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1911 Frame milling Issues


RezRocket
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Ok boys I need some help. I just bought a 1911 milling jig from 1911 builders. Normal set up indicated level and decked the frame.

 

Problem came in when I went to mill the rails. Used a 3/32 woodruff cutter to cut the rails. Touched off and cut first rail 0.005 with a slow feed rate no problems on a 600 lbs. bench mill. Moved over to cut the other rail half way through the 1st cut my cutter suddenly dipped into my jig. I stopped and indicated and was out by 0.020. 

 

Reindicated level and really cranked the vise down. And again same story stupid jig moved🤬.

 

Any recommendations on how to hold it still or any better jigs out there....angle plate....lateral jig? I don't know. Any one else with experience would be very appreciated.

 

Thanks guys.

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Start with the part, is it held in the jig securely? Then jig to the vise, vice to table,  table to the knee. Indicate the travel of the table, some where along the line of testing you will find the problem.

Rich

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6 hours ago, ltdmstr said:

Sounds like the vise isn't clamping evenly.  First guess would be poor machining on the fixture.  

 

1 hour ago, RIIID said:

Start with the part, is it held in the jig securely? Then jig to the vise, vice to table,  table to the knee. Indicate the travel of the table, some where along the line of testing you will find the problem.

Rich

 

I did not consider the jig being out. With a micrometer at the base is 0.020 thinner under the dust cover than the grip side. Enough to make it move apparently 

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12 hours ago, 38super said:

DRO prevents backlash, use that for your next job interview.

I am not the authority on milling and am certainly not a machinist as evidenced by my asking questions here. I mean no disrespect but am just seeking to learn as much as I can to improve. 

 

Correct me if I am wrong. I thought that backlash was a play in the gears or screws that affected movement in the table and head relative to the dial on the handle. Maybe my choice of words was incorrect with "prevents" as I understand that the DRO more so negates the need to ensure backlash is taken out of the gears before starting a measurement based on the handles readings as the Digital Read Out only measures actual movement of the table.

 

If I am wrong in this I would appreciate help to understand better and am open to any input.

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2 hours ago, RezRocket said:

I am not the authority on milling and am certainly not a machinist as evidenced by my asking questions here. I mean no disrespect but am just seeking to learn as much as I can to improve. 

 

Correct me if I am wrong. I thought that backlash was a play in the gears or screws that affected movement in the table and head relative to the dial on the handle. Maybe my choice of words was incorrect with "prevents" as I understand that the DRO more so negates the need to ensure backlash is taken out of the gears before starting a measurement based on the handles readings as the Digital Read Out only measures actual movement of the table.

 

If I am wrong in this I would appreciate help to understand better and am open to any input.

Backlash is the movement allowed by the slop in the lead screws, a DRO will allow you to get to a position without worrying about taking the slack out of the lead screws but the lash is still there and can allow the table to move if it is not locked in place, yes this movement will register on your DRO but it likely will happen during a cut when its too late. 

 

Not saying this is what is happening just an explanation of the point made.

 

 

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Just because I have machinery, doesn't make me a Machinist.  To describe every step would take 3 pages of text, and it would assume the user has a working knowledge of machining.  So in simple terms, your jig should measure equally across all 4 corners while secured in your mill vice.  A word about back lash, it can cause the mill table to jump when you reverse direction.  Practice on some scrap, learn your machine;.

https://www.hobby-machinist.com/forums/

http://www.homegunsmith.com/cgi-bin/ib3/ikonboard.cgi

http://www.weaponsguild.com/forum/index.php?PHPSESSID=h4c7ugkcsn3ko8rj9bujbj8ec0;wwwRedirect

https://www.cncguns.com/

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Dang, you didn't launch the part.  Links to this old tony, oxtools and robrenz.  I like TOT's humor, the last two are worthy of master model maker.  The last is a word about shop safety, pls do not become a casualty.

https://www.youtube.com/channel/UC5NO8MgTQKHAWXp6z8Xl7yQ

https://www.youtube.com/channel/UCZC9LGZLfyjrKT4OZne-JNw

https://www.youtube.com/channel/UCn4U3aEr6L2nLe1m_3as6JQ

https://www.youtube.com/watch?v=S0o8kdh8HWs

 

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