Making a Obsolete Firearm Part
Using CNC Machinery

This particular part will be a hammer for a Savage model 240, a 410 Over/Under, which was apparently a predecessor to the model 24.  The model 240 uses 2 hammers in the same slot.   It also has 2 triggers.  Shown below are the existing LH and the new replacement RH hammer.

Side view of action showing one original & one replacement hammer Top view of hammers, with replacement one having squarer corners & the serrations finer

Since there are no original drawings available (especially old obsolete firearms) from any manufacturer, and they would not supply them if there was, because of product liability now days.  The only way to get a drawing is to use an existing part as a pattern and make your own. 

In any CNC operation, the initial operation is to CAD draw a part.   CAD is an abbreviation for Computer Aided Drafting.  Here however, we need to reverse engineering using an original one to copy.  In this particular case the LH hammer was there, but no RH one available.  The LH hammer was used as a sample to draw the CAD drawing and was then printed off in a scale of 1 to 1.   From this, the existing LH  hammer could be laid on top of the printed drawing, to see if the drawing needed to be altered to match any of the contours.  You will note that not many parallel lines exist on this part, so guessing & measuring from existing holes become important.   A lot of calculated guessing as to locations went into this initial drawing, as the only known locations were the pivot hole, and angles or dimensions derived from the 2 flat portions.  

Then using the LH drawing, it was then mirrored 180 degrees to create the basis for the RH hammer.  An illustrated parts picture from an old parts list showing them both was used to somewhat draw in the differences.   Once the first drawing was printed, the I could locate the pivot pin holes, spur location and firing pin pads better.

As with any CNC machining, the CAD drawing comes first

A prototype RH hammer was then made, put into the gun with the original LH one in place, so a comparison of the 2 could be seen.  Alterations in the CAD drawing were then again made to conform the shape of external spur.  The inner section of the firing pin area was guessed at then, and was then ground by hand and fitted many times, before the proper shape was achieved at the firing pin striking area to achieve proper firing pin protrusion out of the frame.  At the same time give about .015 clearance of the top front of the hammer to the frame at the forward stop position, and have the firing pin retracted to a rebound safe position as was evidenced by the original LH hammer.

Now this modified prototype was used to redraw sections of the RH CAD drawing to match the new needed functioning dimensions for the final part, and the CNC code was rewritten to match the newer configurations.  

The actual run time is not anywhere near the total time involved when you consider all the initial CAD time, redoing the CAD drawings, redoing the code to match the final prototype, cutting the steel to length, deburring the saw cut, deburring the sawed off part, cutting the sear notches, serrating the spur, case hardening the part, making the pins and riveting them in, then making the spring.  The cost of the steel also needs to be figured into the equation.  For this part, there was probably more material in scrap and chips than in the finished part.  Plus there were at least 3 days involved before we even got a semi-finished part.  And the cost of the machinery, tooling, fixture making, etc. adds up also.

As you can see it is not practical to make just one part, and with these particular parts, even making 5 each for possible later resale, a price of $49.50 each is not really a worthwhile project taking into account on how many of these models were made and are still somewhat alive out there.  

In setting up the CNC program for these parts, the overall dimensions were needed, plus an added .100” to each end for cleanup if needed for an overall material length of 2.60”.   The green box around the part drawing indicates the size of the material needed and where to measure from to locate the machine home, which in this case is X0.0, Y0.0 and which is the center of the larger pivot hole. The thickness of material was decided to be ½”, with the width to be 1 ¼”.  This thickness was decided by calculating the finished part thickness, the width of the saw being used to saw the part off, plus the height of the lips of the vise jaws needed to hold the material securely during the machining operation. 

1018 mild steel was selected with the thought that since this part was being made on one flat operation, then sawed off to proper thickness, that if a tougher (4140 Annealed) was used, that deep a saw off cut could become a problem in that the material could become work hardened, ruining a saw (at a cost of about $30 each) unless ran at a VERY slow RPM speed and feed rate.  When the parts were final machined, they were then case hardened to give external hardness, yet a softer ductile core.   This is how it was done originally at the factory, so the final case color of the reproduction part matches the original factory part also.

