Jump to content


Photo

What's wrong with my thinking?

machining

  • Please log in to reply
38 replies to this topic

#21 Larryx

Larryx

    Advanced Member

  • Members
  • PipPipPip
  • 99 posts
  • LocationSouth Florida

Posted 25 January 2020 - 05:58 PM

I completed my  delrin carrier block and  proved to myself that I have the ability to  make the part. The groove is not there but I believe that is a simple  sawing job. In making the part some questions came to mind.  Since the bolts are inserted into the 0.420 holes, does it matter if the 0.281 holes are  not exactly half. Gbull defined the dimension as 0.2405, which I recognize as important but which is not  delineated on the print. My naive thinking is that the small end of the bolt is more firmly captured. The main reason for the question is if the  0.2401 is not critical, I will not  worry myself in making it too precise.

Attached Files


  • bruski likes this

#22 Larryx

Larryx

    Advanced Member

  • Members
  • PipPipPip
  • 99 posts
  • LocationSouth Florida

Posted 25 January 2020 - 06:27 PM

I should have added to the previous post that I will make the "real" carrier block in 2 pieces as suggested.



#23 gbull

gbull

    Advanced Member

  • Members
  • PipPipPip
  • 52 posts
  • LocationGold Bar Wa.

Posted 26 January 2020 - 09:30 AM

Try a good sharp end mill with a .050 aprox. radius on the corners. If it really is Delrin it shouldn’t smear.It usually a very free cutting plastic.

#24 bruski

bruski

    Advanced Member

  • Members
  • PipPipPip
  • 577 posts
  • LocationARIZONA

Posted 27 January 2020 - 03:57 AM

The flats on the front of the carrier block are important but don't stress on them too much. It is better if they are cut .001 or .002 more than not enough. The flats on the bolts will drag on them if not enough clearance.

 

bruski



#25 Larryx

Larryx

    Advanced Member

  • Members
  • PipPipPip
  • 99 posts
  • LocationSouth Florida

Posted 27 January 2020 - 11:56 AM

Thank you for your quick response. I studied the print again and I realized that the flats were the slide way for the bolts. I did not buy the 3 dimensional CD so I am working from the normal prints and I did not catch the function of the flats, 

 

I am at a decision point on the machining of the metal version of the carrier block. I  am  following the suggestion of the group and making the carrier block in 2 pieces. My quandary is should I attempt to cut the existing partially machined block in two or start over with a fresh , un-machined piece of material. By cutting the  existing piece in 2 I will save about 2 days of machine time for me ( 3 or 4 hours per), but  In doing so I will lose a gestimate of 0.200 " in saw kerf and facing work.  I can compensate for the  loss by adjusting the mating parts, but I am not experienced to know if the performance or function will be affected. Opinions?



#26 Sparky_NY

Sparky_NY

    Advanced Member

  • Members
  • PipPipPip
  • 451 posts
  • LocationAnderson, SC

Posted 27 January 2020 - 06:42 PM

Also be aware that the flats on the bolt carrier prevent the bolts from rotating in their bore.    Excess rotation of the bolt may cause the extractor to fail to line up in its relief cut in the barrel plate.        Some clearance is needed for smooth functioning,  excessive can cause problems like mentioned.



#27 maccrazy2

maccrazy2

    Advanced Member

  • Members
  • PipPipPip
  • 215 posts

Posted 27 January 2020 - 09:24 PM

I personally would salvage one side of the carrier and remake the other to full dimension. However on second thought, I would start over so the pin connecting the 2 halves can be used as a true reference between the 2 pieces.

#28 Larryx

Larryx

    Advanced Member

  • Members
  • PipPipPip
  • 99 posts
  • LocationSouth Florida

Posted 27 January 2020 - 09:44 PM

Brilliant idea. I don't know why I didn't think of that. I will salvage half of the current piece, the part that has the  indentation. I spent far too much time making that a perfect fit to  discard it. I have not yet drilled the hole for the locating pin so I should be O.K. there.  Thanks again for the help.!!!



#29 Cutter

Cutter

    Advanced Member

  • Members
  • PipPipPip
  • 1165 posts

Posted 28 January 2020 - 06:03 PM

It’s impossible to give any accurate advise without
knowing all the tooling involved.
One thing I would recommend to anyone starting
a new build is to use a .500 diameter shaft instead
of a hex. This makes it much easier to locate the
three blanks for alignment ( bolt carrier, cartridge carrier, and barrel plate ).
Front barrel plate needs no alignment with a round shaft.
Now, A fixture is needed to locate on the center .500 bore.
Center drill, drill, and ream for the alignment pin , just
put and take the three items at the same setting. I put the
alignment hole through on the cartridge carrier.
Using a round shaft also eliminates the 1” boss & counter bore.
This will work on a rotary table or DRO bolt circle, as long as
you hit the numbers.
I use a cross pin as a driver ( see pic )

