Tilting fixture plate question

[jmarkwolf]

I started fabricating this tilting fixture plate a few years ago (see pic below). Saw some on the web and thought they were pretty clever. Machinist jacks would support the open end.
Unfortunately, a gap opened up between the plate and the round stock , due to slip while drilling I assume. It annoys me so I set the project aside.
I now have an application for it and am thinking about completing it and implementing some suggestions for improvement that "draw the plate into the 90 degree crotch" of the round stock rather than "bolt it down" as I did.
This would entail drilling bolt holes into the crotch of the 90 degree cut-out of the round stock, bisecting the 90 degree angle perfectly. Then drilling and tapping corresponding blind holes into the lower inside corner of the plate, bisecting that angle perfectly . Bolts would then draw the plate tight into the corner.

I've been playing with ideas how to do this, but am concerned the practical aspects of the required fixturing haven't revealed themselves to me yet.

Can anyone advise?

 

[RJSakowski]

If it were me, I would drill the holes in the plate oversized to allow pulling the plate tight. The position could be fixed with a couple of dowel pins, if desired.

 

[jmarkwolf]

That occurred to me as well and would certainly be easier!

 

[talvare]

I agree with RJ's solution but I would probably "slot" the holes with an end mill of the same size as the existing holes so that the plate wouldn't be likely to move side ways. I think the dowel pinning is a good idea as well.

Ted

 

[jmarkwolf]

OP here with an update:

I did some investigation. I tried turning the plate upside down to see if anything improved, it did not. The gap just moved to the other end of the plate. When all 4 bolts are in, there is an approx 0.035in gap at one end, the other end being tight. If I remove 2 of the bolts I can snug up the plate so there is no gap. I started this project on my old Bridgeport, the table was a little loosey goosey, and think it caused the 0.035in offset in the line of 4 holes. Or my vise was out of tram.

I think RJ's solution is the easiest fix. Enlarging the holes slightly will close the gap, and adding hardened dowel pins will lock the plate in place and the bolts with Loctite will keep it in place.

I was wondering how I could hold the plate while drilling for the dowel pins, and I noticed the holes on the back surface of the movable jaw of my Kurt vice will provides the means to clamp the plate tight against the round stock. I think chamfering the lower inside corner will help also. So I think I can get this project in the bag finally.

 

[Bill W.]

Turn the plate end for end and drill holes to match the round stock...???

 

[Cadillac]

Good idea using clamps on the moveable jaw. I made a plate similar to what your doing I use it all the time now. Might wanna think about popping a whole bunch of threaded holes in the plate for hold downs. The only thing I did different was the bolts go through the round stock and thread to the plate so the top surface is flat no protrusions. The only thing I don’t like about using dowels is you don’t get any clamping pressure from them, which putting bolts in the place will help with the strength of the connection between the round and plate. That joint will be seeing some pressure when milling on plate. Good luck.

 

[rgray]

might change to flat head bolts and sink them below the top surface so you can use the entire top surface.

 

[jmarkwolf]

might change to flat head bolts and sink them below the top surface so you can use the entire top surface.

Flat head bolts are the intention. The hardware shown is just temporary for fit-up.

 

[jmarkwolf]

I made a plate similar to what your doing I use it all the time now. Might wanna think about popping a whole bunch of threaded holes in the plate for hold downs. The only thing I did different was the bolts go through the round stock and thread to the plate so the top surface is flat no protrusions.

Holes will come later, once I'm confident the fit-up is good between the plate and the round stock.

I wish I had done mine the way you did yours re the bolts drawing the plate into the crotch. I wasn't confident in my machining skills to get the angles just right. Might I ask what your procedure was?

I'm assuming the "proper" way to have done this would be as follows;

1. Mill the notch in the round stock.
2. Drill the desired holes directly into the crotch, all the way through the round stock, bisecting the 90 degree angle perfectly.
3. Drill the corresponding holes into the bottom corner of the plate, bisecting that angle perfectly.

My questions would be how to bisect the angles perfectly? What kind of setup?