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Modifying (grinding) a spoon bit

Posted: Wed Oct 19, 2016 1:27 pm
by Leus
Hey fellas, it's been a while...

Last weekend I finally managed to rebuild my shop and, to celebrate it, made a pipe. I'm using Brad's spoon bits (I think it's from the first batch) and I had forgotten how they were supposed to be used.

I got my answer in this forum (to one of my own questions, heh, memory _is_ fragile) and went on merrily to make my pipe.

Except, there was a lot of heat and smoke, and a slightly deformed hole as a result. Not a complete disaster but not a smooth ride either.

Now, I remember Todd telling about Brad bits having to be reshaped a little bit, grinding a couple of flats so they have less surface in contact with the briar. I cannot find that message anywhere.

Anybody can show pictures of how to modify spoon bits so they aren't that hard to use?

Re: Modifying (grinding) a spoon bit

Posted: Wed Oct 19, 2016 1:53 pm
by pipeguy
Not for nothing I don't know how this applies to you but are you a supermarket or a tool and dye maker?
Often times I put my pride aside and let the machinery that has the tooling and knowledge to do it
Most of the time I find I save $$$ and aggravation.(just one man's opinion)

Re: Modifying (grinding) a spoon bit

Posted: Wed Oct 19, 2016 3:24 pm
by sandahlpipe
I will have to get out to my shop to take pictures of them, but I had bought some bits that were similar in function to how you describe. A couple of pointers for you to help.

1. Don't use these bits to actually drill the hole out. Start with a pilot hole. Drill said pilot hole with a 5/16" brad point. Make sure the tip of the brad point doesn't go deeper than your airway. Then use the spoon bits to enlarge the hole.
2. When you modify them, you want to minimize the surface area that comes into contact with the briar. What I do is put a mill bit on my metal lathe and tighten the set screws on the shank of the spoon bit on the tool holder and shave off part of the round side of the bit. You could do this part with an angle grinder just fine. Be sure not to grind too close to the cutting edge, and also be sure to allow more than just the cutting edge and the edge opposite the cutting edge to contact the briar when drilling. You want at least one or two other points along the back of the bit to touch the briar. I should also add that I'm not a machinist and am inclined to think that if I can do it, anyone can learn with some reading, thought, and patience.

Alternatively, I've heard great things from the spoon bits that Steve Norse sells. I managed to machine my own that work adequately. Machining my own took me about an hour each once I figured out what the bit was supposed to do.

Re: Modifying (grinding) a spoon bit

Posted: Thu Oct 20, 2016 12:44 pm
by Charl
I think a pilot hole will be your solution.

Re: Modifying (grinding) a spoon bit

Posted: Thu Oct 20, 2016 7:33 pm
by DocAitch
I just machined my first spoon type bit. I wanted a military mortise bit a bit smaller than the 3/8"bit included in the one from Vermont Freehand. It is a little tricky with my HF lathe, but I have one working now. I am going to take Jeremiah's advice and really study the mechanics of the back of the spoon.to get a smoother cut with the next one.
As Charl says, they only work well with a pilot.
DocAitch

Re: Modifying (grinding) a spoon bit

Posted: Thu Oct 27, 2016 10:10 pm
by Leus
Thank you guys.

Yes, I'm using them with a pilot hole.

So I guess it's just matter of grinding a few flats on the back. Lets see what happens next.

Re: Modifying (grinding) a spoon bit

Posted: Fri Oct 28, 2016 2:07 am
by Charl
What size pilot?