Knife Holder    6                    1-2016

Magnets

 

This project is going to require one magnet per knife holder. The magnets that I'll be using are called 'neodymium magnets' and they're super strong. Most people have used a 'rare earth' type of magnet before but these put all the others to shame. Now why would I need a magnet for a knife holder? You'll see soon enough.

I bought two magnets of each size because I wasn't sure which one would work best. The one you see below is 13/16" diameter X .200" thick and the other (not shown) is 7/8" diameter X 1/4" thick. The smaller one below has over 18 lbs. of pull and the larger one has 23 lbs. of pull.

What I'm doing next is test-fitting the magnets on a scrap piece of material to make sure the hole size is correct. What I plan on doing is centering the magnet within the wood so it should have the same amount of pull from either side. It's truly unbelievable how strong these little magnets are once they stick to a magnetic surface.
 

 

 

This test block is 1/2" thick (like my work piece) and the magnet is .200" thick. To put the magnet in the center of the 1/2" block I'll need the pocket .300 deep. This will leave a wall thickness of .100" per side which should work well.
 

 

 

My 6" scale is magnetic and once is was close to the back of the block, it jumped right up to the height that you see here.
 

 

 

Now that I have the right hole diameter for the magnet, it's time to make a plug to cover it with. I used some scrape walnut and made 1 1/2" square blocks X 1/2" thick that will be glued in later. At least that's the plan.

Do you remember back on page one that I decided to make three knife holders in place of two? And did you do the math on the magnets that I just talked about above? Well that means one of the knife holders will end up with a larger diameter magnet than the other two. And come to find out I don't have a cutter that will work for the larger magnet so I needed to find a way to use a larger one in place of buying another small one.

 


 

 

Working with Magnets

Magnets don't do well when you try to machine them as they can crack, chip and break most of the time. So how am I going to make the larger one fit into the hole that I have now? Well....I thought that I could sand the outside diameter with my belt sander which should make short work out it. Yeah...that's it....at least that's what I thought would happen.

If you've ever used a belt sander like the one I have (belt size is 1" X 42"), you know to hold your work with a light touch so you have finesse while working. Once I got close to the sander, that magnet jumped out of my hands straight to the belt and down against the tool rest. You talk about get'n someone's attention...this was it!! With my eyes all big and the magnet held fast against the belt sander along with all this terrible noise, I couldn't find the off switch fast enough.

What happened was I had forgotten there's a small steel plate that is about 4" long that rides behind the belt which is placed between the tool rest and the top pulley. And I forget that I was actually working with a magnet. I mean, this was my first time trying to sand one, so quite laughing and cut me a break here :-] 

After realizing what happened, I put a death-grip on it this time and started removing material. And where do you think all the magnet dust went to? Right back onto the magnet...that's where!! I had to use a rag and my fingers to remove all the grit from the magnet, which wasn't fun at all. But after a few minutes I had the size I was looking for. On the other hand, that magnet wasn't pretty anymore because there wasn't any chrome plating left on it after I was done with it.

 

 

I'm going to use my boring head to make the plugs with. Now normally you use a boring head to make a hole with, but in this case I turned my boring bar 180 degrees to leave an area standing in place of making a hole. I traced around the magnet to give myself a reference line and ran the boring head direction backwards to cut the plug.
 

 

 

After a few minutes and a couple of adjustments, I now have the diameter that I need for my plugs. I made the height of the plug (raised area) .050" taller than I needed. That way when the bottom of the plug is against the magnet, I should have clearance between the plug and my work piece.
 

 

 

I cutoff the corners and then sanded the edges so it would be easy to work with. Now it's time for a test fit.
 

 

 

This shot should give you a better idea of what the clearance between the plug and work piece will look like. After a small amount of sanding the plug fits nice and snug and the plug is seated against the magnet without the two surfaces touching which ensures me it's bottomed out. With everything checking out it's time to put a pocket in my work piece.
 

 

 

I used two cutters for this operation: one for roughing and one to finish the hole. This worked out great but one of the knife holders will need to have a different depth because one magnet was .050" thicker than the others (the one I sanded). This meant that one knife holder will be .025" deeper and I used Tracey's for this. Why hers? I'll show you later.
 

 

 

I'm ready to glue in the plug and see what happens. I'm not sure if it will work but that's the plan.
 

 

 

I dabbed some glue around the plug and pushed it in but it didn't go all the way down. I believe the close fit that I had along with the thickness of the glue made it fit tight. Once I placed my clamp on it, the plug seated and I was good to go.
 

 

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