holds a cylinder head or something at the right angle so you can do something to it? That's just a guess.
Its a pair of nest plates for holding work at an angle for machining; probably for milling since they don't appear to be ground. The little steps on the back are probably for toe clamps to hold them to mill table and the round rods are to keep them aligned during set up. Looks like a 30/60 degree triangle, but they could have been made for a special operation.
Many of these specialty jigs are not for a common part that we might recognize. Sometimes machinists build these jigs for a particular part that they need a certain angle, and when the part is done they may never use it again. Most the machinists I know save the jigs, just in case they do another, or it could be modified for some other use later.
Tend to agree with this, however, there aren't any tapped holes to hold the "workpiece" to the angled surfaces. perhaps the part itself had some bosses that could be clamped on to hold it to the mill bed, forcing it into the corners towards the front. Another guess is an inspection fixture of some sort. The angled surfaces appear to be milled, rather than ground; which doesn't necessarily preclude accuracy.
Those are probably for holding a cylinder head at the right angle to drill and tap the rocker studs. I'd bet they're something that someone made - because their drill press (or whatever they were using) didn't have a tilting table on it. Those look pretty nice, I'd like to have something like that myself.
I made something similar to these several years ago to drill and tap Harley heads for dual spark plugs. Looks like a fixture for a milling machine.
I agree that they look to be a "quick and dirty" fixture for some unknown milling job.Job shop work requires this kind of stuff on a daily basis. Because there is no method for holding anything to the fixture, I suspect that it is used with a vice that actually holds the part. I've made tons of this kind of stuff over the years.
It holds a wobbly shaft while you put on a rickety gear. Tricky operation, most of the time completed while consuming cold adult beverage.
All of the above responses are a possibility. Only way to know for sure is ask the guy who made it. Most machinist over the span of a working life make many such fixtures. You can be most assured it was for performing it's purpose through many repetitions. Clever machining pros can devise really neat ways to accomplish a one off operation without resorting to a purpose built fixture. Frank
I agree with all of the above as possible uses. Looks to be a jig fixture; possibly for 30 degree or 60 degree set ups; with adjustable width; to go on a milling machine and could be used for repeat set ups. Don't know what the maker had in mind when it was made, but its a trick yet simple design... I like it
It was not uncommon for me to spend more time making a fixture, than it took to machine the part, once the fixture was done. This is why machine work can get expensive.
It would have been better to take a picture straight on and from the side to get a better look. I would add it appears that it would be or could be used mounted to a magnetic table mount, like on a tool grinder. It does appear that you could mount a brake press tool on it to grind a specific angle on it.
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