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| Accurate Drilling - centering microscope, USB cam, optical punch? |
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| picclock:
The problem as I understand it is to accurately transfer a running gearfit dimension to the plate to be drilled. As a possible thought, has anyone considered making the chuck on the mill part of the depther. So to get a correct gearfit, utilise a spindle with the gear fitted into the chuck and the meshing gear and spindle fitted to the plate. An additional block may need to be made to ensure that the plate gear spindle is truly vertical, just a block with a long hole on the top to align the spindle, the bottom part of which can be milled away to clear the gear. This method would allow adjustment of the fit to the correct distance, then the spindle in the chuck could be replaced with a centre for making the drill start. This eliminates the depther and should give far higher accuracy without any need for centre punching or transfer of dimension. Hope it makes sense. Best Regards picclock |
| kwackers:
--- Quote from: John Hill on June 27, 2011, 05:20:19 PM ---You need some idea of the layout of the gear train unless you have designed the clock entirely in your head. Here is my suggested process in some detail. 1. sketch layout of gear train. 2. use depthing gauge to determine distances between drill points and mark these on your sketch. 3. drill first hole. 4. refer to sketch for distance and direction to next hole. 5. use DRO to position for next hole. 6. drill 7. rinse, lather and repeat. Note that each position is determined relative to the one before therefore errors do not accumulate. --- End quote --- My problem with that is measuring the distance between the points on the depthing tool with any accuracy. Where you have a train of gears the inaccuracies add up. Although tbh I think everyone is thinking like engineers and as I said earlier, engineers build poor clocks for the simple reason they make everything an engineering fit... Clocks aren't made that accurately. The most important bit is finding the correct mesh between two gears and the distance between them. Once you have that you can happily drill the hole by eye on a pedestal drill - don't even need a mill... Whilst 10 thou might be a bit poor getting it within one or two isn't an issue - there should be around a thou play in the axle anyway! The holes for the axles are usually tapered too so has to prevent any chance of racking jamming the gear. The problem Chris (OP) has is he's thinking it all needs to be super accurate, it doesn't. It needs to be free. |
| John Hill:
Kwackers, I see little point in explaining further so I and done with this. |
| raynerd:
--- Quote from: kwackers on June 28, 2011, 04:32:43 AM ---The most important bit is finding the correct mesh between two gears and the distance between them. Once you have that you can happily drill the hole by eye on a pedestal drill - don't even need a mill... Whilst 10 thou might be a bit poor getting it within one or two isn't an issue - there should be around a thou play in the axle anyway! The holes for the axles are usually tapered too so has to prevent any chance of racking jamming the gear. The problem Chris (OP) has is he's thinking it all needs to be super accurate, it doesn't. It needs to be free. --- End quote --- Qwackers, I know in Colin Thrones Book - "Clock Building for the Model Engineer" he just explains that the marked out points are then drilled - he doesn`t say how and I presume it is just done by eye. What would be your method, centre pop and then drill ? The hole I`m drilling is 0.8mm so literally, how would you go about from a marked out point to drilling the small hole? I`ve been watching every single post made in this thread with interest and I didn`t want to throw in any stupid comments so I have stayed out. My issue does lie as many have said with having a hole with no co-ordinates and therefore just wanting to drill from the marked point hence the suggestion that an optical scope or punch may be needed. You have all made many very very good suggestions but I would like to consider my options now as if a DRO was not available and just spot drilling to a cross marked position. :mmr: I am kind of pleased that my thread has sparked all this discussion and that my issue is clearly one that can be done in many way as I presumed! I just find when I currently mark out my position and then drill a hole, the hole is not perfectly central to the "cross hairs" mark! A few have suggested a pointed in the chuck/collet - this could possible work well! Chris |
| Jasonb:
As I said use a sharp DOT punch not a centre punch. Lean it slightly so you can see the end as you place it on the intersection of your two marked lines, you should be able to feel it sit into the scribed line. Bring it vertical and give a light tap, inspect this punch mark with a magnifying glass, if it is off the punch can be tilted and tapped at an angle to pull the punch mark to where you need it. Once happy with the dot punch mark follow up with a sharp centre punch. You can then locate the centre punch mark in your drill or mill with a centre finder, the pin type will do and drill your hole. Jason |
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