POTD was too long in the making. I bought my first mill in around 1985 (Grizzly mill drill) and have been dealing with parallels tipping over in the vise for over 30 years. Had parallel keepers on my “to do” list, just never got around to them. I’ve contemplated making the spring-loaded Kurt style, pieces of packing foam in various widths, steel strapping bent in a “V” to form a spring, etc. Saw a design I liked on eBay (search “magnetic parallel keepers” from multiple sellers) that cost about $16 for a set of 4. Not too bad of a price, but I went the shop made route instead. Bought some ½” diameter x 1/8” thick rare earth magnets off eBay for about $0.50 each and went to work on the mill making the keepers.
Sketch of the design
Started by facing a piece of ½” thick aluminum, then band sawed to a touch over 1" and faced to 1” wide. Flipped it flat and milled the surface to the appropriate profile with a ½” end mill. Used the same end mill to pop in a series of ½” blind holes for the magnets.
Faced, band sawed to rough width and faced the
opposite side to 1" width
Used a Borite electronic edge finder to locate the edge
1/2" end mill cutting the profile
Same 1/2" end mill cutting pockets for the magnets
Strip of aluminum ready for the last pass
Finished the profile with a ¼” end mill. I made a couple of passes so the width of the groove in the profile is slightly over ¼” just in case I ever use ¼” parallels (my go to’s are 1/8” thick).
Final profile cut using a 1/4" end mill
Cut one to rough width on the band saw, then cleaned up both cut ends on a 2” x 42” belt sander. Finished pieces got deburred with a Scotch-brite wheel on a bench grinder.
Mill work finished, time to cut the pieces to length on
the band saw and sand the rough edges
Cleaned the keepers with lacquer thinner and put a drop of red Loctite in the magnet hole. Pressed the magnets in with a dowel/hammer.
Loctite in place, tapped in the magnets with a dowel
They work great for holding the parallels in place.
My only concern is accumulation of chips because of the magnets, time and use will tell. Took a little over an hour to make 12 of them. I ran my mill vise back/forth with a large parallel in place and they worked great.
In retrospect, I probably should have gone with 3/8" diameter magnets and a 1/2" width for the keepers as that's the height of my narrowest parallels. I can always sand a notch in the tops/bottoms about 1/8" deep so they'd stay below the surface of a 1/2" parallel. Yeah, the stars will have to align for that to be a problem . . .
Thanks for looking,
Bruce