✅ - Wood Filling over sanding? How do you know when you're done Sanding?

[lost bronze]

I'm learning how to use woodfiller/primer/and sanding, trying to understand as much as I can before reaching diminishing returns on the topic. Yesterday I experimented with my new palm sander on the bow shaft I have printed out. It got rid of all of the nasty support residue, and the prints were grainy, so it smoothed them out too.
However It's a bent shape and I wasn't paying attention and it cut into the end tip of the bow shaft, cutting a hole through the wall.

My questions are:

• Can I just use Wood filler to fill in that hole?
• At what point in time do I know that I'm done sanding? Do I continue to keep sanding with higher grit? If so, when do I know the threshold for being done with each grit? This whole thing confuses me.
• Finally, in this video (timestamped) Frank mentions using sandpaper to reach the recesses, but why wouldn't you just use more wood filler to fill in those recesses?

https://youtu.be/FKjVPYnqDug?si=EvACP3WY1neols4E&t=1311

[spring prairie]

Hey @lost bronze, thank you for contributing to this forum.
Please provide as much information (images, video, description) as you can. This will increase the chance that someone can help you with your issue.
Use the Close button when your issue is resolved.

[mystic siren]

My questions are:

• Can I just use Wood filler to fill in that hole? Yes, build up layers don’t do too much in one go as it might take ages to dry, build the filler higher than the hole then sand it down flush to the rest of the print.
• At what point in time do I know that I'm done sanding? Do I continue to keep sanding with higher grit? If so, when do I know the threshold for being done with each grit? Sand starting at lowest number and work your way up, I use 80 to 100 for rough prints with lots of layer lines, and then 240 or 320 for finer quality prints, I wouldn’t go about 360 or 400 with a raw print. Sanding is learning by doing, basically you need to make the surface smooth and even, a simple test is run a finger nail or tooth pick over the print, if you feel ridges keep sanding until there fingernail runs smooth over the print, then sand it once more at the same grit as last sanding. Then spray a coat of primer on the print, this will highlight spots that you have missed when sanding and this is much easier to see when primed, then you have the simple case of sand, prime and repeat until you are happy with the finish. From there you can paint your base and colours.
• Finally, in this video (timestamped) Frank mentions using sandpaper to reach the recesses, but why wouldn't you just use more wood filler to fill in those recesses? The point of filler is to even out the surface so it can be sanded smooth, if you get wood filler in the recesses you loose the detail as the lines become full of filler. You can add filler and then sand the details back in, but sometimes the filler isn’t required and just a sanding of the print and a few layers of paint will help it look good.

In summary, sanding is learning by doing, you quickly learn what the limits etc are and with most things there isn’t one exact method that works for everyone, take advice and do tests and you will have a method that works for you.

Happy to answer questions if needed, and good luck.

[lost bronze]

Thank you for your response; I really appreciate it! One last clarification: You said on the last bullet point "The point of filler is to even out the surface so it can be sanded smooth, if you get wood filler in the recesses you loose the detail as the lines become full of filler. You can add filler and then sand the details back in, but sometimes the filler isn’t required and just a sanding of the print and a few layers of paint will help it look good."

But wouldn't it just be easier, simpler, and less work to just fill in those tiny areas as opposed to attempting to sand the entire area around them? There's no real detail needed to be preserved here as it's just the flat(ish) dome of the helmet.

[mystic siren]

You are correct, if there isn’t much detail to the piece you are sanding, hit it with filler and it will be good.
On the other hand if the piece is detailed then adding filler can lose those details, so it’s a decision based on what you are making.
So more detailed model less filler, less detailed model more filler, and balance both out with a side helping of sanding.

[lost bronze]

Perfect, thank you!

[spring prairie]

This thread is closed now :white_check_mark: