Spoon bits -- is there something I'm missing?

[d6monk]

Hi everyone, for the past couple of months I've been saving up for a metal lathe (a jet 9x20) and have a preemptive question regarding spoon bits:

Once I get the metal lathe I am going to start trying some shaping first then drilling, and I have read that hand drilling is easiest with spoon bits. However, from what I can find it seems that spoon bits are insanely priced. I imagine that I could easily buy some 3/4" drill rod, cut off a piece of appropriate length, turn the general shape on the metal lathe, and then grind about half of it off (leaving about 51% seems to be the consensus on these forums). Am I crazy?

Also, is there anything special I should know about the shape of the spoon bits that I couldn't just tell from an internet picture (aside from leaving about 51%)?

Thanks.

[KurtHuhn]

That's it in a nutshell. Don't forget to heat treat the bit once you've got it shaped. Other than that it's pretty simple.

[JHowell]

Also helps to turn a shank so there is a shoulder to stop the bit getting pushed into the chuck. Enco usually seems to be having a sale on A2 drill rod, which has good wear resistance and seems to do pretty well in briar even without hardening.

Jack

[ToddJohnson]

The easiest way to profile them is with an angle grinder and the drill rod spinning in your lathe. If they're not very sharp then they are very dangerous. That might be what you're "missing."

Todd

[d6monk]

Thanks everyone, that's some very helpful advice. My friend has a book on toolmaking that covers heat treating so I am going to borrow that from him (there's never a lack of things to learn when pipe making), and I'm going to stop by home depot sometime this week and get an angle grinder (the standard 4-1/2" should be sufficient right?).

Anyway, here is my preliminary diagram for the spoon bit and a few questions:



Questions:

1. (see side profile view) Do I grind the bit straight or at an angle here?
2. (see top profile view) Should I grind the bit flat (with the angle grinder) or slightly curved (with a grinding wheel)?
3. What grit do you sharpen them to?
4. Does this look like a good "general purpose" spoon bit or is there anything out of whack (profile, dimensions, etc.)?

Thanks again, you guys are a huge help.

[Leus]

After a failed attempt to make spoon bits myself, I think this is becoming a really interesting thread.

[KurtHuhn]

On my spoon bits the cutting face is not angled from tip to rear. It's a straight line parallel with the axis of rotation. Also, the face is perfectly flat.

A slightly concave face may actually benefit the cutting power if you can work out how to keep the line parallel and uniform. But sharpening that face, if it becomes necessary to do so, may prove problematic.

Angling the face from tip to flange could also prove problematic. If that face isn't parallel to the axis of rotation, it seems to me that it would be prone to wander. I can't say that for certain, but something tells me it might be the case.

[Ryan]

All of the bits I have made are strait from tip to bottom. like Kurt pointed out, concave would be the best for cutting, but then you wouldnt be able to sharpen it as easily. A convex face would make for a poor cutting edge.

here are the ones I hade made;

[d6monk]

Thanks Kurt and Ryan. I have an old rock grinder that has a 5" wheel that takes sanding belts about 3" wide. I'd imagine that you could get a parallel and uniform convex face using that. Or use the curved part of a belt sander.

[caskwith]

Hey Ryan, any chance of some Info on how you made yours? Im thinking of moving away from my ground spade bits and end mills and id like some tapered spoon bits.

[Ryan]

I turned the profile I wanted on the lathe sanded and then polished the bit. Then using a vice I clamped it in the jaws. Using a recipricating saw I cut of about 40% and then ground off the remaining. Finally I heat treated it.

I have to say though, there is really no need to use a spoon bit unless you are freehand drilling. If you are using a drill press or drilling the block in a lathe using the 2 jaw chuck method, a ground spade or even better a profiled s&d bit would work better.

The spoon bits generate a lot of heat and can easily burn the walls of the bowl and they dull quickly (even being hardend).

[KurtHuhn]

I have to say though, there is really no need to use a spoon bit unless you are freehand drilling. If you are using a drill press or drilling the block in a lathe using the 2 jaw chuck method, a ground spade or even better a profiled s&d bit would work better.

Yes, spoon bits are relatively worthless unless you're doing freehand drilling. The single best bit I've found for doing standard drilling is a reshaped S&D bit. It will eject shavings much more efficiently, doesn't get particularly hot, leaves a clean wall to the chamber, and doesn't require a guide hole. They also require far less time investment to make.

[caskwith]

Well thanks for the info guys.

Most of my drilling is done using a 20mm ball nosed end mill, this is my prefered chamber size and shape for about 75% of my pipes. The rest are done using spade bits i grind to shape myself, either round nose or taper. Im not really considering free-hand drilling at the moment so i think ill stick with my current setup and just make a few more spade bits, they work very well if you put the effort and care into their shaping.

[Ryan]

Ken Lamb has really good s&d bits that he sells or if you send him a bit he will regrind it. They work much better than the spade bits.

here are a few of my s&d bit with different profiles

[Frank]

Trent Rudat also does S&D bit regrinding: Briar Pipe Tooling
Send him an email for a quote.

[d6monk]

Ryan, how did you go about grinding your spoon bits perfectly flat? What did you use for the rough grinding, and did you finish them off with a diamond hone or oilstone or anything like that or is that overkill?

[Ryan]

Ryan, how did you go about grinding your spoon bits perfectly flat? What did you use for the rough grinding, and did you finish them off with a diamond hone or oilstone or anything like that or is that overkill?

I used a bench grinder for the majority of it and then a file to make it flat and bring it down very close to my final depth, finally a course/fine whet stone.

q

[d6monk]

Thanks Ryan.

Well it looks like I'm all set to give it a try once my metal lathe comes in sometime next week. I'll post pictures when I'm done.

[d6monk]

Ok, I still need to clean it up a bit from the lathe tool marks and the heat treating process, but here it is:



I used Todd's method with the angle grinder which worked pretty well, and I heat treated it as per Kurt's advice using a little furnace I made out of two fire bricks.

Thanks again for the help everyone!

[daniel]

Ken Lamb has really good s&d bits that he sells or if you send him a bit he will regrind it. They work much better than the spade bits.

here are a few of my s&d bit with different profiles

i didn´tt find an aswer,
but how have you done these?
i have had the eager to do these for a long time as they seem to be the only bits i could possibly do my self,
but i really have no idea, how I can keep the cutting edge
identical on both sides of the bit.