The Small Flat Rate Box was not intended to jam as many blades and shears inside and ship like the TV commercial says "If it fits-It Ships". WRONG. Let me say from experience that your not saving any money what so ever if equipment gets damaged or lost. We have received 24 blades and two pair of shears in a very over packed SFRB, and they were upset that I wasn't going to ship back to them that way. It's insane trying to save a couple bucks by risking all your equipment.
When you pack blades into any box you have to have the proper "packing" to make sure blades are safe. They can't bang into each other, or they can't bang against a pair of shears during shipment either. The SFRB is small enough where the postal worker is going to throw it into a bin rather than placing it there. If your SFRB is filled and heavy with all that metal, it may burst open when it hits the back of the bin because of the lack of proper packing. The SFRB is constructed of very thin cardboard, its not as thick as the bigger boxes. This alone will invite cracks and splits if its overpacked and dropped or thrown. Remember this, if your box bursts open during shipment, it will probably just get swept up and forgotten. It will not be forwarded in that condition.
To head off any disappointment, pack your equipment properly in a shipping box thats the appropriate size to hold the amount of stuff your sending properly packed. So its not a flat rate box, if you jam everything you can into a SFRB to save a couple dollars, you stand to loose alot more than just the savings on the shipping. Breaking one tooth on a blade during shipment will cost you $20 to replace that blade, you didn't save anything. Getting the right box, or even a blade box to secure those blades will save you money in the long run.
If you insist on using a SFRB, use this as a guide. Use a SFRB when you have 6 blades or less, wrap them real good in bubble wrap and they may be good. Fill in any spaces with packing media so you hear nothing moving when you shake the box. A couple small pair of 6 inch shears is good as well (8" shears are too long). Wrap them in bubble wrap and make sure they are small enough not to poke out the sides. They see that, the box will go no further. Fill in any spaces with packing media as well.
The SFRB is a very needed mode of shipping for something small, without costing alot of money. Please don't missuse the SFRB by over packing it, it's just not worth it. Use the right size box. Below is the proper box containing blades in a blade box and shears wrapped in bubble wrap. The weight difference between putting this much stuff in a SFRB and the one used below was one pound, and the difference in the shipping costs was $2.70. Isn't it worth $2.70 to make sure nothing gets broke in the mail???
I hope these examples will help you feel not so scared to ship equipment for sharpening.
Have a blessed day and read those labels