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Posted (edited)

Am I at risk of removing too much material grinding a sword blade at 400 grit after hand sanding it at 220 grit? What if I hand sand to 400 grit and then run it through the grinder at 400 grit for my own aesthetic purposes, will it remove too much material and affect the flex and dynamics of the sword?

 

Apologies if this is in the wrong section. 

Edited by Matt Robert
Adding information for clarity
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Unless you grind on it for a very long time at 400, no, you won't lose a lot of material.  You do risk ruining the temper, so keep it wet if possible.  

 

I assume you want the 400 grit for a finish, and this is on a heat treated blade finished by someone else?

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Posted (edited)
1 hour ago, Alan Longmire said:

Unless you grind on it for a very long time at 400, no, you won't lose a lot of material.  You do risk ruining the temper, so keep it wet if possible.  

 

I assume you want the 400 grit for a finish, and this is on a heat treated blade finished by someone else?


Correct. So making certain the temper isn’t ruined is extremely important.

 

I assume it would be a very, very small amount of material loss. 

Edited by Matt Robert
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Just wet it regularly to keep it cool. If the steel is too hot for your bare fingers to touch, it‘s time to cool it down. You’ll need to get it to 400°F+ to endanger the temper. Biggest concern is the edge, where it‘s thinnest—that‘ll heat up the fastest. Take your time and you’ll be OK. 

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At 400 you are at much higher risk to affect the temper than the point of balance using a grinder. Do *not* underestimate how easy it is to get the edge too hot. The higher the grit and the thinner the metal, the faster it will heat up. As you get comfortable, you will have a tendency to push it further and hotter. That tendency is your main enemy. Remember that the edge may be (is likely) a lot hotter than the rest of the blade. If you see a change in color, stop immediately and pray it's not already too late. The safest thing to aim for is to purposefully cool the blade more often than is necessary. Imo, lacking experience in this specific case can be effectively compensated by an abundance of caution.

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50 minutes ago, Matt Robert said:

so the small amount of material loss won’t really alter the POB or flex of blade then by much if anything correct?

 

Correct.  We're talking maybe half a gram of material at most, and that will be evenly spread across the entire blade. Any difference should be imperceptible.

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2 hours ago, Francis Gastellu said:

At 400 you are at much higher risk to affect the temper than the point of balance using a grinder. Do *not* underestimate how easy it is to get the edge too hot. The higher the grit and the thinner the metal, the faster it will heat up. As you get comfortable, you will have a tendency to push it further and hotter. That tendency is your main enemy. Remember that the edge may be (is likely) a lot hotter than the rest of the blade. If you see a change in color, stop immediately and pray it's not already too late. The safest thing to aim for is to purposefully cool the blade more often than is necessary. Imo, lacking experience in this specific case can be effectively compensated by an abundance of caution.

 


Would I be able to achieve the aesthetic then by using used blue scotchbrite belts and this could present less risk? Will my ridgelines still be crisp/sharp? 

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Scotchbrite belts will round over the ridges.  If you're really after a satin finish, hand-sanding with 400 will do it.  Single sheet on a hard backer will keep the ridges crisp.

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Posted (edited)
15 hours ago, Matt Robert said:


Would I be able to achieve the aesthetic then by using used blue scotchbrite belts and this could present less risk? Will my ridgelines still be crisp/sharp? 

 

What Alan said. Though hand sanding is slower and is more work, it's also a lot less risky and will give you infinitely more control over what you are actually doing to the blade.

 

Make sure you end with long uninterrupted strokes for a good finish (short strokes will leave unsightly little wiggles everywhere)

Edited by Francis Gastellu
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On 7/5/2024 at 3:37 AM, Francis Gastellu said:

 

What Alan said. Though hand sanding is slower and is more work, it's also a lot less risky and will give you infinitely more control over what you are actually doing to the blade.

 

Make sure you end with long uninterrupted strokes for a good finish (short strokes will leave unsightly little wiggles everywhere)


My main interest is getting the satin finish and keeping the grinder lines perpendicular to the blade as I prefer this look. So it’s keeping those ridge lines crisp while getting the lines as well. Hand sanding across the blade I don’t think will replicate that look so I’m trying to figure out the best way to approach things. The information you fine folks have shared is very helpful and appreciated. 

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You might be surprised.  As long as you keep the sandpaper on a hard backing board and be sure to cut in one direction only (don't rub back and forth, just one way) you can certainly lay perpendicular sanding lines if you're starting with a surface that's finished to an equal or higher grit to begin with.  It does take longer by hand, of course.

 

I see no problem with machine grinding it, just be sure to keep things cool.  If you can slow down the grinder that's best, otherwise grind wet if possible.

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