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Machining the handwheel rim


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#1 Larryx

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Posted 08 August 2020 - 01:20 AM

I'm curious how the people who know how to do these things machined the handwheel. The holes on the bolt circle and the other basic features are quite straight forward. I have only manual equipment so I am interested how the curve is machined on the rim to the 0,500 diameter curvature? 

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#2 Swarfmonger

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Posted 08 August 2020 - 02:30 AM

As coincidence would have it, I was able to get the lathe work on mine completed today among other things and it was done on a conventional lathe. Having a programmable digital readout is not necessary but it certainly does help. If you don’t have one it will have to be done either with a ball turning attachment, shop math skills, a forming tool or good old-fashioned eyeball work. The good news is it’s not particularly critical to the functioning of the elevating mechanism so a little creativity will not hurt anything.

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#3 rayhawk

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Posted 08 August 2020 - 12:31 PM

I used a radius cutter from mcmaster, #3359A38. Just have to adjust the angle a few times to get all the way around. I did the internal features while I had a decent size piece to grab, then put a center in it to machine the outside when you only have a small boss to grab onto. Take your time, and consider making a test piece out of aluminum to work on your technique.


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#4 20Gun

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Posted 08 August 2020 - 06:23 PM

Your a little ahead of me on this project, but my plan was to finish the whole part, except the outside edge. Then mount the hand wheel  on a mandrel with a live center. Then clamp two 1/2" HSS tool blanks together. Mark ends with dykem. Use a divider with a scribe, and scribe a 1/2" semicircle.  , Then separate the tools, and bench grind to the line, with a relief angle. Then I would have a LH, and RH 1/2" forming tool, for both sides of the hand wheel radius.


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#5 Larryx

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Posted 08 August 2020 - 06:33 PM

Thank you to all who responded.

 

I am thinking of making a form tool. but it will be my first attempt to do so.

 

There are several videos on YouTube which remind one to "built in" the clearance angles in 2 directions, so I at least will not have to learn that one by screwing up a part. I will do the suggestion of trying out the technique on a practice piece. I guess we can't stay a virgin forever.


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#6 DonLans

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Posted 14 August 2020 - 03:58 PM

It's been years since I finished my gun, but it seems that I used a 1/4" radius rounding cutter and fly cut it on a vertical mill. I centered it on the rotary head and cut away. When you get one side done you flip it over and fly cut the other side. You can also drill your holes in the same setup. Bought a cheap router cutter from harbor freight to fly cut with.


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#7 Larryx

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Posted 17 August 2020 - 11:36 PM

Absolutely brilliant idea! This is another of those things where I say "Why didn't I think of that". I looked in my router  stash and I have several bits that look like they will do the job. Thank you for the idea.



#8 Larryx

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Posted 23 August 2020 - 01:19 AM

I took rayhawks suggestion and started with a hand wheel made in aluminum. I finally decided to make a form tool and turn tt that way. The result was very successful. What really surprised me during the process is how difficult it is to find W1 tool steel. Lacking a programmable heat treating oven, I wanted to machine in the annealed state and then do the time honored technique - cheery red, quench clean- heat to straw color etc. None of the metal dealers had the W1 tool steel. I finally ended up taking a master machinist friend's suggestion and ground the form tool onto a appropriately sized lathe tool. The quarter circle profile is not difficult to grind, including the reliefs. I am very proud of my result ( but not enough guts to post a picture) 


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#9 Sparky_NY

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Posted 23 August 2020 - 11:06 AM

I quit using W1 steel pretty quick years ago.   It moves and distorts quite a bit.   I found O1 is easier to find,  and moves/distorts far less during the heat treat process.   Its not really any different to use than W1 except the quench is oil instead of water.   Many of the parts in my gats were made with O1.    I found pieces on ebay fairly common.  

 

I will mention, in case you didn't know, another method of judging when its been heated enough.   The goal is to heat the metal to what is known as the "critical temperature".    When a piece of steel hits the critical temperature it goes non-magnetic !     You simply heat the piece and check it with a magnet when you think you are getting close.  When the critical temp is reached a magnet has no effect at all.   Its a more precise and guaranteed method than judging by color of red.

 

Nice to see that some are progressing with building their gats !!     With the big run of Cutters design bolts a while back I thought there would be more building going on.


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#10 maccrazy2

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Posted 23 August 2020 - 11:10 PM

I have been itching to get going on mine again. I’ve been dealing with back issues over the last several months so unfortunately no progress lately
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#11 Larryx

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Posted 27 August 2020 - 01:05 PM

I am ready to put the finishing touches on the hand wheel and I have a question regarding it's mounting location.  The creation of this part was a significant effort for me as a newbie but apparently Murphy was busy elsewhere and it looks like my efforts are going to produce a very nice looking  part. The print shows the hand wheel mounted below the elevating plate but putting it there will hide most of the hand wheel features. 

 

My question is this: is there any mechanical reason that the mounting of the  hand wheel and it's attaching acme nut (coyote industries?) cannot be reversed? I am concerned that an               unanticipated interference or similar situation could appear.


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#12 rayhawk

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Posted 27 August 2020 - 03:25 PM

I flipped mine to the top for the same reason. I did modify the elevating plate design to give it a downward offset, and made my yoke standoff a bit taller than the drawings called for though.


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#13 Larryx

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Posted 27 August 2020 - 04:24 PM

Thank you for the encouragement.  I understand the reduction on range of movement but it looks like the reduction on spacing will only reduce the ability to raise the  end the bullets come out of and at this time i have no plans to shoot at flying objects.

 

I have been working on the individual pieces for overt 2 years, and now that  most of I am working on is very close to or at finished pieces, the pucker factor rises quite steeply every time I take a tool to a part.


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