Sharpening a step drill bit?

[Beerhippie]

I had to purchase a new step drill yesterday. I guess I'd forgotten how expensive they are!

Anyhow, that gives me incentive to figure out how to sharpen my dull ones, or find somewhere to have it done if DIY isn't practical.

Suggestions?

 

[PCustoms]

I had to purchase a new step drill yesterday. I guess I'd forgotten how expensive they are!

Anyhow, that gives me incentive to figure out how to sharpen my dull ones, or find somewhere to have it done if DIY isn't practical.

Suggestions?

Never tried it, but in theory you just need to work the straight section/edge. Run a stone across it?

 

[Kscardsfan]

I guess you could file, stone and strop them. I just circle file them and get new ones even though it hurts. I kind think of them as consumable items.

 

[tarbellb]

Totally doable, very easy on the straight fluted versions. Spiral fluted get tricky.

Also, the HF cheapos are surprisingly good

 

[Beerhippie]

Totally doable, very easy on the straight fluted versions. Spiral fluted get tricky.

Also, the HF cheapos are surprisingly good

Can I use a flat stone to sharpen the edge of the flute to 90 degrees, or is there back-cut clearance?

 

[Jgaz]

I have only touched up the flutes at 90 degrees.

I tightened it in a drill check mounted on my ShopSmith and used a small stone.
Doesn’t cut as good as new but kept me going on a project at the time

 

[RTM]

Run a stone across it?

guess you could file, stone and strop them

I would worry about having safe edges. When sharpening auger bits, a file with a safe (no teeth) edge is used, to avoid fouling the geometry of the adjacent edges.

I would think a diamond hone might be safer than a stone as the adjacent edges are important to the finished hole's geometry.

Just thinking aloud, YMMV.

 

[finn]

I just keep a stock of the cheap HF step bits on hand for most “casual, non critical” use and reserve the more expensive brands for use when needed.

The last HF step drill bits I picked up were something like $4.00 for two.

 

[Beerhippie]

I would worry about having safe edges. When sharpening auger bits, a file with a safe (no teeth) edge is used, to avoid fouling the geometry of the adjacent edges.

I would think a diamond hone might be safer than a stone of the adjacent edges are important to the finished hole's geometry.

Just thinking aloud, YMMV.

By stone, of course, I mean diamond hone.

With the geometry of the step bit, it doesn't seem like there's anything to damage, "safe edge" or not. It's just a gullet.

 

[FigN⋅m]

I would say it's time to FAFO...

Much to some folks' chagrin, the Harbor Freight cheapies really are decent enough.
If I don't break one by accident, I can easily get over a few year's solid use out of them.

 

[PCustoms]

I bought a couple sizes of HF step drills (a 3 pack and 1 big one) about 15yrs ago.

Drilled plenty of things, including 1/2" flatbar, over the years. Only issue I had was when the big one tipped the drill over off the edge of the bench, it landed tip down and must have cracked at the shank, next hole it fell right off.

 

[no704]

I’ve done it with a small stone in a dremmel. Not perfect but it did work.

 

[tarbellb]

Here's a older bit that got resharpened

 

[RoninB4]

-Without going into detail on the geometry I'd say you'll likely have to remove .007-.010 to have a sharp edge. Using a hand stone will take all day and your fingers will go numb before you're done. Use a cutter grinder for best results that will only take a few minutes. It won't be as good as new (cutter geometry relation to centerline) but it should work better than a dull one. If you've got one of those crappy coated ones (TiN or others) then the coating will trash the grinding wheel.

 

[Bert_]

I do it on a bench grinder. Can be done quick. Might not get it perfect but get a lot more use with a few sharpenings.

 

[Rusted Nut]

I’m on a project where we’ve been using step bits, quite a bit. Tried sharpening a few, meh.. You can resharpen, but you shrink the hole size they drill when ground down. In general, step bits aren’t a precision tool, but shrinking didn’t work well for us. I‘m all for sharpening things, but step bits now go in the recycle bin.

 

[RTM]

You can resharpen, but you shrink the hole size they drill when ground down.

If you stay aligned to the center with your abrasive, it should not change the diameter, should it?

 

[Rusted Nut]

If you stay aligned to the center with your abrasive, it should not change the diameter, should it?

As you grind stuff off, the bit diameter shrinks.

 

[Beerhippie]

As you grind stuff off, the bit diameter shrinks.

I need some diagrams. Seems to me, each step is a concentric ring, which does not get smaller with sharpening the edge of said ring.

 

[RTM]

As you grind stuff off, the bit diameter shrinks.

In my world, I'd want to sharpen along the red line, slightly undercutting the existing edge, with my abrasive "coming out of the page". This would push the red face "left", but would not reduce the diameter of the bit. I don't see how this would shrink the bit diameter.

 

[Bert_]

You don't grind the outside. You grind in the groove.

 

[Kurt4440]

You don't grind the outside. You grind in the groove.

You know it!
If you grind in the groove the shaft diameter increases.



Edited for additional humor.

 

[RoninB4]

I need some diagrams. Seems to me, each step is a concentric ring, which does not get smaller with sharpening the edge of said ring.

- I don't own one so I don't know for certain but...each step should be a spiral rather than a series of concentric diameters. If the steps were constant diameters it would rub/drag behind the cutting edge. This is sometimes called radial relief and allows the cutting edge to "bite" the material, without radial relief (constant diameter) there would be no reason for only the cutting edge to contact the material first. The same principle exists in single flute countersinks or other cutting tools. A simple test would be to carefully mic the step at 3-4 places around the diameter. I'd do this but don't use step drills so I don't have one to test. If I drew this on paper it would make immediate sense. Without more coffee I may not be making any sense at all right now.

 

[RTM]

simple test would be to carefully mic the step at 3-4 places around the diameter. I'd do this but don't use step drills so I don't have one to test. If I drew this on paper it would make immediate sense.

Chuck it up, put a dial indicator on it, watch the diameter decrease as you move away from the cutting edge?

the steps were constant diameters it would rub/drag behind the cutting edge.

I could buy into that argument @Rusted Nut may be right.

 

[jayemm]

Another thread going out into the ozone.

 

[PCustoms]

- I don't own one so I don't know for certain but...each step should be a spiral rather than a series of concentric diameters. If the steps were constant diameters it would rub/drag behind the cutting edge. This is sometimes called radial relief and allows the cutting edge to "bite" the material, without radial relief (constant diameter) there would be no reason for only the cutting edge to contact the material first. The same principle exists in single flute countersinks or other cutting tools. A simple test would be to carefully mic the step at 3-4 places around the diameter. I'd do this but don't use step drills so I don't have one to test. If I drew this on paper it would make immediate sense. Without more coffee I may not be making any sense at all right now.

You should go buy one then edit this post.

 

[Rusted Nut]

You don't grind the outside. You grind in the groove.

Tried at first, they didn’t cut well.

 

[RoninB4]

You should go buy one then edit this post.

-I don't buy tools I don't intend to use or that I consider inferior to what I have. Perhaps you should use your step drill as a basis for a reply.

There is another relief possible I have purposely not mentioned and will await further informed replies,

 

[alwaysFlOoReD]

In my world, I'd want to sharpen along the red line, slightly undercutting the existing edge, with my abrasive "coming out of the page". This would push the red face "left", but would not reduce the diameter of the bit. I don't see how this would shrink the bit diameter.

This is how I sharpen mine. It doesn't get back to new sharp but close. You have to take the worn edge off so sometimes up to 1/8" disappears.
I've never needed exact hole size so didn't worry about diminishing diameter. I've also tried sharpening the spiral flute bits. That sort of worked. Good enough for what I was doing.
I used a 4.5" handheld grinder with a new disk.

 

[RoninB4]

Chuck it up, put a dial indicator on it, watch the diameter decrease as you move away from the cutting edge?

-Maybe. There are two types of relief used in good cutting tools. Since I don't own a step drill I can't say whether one or both are present. I agree with you, chuck it up and put an indicator on it. As you rotate the drill it MAY show a reduced diameter. If not then only the other type of relief is used. Report back if you do this so we can all learn something.

 

[PCustoms]

-I don't buy tools I don't intend to use or that I consider inferior to what I have. Perhaps you should use your step drill as a basis for a reply.

There is another relief possible I have purposely not mentioned and will await further informed replies,

Look at the pictures, the geometry is clear.

I don't understand why you would post in this thread if you have superior tools and this no knowledge of or use for the tools being discussed.

 

[ecotec]

I have never thought to try sharpening one.

On a job, I call my foreman and tell him I need a new one. I can wait.

At home, I go to my toolbox of consumables and grab another one.

I have been increasing my consumables drawers from enough to stupid amounts over the years. I don’t see how I could ever live long enough to use a fraction of my consumables up (drill bits, Roloc discs, grinder discs, acid brushes…). I, probably, have enough of some categories of consumables for a few long lifetimes.

