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Filling, sanding and all that fun stuff


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Setup for my question.  Filled ejector pin marks on some parts on this dog of a kit I am messing around with mainly to learn new techniques.  Used tamiya basic putty. 

20180421_072412

 

1.  I feel like I put down way to much putty, but this stuff feels like it sticks to everything and I am just not sure how I could have put down less.  Any tips?

 

2.  The left one I sanded with some P400 grit sandpaper and it is some slow going.  I was worried about putting too deep of scratches if I used anything coarser, so what do you start out with when sanding putty?

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With practice you’ll get better at putting less putty down. Remember though, it shrinks, so some extra is good. Using things like toothpicks, popsicle sticks, etc, can also help limit to an appropriate amount for the job. 

 

Use 150-180 grit to sand it down, then work through 240, 320, and maybe even a 4-600 grit to smooth it all out. 

 

Also, be warned that putties are more porous than plastic. So you’ll see it under a coat of paint. Prime the area, lightly sand with a 4-600 grit, and then hit it again and you won’t see the difference between plastic and putty. 

Edited by ESzczesniak
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I use clay modelling tools, palette knives, sandwich picks, or toothpicks to apply putty. These allow me to apply and shape the putty blob, including scraping it off.

 

The next step is to use a cotton bud dipped in Mr Color Thinner to wipe away the excess putty once it has set. This thinner is safe for the plastic. Don't go using some hardware store lacquer thinner--it will melt the plastic. Anyway, with practice, you can get the putty pretty close to final shape. The key is not to remove putty below the plastic surface. On a fillet, like between stabilizer and fuselage or along a nacelle, you can often be done at this point. Like all things, practice will improve your skills.

 

Next come the files, sanding sticks, and sanding pads. Quality Swiss pattern needle files, from cut 0 to cut 6, are an excellent tool to have. Cut 0 will aggressively remove materia. Cut 6 will allow you to get a ready-to-paint surface. Some modelers only use cuts 2 and 4; I have 0, 2, 4, and 6. They work best on a flat or convex surface. On a flat surface, their rigidity prevents you from going below the surface unless you get too heavy handed and gouge the material. With practice and the right cut, you can get a marvelous result on a single or multiple curve surface. See Paul Budzik's Facts on Files for a good treatment on shapes and cuts. I got the Grobet files linked earlier and couldn't be happier; they're my go to abrasive. If you do get quality files, treat them well! I keep them in a block like Paul's Fig 9.  If you sign up for MSC's emails, they send out some good coupon codes, like 25% off.

 

Sanding sticks are more flexible, especially for a concave surface. But, you can also use the flexibility to advantage on a convex surface. Like a file, their stiffness helps to avoid undercutting the surface. Along with your LHS, go to the local beauty aisle and get their nail buffing sticks. The nail buffers can get you a mirror-like finish, especially useful on clear parts.

 

Sanding pads are more flexible still, so they're easier to use on curved surfaces. Just be careful not to undercut the putty below the plastic or resin surface. The 12000 grit pads work great to as the final step in fixing seams and scratches on clear parts.

 

Sanding paper and emery cloth are too flexible for my general use. One way I use this stuff by laying it grit side up on a flat surface. This is great for truing parts, like fuselage or wing halves. The only other way is wrapped around a form of some sort, but this becomes a lot like a stick or pad, which I already have.

 

The key to all abrasives is to start at the coarsest cut or grit and use successively finer cuts/grits until you're done. Each step will clear any gouges from the previous step. Don't try 12000 grit right after that work above with 400 grit. Since you started with 400 grit (I wouldn't go too much coarse then that), use 600 next, then 1000, then on from there.

 

HTH

-- 

dnl

Edited by dnl42
Typo, what else...
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On 4/21/2018 at 9:11 AM, ESzczesniak said:

With practice you’ll get better at putting less putty down. Remember though, it shrinks, so some extra is good. Using things like toothpicks, popsicle sticks, etc, can also help limit to an appropriate amount for the job. 

 

Use 150-180 grit to sand it down, then work through 240, 320, and maybe even a 4-600 grit to smooth it all out. 

 

Also, be warned that putties are more porous than plastic. So you’ll see it under a coat of paint. Prime the area, lightly sand with a 4-600 grit, and then hit it again and you won’t see the difference between plastic and putty. 

 

Wow, 150-180 grit to start.  I would have thought that was a little too aggressive on plastic.  And I like the idea of priming, then sanding again.  Thanks!

 

On 4/21/2018 at 9:17 AM, dnl42 said:

I use clay modelling tools, palette knives, sandwich picks, or toothpicks to apply putty. These allow me to apply and shape the putty blob, including scraping it off.

 

The next step is to use a cotton bud dipped in Mr Color Thinner to wipe away the excess putty once it has set. This thinner is safe for the plastic. Don't go using some hardware store lacquer thinner--it will melt the plastic. Anyway, with practice, you can get the putty pretty close to final shape. The key is not to remove putty below the plastic surface. On a fillet, like between stabilizer and fuselage or along a nacelle, you can often be done at this point. Like all things, practice will improve your skills.

