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Tips on Using Magnetic Chuck Parallels and V-Blocks
John Fisher, the manufacturer of Fisher Machine Shop products, has these tips on using the Magnetic Chuck Parallels and V-Blocks.
They are not magnetic themselves. They need a magnetic chuck--they are a magnetic transferring tool
Using any transferring device you will loose a percentage of your holding power. Probably 25% or more.
Block around the part (or at least in the direction the part wants to move usually on the left side of the part) being ground whether or not using a mag chuck parallel or v-block. If you are not able to block the part take extra light cuts.
Before grinding any part do the "wiggle test." Try to move the part. You will be able to move any part on a magnetic chuck given enough force. Blocking will help keep the part from moving. You need to use common sense and experience to determine what is enough holding power.
The success of holding a part is based not only on the part but on the magnetic chuck. I hope every one knows that you need to grind on a steel that is magnetic! The holding power of a magnetic chuck varies greatly. From worst to best holding power is ---permanent magnet with wide poles---permanent magnet with narrow poles---electro magnet with wide poles---electro magnet with narrow poles (best). A lot of the cheap imports are permanent magnets with wide poles. These are OK for parts that are a at least a inch long and you can cover 2 poles but smaller parts can be a problem. You can also do a check and find the strongest area of a chuck and only use that area for small parts.
For magnetic chuck parallels you need to line up the poles to the chuck as best as you can. this will give the best holding power. On a wide pole chuck you may not be able to get a very good line up and therefore poor holding.
For our magnetic chuck v-blocks they also work best if poles are lined up. But they also work OK when not lined up. Take a look at the end of the v-block. You will see that the right and left sides are separated by aluminum. This allows the magnetic field another path to complete its circuit. We patented this feature years ago and a few companies stole the idea.
