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Opinion - O-ring machining.

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fergy

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I think you might be happier without tapping those things...it tends to become a PIA over time. That's why I don't do it. But, it's up to you.

You want an upspiral to pull the chips out of the cut. If you want a good cut, look at the finisher bits from Onsrud. Make sure you get a 2-flute for hand use like this. I use the single flutes in the CNC.

BRIAN
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agiacosa

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You guys lost me. How deep is the channel that the tube sits in? Also, why use 40 instead of the 4?

Lastly, I was thinking of tapping as well. Why is this a pain later?

Thanks.

Art
 
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hfmann

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Art, you beat me to the question about the PIA threaded. I've got those on an auto shutoff unit for my skimmer and it is so convenient when removing the lid. So I'm anxious to hear Brian's elaboration on this.

On the depth of the channel, he's saying 5/100 of an inch. Seems like just enough to quickly locate and seat the tube without giving up any of the strength of the 3/8" thick flange. Way too precise for my capability. I trust 1/16" will be fine.

He must be using #40 instead of 4 because the capillary action in the channel wouldn't be all that great. Pins/wires would probably not fit in the channel. Also, I'm thinking that putting the solvent in first and then putting the tube on top of it probably requires the greater viscosity and working time to avoid big bubbles. But that's just my imagination. We'll see what the master says. (Darn, now I've got to take my #40 out of the frig and let it warm up for a day.)

Brian,
Confused on recommended bit.
Make sure you get a 2-flute for hand use like this.
Click to expand...
Hand use? Meaning = hand router? If so, is this the bit? http://www.onsrud.com/Products.asp?Action=View&ID=907&RequestID=4/20/2003+5:32:31+AM I used Onsrud's search using "hand router" rather than "pin router".

Hal
 
F

fergy

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Hal: This is the bit I use for cutting acrylic. It is much quieter, has less chatter, and leaves a nicer edge. It is an O-grind. You might have trouble finding it in a 2-flute version, however. Single-flute bits should not be used in a hand-held router.

http://www.plasticrouting.com/Products. ... ew&ID=1641

Guys, regarding the use of tapping for these flanges, I covered it in the class why I don't think it's a good idea. You should make sure you read the discussion logs.

In summary:
Acrylic is notch sensitive
Salt creep
Broken thumbscrews
Not enough pressure on the seal in high-pressure situations

I use #40 for attaching my flanges to the tube for several reasons. You can fill the channel with #4, if you want, but in general, you need to cut the channel oversized for the tube, because of the poor tolerances of the tube's diameter when mass producing parts. For me, I machine the groove at 6.1" OD x 5.45" ID. That way, I can compensate for fluctuations in tube wall thickness. When you fill this channel with solvent, there are several problems. First, you're standing there breathing a volatile solvent that is evaporating from the surface of the material. You have to keep refilling the channel for a while, to soften the surface, much like you would do for the dip and soak method. Then, when you put the tube into that channel of solvent, and it cures, you are left with that small oversize gap, and it looks strange. #40 makes what is called a fillet between the two surfaces, and looks better. It all looks like a solid piece. You can use the #4 for this, and you can alleviate bubbles by putting a weight on top of the tube, and perhaps for smaller numbers of parts, you can reduce the OD of the channel to perfectly match that section of tube you are dealing with. I have to machine 20-30 identical pieces at a time, so I have to take this into account.

BRIAN
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hfmann

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Thanks for the info Brian,

Hal: This is the bit I use for cutting acrylic. It is much quieter, has less chatter, and leaves a nicer edge. It is an O-grind. You might have trouble finding it in a 2-flute version, however. Single-flute bits should not be used in a hand-held router.
Click to expand...

So, better to get the single flute, non O-grind? I take it the single flute is dangerous in my setup?

Made another template last night to play with (I screwed up the first trying to put the keyholes in it.). This pin setup is really fast.

My "contraption" :) doesn't have the precision of your CNC (obviously). When I went to layout the tube channel on the template, I found when allowing for the inconsistent side wall, it actually overlapped the O-ring channel by a smidgeon. Is that right? I take it that if there is a little overlap, the actual channel for the tube on the acrylic is so shallow (1/16"), there won't be a problem since they are on opposite surfaces of the flange. Does that make sense?

