Diy hand sanding machine. Opinion?

[Tehemton]

Hi,
Like most, I hate hand sanding and built this machine for making it a bit more convenient.
This is the first prototype that cost less than $10. The motor is an old windshield wiper motor. Although it might be a little slow at the moment, it has more than enough torque to not stall even under heavy downward pressure on the knife.
For now it is just mounted on cheap telescopic drawer channels as the bearings that cost less than 2 dollars for a pair.
https://drive.google.com/folderview?id=1iX8mTQD-thZoqyv-l1rJIUjwbG7RI2LG

I'm looking for tips on how to make this better or if I should just use some elbow grease and leave such toys aside. One obvious point is to make it reciprocate faster. That would involve using a bigger more powerful motor.
Have any of you used something like this for hand sanding?

 

[AVigil]

I like making machines as well.

But if you hate hand sanding that is not the answer to making it easier.

What I like to do it move up the grits then switch to a 400 grit cork belts with compound, then to a 1000 grit belt with compound. It is almost at a mirror finish at that point. You can then move down a few grits and take 20 minutes to hand sand to the level you like.

Let the belt grinder do all the hard work, then you will be surprised how quick hand sanding will become.

 

[JTknives]

I love to build machines to but I never understood the thought behind mechanising hand sanding. I spend more time changing paper then actualy sanding. I feal like a machine would take longer as now I got to stop it and change out the paper and start it back up and watch it do 5-10 strokes and stop it agian.

 

[SV-97]

Hi,
Like most, I hate hand sanding and built this machine for making it a bit more convenient.
This is the first prototype that cost less than $10. The motor is an old windshield wiper motor. Although it might be a little slow at the moment, it has more than enough torque to not stall even under heavy downward pressure on the knife.
For now it is just mounted on cheap telescopic drawer channels as the bearings that cost less than 2 dollars for a pair.
https://drive.google.com/folderview?id=1iX8mTQD-thZoqyv-l1rJIUjwbG7RI2LG

I'm looking for tips on how to make this better or if I should just use some elbow grease and leave such toys aside. One obvious point is to make it reciprocate faster. That would involve using a bigger more powerful motor.
Have any of you used something like this for hand sanding?

I actually like the idea of having a machine like this but I'm not exactly a knife maker. But everytime I do something the hand sanding sucks ass

Maybe add linear bearings to reduce friction - especially when pressing down while sanding. Best add them centered under the work-platform and try to encapsule them from dust as best as possible. Also dust protection for the motor may be a good idea. Also: Mains motor instead of the 12V,18V or 24V or whatever you're using here. Maybe an electromagnet under the platform to allow for surface grinding

 

[TDPurcell]

There is a similar machine around the 8:45 mark in this video.

 

[Tehemton]

There is a similar machine around the 8:45 mark in this video.

Wow! His machine is like mine, but on steroids. I checked out another video on his channel that shows a more detailed picture of his build and that's precisely what the final concept would be like.
I agree, that simply hand sanding would be much faster, but I'm sure you know that feeling when an idea is in your head and you've got to make it just to see if it worked.
I don't plan on getting a huge motor and spending a lot of money on this at the moment, but this could be a fun future build.

 

[kuraki]

PEU made a very nice one in another thread.

I'm in Adam and JT's camp. At first, I hand sanded to correct grinding mistakes I couldn't help but making. Then, I hand sanded earlier in the process to just avoid those mistakes. I thought about making a machine, or using an orbital sander, or some other device like a platen that allowed grinding lengthwise, even tried some of them. Then I realized I should just get better at grinding if I really want to cut down the amount of work there is in hand sanding. A disc grinder can make it easier too if you're doing flat grinds. VFD controlled grinders help a lot too.

A big bowie knife with tall flat bevels coming off the disc grinder at 600 grit takes me about 20 minutes to be hand pulled 600 grit. Maybe an hour or 2 hours to be 1200 grit.

Anyway- my only point is it's possible to be good enough at machine grinding to eliminate 75% of the work you're doing hand sanding. Knowing that, I really think it's worth the time to work on developing that ability. If it takes you 100 hours to learn, but saves you 2 or 3 hours per knife, it's definitely worth it in the long run.

