This is a system for holding vise parallels in place, rather than chasing them around and constantly taking them out to clean chips out from underneath. There is a commercially available system, at $1000 for a starter set. You can make them in your shop. In the past, I've had apprentices or new hires make them. I'm making this set for my current job, as I make multiple parts in a CNC, and I'm tired of jury-rigging springs or whatever.
You make new vise jaws of tool steel. There is a half a 30 degree dovetail at the bottom. A 'key' with a matching angle is bolted to a mill parallel, and fits in the jaw. A spring loaded ball plunger maintains pressure on the key yo keep it down and back against the jaw. I bought a cheap ($30) set of 1/8" vise parallels off of ebay. The system doesn't work well on the 1/2" or 5/8" parallels as they get cocked, so you need 8 pairs, or 16 keys total, and of course, two vise jaws. I'll have to add dimensions in my description, as I couldn't label angles in SketchUp.
As I said, the dovetail and keys have a 30 degree angle. I also put a 30 degree lead-in and blended a radius on each end of the key so they slide in easily. There is a 1/4-20 tapped hole in the middle of the jaw on a 10 degree (from vertical) angle. The spring loaded plunger is 1" long plus a 3/16" plunger, and has a maximum pressure of 13 lbs. They are available from McMaster or MSC. To drill and countersink the parallels, you'll need a carbide drill and countersink. The cheap Chinese parallels are pretty hard, and surprisingly accurate, too. I attach the keys with #5-40 flat-head screws. The jaws are dimensioned to fit a standard Kurt mill vise. I also added 1/4-20 tapped holes to each end of the stationary jaw for attaching a stop when needed.
The length of the keys isn't critical; my first set, I made them 4" long, but didn't have big enough material this time, so I made them 2-1/2" long. They function just the same, and could be even shorter. The jaws and keys are made from tool steel, which will be hardened. I'll grind the jaws, but there is no need to gring the keys if you get them reasonable smooth. I made the keys and parallels so that when installed, the key is about .010-.015 ABOVE the bottom of the parallel. That way, the parallel rests against the bottom of the vise without interference from the key.
Here's some pics-
You make new vise jaws of tool steel. There is a half a 30 degree dovetail at the bottom. A 'key' with a matching angle is bolted to a mill parallel, and fits in the jaw. A spring loaded ball plunger maintains pressure on the key yo keep it down and back against the jaw. I bought a cheap ($30) set of 1/8" vise parallels off of ebay. The system doesn't work well on the 1/2" or 5/8" parallels as they get cocked, so you need 8 pairs, or 16 keys total, and of course, two vise jaws. I'll have to add dimensions in my description, as I couldn't label angles in SketchUp.
As I said, the dovetail and keys have a 30 degree angle. I also put a 30 degree lead-in and blended a radius on each end of the key so they slide in easily. There is a 1/4-20 tapped hole in the middle of the jaw on a 10 degree (from vertical) angle. The spring loaded plunger is 1" long plus a 3/16" plunger, and has a maximum pressure of 13 lbs. They are available from McMaster or MSC. To drill and countersink the parallels, you'll need a carbide drill and countersink. The cheap Chinese parallels are pretty hard, and surprisingly accurate, too. I attach the keys with #5-40 flat-head screws. The jaws are dimensioned to fit a standard Kurt mill vise. I also added 1/4-20 tapped holes to each end of the stationary jaw for attaching a stop when needed.
The length of the keys isn't critical; my first set, I made them 4" long, but didn't have big enough material this time, so I made them 2-1/2" long. They function just the same, and could be even shorter. The jaws and keys are made from tool steel, which will be hardened. I'll grind the jaws, but there is no need to gring the keys if you get them reasonable smooth. I made the keys and parallels so that when installed, the key is about .010-.015 ABOVE the bottom of the parallel. That way, the parallel rests against the bottom of the vise without interference from the key.
Here's some pics-
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