I would like to point out that the link "bosspics" which Brad just linked shows a boss machine with the upright section, possibility, mounted backwards. At least it is not the same as mine. The upright stand, which is mounted to the seat has the head out in front and the latches are on the left side(sitting on the machine). I wonder if someone had the ratchet/angle bolt out and reinstalled the whole unit backward? It should still work and may be the last person to use it was left handed?

Tim

Tim -- that's backwards from ours too.

Gabel, did you mention what the ratio was for your William Ball and Co. manchine? How many turns of the chuck for one turn of the handles? That would be a good machine to bring for show and tell at a conference or other guild event. Does it seem heavy compared to some of the other machines? With that solid steel square rack in the center I thought it might be a bit.

Brad, it is heavy compared to an ajax and a boss.

The ratio is pretty fast -- almost identical to the fast side of the boss. I can't remember exactly what it is at the moment, I'll check when I get to the yard and report back.

As far as I can see that bosspic's machine was put together backwards.
Every machine we have sold had everything the other way around....

Jim Rogers

Yeah, I was just looking for pics for quick reference. You video showed it all though, Jim.

If you get a chance Gabel, that would be great. I want to make a little chart that shows the gear ratios of the various boring machines that we know of.

Here's the ratios of the machines we have:

Ball and Co.: 4 to 3 (4 bit revolutions for 3 handle turns)
Boss (fast side): 3 to 2 (3 bit revs for 2 handle turns)
Ajax: 1 to 1

forgot to check the boss' slow speed

Thanks Gabel.
FYI, for anyone who doesn't know, The best way to determine the ratio is to count the number of teeth. I just received my Boss gears and for the numerically low ratio (for hardwood), there a are 24 teeth on the chuck shaft gear, and 14 teeth on the handle shaft gear. So you would call this a 14:24 ratio, or to simplify it, 14/24=.58, so the ratio would be .58:1, for every 1 turn of the handles, the bit rotates .58 of a turn.

For the softwood side of the Boss, the ratio is 16:12, which equals 1.33:1 (rounding). For 1 turn of the handles, the bit rotates 1.33 times.

I guess if I want to make a chart, handle length should also be included, perpendicular distance from the center line of handle arm shaft to center line of the handle/knob pivot shaft.

Thanks for the reminder, Brad.

On the two machines in the last video the ration is .625 on both, 10/16 or to reduce the fraction 5/8's...... if I was to switch the gears I would get a l.6:1, a little faster than the fast gear on the Boss. I am just thinking about pegs. I wonder what the grunt factor would be turning a 1-1/2" bit in white pine at that ratio?

The handle lengths are and interesting concept, I find the fixed handles to be very comfortable, much longer and the ergonomics is off.

Brad, what does the diameter of the gear contribute to the equation? Say a 4" gear with an accommodating correctly sized gear, to hit a ratio already known , either bigger or smaller?

Tim

There are a number of factors that go into gear design. In simplest terms for regular spur gears, you need to size the tooth to handle the loads it will see. Root stress, bending stress, contact ratio(how many teeth are in contact at once), etc. Using the input torque (from the handles) and the resistive torque from the wood, you translate that into the force that occurs at the point of contact on the tooth. You can then calculate the stresses to determine if the stress is within the yeild stess of the material with sufficient margin of safety(for the given ratio etc). Once you've found the suffecient tooth design, the ratio used will determine the diametral pitch and the overall diamter of the gear. So overall diamter, or the more commonly used pitch diameter, is more a function of the tooth design and ratio needed. I actually started out designing gears in my first job. It's been awhile, but I could pull out my books again if I needed to.
I've been wondering if any of the boring machine gears are worth quoting a limited run? If a gear company could hob or shape some gears at a cost people would be willing to pay. Has anyone tried this? What gears would be first on the list to have done? I was just thinking...

The diametral Pitch radius would factor into the calculation of torques to forces and visa versa, and the caculation of stress on the tooth.

There are a few different terms when dealing with bevel straight gears, like on the boring machines, but the concepts are basically the same. Bevel gears allow you to change the direction of motion by 90 degrees per pair, but the drawbacks are that there are higher toques on the shafts for bevel gears, the mounting distances must be accurate so that the teeth mesh properly, and one wheel of such gear is designed to work with its complementary wheel and no other, without having to change the center distances/mounting distances.