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ETC chamber design and machining questions

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ETC chamber design and machining questions

Unread postAuthor: rp181 » Wed Apr 15, 2009 8:59 pm

Hello all,
I am in the process of designing a ETC (Electrothermal-Chemical gun) chamber. Here is what I have so far:
1.875" 1045 high carbon steel
11" long
designed for .5" OD barrel
Here is a CAD:
Image

All the small holes are what hold it together. Threaded rod goes through, and I tighten it up. The barrel also acts like the interior sacrificial layer to take all the burn. The aluminum slides in, and screws through the bottom right piece tighten to hold it there. Does anyone have any suggestions for improvment?

A machining question.
How can I make sure that I can Drill straight down, without the hole slanting? I do not have accsess to a metal lathe to turn it down.

Any comments or suggestions or critisism welcome. Please refrain from brining up the actual fuel. I will not answer any questions regarding that. I have talked to DYI and some other people concerning this, and will be similar to his, if anyone kept track of that.
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Unread postAuthor: MountainousDew » Wed Apr 15, 2009 9:08 pm

My guess to your question would be a drill press, but that might be only available at a metal lathe...
Hope it helped.
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Unread postAuthor: rp181 » Wed Apr 15, 2009 9:14 pm

What? I have accsess to a 15" drill press (A nice one too). I can still get it slanted. My question is how to get the faces parallel, and perpendicular to the side.
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Unread postAuthor: Hotwired » Wed Apr 15, 2009 9:25 pm

You're going to bore 8 individual holes through 11" of steel to hold the endcaps on?
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Unread postAuthor: rp181 » Wed Apr 15, 2009 9:57 pm

yep. Have any better idea? I dont have accsess to tap it.
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Unread postAuthor: Moonbogg » Thu Apr 16, 2009 12:40 am

rp181 wrote:yep. Have any better idea? I dont have accsess to tap it.



What do you mean no access to tap? You can create what's called "counterbores" on the far outsides. This lets whats called 'sock head cap screws" to sit beneath the outside surface so that it remains flush and the first part of the screw can either be threaded or not, but the end of it is surely threaded. The outside pieces you show can have a "thru hole" so that the screw passed right through that, but then screws into a tapped hole on the ends of the large center piece.
You can buy a hand tap at home depot for like 15 bucks or less maybe. It comes in a little packet with a drill bit and then a tap. If you don't want to buy a hand grip for the tap, use a friggin socket wrench or even a regular crescent wrench to grip the thing. Make certain you get a little can of something called "tap magic" or a similar product. This lubricates the hole and allows you to tap easily.
When tapping by hand, make sure you back out the tap every 1.5 turns or so, otherwise it gets clogged and you will snap the tap. They are very brittle.
Hope this helps, if you don't get it I will draw you a quick little sketch to show exactly what I mean. I hope I understood you and answered the question properly.
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Unread postAuthor: psycix » Thu Apr 16, 2009 3:59 am

My question is how to get the faces parallel, and perpendicular to the side.

I'd say: use a milling machine.
Then use a three jaw chuck (like the one on a lathe, but then for the mill.) You can drill one hole, rotate exactly 90* or another angle and drill again.
I believe this is called an indexing head, its the same as a rotary table, but then holding the workpiece horizontal.
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