How do I hold this

Topics include, Machine Tools & Tooling, Precision Measuring, Materials and their Properties, Electrical discussions related to machine tools, setups, fixtures and jigs and other general discussion related to amateur machining.

Moderators: GlennW, Harold_V

Post Reply
SteveM
Posts: 7763
Joined: Mon Jun 27, 2005 6:18 pm
Location: Wisconsin

How do I hold this

Post by SteveM »

I need to make some clamps for attaching the vertical head on a P&W3c mill.

The features on the clamp are all circular, with radii ranging from about 2" to 4"
PW_Clamp.jpg
Rather than milling each piece one at a time on a mill with a rotary table, I figured turn a disk on the lathe with the cross-section profile of the clamp and then slice it like a pizza (a seven-section pizza, oddly).

I have a piece of 3/4" thick 8" diameter steel that I can use.

Question is: what would be the best way to hold the work?

I was thinking this:
Start with a a 2" diameter chunk of aluminum rod, face in the lathe for perpendicularity and flatness
Drill three holes (tap size) on a 1"-1-1/2" diameter circle in the center of the disk
Bore matching holes in the aluminum and tap them
Open up the tap-sized holes on the disk to clearance holes (tap holes first was to get accurate location for the aluminum)
Bore the soft jaws to fit the aluminum rod (using soft jaws because of the larger contact area)
I should probably face the soft jaws to ensure that the disk sits flat.
Mount the aluminum in the soft-jaw chuck and face to get a flat surface
Bolt on the disk

I figure I should make a profile template that fits into the clamp so that I can machine to where the template fits my machined disk.

Any other ideas?

Steve
User avatar
ctwo
Posts: 2996
Joined: Tue Mar 27, 2012 12:37 pm
Location: Silly Cone Valley

Re: How do I hold this

Post by ctwo »

You're going to make 7 of those pie-shaped clamps?

I would probably turn them all as you suggest from one piece. It looks like the stock could be held normally with vice jaws - face/turn the back side, then flip and turn/face the steps. Then I would probably drill the holes for each clamp as a place to clamp for milling out each piece of the pie, probably on a RT. Once set up there, you should be able to mill the relief. You might need a pallet with drilled/tapped holes on your RT.
Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...
SteveM
Posts: 7763
Joined: Mon Jun 27, 2005 6:18 pm
Location: Wisconsin

Re: How do I hold this

Post by SteveM »

My rotary table doesn't fit the mill I have operational right now, so the cutting will be hand or bandsaw (ouch!), then cleaning up the sides on the mill.

The face that is down in the picture only has a counterbore in the hole, so that can be done on the drill press or mill at the same time as the hole is drilled. No turning will need to be done on the back face.

There is the little relief on the clamping tab which ensures that it clamps out at the widest part and not just in the middle. That will be a quick job on the mill using a fixture or some clamps on my pallet to hold it.

I drew it out a while back and it worked out to 7 pieces. I might make it 6 just to give me more room for messing up the saw cuts.
whateg0
Posts: 1114
Joined: Sat Mar 28, 2009 3:54 pm
Location: Wichita, KS

Re: How do I hold this

Post by whateg0 »

If you turn them on the lathe, why is a rotab needed? You'll have all of the concentric surfaces from the turning operation. Just chuck the piece and turn it. The pie pieces will leave some waste, but all of your radii will be done. If you don't have a chuck big enough to hold the 8" piece, mount it to a face plate. I'd drill the holes first, but undersize such that a SHCS will fit down in the work, recessed so you aren't cutting the heads of the screws. Then after it's done, saw out each pie piece and drill the holes to size. The only mill work needed, would be cleaning up the edges, and the what-looks-to-be square-sided recess along the clamping edge.
whateg0
Posts: 1114
Joined: Sat Mar 28, 2009 3:54 pm
Location: Wichita, KS

Re: How do I hold this

Post by whateg0 »

Here's what I'd envision. Sorry for the line errors. All I have on my work laptop to draw with is Visio.
pic-clamps.jpg
pic-clamps.jpg (7.3 KiB) Viewed 3904 times
User avatar
ctwo
Posts: 2996
Joined: Tue Mar 27, 2012 12:37 pm
Location: Silly Cone Valley

Re: How do I hold this

Post by ctwo »

How do you cut out the pie pieces, and then how do you hold them to finish the edges and then locate the hole, without a rotab?
Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...
SteveM
Posts: 7763
Joined: Mon Jun 27, 2005 6:18 pm
Location: Wisconsin

Re: How do I hold this

Post by SteveM »

whateg0 wrote: Thu Jan 18, 2018 12:54 pm Here's what I'd envision. Sorry for the line errors. All I have on my work laptop to draw with is Visio.
Image
That's exactly what I am thinking.
ctwo wrote: Thu Jan 18, 2018 6:42 pm How do you cut out the pie pieces, and then how do you hold them to finish the edges and then locate the hole, without a rotab?
Bandsaw them, then clamp them in a vice and mill the edges to finish. The sides are not important dimensions.

For the holes, I will just use a pointed tool in the lathe to draw a circle. Then I can just estimate the position - the distance from the edge is more critical than where along that circumference.

I might just go with six, as it will give me more leeway to mess up with the bandsaw, and then I can also use the 60-hole indexing feature on my bull gear to mark the exact position along the circumference of the scribed circle,

Steve
whateg0
Posts: 1114
Joined: Sat Mar 28, 2009 3:54 pm
Location: Wichita, KS

Re: How do I hold this

Post by whateg0 »

The radius on the outer edge will, of course, determine how big of a piece you have to start with to do it this way. The width across the wide end will determine how many pieces you can get out of one circle. Once you have the turned features in the workpiece, it's not much more work to make the 7th piece, IMHO.

Dave
Post Reply