Instrument maker

[Boyan Silyavski]

Here is an example. I work mainly with pine. No hard woods in my case, but otherwise some of them really hold that 0.01 precision after machining and can be machined to almost perfect finish.

On a slow machine that below / roughly 200mm diameter, 18mm thick overall/ could take 15-20 min to machine. As you not thickness is exactly 6.5mm.






But later it will need sanding, otherwise i could have machined it straight to 6mm from the beginning but it would have taken a lot of time to almost same finish as sanding it for just 1-2 minutes . So not worth machining it too much. As sanding it is much faster.


So as you see it needs sanding, otherwise i should have wasted unnecessary time to change bits, slow the speed and so on.




But too fast is also bad. As the machine does not have problem to make it for 4 minutes but many pieces chip:



So a compromise time of 6 min. Where i offset profiling toolpath 5mm. So if it chips like picture above its no problem. Then i make another profiling toolpath that takes the last 5mm only. 1.5 min more, but its worth.

Even so, i leave extra 1mm because finnish is not perfect and when 2 pieces glued together and dry, then i take out the last 1mm on the sanding disk, where it takes mere 30 second using 60 grit.




So i could finish this perfectly from the beginning but i will have to tool change, use always sharp bits, use expensive bits. Now i use one bit for 100 pieces then sharpen it by hand using diamond plate. And sand paper finish.

But that said, just yesterday i spend 100 euro on a CMT exchangeable blades bit, which i will use only for finishing, so maybe i will take one operation out, from what i am doing now.



This is just an example. Hard woods as i said could be finished too a much perfect finish, but sometimes a compromise here and there should be made, depends what how much costs you. BUt to warn you from now that even on the best 3d job, after that you have to sand a lot by hand :-) to make it to a high standard