 

Next come the files, sanding sticks, and sanding pads. Quality Swiss pattern needle files, from cut 0 to cut 6, are an excellent tool to have. Cut 0 will aggressively remove materia. Cut 6 will allow you to get a ready-to-paint surface. Some modelers only use cuts 2 and 4; I have 0, 2, 4, and 6. They work best on a flat or convex surface. On a flat surface, their rigidity prevents you from going below the surface unless you get too heavy handed and gouge the material. With practice and the right cut, you can get a marvelous result on a single or multiple curve surface. See Paul Budzik's Facts on Files for a good treatment on shapes and cuts. I got the Grobet files linked earlier and couldn't be happier; they're my go to abrasive. If you do get quality files, treat them well! I keep them in a block like Paul's Fig 9.  If you sign up for MSC's emails, they send out some good coupon codes, like 25% off.

 

Sanding sticks are more flexible, especially for a concave surface. But, you can also use the flexibility to advantage on a convex surface. Like a file, their stiffness helps to avoid undercutting the surface. Along with your LHS, go to the local beauty aisle and get their nail buffing sticks. The nail buffers can get you a mirror-like finish, especially useful on clear parts.

 

Sanding pads are more flexible still, so they're easier to use on curved surfaces. Just be careful not to undercut the putty below the plastic or resin surface. The 12000 grit pads work great to as the final step in fixing seams and scratches on clear parts.

 

Sanding paper and emery cloth are too flexible for my general use. One way I use this stuff by laying it grit side up on a flat surface. This is great for truing parts, like fuselage or wing halves. The only other way is wrapped around a form of some sort, but this becomes a lot like a stick or pad, which I already have.

 

The key to all abrasives is to start at the coarsest cut or grit and use successively finer cuts/grits until you're done. Each step will clear any gouges from the previous step. Don't try 12000 grit right after that work above with 400 grit. Since you started with 400 grit (I wouldn't go too much coarse then that), use 600 next, then 1000, then on from there.

 

HTH

-- 

dnl

 

Thanks dnl for all the info and the links.  Excellent info in here.  Now to go get some files and sanding sticks.  I have some emery boards, including one of those multi-grit buffing sticks I found at one of the big box stores for really cheap. I will work with it and see how it does.  

 

Gentlemen, I apologize for my tardy response.  I saw this info Saturday when you replied, but did not get around to thanking you until today.

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12 hours ago, JesusNut said:

 

Wow, 150-180 grit to start.  I would have thought that was a little too aggressive on plastic.

 

 

Don't press hard. You just want to knock off the waves in the putty in the first passes.

 

And wait a day for the putty to set. It shrinks as it dries. If you sand after a few hours when it looks set it won't look right the next day.

 

Edited by spejic
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7 hours ago, billi said:

I use one of these simple punches with 5 thou plastic to generate small discs as my first go-to. Putty is a last resort. Some kits end up looking like they have freckles. The punch sizes come close to most ejector-pin sizes.

Cheers

Bill Inglee
http://www.leevalley.com/en/wood/page.aspx?p=51577&cat=1,43456

 

Very interesting.  I would not have thought of that.  Thanks!

1 hour ago, spejic said:

 

Don't press hard. You just want to knock off the waves in the putty in the first passes.

 

And wait a day for the putty to set. It shrinks as it dries. If you sand after a few hours when it looks set it won't look right the next day.

 

 

Good point.  I would like to say I knew that, but now I am not sure.  I think so far it has always worked out that way just because I did not have time to work on it a couple hours after filling.  Something to keep in mind as I go forward.

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My $.02 worth.  Go to a cosmetics supply store or counter and grab assorted nail file sanding boards (no emery). They come in various grits, the most useful being one that has two grits on each side, for a total of 4 on the stick. With these, you can start wet sanding with the roughest grit, down to final polishing canopies with the finest grit.  Also, the sanding twigs are useful, as they are the above type sanders cut into 1/8 square (approx.) widths. Saves wear and tear on nearby details. The twigs are available through many modeling suppliers.

 

For putty, I use Bondo Glazing and Spot putty, available from auto parts places. A big tube is cheaper, and lasts much longer than modeling putties. In addition, it can be sanded to a feather edge without pinholes. I always prime over it, and if re-scribing panel lines or detail, I give it a topcoat of CA glue, to give a more plastic-like surface to scribe.

 

For filling areas that I don't like to sand, like wing to fuselage joints,  I use Perfect Plastic Putty, smoothed with a rounded strip of credit card (or my finger, if room). It does not work well for major filling, but for fillets, it's the bee's knees!

 

Ed

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  • 3 months later...

I just use my finger to smear it on, you have more control and can "feel" the thickness of the putty.

Another technique to remove ejector pin holes is to use a small curved blade and scrape away the divot, I did a video for Luis's Y/T channel, I'll post it if I can find it.

 

https://www.youtube.com/watch?v=n8-NF_JV26s

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  • 4 weeks later...

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