Home Built Surface Grinder

[Natlek]

Why is everyone without a mill using rectangular magnets? When I eventually get around to building one of these I'm planning on turning a plate into swiss cheese and pressing round magnets into the holes. Is there something I'm missing?

No , you don t miss anything ......they would work perfect and was so easy to install them .This is picture of mine magnet plate before i install round magnets 10 x 10 mm , for now I don't have a picture with mounted magnets............

 

[Hubert S.]

I don't have a mill, so my plan was to find a file about the width of the magnets, grind a chisel edge on it, and hand scrape the channels. Just clamp a straight piece of steel accordingly so as not to make crooked channels. We'll have to see if this idea actually works, though.

That sounds like a lot of work, maybe the round magnets are not such a bad idea. Forstner bits work well in aluminum and can cut mostly flat bottomed holes. I could see that working well for putting magnets in.

Maybe you have some other power tools that could be used to cut slots, though. One option would be a table saw with a cross-cut sled. I've cut pretty thick aluminum on a table saw with no issue. You should be able to cut 1/4" deep slots, move the stock by not quite a blade width, cut again. Repeat until you reach the desired width. With a cross cut sled or a decent miter gauge, this is a pretty safe operation. There will be some ridges at the bottom of the dado using this method with a standard saw blade with an ATB tooth profile, but that should be easy to clean up. Or leave the ridges and say they give the epoxy a better grip... A similar method would be to cut the slots on a sliding miter saw that has a depth stop for cutting dados. For either method, a spacer block or kerfmaker jig would help to get consistent slot widths.

A hand held circular saw with a jig would be another option to cut the slots. You could probably build a jig from wood scraps pretty quickly to make this work. If you have a track saw, this would be even easier, but a piece of plywood with a fence for the saw to ride against will do the same thing for a regular saw. Add a fence for the aluminum to butt up against and a clamp or two, and you should be in business. Depending on the kerf of your blade, this might take a few more cuts than the table or miter saw, but it will be a lot quicker than scraping by hand with a chisel...

My least favorite option would be to use a router table, again with a miter gauge or sled. With the router table, you will probably need several passes to reach the full depth of the magnet. Router tables scare me a bit and I would want to have a good sled if I were to attempt this. I would prefer to use a saw over the router table, but I'd probably use the router table before scraping by hand if those were my only options.

 

[Natlek]

I don't have a mill, so my plan was to find a file about the width of the magnets, grind a chisel edge on it, and hand scrape the channels. Just clamp a straight piece of steel accordingly so as not to make crooked channels. We'll have to see if this idea actually works, though.

Why you not cut strips of aluminium and bolt them to main plate , it's easy and simple to do and doesn't need any special tools .

 

[Ken H>]

Ooops, my idea already posted. You'll LOVE your SGA when you've got it going. Do you have a drillpress? Some folks have used a drill press as a mill for the slots.

 

[N.W. Gean]

My dad has a drill press. I don't want to hurt it by trying to mill with it.

Bolting aluminum strips isn't a bad idea. Neither is the saw.

 

[Signalprick]

I don't have a mill, so my plan was to find a file about the width of the magnets, grind a chisel edge on it, and hand scrape the channels. Just clamp a straight piece of steel accordingly so as not to make crooked channels. We'll have to see if this idea actually works, though.

Ask a buddy with a mill to help you out with this. You'll be glad you did. It may cost you or better yet, your a knife maker we barter with each other all the time.

 

[N.W. Gean]

Ask a buddy with a mill to help you out with this. You'll be glad you did. It may cost you or better yet, your a knife maker we barter with each other all the time.

Sounds like you're trying to make a deal with me, Jason

I'll ask around my town. I don't know that anyone in my neighborhood has a mill but it doesn't hurt to ask.

 

[Signalprick]

Sounds like you're trying to make a deal with me, Jason

I'll ask around my town. I don't know that anyone in my neighborhood has a mill but it doesn't hurt to ask.

Not necessarily but I mention it because I'm doing some fixture work for a maker coming back from hiatus who does not own a mill. I will be making him a mag chuck among other things in trade for something special.

 

[N.W. Gean]

Not necessarily but I mention it because I'm doing some fixture work for a maker coming back from hiatus who does not own a mill. I will be making him a mag chuck among other things in trade for something special.

I'll see what turns up. If nothing else, I'll hand scrape and enjoy the meditation

 

[ashwinearl]

No , you don t miss anything ......they would work perfect and was so easy to install them .This is picture of mine magnet plate before i install round magnets 10 x 10 mm , for now I don't have a picture with mounted magnets............

Why does a commercial tool like this not exist? Other than the small benchtop Sanfords (which are collector's items, expensive and hard to come by) there are no small benchtop dedicated belt-based surface grinders. I think there is a market here for the hobby machinists, knifemakers, who need something small but not need high precision. I know that one of the key things about a good surface grinder is mass, but I could never get one down in my basement shop.

 

[N.W. Gean]

Why does a commercial tool like this not exist? Other than the small benchtop Sanfords (which are collector's items, expensive and hard to come by) there are no small benchtop dedicated belt-based surface grinders. I think there is a market here for the hobby machinists, knifemakers, who need something small but not need high precision. I know that one of the key things about a good surface grinder is mass, but I could never get one down in my basement shop.

A 2x42 or even a 1x42 if the table could move side to side would be perfect. I nominate Harbor Freight to develop and sell it for 199.99!

