Turning spirals on drillpress.

[Eric Brown]

Lately I ran across a way to turn spirals on a drillpress using Forstner bits.
I tried several things but eventually was successful.
First, I drilled a hole the size of my dowel. (1 1/8" poplar) in a block of maple.
I mounted the block to my drillpress and tilted the table to 22 degrees.
The speed was 1750 rpm with a 1" smooth rimmed bit. (Note: sawtooth didn't work)
The bit was positioned to about the halfway point on the hole in the block
and the block was shifted to provide the amount of removal.
The drill was started and the dowel fed in from the bottom with a twisting motion.
As the bit engages, it soon forms a channel and the bit produces a nice spiral.
It helps to have a vacuum for chip removal too.
In the picture I had re-inserted the dowel after I had cut off the excess.

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Experimenting may provide better settings and a variety of spirals.

Enjoy. Eric

[Jon McElwain]

Cool technique! What make the spiral consistent? Is it the angle of the table?

[Eric Brown]

Not really sure. The spiral rate is probably a combination of the table angle and the head of the Forstner bit.
The one in the picture fed smoothly with just light hand pressure.
Trying an angle of 45 degrees it was harder to control but I was thinking maybe
a pin in the groove just cut might better regulate the spacing.
One other issue I had was getting the dowel round again so it would fit the hole well.
Best thing I can tell you is to try it. Experiment. Learn. Share.

Best wishes. Eric

[Ed Morgano]

Eric,
I really thought this was a great idea and finally got around to making a fixture to try it. I wanted to keep my drill press table level so I made a fixture that would allow me to tilt the block with the hole in it. I also made a 2" hole in the block with the intent that I could make different size bushings for different size dowels. So far so good. It's not perfect but I think I will be able to tweek it to get some nice pieces that I can use for moldings. Thanks for sharing this idea.


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[Andrew Schlosser]

now that is very cool! I can use that!
I think this is a similar philosophy as the Beall threader.

[Eric Brown]

Beautiful job Ed! I was hoping someone would give the idea a try. Could you tell us more about what you have found works and what doesn't?
I could not get sawtooth forstners to work for instance. That, and the height of the bit seemed critical. Seemed to me that the center of the bit worked best at about the center of the dowel. What have you found? Did you notice that you are turning a left hand thead? Positioning the bit on the other side should get a right handed thread, but I haven't tried it. BTW, love your jig idea.

Thanks. Eric

[Dave Zellers]

I don't understand how you control the feed so the spiral is uniform.

[Van Huskey]

That indeed is very cool!

[glenn bradley]

Trippy idea and a great result. Thanks for sharing that.

[Eric Brown]

Dave, the basic answer to your question is that the forstner bit has a cutting edge followed by a ring of metal.
This ring follows the cutter. So as you feed the wood, the ring has to follow in the groove cut by the cutter.
The rate of the spiral is determined by the angle of the jig.
It's almost like a tap, but with one round cutter.

Here is a picture of a display that Sandy Moss of SydnasSloot.com has.
It is believed a display like this was used in several centennial celebrations
where the bit won awards.

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Enjoy. Eric

[Ed Morgano]

Beautiful job Ed! I was hoping someone would give the idea a try. Could you tell us more about what you have found works and what doesn't?
I could not get sawtooth forstners to work for instance. That, and the height of the bit seemed critical. Seemed to me that the center of the bit worked best at about the center of the dowel. What have you found? Did you notice that you are turning a left hand thead? Positioning the bit on the other side should get a right handed thread, but I haven't tried it. BTW, love your jig idea.

Thanks. Eric

Eric,
I made several adjustments yesterday but it seemed that everything I did made it worse. My first problem is that I have a rinky-dink drill press. The spindle doesn't have a lock on it so I had to make any height adjustments with the table.....a real pain. The height is critical. The bit needs to be exactly on center. If it is too low, the wood starts rubbing on the side of the fortsner bit befor the bit starts cutting, and it will generate gobs of heat and then, very quickly, smoke. If the bit is too high it doesn't ride tightly in the groove that it's cutting and the spiral will become irratic (not evenly spaced.) I did try a right hand thread and it works equally well but with the same limitations on my drill press. We do have a milling machine over in my son's shop so I might bring my fixture over there and give that a try. In the mean time, I'm going to give up on trying to use my drill press. It was lot of fun though.

[phil harold]

That is great!
thanks for sharing

[Alan Schaffter]

That is neat- dang, another "round tuit" project!

I haven't tried it yet so this may just be ramblings, but I'm pretty good at 3 dimensional stuff.

As Ed discovered, bit position is important. I think it is important too- but in two ways- vertically and also horizontally with respect to the centerline of the turning. I think you can control the depth of the spiral flutes if you offset the bit from the centerline of the work and adjust the height of the bit. The tilt of the piece controls the pitch of the spirals - shallow angle= fine pitch, steep angle= coarse pitch.

It may be necessary to position the work first, lower the bit, then start the rotation. This method will only work if rotation of the stock is into the bit. You should be able to reverse the direction of the spiral for left or right-hand threads, by off-setting the work to the other side of the bit.

Rotation of the bit likely has an effect- but I think it mainly affects the difficulty rotating the stock. It may be much harder to rotate the stock for left hand thread than it is for a right hand thread, or visa-versa.

Also, it may be necessary to have a second bearing block above the bit, or even a cradle to support the stock after it is cut, especially if you are trying to make deep, fine pitch spirals in small diameter stock.

It may also be helpful to make an accessory handle so it is easier to rotate the stock. Of course, sharp Forstner bits will help.

It would also be helpful to be able to move your DP table so you can work with longer pieces (I can just rotate the headstock)

So who wants to verify all this?:)

A good investigation and samples could lead to a nice little magazine article.

Hmmm, how about designing and marketing a jig for this?? - a drill press/poor man's Legacy mill?

Ed, what is it like to be truly retired? Do you miss CV? Here is an opportunity. (I'll be BP :D )

[Van Huskey]

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Enjoy. Eric

That display is cool! Makes me think of the forstner as a design tool as well. That really opened my eyes. Thanks for sharing that as well. Maybe now I can have my forstners earning their keep, they were expensive!

[Ed Morgano]

That is neat- dang, another "round tuit" project!

Ed, what is it like to be truly retired? Do you miss CV? Here is an opportunity. (I'll be BP :D )

Alan,
Being retired has been great so far. I've had the time to tackle some projects that have been waiting for years and it feels good to finally be able to finish some of them. I really haven't missed Clear Vue. I loved doing it when we had it but it really got to be more than I wanted to handle at 69 Years Young. I was really ready to get off the merry-go-round. As to the opportunity, no thanks. I'll leave that to some of the younger guys to pick up the ball and run with it. There are opportunities everywhere you look if someone is interested. Realize too that there is a lot of work involved in running a business.
Best Regards.

Ed

[Alan Schaffter]

Alan,
I'll leave that to some of the younger guys to pick up the ball and run with it. There are opportunities everywhere you look if someone is interested. Realize too that there is a lot of work involved in running a business.
Best Regards.

Ed

You have me by a few years, but still. . . That is why I licensed my last design and hope to do the same for a couple of others. I do the initial design and tinkering, then let them do the hard work?

Speaking of designs- I always thought it would be easier to make a cyclone by injection molding, blown molding (like a plastic Coke bottle), vacuum forming, or roto-molded PE, etc. The roto-molded concept would work better with a "push-through" cyclone. You could keep it thin since you wouldn't need to worry about it collapsing. Once you get past the initial tooling you could pop those suckers out cheaply, in nothing flat!