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kwackers:
There are two points of note with a depthing gauge.

First it lets you run two gears together until you're happy they're meshing correctly - at that point the points on the guage are correct for marking the clock plates.

Second - and more important from a marking out point of view, they behave like a compass. So you start from your reference and mark the next gear, then set up for the next and mark an arc and so on using the intersections of arcs to correctly place all the gears.
It's this method of marking out that means you can't use the DRO easily. You'd need a DRO that you could give multiple arcs to and it would calculate the intersections.

What you could do I guess it put them into a CAD package and read off the absolute positions, but that somehow seems harder than simply marking out the positions of the gears...

John Hill:

--- Quote from: kwackers on June 27, 2011, 05:49:07 AM ---There are two points of note with a depthing gauge.

First it lets you run two gears together until you're happy they're meshing correctly - at that point the points on the guage are correct for marking the clock plates.

Second - and more important from a marking out point of view, they behave like a compass. So you start from your reference and mark the next gear, then set up for the next and mark an arc and so on using the intersections of arcs to correctly place all the gears.
It's this method of marking out that means you can't use the DRO easily. You'd need a DRO that you could give multiple arcs to and it would calculate the intersections.

What you could do I guess it put them into a CAD package and read off the absolute positions, but that somehow seems harder than simply marking out the positions of the gears...

--- End quote ---

Marking out the positions is only a step along the way, it is not easy and neither is it necessary. Much easier to use the DRO to move from one drill position to the next. For example, first draw the positions of the required holes after accurately determining the distance between positions. You will need to solve some very simple right triangles to get the required DRO coordinates, using a protractor to get the angles from your paper drawing.

kwackers:

--- Quote from: John Hill on June 27, 2011, 06:19:15 AM ---Marking out the positions is only a step along the way, it is not easy and neither is it necessary. Much easier to use the DRO to move from one drill position to the next. For example, first draw the positions of the required holes after accurately determining the distance between positions. You will need to solve some very simple right triangles to get the required DRO coordinates, using a protractor to get the angles from your paper drawing.

--- End quote ---
I don't follow, where did the paper drawing come from? Did you draw it yourself? If so how's that easier than simply marking out using a depthing gauge?

I think people are getting carried away here, marking out clock wheels using a depthing gauge and then drilling the points isn't a big issue. It doesn't need to be super accurate on a per hole basis but it does need to allow for accumulated error.
The system of using a depthing gauge and drawing arcs fits those parameters perfectly. As soon as you start measuring and calculating you accumulate errors and risk the whole thing going pear shaped.

spuddevans:
Another reason to use a depthing gauge is that it allows you to set, very precisely, the spacing and thus the depth of engagement of the two gears. The importance of this is realised when you consider the effects of not meshing the gears well will result in greater friction, a thing most undesirable in a clock train, and will also result in premature wearing of the gears.

So when you add home made gears into the equation, which most likely will not be precisely the diameter called for in the plans, the need for meshing the gears on a depthing gauge prior to marking those positions on the frame of the clock becomes essential for the smooth running, and therefore the accuracy of the clock.

Tim

Jonny:

--- Quote from: craynerd on June 26, 2011, 05:22:42 AM --- these holes are drilled sequentially as the back plate is built up as and when the wheels are made
--- End quote ---

Issues such as runout i wont go into.
Since as stated holes drilled sequentially with the actual wheel to be used, this is quite easy. Nothing more than basic equipment such as a drill press.

Used to do this all the time on irreplaceable one offs of significant value.
Offer up the wheel and position where required. Then you could clamp but i never did and drill through the offered up wheel and in doing so marking the plate. By some chance if it veeres off may need a centre drill in centre of hole that was started, it should self centre.
Works even if a smaller hole is required in the plate such as a tapped hole.

Could show a piccy of a one off built up in similar fashion assembled product done in such a way but may not go down to well out of the ballistics section.

Used to use dividers all the time the trick is to catch the light right and get the point of a punch exactly where you want it.

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