bench grinder, must make a jig for this craic, sorry no ropey pics of doing that for you guys, but am going to knock something daft up soon for the angle grinder to mill the washer welded to the screw repair/upgrade that got done.

The washers look rather fancy, but should last compared to the other things.
Eager to get back at this now.
Tom

 

[julianf]

I acquired one of those expensive drill doctor things.

I actually read the manual - it said that split point was optional.

I sharpened all of my drills. Took a while....


None of them would cut.


Turns out split point is kind of important....

 

[Ttrees]

The expensive cobalt ones I bought were split point aswell, the same brand ones didn't cut into some stainless brackets without sharpening, but flew through those 5 or 6mm holes very well afterwards, hence why I bought them after using cheapies for ages.
I didn't try and replicate the split point and just ground as standard.

As said the holes were bigger than the web so that doesn't come into it.
I still am unclear if it must look a certain way when looking at the last photo in my first post, (from the side of the bit)
Should the web be flat, or canted on both lips for the tool not to rub off the heel?

I'd love to see someone grind a non carbide bit for a job on tough steels.
I suppose its not done that often as folks have more sense than I, and anneal the metal first or stick eye wateringly expensive carbide in the mill.

I got onto instagram and looked for tubalcain, maybe he has a few channels, as the one I saw had little in it.
Must have another search.
Cheers
Tom

 

[ptturner]

Ttrees tubalcain, goes by the handle of mrpete222 on youtube if thats any help.

 

[Bod]

I acquired one of those expensive drill doctor things.

I actually read the manual - it said that split point was optional.

I sharpened all of my drills. Took a while....


None of them would cut.


Turns out split point is kind of important....

Last place I worked, had a Drill Doctor machine, took a bit of getting used to, but did a proper job.
Could adjust the cutting angles, between normal use, and hard material use. Which did make a difference in stainless steel.

Bod

 

[julianf]

Yeah, its a nice enough machine. There's some proper margins being made by the manufacturer of them, but the machine certainly works.

I still have not gotten around to rehappening all mine with the split point though!

 

[Vulcan]

Tom, regarding your last summary: -
The chisel point is of no consequence when you have already drilled a pilot hole - the point of you larger drill is not cutting ! Point thinking is only beneficial if you have a thick web and are drilling into solid material.

Yes, quite right. I always start the job with a spotting drill first (not a centre drill) when working on the lathe or mill. I then use a small drill bit and go up in size. I think there must have been occasions when I needed to start with the final size but I can’t remember when. Point thinning might very well be useful in industry though to reduce the number of operations.

 

[imageel]

I am no engineer, nor skilled woodworker for that matter but when drilling large >10mm holes I always worked up toward the final size, and the only disadvantage apart from speed of this approach is that in some materials taking in effect a maybe 1-2mm skim cut at the larger sizes meant higher a risk of the drill grabbing.
At the other end of the scale there is a chap down-under by the name of CEE who regularly works on big Cat parts and he often will spot the centre and then cut a 25mm or larger hole in one go. I guess for him time is money plus he likely will skim the last few mm with a boring bar or a reamer if the dimension is critical.