 

[RoninB4]

Look at the pictures, the geometry is clear.

-Wow, you have far better vision than most people and probably don't ever need measuring instruments.

I don't understand why you would post in this thread if you have superior tools and this no knowledge of or use for the tools being discussed.

-I was attempting to help and inform others what cutting tool geometry was. You are clearly beyond being helped and I don't understand why you would post in a thread when you had no useful information to contribute. Trolling perhaps?

 

[Beerhippie]

Wow! I had no idea that this would be a controversial subject!

Here's a dull step bit before attempting to sharpen it:



And after using the very edge of a somewhat worn and rounded-over flapwheel on my 4 1/2" AG:



I was able to get some back-relief on the face of the bevel--at the expense of the size markings.

It cuts and throws big, beautiful curls:



And, as the picture clearly shows, the steps are indeed concentric and not spiral.

For the worriers (and OSHA spies) among you all, I removed the clamp for the picture.

Unfortunately, it cuts to right there and no further. I may need to screw around with it some more--or send it off to pasture. "No, honey, we're sending him off to a nice farm for old drill bits."

Step bits are far from my most used tools. When I need one, I need it, but most of the time I don't. That's why I was so surprised at the cost of a new one, as I haven't bought one in this century. Sharpening was mostly a experiment.

I usually give my dull bits to a blacksmith I know who makes beautiful knives from them.

I have never thought to try sharpening one.

On a job, I call my foreman and tell him I need a new one. I can wait.

At home, I go to my toolbox of consumables and grab another one.

I have been increasing my consumables drawers from enough to stupid amounts over the years. I don’t see how I could ever live long enough to use a fraction of my consumables up (drill bits, Roloc discs, grinder discs, acid brushes…). I, probably, have enough of some categories of consumables for a few long lifetimes.

Eco: I know what a burden having too much of anything can be and I'm willing to sacrifice some of my shop space to help out. I'll pay shipping.

 

[ecotec]

Wow! I had no idea that this would be a controversial subject!

Here's a dull step bit before attempting to sharpen it:



And after using the very edge of a somewhat worn and rounded-over flapwheel on my 4 1/2" AG:



I was able to get some back-relief on the face of the bevel--at the expense of the size markings.

It cuts and throws big, beautiful curls:



And, as the picture clearly shows, the steps are indeed concentric and not spiral.

Unfortunately, it cuts to right there and no further. I may need to screw around with it some more--or send it off to pasture. "No, honey, we're sending him off to a nice farm for old drill bits."

Step bits are far from my most used tools. When I need one, I need it, but most of the time I don't. That's why I was so surprised at the cost of a new one, as I haven't bought one in this century. Sharpening was mostly a experiment.

I usually give my dull bits to a blacksmith I know who makes beautiful knives from them.


Eco: I know what a burden having too much of anything can be and I'm willing to sacrifice some of my shop space to help out. I'll pay shipping.

It’s not too much, if I can still close the garage door.

 

[FigN⋅m]

Wow! I had no idea that this would be a controversial subject!

I usually give my dull bits to a blacksmith I know who makes beautiful knives from them.

That thing's gonna cut all kinds of crazy...

 

[Beerhippie]

That thing's gonna cut all kinds of crazy...

Snow knife?

The blacksmith is my landlord. He makes pattern-welded blades and was featured on the original season of Forged In Fire. He'd be the high-school teacher from Wallowa.

 

[whateg01]

I would worry about having safe edges. When sharpening auger bits, a file with a safe (no teeth) edge is used, to avoid fouling the geometry of the adjacent edges.

What adjacent edge is there to worry about? I would hope a quality step drill would be harder than that anyway.

 

[whateg01]

I usually give my dull bits to a blacksmith I know who makes beautiful knives from them.

I went to boot camp with a guy who came from a well to do family. He has never worn a pair of skivvies twice. Wear them once and throw them away. He was appalled that we washed them and wore them again. I can't imagine just throwing away a 3/4" drill twist drill because it needed to be sharpened.

 

[Beerhippie]

I went to boot camp with a guy who came from a well to do family. He has never worn a pair of skivvies twice. Wear them once and throw them away. He was appalled that we washed them and wore them again. I can't imagine just throwing away a 3/4" drill twist drill because it needed to be sharpened.

1/2" and up get resharpened. In fact, I'm taking a bunch down to my guy this afternoon.

Do you think a guy trying to resharpen a step-bit and driving a 32-year-old car is a just-throw-it-away sort?