Author Topic: Bowling Ball Mortar (Read 2968 times)

moose53 · « **Reply #30 on:** February 09, 2012, 03:04:09 PM »

Milling the segments are straitforward , but slow . Will use about 4 1/2in end mills to finish the screw . Next ones I will use my horizontal fixture with a carbide cutter

Cat Whisperer · « **Reply #31 on:** February 10, 2012, 12:44:31 AM »

Good pix!

Nice to have a collection of machining process pix - saves a lot of time in planning.

moose53 · « **Reply #32 on:** February 21, 2012, 03:51:52 PM »

I set up my horizontal mill fixture up to finish segmenting the breech screw. Used a 4 inch carbide cutter , a 5 inch HSS cutter with more teeth would be smoother. The rusty steel at far side of screw is curved section used for fill in to clamp in vise.

Double D · « **Reply #33 on:** February 21, 2012, 06:28:49 PM »

Can wait to see how you relive the internal threads!

moose53 · « **Reply #34 on:** February 21, 2012, 07:12:12 PM »

me nether, as I said before I am learning this as I do it.

GGaskill · « **Reply #35 on:** February 21, 2012, 09:37:47 PM »

What kinds of machine are available for this?

moose53 · « **Reply #36 on:** February 22, 2012, 05:42:20 AM »

As far as I can tell a shaper would be best , but I am limited to a mill and imagination. The depth of cut is about 6 inches , so a extended end mill should work for roughing it out . And then finish by hand with carbide bur.

jamesfrom180 · « **Reply #37 on:** February 22, 2012, 08:01:44 AM »

Do you have a rotary table for a mill? Either way sounds like alot of shaping by hand.

moose53 · « **Reply #38 on:** February 22, 2012, 09:52:14 AM »

I do have one but really shouldn't need a rotary table, there also might be a height restriction to using a table with a extended end mill. I will use a set diameter ring on breech to indicate end mill position. And scribe segment positions after breech screw is in final position. Then its a matter of removing material from one side of line.

Double D · « **Reply #39 on:** February 22, 2012, 10:28:15 AM »

A shaper or broach?

moose53 · « **Reply #40 on:** February 22, 2012, 11:21:50 AM »

Neither , will use a regular end mill and plunge cut. The radius in the corners will be cleaned up by hand grinding with carbide bur

jamesfrom180 · « **Reply #41 on:** February 23, 2012, 03:25:52 AM »

I am wondering if the breach is a separate assembly from your barrel?

moose53 · « **Reply #42 on:** February 23, 2012, 05:50:03 AM »

The breech is a separate round block 14 inch x 10 inch , after machining it will permanently screw into the barrel 5 inches . Having a short breech allows me to mill out the thread segments on the mill.

jamesfrom180 · « **Reply #43 on:** February 23, 2012, 05:52:03 AM »

that is exactly what I was wondering

Can't imagine what this thing is going to finally look like. Imagining a very high quality to it.

moose53 · « **Reply #44 on:** February 24, 2012, 04:32:32 PM »

Roughed out the rubber obtruatior and handle ring , also detailed the screw to see how it would look . Having worked on the screw I realized the breech block is going to be more work then I want to handle . Will change design and use my other breech screw that is double pitch , it will screw in with 5 revolutions and be so much simpler to set up.

GGaskill · « **Reply #45 on:** February 24, 2012, 06:19:58 PM »

Sad to waste all that nice work. $:-\$

Frank46 · « **Reply #46 on:** February 24, 2012, 06:21:57 PM »

I have to ask this question. From your pic of the breech block it appears that you are using a buttress thread. Right?. Would their be any strength issues in cutting a standard 60 degree thread? Not much on machining but am curious about the merits of the buttress thread versus the standard 60 degree threads. I can see that this is going to be one heck of a build. Frank

Double D · « **Reply #47 on:** February 24, 2012, 06:22:59 PM »

Learning is never a waste.

moose53 · « **Reply #48 on:** February 24, 2012, 07:38:21 PM »

Not out that much because I had another breech screw from a few years ago I can now use. Look on Wikipedea for Buttress thread
Buttress thread in machinery In machinery, the buttress thread form is designed to handle extremely high axial thrust in one direction. The load-bearing thread face is perpendicular to the screw axis.^[2] or at a slight slant (usually no greater than 7°)^[3] The other face is slanted at 45°. The resulting thread form has the same low friction properties as a square thread form but at about twice the shear strength due to the long thread base. This thread form also is easy to machine on a thread milling machine, unlike the difficult to machine square thread form. It can also compensate for nut wear using a split nut, much like the Acme thread form.^[4]
Buttress threads have often been used in the construction of artillery, particularly with the screw-type breechblock.^[1] They are also often used in vises, because great force is only required in one direction.^[4]

moose53 · « **Reply #49 on:** February 25, 2012, 03:46:36 PM »

Back headed in the right direction again . Need to modify my supermax lathe so it will turn 1 in pitch threads , then good to go .

moose53 · « **Reply #50 on:** October 18, 2012, 09:13:02 AM »

The ATF letter came today, looks like project is good to go except I am now working on the new years cannon . Thanks for your assistance DD.

Double D · « **Reply #51 on:** October 18, 2012, 05:19:44 PM »

Make copies!!!

Frame it!