Attached Files

  • Attached File  002.JPG   66.92KB   1 downloads

  • rayhawk likes this

#30 Larryx

Larryx

    Advanced Member

  • Members
  • PipPipPip
  • 99 posts
  • LocationSouth Florida

Posted 28 January 2020 - 08:54 PM

thank you for your experienced advice regarding the round shaft. I have a lot of

I want to make certain I understand the comment regarding "a fixture". I read your earlier post comments regarding the aluminum disk and the rotary table . is that what you refer to as a fixture? By way of equipment, I have abandoned my handy, dandy Hardinge collet indexer for the task and will use a rather precise rotary table. I understand you suggestions on the earlier post and will follow that procedure unless you tell me I misunderstood and provide further comments.

#31 Cutter

Cutter

    Advanced Member

  • Members
  • PipPipPip
  • 1165 posts

Posted 28 January 2020 - 10:11 PM

Yes Larry,
Mount a piece of Aluminum on your rotary table and cut the
.500 diameter locating boss using the rotary table.
That will assure the boss is centered on the table.
A 1/4-20 thread in the center of the boss for clamping down 


#32 maccrazy2

maccrazy2

    Advanced Member

  • Members
  • PipPipPip
  • 215 posts

Posted 28 January 2020 - 10:13 PM

This is what I used based on what I understood from Jerry. The only thing I would do differently was make the shell holder first as it uses smaller diameter holes than the bolt carrier. Only reason being there would be no burr to clean up if the aluminum supports the hole exit. Granted it was very minimal.

Attached Files


  • Cutter likes this

#33 maccrazy2

maccrazy2

    Advanced Member

  • Members
  • PipPipPip
  • 215 posts

Posted 28 January 2020 - 10:16 PM

Carrier

Attached Files


  • Cutter likes this

#34 maccrazy2

maccrazy2

    Advanced Member

  • Members
  • PipPipPip
  • 215 posts

Posted 28 January 2020 - 10:24 PM

You can see the drill holes and the slightly larger boreholes

Attached Files


  • Cutter likes this

#35 Larryx

Larryx

    Advanced Member

  • Members
  • PipPipPip
  • 99 posts
  • LocationSouth Florida

Posted 28 January 2020 - 10:29 PM

I believe I understand.

 

Now for a nit-picking detail.In accordance with my latest guidance from you guys, I went to my supply bin and found 2 sort of suitable pieces of material to make the main shaft out of. One is a piece of stressproof steel with a diameter of 0.625. The other is a Gold plated ( yes 14 ct gold) brass rod with a diameter of 0.472. ( got the brass rod from a defunct furniture maker - high end stuff)  I can look further if suggested but- Are either of these suitable. Obviously if my main shaft is not 0.500 " I will adjust required dimensions appropriately.

 

As I said, this borders on the "don't you know anything?" But at this stage of life I am starting to read the directions BEFORE all else fails. 



#36 Cutter

Cutter

    Advanced Member

  • Members
  • PipPipPip
  • 1165 posts

Posted 28 January 2020 - 11:23 PM

I believe I understand.

 

Now for a nit-picking detail.In accordance with my latest guidance from you guys, I went to my supply bin and found 2 sort of suitable pieces of material to make the main shaft out of. One is a piece of stressproof steel with a diameter of 0.625. The other is a Gold plated ( yes 14 ct gold) brass rod with a diameter of 0.472. ( got the brass rod from a defunct furniture maker - high end stuff)  I can look further if suggested but- Are either of these suitable. Obviously if my main shaft is not 0.500 " I will adjust required dimensions appropriately.

 

As I said, this borders on the "don't you know anything?" But at this stage of life I am starting to read the directions BEFORE all else fails. 

 

 

If it’s round and straight, either will work



#37 Larryx

Larryx

    Advanced Member

  • Members
  • PipPipPip
  • 99 posts
  • LocationSouth Florida

Posted 29 January 2020 - 12:11 AM

I will use the steel bar. It is drill rod from the drops of a company that makes of all things, drills. 


  • bruski, Sparky_NY, Roller and 1 other like this

#38 Cutter

Cutter

    Advanced Member

  • Members
  • PipPipPip
  • 1165 posts

Posted 29 January 2020 - 09:03 PM

Good choice MrX


  • bruski and Sparky_NY like this

#39 Roller

Roller

    Advanced Member

  • Members
  • PipPipPip
  • 151 posts

Posted 29 January 2020 - 11:42 PM

I will use the steel bar. It is drill rod from the drops of a company that makes of all things, drills. 

You have chosen wisely!


  • bruski and Cutter like this




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users