Also liked your idea of using another pin channel for the center waste. Very nice indeed.

Thanks for all the guidance.
 
F

fergy

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Given a good pin router setup, you should actually be able to have really good tolerances. I'd use one of the inverted pin routers if I had the space and money. It would seriously cut down on my time.

It's okay that those overlapped. The tube surface on the backside of the flange will make up for what you removed.

BRIAN
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H

hfmann

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Given a good pin router setup
Click to expand...

lol...that may be the problem - emphasis on "good" -

My problem really seems to be getting the template built to precision. I'm using a circle cutting jig to cut the channels in the template, but measuring from the center of the pivot point to the edge of the router bit isn't so precise that I can get any better than a 1/16", and that's a little iffy.

I'd use one of the inverted pin routers if I had the space and money.
Click to expand...

I woulda thunk that your CNC setup was a lot more expensive than that Onsrud inverted pin router. :)

Take care,
Hal
 
F

fergy

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Nope, think again. That ShopBot was quite inexpensive. And it's not mine, I just hooked the owner up with it. I rent shop time from him.

BRIAN
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F

fergy

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H

hfmann

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Ok Brian,

I liked the look of the threaded thumbscrews so much better than the wingnuts. However....

I think you might be happier without tapping those things...it tends to become a PIA over time. That's why I don't do it. But, it's up to you.
Click to expand...
So far I've only got the KW reactor running. This is the one with the threaded screws on the top. So I can't yet compare it to the wing nut approach, but.....

I'm guessing the wingnut strategy will be easier to tighten. I've had to use a pliers to tighten the bolts enough to stop the leaks, and even then I think it was dried KW that actually completed the seal. Even when I had tightened the bolts to the point where I thought they'd break, there was a very small drip from the bottom of two screws. When I refill the reactor, I may go to a 1/4 o-ring instead of 3/16 and see if that works better.

So before I officially say "you were right", I've got to see how the wingnut works on the Calcium Reactor this weekend. (Yet to get my CO2) This may not be a fair comparison though since the CR uses a gasket rather than an o-ring.

Having said all that...the next one I make will be WINGNUTS!

Take care,
Hal
 
A

agiacosa

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Guys,

I made a DIY version of an inverted pin router. A little bit of wood and a screw with a 1/4" head. The slot for the tube came out perfect using a straight cut bit. However, I was disappointed with the O-ring grooving. Even though I attempted to maintain even pressure, the groove come out uneven with slight ridges as if the router bumped along the groove rather than making a smooth cut.

I may attempt to use a circule cutting jig to route the grooves next time.

Regards,

Art
 
A

agiacosa

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That's just it. It worked OK for the tube channel. The O-ring channel didn't come out so well. The channel isn't even. I think it is diificult to keep even pressure over the template and rotate it at the same time. I'm trying to sand the channel to try and even it out. Hopefully it won't leak.

Art
 
F

fergy

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Try making more than one pass...spin it over the bit several times. It has to do with dirt and chips that accumulate on the table, lifting the piece slightly. A tiny speck of plastic will make a big difference on the channel.

BRIAN
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H

hfmann

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Hey Art,

We really want to see those pix of the inverted pin router. I've been looking at some woodcraft fixtures and trying to figure out how to do it. Particularly, how do you raise your router into the stock? The Master R' lifts I see look like they use a crank on top of the table to raise the router. And that looks like it'd get in the way of the template.

Come on Art, don't be embarassed! Inquiring minds want to know! :lol:

Take care,
Hal
 
H

hfmann

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Hey Fergy,

Nothing like the voice of experience...
I think you might be happier without tapping those things...it tends to become a PIA over time. That's why I don't do it. But, it's up to you
Click to expand...

I finally got my Calcium Reactor plumbed and tested. And the winner of the "threaded versus wingnuts" debate is...

WINGNUTS

They were so much easier to tighten and deal with. I had to tighten my threaded fittings with a wrench. As I said in a previous post, I had some trouble getting a good seal with my threaded bolts and o-ring. The wingnuts tightened up on the gasket by hand and without a problem. Not a single leak on the first try.

Next time and for-ever-more, o-ring and wingnuts!

Thanks.
Hal
 
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