squarewave

Machined Spacers Not Passing eMachineShop Checks
« on: December 07, 2018, 12:10:20 PM »
I want to make two spacers to retrofit a bantam jack into a double layer panel that looks like this:



So the panel is 1/8" w/ 0.55" hole (shown in green) + 1/16" w/ 0.375" hole. The trick is how to mount that bantam jack into that hole.

I could drill a hole w/ countersink into the 1/16" panel but there are multiple problems with that so I won't get into it.

The best I could come up with is making parts like the above graphic. So the bantam jack would bolt onto the spacer nut with a 4-40 screw (holes are outer diam). Then a flange spacer (shown in black) threads into that through the panel and clamping the whole assembly in place.

However, the eMachineShop software reports that the two threaded holes are too close and that the material between them may become deformed or missing. This part is behind the panel so I actually don't care so much. It seems a slot could be cut between the holes like one might do with a clamp. Although I don't know how to actually make a threaded "clamp" because after I add the slot, I can't figure out how to thread the hole as it is no longer just a circle.

Also, EMS reports that even the 3/8-24 thread on the boss of the flange spacer (shown in black) is too close to the 1/4" bore. But it seems to me it should be possible to thread a 3/8" boss with a 1/4" bore. There's plenty of meat there.

Finally, another issue is that EMS wants 1 million USD to make these parts (and that's after the "student" discount).

Does anyone have any ideas?

UPDATED in Reply #4
« Last Edit: December 08, 2018, 06:54:28 PM by squarewave »


JohnRoberts

Re: Machined Spacers Not Passing eMachineShop Checks
« Reply #1 on: December 07, 2018, 12:22:18 PM »
can you simplify to just screw through the 1/16" panel and leave the bantam bushing poking through unfinished.

JR
John Roberts
http://circularscience.com
Tune it, or don't play it...

squarewave

Re: Machined Spacers Not Passing eMachineShop Checks
« Reply #2 on: December 07, 2018, 12:53:42 PM »
can you simplify to just screw through the 1/16" panel and leave the bantam bushing poking through unfinished.

JR
There are multiple problems with that.

First, the bantam jack is 1/4" and the hole is 3/8". So the hole for the 4-40 screw would be too close to the 3/8" hole. The countersink would overflow the edge.

Second, it would look like hell:



However, I could create another panel and bolt the bantam to that and then mount that by using the 1/4-40 bushings of 4 toggle switches that will also be mounted on the panel. That would be structurally sound but it would still be ugly. There would be a big 0.55" hole and then an unfinished inner panel with 0.375" hole and then you would still see the countersunk screw for the bantam. I suppose a could have a black plastic part that fits tight around the barrel of the bantam.
« Last Edit: December 07, 2018, 03:08:53 PM by squarewave »

Gold

Re: Machined Spacers Not Passing eMachineShop Checks
« Reply #3 on: December 08, 2018, 12:34:53 PM »
Would the OD of the bantam jack fit in a threaded 3/8” bushing? If so you could epoxy the bantam jack in the bushing and fasten it with a panel nut.

squarewave

Re: Machined Spacers Not Passing eMachineShop Checks
« Reply #4 on: December 08, 2018, 06:53:05 PM »
Would the OD of the bantam jack fit in a threaded 3/8” bushing? If so you could epoxy the bantam jack in the bushing and fasten it with a panel nut.
The standard metal bantam jacks are like this:



The barrel is 1/4" and mounted using the offset hole. So too small for 3/8". Therein lies the problem.

My latest plan is to make a mounting plate and bolt the 4 bantam jacks and 4 toggles to it. Then that whole assembly fits behind the panel and uses the toggle bushings as "bolts" to secure it and thus the bantams.



Of course the parts would not be bright green. I would love black anodized but I'm already way to carried away with this project. It's going to have to be unfinished aluminum. I can probably clean them up a lot with a scotch brite pad.

I've never used eMachineShop before but it is actually affordable if the design is 2D and uses a stock thickness. So in my case, all of the parts are 0.125". If anything does not have the same Z value the price jumps 100%. With just 2D you can put multiple designs into one order.

The problem with my current design is that only the rings for toggles are 1/4-40 threaded. The rings for the bantam jacks would have to glued on mounted with adhesive. It is designed so that stress on the bantam jacks is transferred mostly to the plate and then to the toggle thread bushings.

Not ideal but at least I won't be drilling into such an old piece (Allison Labs 2ABR) so if it's a failure no harm is done.

squarewave

Re: Machined Spacers Not Passing eMachineShop Checks
« Reply #5 on: December 08, 2018, 07:11:33 PM »
Would the OD of the bantam jack fit in a threaded 3/8” bushing? If so you could epoxy the bantam jack in the bushing and fasten it with a panel nut.
Actually I didn't get this at first but yes. A 3/8" OD bushing with 1/4" bore would work and it is a clever solution. Although I think my current plan might be a little prettier because there are no bushings exposed.

Gold

Re: Machined Spacers Not Passing eMachineShop Checks
« Reply #6 on: December 08, 2018, 08:26:36 PM »
Actually I didn't get this at first but yes. A 3/8" OD bushing with 1/4" bore would work and it is a clever solution. Although I think my current plan might be a little prettier because there are no bushings exposed.

I think your plan looks better too. My suggestion could probably be done with off the shelf parts though.

Marik

Re: Machined Spacers Not Passing eMachineShop Checks
« Reply #7 on: December 17, 2018, 03:29:51 AM »
Press fit with Loctite 609
Samar Audio & Microphone Design

www.samaraudiodesign.com

The Art of Ribbon Microphones

squarewave

Re: Machined Spacers Not Passing eMachineShop Checks
« Reply #8 on: January 02, 2019, 02:10:32 AM »
The final result:



The eMachineShop machining was not super great. I guess 2D means it's cutout on a water jet.
« Last Edit: January 02, 2019, 02:13:46 AM by squarewave »

 

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