I was doing the same thing with handles. Last night was the first time I finished a handle almost 100% at the grinder and was happy with it. Prior to that I really would just rough them out at 36 grit then file and hand sand until they were done because I just could not get it to click for me at the grinder.

 

[PEU]

PEU made a very nice one in another thread.

Thanks Kuraki! I posted a video of it in the videos thread sticky

I love to build machines to but I never understood the thought behind mechanising hand sanding. I spend more time changing paper then actualy sanding. I feal like a machine would take longer as now I got to stop it and change out the paper and start it back up and watch it do 5-10 strokes and stop it agian.

I get rolls of off-cut belt abrasives from my belt provider for almost nothing, and instead of sandpaper I use about 12" strips and a piece of wood, that is way faster than constantly changing pieces of sandpaper. You can do the same by cutting a fresh belt at the seam. I can remove 240 grit scratches from the grinder using 220grit on the mechanical sander in literally minutes. I use kligspor flex belts (the yellow ones)

Pablo

 

[jdm61]

IIRC, Burt Foster told me about doing the "cross hatch" sanding in the grinder and only doing the pull stokes by hand. I use EDM stones up to 400 and then go back with 400 grit paper and go form there. If you do it right, a 400 grit hand rubbed finish can look good even on a kitchen knife. Burt showed me a good looking knife at blade and asked me to guess the grit. I guessed 400-600 and it was actually 220.

 

[Tehemton]

PEU made a very nice one in another thread.

I'm in Adam and JT's camp. At first, I hand sanded to correct grinding mistakes I couldn't help but making. Then, I hand sanded earlier in the process to just avoid those mistakes. I thought about making a machine, or using an orbital sander, or some other device like a platen that allowed grinding lengthwise, even tried some of them. Then I realized I should just get better at grinding if I really want to cut down the amount of work there is in hand sanding. A disc grinder can make it easier too if you're doing flat grinds. VFD controlled grinders help a lot too.

A big bowie knife with tall flat bevels coming off the disc grinder at 600 grit takes me about 20 minutes to be hand pulled 600 grit. Maybe an hour or 2 hours to be 1200 grit.

Anyway- my only point is it's possible to be good enough at machine grinding to eliminate 75% of the work you're doing hand sanding. Knowing that, I really think it's worth the time to work on developing that ability. If it takes you 100 hours to learn, but saves you 2 or 3 hours per knife, it's definitely worth it in the long run.

I was doing the same thing with handles. Last night was the first time I finished a handle almost 100% at the grinder and was happy with it. Prior to that I really would just rough them out at 36 grit then file and hand sand until they were done because I just could not get it to click for me at the grinder.

Yeah, I have a couple of different 400 and 600 grit belts to try out as well. Currently I've been hand sanding 220 grit upwards. Letting the grinder take the blade to a finer finish is a better approach. Also in Mumbai, we don't have access to cork belts and such. And scotch Brite belts are extremely pricey even if you find some. So for now I guess practicing to get better at close to finishing the blade on the grinder is what will pay off in the long run. Thanks

 

[JG Custom Metal Works]

I hear you on a the whole hand sanding machine idea. I’ll probably try and come up with one at some point.

Also, when using higher grit belts, they have a tendency to make your knife bounce against the platen every time the splice comes around. There’s a couple ways to mitigate this. One, you can add a soft surface on the face of your platen. I use a piece of leather. You could also maybe try and use a piece of felt. I’ve found that it also helps the belt get into crevasses that the flat platen may not have been able to. It can wash out crisp transition lines, like the transition line between the flats and bevel. That is why you don’t want the material you use to be too soft.

Another way to prevent the bounce would be to sand down the spliced area of the belt(on the grit side). I got that idea from Travis Wuertz. I was using his surface grinder and was getting small waves on my finish. You’d probably want to get a diamond sanding sponge or something as regular sand paper might not work as well. To be honest, I haven’t used this method, as I prefer using a trizact belt at the end and it takes care of the waves.

Lastly, you can use trizact belt, as they have the abrasive material stacked real high above the surface of the belt. So high that it really makes it so the splice area doesn’t make a difference. The abrasive material is built up higher than the splice. Good luck and let us know if you have any good developments with the hand sanding machine.

 

[Stromberg Knives]

As I've mentioned before, I've found that lengthwise grinding takes away a lot of the hand sanding. It also makes plunge cleanup very painless.