 

[N.W. Gean]

Alrighty, here's where I'm at with this project. I did not need to cut the aluminum bar stock into 2 arms, but I wasn't sure how the wheel would line up with the chuck. I was expecting to have to offset it, but wouldn't you know it, it landed almost perfectly where it should be.

I decided to use a thick piece of angle iron as the chuck and steel square stock to make the slots. As you can see, the chuck is crooked by about .030 from end to end. I drilled the holes in the angle iron slightly off Do I try to fix this by re-drilling the holes, or would surfacing the chuck (as I need to anyway) fix the issue? I could also shim the connection between the 2 arms when I bolt them together.

Overall, if you don't count the aluminum bar stock that I did not use for the chuck, I'm in this thing for $350. Not a bad cash savings over a $1k prebuilt. Still need to buy a dial indicator so I can see how much each pass is taking off. In initial testing with the 2 arms clamped together, I am rounding off edges badly, but I know that the chuck hasn't been surfaced yet and I'm likely taking too much per pass.

 

[Natlek]

That washer on contact wheel bolt seems to big to be there ..........Look like both inner and outer race of bearing are in contact with that washer ?

 

[N.W. Gean]

I am guessing that they are. Should I only be using the smaller washer?

 

[Ken H>]

The nut/washer should only be putting pressure on the center bearing race.

I wouldn't take more than 2 or 3 thou for light passes if wanting a good finish. I'll crank down for .005" perhaps when doing a rough cut with 36 grit belt.

 

[Natlek]

I am guessing that they are. Should I only be using the smaller washer?

Yes

 

[N.W. Gean]

Thanks guys. Natlek, you have so many grinding wheels that I think you're the forum authority on contact wheel matters

I haven't intended on taking heavy passes. Just need more experience.

Should I grind out the imbalance in the chuck or try to straighten it?

 

[Natlek]

Thanks guys. Natlek, you have so many grinding wheels that I think you're the forum authority on contact wheel matters

I haven't intended on taking heavy passes. Just need more experience.

Should I grind out the imbalance in the chuck or try to straighten it?

Last step in building before you start to grind real steel is to surface grind chuck........

 

[REK Knives]

Alrighty, here's where I'm at with this project. I did not need to cut the aluminum bar stock into 2 arms, but I wasn't sure how the wheel would line up with the chuck. I was expecting to have to offset it, but wouldn't you know it, it landed almost perfectly where it should be.

I decided to use a thick piece of angle iron as the chuck and steel square stock to make the slots. As you can see, the chuck is crooked by about .030 from end to end. I drilled the holes in the angle iron slightly off Do I try to fix this by re-drilling the holes, or would surfacing the chuck (as I need to anyway) fix the issue? I could also shim the connection between the 2 arms when I bolt them together.

Overall, if you don't count the aluminum bar stock that I did not use for the chuck, I'm in this thing for $350. Not a bad cash savings over a $1k prebuilt. Still need to buy a dial indicator so I can see how much each pass is taking off. In initial testing with the 2 arms clamped together, I am rounding off edges badly, but I know that the chuck hasn't been surfaced yet and I'm likely taking too much per pass.

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Looking good there! So I thought I'd point out a couple things just as an fyi...

First, the dial indicator is helpful but not exact (esp. when starting with a new belt at ~50 grit or below). The reason for this is because the grit breaks down and you have to grind off what appears to be more than it really is on the dial indicator. Time and experience will help you gauge for sure.

Secondly, what duro is your wheel? Ideally a metal wheel is best imho, which is what I'm using. But even with that you will still get some uneven grinding at holes and edges due to belt compression (with a metal wheel and 120 grit belt I measured about .0015" which isn't bad at all). The nice thing I like about an SGA is that it gets me close QUICK if I need to remove a lot of material. I haven't played around with putting removable scales on directly after an SGA finish yet (without any air gaps in between) but will be looking into that soon so see if doable. So for example, here are some blades done on a metal wheel at 120 grit (yes the chuck had been freshly matched and surface ground to the wheel) and then taken to my real surface grinder. The dark spots are the high spots where the stone wheel was removing metal.

 

[N.W. Gean]

Looking good there! So I thought I'd point out a couple things just as an fyi...

First, the dial indicator is helpful but not exact (esp. when starting with a new belt at ~50 grit or below). The reason for this is because the grit breaks down and you have to grind off what appears to be more than it really is on the dial indicator. Time and experience will help you gauge for sure.

Secondly, what duro is your wheel? Ideally a metal wheel is best imho, which is what I'm using. But even with that you will still get some uneven grinding at holes and edges due to belt compression (with a metal wheel and 120 grit belt I measured about .0015" which isn't bad at all). The nice thing I like about an SGA is that it gets me close QUICK if I need to remove a lot of material. I haven't played around with putting removable scales on directly after an SGA finish yet (without any air gaps in between) but will be looking into that soon so see if doable. So for example, here are some blades done on a metal wheel at 120 grit (yes the chuck had been freshly matched and surface ground to the wheel) and then taken to my real surface grinder. The dark spots are the high spots where the stone wheel was removing metal.

Thanks!

I just need a way to see roughly where I'm going with each pass. Time and experience, I have to agree with as well. My first couple passes on an unground chuck have been rough.

75D. That is as hard as Sunray would put on the wheel. I'm not sure where I could get a 6" aluminum wheel. I was hoping that light passes could minimize the issue.