2nd Product off the Haas

[TravisR100]

Well here's the next product for the Haas. This one is admittedly a simple project but it's still been fun. This is simply a mounting bracket. The little square brackets are 1.25" square and .450" thick. They're best understood by looking at the render of the fixture with the parts on top. The pocket that is milled on the parts is actually on the bottom side of the part. There is an existing bracket in the aircraft that is used for a gust lock tie down. This bracket will fit over the profile of the existing bracket. The top of this part will simply have a 3/8" threaded hole in the top of it. What's the point? There are very few mounting points in this aircraft. This bracket made to fit over an existing bracket will offer a 3/16" threaded hole offset from the interior side of the aircraft to allow a RAM mount 1" ball to be screwed in permanently to the top side. If you're familiar with RAM mounts (ram-mount.com) you know that once you have the 1" ball you can choose to mount pretty much anything with their mounting system.

While it's a very simple part it's been fun. It's given me yet another chance to practice my CAD and CAM skills. The fixture uses pitbull clamps from mitee bite. They actually seem to work very well. I could have used a much larger fixture to do more at a time however I'll probably only be making about 50 to 75 of these so 4 per fixture and using two fixtures should work fine. It also happens that I had a piece of material just the right size and the pitbull clamps come in packs of 8.

I'll be going back to slightly round off the corners on the front of the bracket and possibly add an additional 1/4"-20 tapped hole just to have it.

I'll post more pics as I get a little further along with these.

[TOTALLYRC]

Hi Travis,
Starting small amd working ones way up is the way to go.

If you started out with a massively complex item and had to redo it 30 times you would be very discourged by now.

It may not look like much but I think it looks great. Just think, how many people out there can't do what you did?

Merry Christmas,
Mike

[mactec54]

Hi TravisR100
I see one thing, you may have trouble with is the pitbull clamps, they will push back into the aluminum after some use, You could put a steel rail along that face or just some steel buttons for the pitbull to push against. You could also just mill a slot with a T slot cutter for a piece of keysteel to fit in there as well, this would be my choice.

But great to see you moving forward

[TravisR100]

Totally, oh I'm not playing it down! Pretty happy with what I've gotten done thus far.

Mactec, thanks. I've never used them before and never even thought of that. They do seem to work pretty well however.

[Cory]

Originally Posted by mactec54 Hi TravisR100 I see one thing, you may have trouble with is the pitbull clamps, they will push back into the aluminum after some use, You could put a steel rail along that face or just some steel buttons for the pitbull to push against. You could also just mill a slot with a T slot cutter for a piece of keysteel to fit in there as well, this would be my choice. But great to see you moving forward

Will it matter? The pitbull clamps have a good deal of travel. They should be able to accommodate any extra distance they have to travel due to the deflection in the rear wall of that slot.

[mactec54]

Cory
Nothing to do with deflection, over time they will eat into the back face, & then you will not have enough travel in the pitbull to clamp the part

[crabbass]

Inserting hardened buttons, and building fixtures from steel is the way a production fixture would be designed. However, for your small run fixture, and to keep cost down, aluminum is practical. Another approach you might want to consider in the future is to use hardened dowel pins for the stop positions. To save time and money, you could have milled the minimal amount off the block(just enough of a step for the pitbull clamp), drilled and reamed holes for the dowel's(two pins in the back and one to the left), and drilled a slightly larger hole than the major diameter that you are tapping (like a 7/16" hole maybe 1/8" deep below each of your four parts). In the end you would have machined much less material away from the block (since this is a small run job, you can make something else from this billet in the future). I have several similar sized blocks of aluminum that I use and re-use for small jobs like this. If it is a repeat job, I prefer to make a purpose built fixture from steel.
One question on your material choice. Is there a reason (cost or convenience) that you are using the 1.25 x 1.25 bar sawed to >.45"? I would think it would be easier (to saw, locate, and square up) a piece of rectangular stock that was 1.25" x .5" sawed at >1.25" long. Just curious.

[TravisR100]

Originally Posted by crabbass One question on your material choice. Is there a reason (cost or convenience) that you are using the 1.25 x 1.25 bar sawed to >.45"? I would think it would be easier (to saw, locate, and square up) a piece of rectangular stock that was 1.25" x .5" sawed at >1.25" long. Just curious.

Yeah, because I didn't use my head and think about it beforehand. You're right. It would have been much easier to square stock that was 1.25x.5.

[Geof]

An alternative way to approach something like this is to use vises and grip a length of flat bar in very shallow step jaws; the length of the bar being a bit shorter than the X travel on the machine. Then you do all the machining, including taking a cut around the perimeter on ten or a dozen parts so you have the almost finished parts all held together by a thin web. Now cut them into pairs and again grip them in the vise and face off the web to separate the parts and tap the hole.

An advantage in doing it this way is that even though the step jaws are very shallow and may only be gripping about 0.04" of material with two vises the grip is 12" long so it is very secure. This can permit much faster material removal than is possible with individual clamps, also there is a time saving in not having to cut the individual pieces from bar stock.

[TravisR100]

Geof, I assume you mean custom machined jaws?

[Geof]

Originally Posted by TravisR100 Geof, I assume you mean custom machined jaws?

Not for these particular parts because they have parallel sides so regular straight jaws will do. You just need to rig a stop so they all go into the vise in the same place.

For non repeating short run parts when custom jaws are needed I do not make real bolt-on jaws. I have two vises side by side so I grip a length of aluminum bar spanning the two vises in one vise and then machine the custom shape in this at the location of the other vise; the free custom jaw being a short length of aluminum clamped against the fixed bar with a 1/16" to 1/4" spacer. Doing this avoids switching back and forth between regular and custom jaws; also one length of aluminum bar can have up to four custom jaws machined in it.

[TravisR100]

Originally Posted by Geof Not for these particular parts because they have parallel sides so regular straight jaws will do. You just need to rig a stop so they all go into the vise in the same place. For non repeating short run parts when custom jaws are needed I do not make real bolt-on jaws. I have two vises side by side so I grip a length of aluminum bar spanning the two vises in one vise and then machine the custom shape in this at the location of the other vise; the free custom jaw being a short length of aluminum clamped against the fixed bar with a 1/16" to 1/4" spacer. Doing this avoids switching back and forth between regular and custom jaws; also one length of aluminum bar can have up to four custom jaws machined in it.

I'm usually good a picturing what you describe but I'm a little lost on this one. Do you have a picture?