Workholding and milling an awkward part - ideas needed

[picclock]

Hi Experts

I've got an aluminium part to manufacture which is required to seal against another part using O'rings. The part is approx 250x125x25mm. One end of the part needs to have 2 x 3mm wide circular grooves milled for the O'ring seals with holes drilled in the middle. I figure I can do it by swivelling the mill head 90 and mounting the rotary table on a spacer block to allow for the overhang of the part.

However I'm not sure how to mount such a long piece to the rotary table. The best I can figure is to leave the part long then drill and tap into it a short way so it can be mounted onto a plate which is fixed to the table. The plate can be made with the correct offset built in and the part removed and rotated 180 for the other groove. After machining the end of the part can be milled off, removing the manufacturing fixings.

I added up the clearances on my mill and vertically I can only manage 115 mm after all the distances for collet holder, collet and rotary table are taken into account. Short of a 6" head extension I'm sort of stuck for other alternatives.

Any better ideas for achieving this much appreciated.

Best Regards

picclock

 

[jonesie]

just use a mill that is the size of the o ring o. d. or use a boring bar to get the right o.d. drill the center hole first . you do not need the inside dia. the o ring will still seal. use a little silicone on the o ring. jonesie

 

[imagineering]

Round Nose Milling Cutter & CNC perhaps?

Murray.

 

[dvbydt]

+1 for Jonesie's method, I have done this on small rings. Otherwise, mount the job on an angle plate and use a rotary broach cutter that is about the right size for a suitable "O" ring. The normall squish of the ring is 10 percent of the section.

Ian

 

[MachineTom]

As Jonies said with a boring head. I'd suggest a right angle clamped to the table, the work hung off the side. A boring bit normally has a relief angle on the bottom edge, so grind it flat and smaller to get a flat bottom to the groove.

Check the website of Parker Hannifin, more info on Orings than you'll ever need.

 

[picclock]

@ Jonesie - Need the inside ring as pressure is from outside and hole is at low pressure.

@ MachineTom - I would love to hang the work off one side of the mill but its not a round column mill, and the mill head is always fixed over the table. Hence the reason for rotating the head 90 degrees.

The problem is not milling the circular slots - done loads. In a nutshell, the problem is that the work is too long to fit under the mill head and if I turn it horizontal there will be a 10" unsupported overhang.

Many thanks for your suggestions though.

Best Regards

picclock

 

[jonesie]

is there a way that you can make a table extension. if you only have one you could make something to support it and just shim it up so that the surface for the o ring indicates flat a pic. of what you are trying to hold would help. jonesie

 

[kmp]

Hi, not totally sure that I understand from your description but why not use a boring head with a round nose tool in the same manner as a trepanning tool (or a flycutter with a correctly ground tool will do the same job). As long as you can get the centre of the holes you need under the spindle, the groove is circular and the radius you need will fit between spindle centre and column you don't need to move the work at all. Apologies if I have miss-understood your need.

Regards

Keith

 

[picclock]

Hi Jonesie et al

Here is a sketch outlining the part. The part has a top shown on the end view but that's of no consequence. The inside and ends of the part need a fair amount of machining which I can do easily, however the O'ring grooves need creative thinking.

@Keith >>As long as you can get the centre of the holes you need under the spindle,
Sadly I Can't. See third paragraph first post.

Hope this clears up any misconceptions.

Best Regards

picclock

 

[Diy89]

Just throwing it out here...What about removing the compound and using the cross slide on the lathe? Of course your going to need some sort of mount, perhaps a angle block and rocker clamp.

 

[jonesie]

do you have a drillpress that will let you hold the piece,you could mount an angle plate to a drill press table and let the pic. hang down off the side, swing the table so spindle is under the hole center, then use a treepan tool. this might work if you only have two holes. good luck jonesie

 

[picclock]

@Diy89 A 4 Jaw chuck on a lathe with a large swing may work but with the same overhang problem.

@Jonesie I have an old drillpress so that might be the way to go, but I think I'm going to try it with the mill head rotated and a rotary table first. If I make up some support pieces to ensure the work remains at right angles to the rotary table I may get away with it. It will be the first time I've used (abused ??) my mill in this way so I'll post a photo of the setup successful or otherwise. At least its only aluminium 6062 and not the steel that most of my work is with. I'll do that part first and if its nbg I can just face of the work and try another method.

Many thanks for the comments and ideas. The metal should arrive tomorrow.

Best Regards

picclock

 

[Diy89]

I was thinking more of putting the work on the cross, and the tool in the chuck.

 

[Twmaster]

Picclock...

I'd put the head of your mill at 90deg as you are thinking. But, I would use a boring head or trepanning tool to cut the groove. and hold the work stationary.

 

[MachineTom]

No need as I see it to tilt to 90°, the right angle plate a 4-5 inich plate, work clamped to plate with work at 30-60 angle, tilt your head to match, machine with boring head. a 10" piece 1 x 4" in a rotab, and your going to machine the end is like a wet noodle, you need some support to the work.