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Old 12-19-2012, 09:39 PM
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BBShark BBShark is offline
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Default Lapping Aluminum?

I want to make a conical seal, like a valve and seat on an engine, out of 6061-T6 aluminum. This will be about 2 1/2 dia with 45 degree seat angle. The surfaces do not need to make an airtight seal but need to seal fluid about the viscosity of diswashing liquid. There is also very little seat pressure and basically no pressure differential.

So with that in mind, I'm thinking I might be able to lap the faces of the aluminum seal just like a valve. The only information I can find on lapping aluminum is for gun sights. I don't know anything about this but understand that guys are lapping (some kind of) ring that is made out of aluminum.

I know this is a longshot but, do any of you guys know anything about this?
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Old 12-20-2012, 03:24 AM
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Ok, so I'm just really lazy.

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They're already bent for a 37* flare. but they're really soft too.
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Old 12-20-2012, 04:12 AM
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Originally Posted by BBShark View Post
I want to make a conical seal, like a valve and seat on an engine, out of 6061-T6 aluminum. This will be about 2 1/2 dia with 45 degree seat angle. The surfaces do not need to make an airtight seal but need to seal fluid about the viscosity of diswashing liquid. There is also very little seat pressure and basically no pressure differential.

So with that in mind, I'm thinking I might be able to lap the faces of the aluminum seal just like a valve. The only information I can find on lapping aluminum is for gun sights. I don't know anything about this but understand that guys are lapping (some kind of) ring that is made out of aluminum.

I know this is a longshot but, do any of you guys know anything about this?
Can't offer any help here, but I do have to say you come up with some very unusual and interesting posts. I have no idea what you are working on most of the time, but you certainly get my curiosity going. I don't think I'm the only one here that would enjoy hearing more of the technical details of some of your projects (assuming it's not some secret DoD project, of course).
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Old 12-20-2012, 01:08 PM
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Mike, I guess I do come up with some weird stuff and you are correct, this is not an automotive project. This is a project I am doing for work. I need to optimize the sealing angle of this "valve" so I may end up having 5-10 made. The only accurate method proposed (so far) is to EDM the pieces and electropolish. That will take lots of time and $. I just thought there has to be a quicker/cheaper way to do this.

Tim, the conical ring is about 2 1/2 inches in diameter with no gap between the seal surfaces. So those seats won't work.

The only thing I have found on lapping aluminum is related to making scopes for rifles. I have no knowledge of that process and don't really understand what they are talking about.

I posted this here because I thought, if anyone knows how to do this, it will be someone at VM. Very smart people here with a lot of experience!
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Old 12-20-2012, 05:10 PM
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Mike, I guess I do come up with some weird stuff and you are correct, this is not an automotive project. This is a project I am doing for work. I need to optimize the sealing angle of this "valve" so I may end up having 5-10 made. The only accurate method proposed (so far) is to EDM the pieces and electropolish. That will take lots of time and $. I just thought there has to be a quicker/cheaper way to do this.

Tim, the conical ring is about 2 1/2 inches in diameter with no gap between the seal surfaces. So those seats won't work.

The only thing I have found on lapping aluminum is related to making scopes for rifles. I have no knowledge of that process and don't really understand what they are talking about.

I posted this here because I thought, if anyone knows how to do this, it will be someone at VM. Very smart people here with a lot of experience!
Damn sure I can't help you.....
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Old 12-20-2012, 07:26 PM
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I understand that the seat will be roughly 2-1/2" dia, but the question is how to mount the part and in what, for initial machining. I assume the actual seat width won't be too wide.
If it can be mounted to a lathe for turning or mounted to a mill?
In either case, an inexpensive method would be to fabricate the toolbit for either machine (cnc of course). Any tool room guy with the proper experience should have no problems creating suitable cutting bits. Proper cutting should produce a finish that probably would require no lapping at all for that viscosity.

If lapping is needed, then Clover compound is good, up to 1200 grit for a polished finish.
Important that the lapping tool be softer than the part. Shaped hardwood is a good choice.

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Old 12-21-2012, 05:36 AM
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I understand that the seat will be roughly 2-1/2" dia, but the question is how to mount the part and in what, for initial machining. I assume the actual seat width won't be too wide.
If it can be mounted to a lathe for turning or mounted to a mill?
In either case, an inexpensive method would be to fabricate the toolbit for either machine (cnc of course). Any tool room guy with the proper experience should have no problems creating suitable cutting bits. Proper cutting should produce a finish that probably would require no lapping at all for that viscosity.

If lapping is needed, then Clover compound is good, up to 1200 grit for a polished finish.
Important that the lapping tool be softer than the part. Shaped hardwood is a good choice.

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Yes to everything said above,especially about the lapping tool,the idea being that the compound imbeds in the tool and cuts the part.Will cut quickly in aluminum.I've lapped A6 tool steel to brass and alum. works great!!
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Old 12-21-2012, 02:07 PM
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a 3 inch globe valve would have a seating surface very much like you describe. Typically the seating members are machined with a small angular mismatch i.e. 45* seat and 44.5* plug this results in a line contact. Assuming good quality turning machines make the parts (don't squeeze the seat ring in a hard jaw or you get a 3 lobe hole) A quick pass with very fine lapping compound should true up the seating surface for liquid tight seal. Aluminum is not a typical valve material but brass and bronze are and they are lapped.

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Old 02-15-2014, 03:53 AM
Ralphy Ralphy is offline
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From link below
6000 Series.editedThe most commonly used are 6061 and 6063. Almost black at .002” (.0508 mm), the maximum practical coating is .0025 - .003” (.0635 - .0762 mm). 6063 is used for extrusions, 6061 forms excellent hardcoat for grinding, lapping and honing. Excellent dimensional stability, although a little “stringy” to machine.Aluminum can be ground.

Get Crisco and keep reapplying. The material will load into the Crisco and not the stone. That will get a good start. I've heard, heat up the grease and pour it into the wheel. I just paste brushed the aluminum.

Also I'm thinking the flatter the angle. The less chance of galling.
Similar metals will gall from repeated use.
Anodizing aluminum will surface harden, don't know if there could be any distotion from the process.
You may be able to lap after the anodizing.

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Ralphy

Last edited by Ralphy; 02-15-2014 at 04:51 AM..
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