Minilathe Boring Bar Holder

Boring Bar Holder for the Minilathe

This is a very simple project. It is probably a good first project for a beginner. Come to think of it, it was...

After getting my 7x12 Speedway minilathe from Homier, I ordered a cheap 3/8" boring bar set from Enco. Before I could use them, however, I needed a holder to hold them. I suppose I could have ordered one from Enco, but I figured I'd make one instead.

The design starts with a 1/2" by 5/8" by 1-5/8" block of aluminum or other metal. This block is carefully cleaned up square and flat, and placed in the tool holder of the lathe. Label which side is the top.

The block is carefully lined up with the chuck of the lathe. Insert a stiff rod (I used 1/2" mild steel) in the chuck and adjust it to run true. When it does, loosen the toolpost and drive it up against the side of the rod. With it still in contact, tighten the toolpost down. This should align the block so it is perfectly parallel with the axis of the lathe.

Carefully step-drill a 3/8" hole in the block, 1" deep. I started with a small center drill to make sure the hole was where I wanted it. The I progressed to a 1/8" drill, 1/4" drill, and finally a 3/8" drill. (Actually, I used an end mill for the last step.) The hole must be exactly centered and the block must be exactly lined up with the axis of the lathe, or the hole will pop out the side of the block. Be careful not to bump the cross slide feed, or you'll misalign the the hole and the bit! It would be a good idea to clamp the cross feed in place.

The last step is to put the block in the vise with the hole up, and hacksaw a slot through the center of the hole, for it's full depth.

Piece of cake

Using the boring bar holder is simple - just put it in the tool post, but don't tighten down too hard on it until there is a boring bar in it. Then tighten the toolpost screws down hard enough to compress the block, slightly closing the slot, and clamping down on the boring bar.



© 2003 W. E. Johns