The CAD drawing was produced in this instance on BobCad version 17.   CNC computer code was written using the BobCad program also, which when in the Numerical Code mode, will when you click onto a line in the drawing, get the cutter path going in a climb mill direction, it will write a line of computer code when you click on each subsequent line.  When you have went around the whole part in your CAD drawing, you now have a computer generated CNC code that the CNC milling machine can read.  This code is in the form of X, Y and Z.    X movement is right and left, and has a plus or minus attached to it depending which side of established Zero you set, here being the center of the pivot hole.  Anything to the right of 0.0 has a plus (+) attached to it, if to the left it will be a minus (-).  For simplicity most codes will not show an actual +, as that being taken for granted if none is listed, however the minus will always have to be listed as a minus (-) preceding the number.  Any movement forward and back is a Y movement, using the same stipulations as previously explained with Y+ to the rear of 0.0.  Z movement is up and down, and as with the others, a set 0.0 is the reference point which is in this instance the top of the material.  You need to set all of the X, Y and Z 0.0 set ups on the machine for the particular part you are making.  Once these are set, this becomes “Home” for that part.

CNC code writing is like learning another whole language.  CNC code for a straight line is G01, a left hand arc is G02, while a right hand arc is G03.   Feed rate is listed as F5. which equals 5 inches a minute.   Spindle speed of 2000 RPM is shown as S2000.  Code for tool #3 would be T3, H3 would be height for tool #3, and D3 is for the diameter of the cutter again for tool #3. 

There are codes in letters or combinations of letters for additional things like, turning the spindle on in either RH or LH rotation, spindle start or stop, coolant on and off, rapid moves, cutter compensation plus many more that tell the machine what to do.   If something goes wrong, it is not the machine, it is that you did not write the code right.

On a CNC vertical milling machine, the machine’s head and subsequent cutter stays stationary, while the table moves in X and Y directions.  It can do a multiple move at an angle or in an arc.  For any up or down move (Z) the normal machine’s spindle will move within the head. 

Jim in front of one of our CNC vertical milling machines
 

A water based coolant is used to keep the cutters cool and promote longer cutter life.   Most coolant on smaller machines will usually be a mist type system, which is compressed air siphoning a water based anti-rusting, environmentally friendly, anti-irritating coolant from a small tank, mixing with the air and directed onto the cutter to cool the cutter in a spray form.  Larger enclosed machines will use a higher quantity of pumped coolant called a flood type.

Once the computer CNC code is generated, you will usually have to proof it to be sure you have not forgotten something as for a rapid move into just outside of the material, no interference with pickup & move to points, spindle speed for the cutter assigned, & a multitude of other things.   Below is the code required to make the LH part.  You will notice some lines of code have a semi-colon (;) either preceding the line or in the middle of a line.  This semi-colon allows the code writer to enter information that the machine skips over when processing the code.  

You will also notice that the code was changed, altering the sear notch location after the parts were run.  This came about when the parts were set up to do the actual notch cutting and it was discovered that the code should be slightly altered for the next run, (if there ever was one).

;S240-701L.                 cnc code revision 09-06-05
;
;CNC JOB SHEET:     WISNER'S INC     360-748-4590
;CUSTOMER:
;PROGRAM #:            S240-701R.cnc
;DESCRIPTION:         SAVAGE 240 LH HAMMER, #240-701L
;PROGRAMMER:       LEEROY WISNER
;DATE:                         05-04-06
;CODE PROOFED:     OK 05-03-06
;RUN PROOFED:       OK 05-03-06
;LAST MODIFIED:     05-08-06 3:10 AM (RUN PARTS)
;LAST MODIFIED:     05-09-06 4:10 PM (ALTERED SEAR NOTCHES)
;LAST RAN/QTY:      05-09-06 / QTY 5
;LAST OPERATOR:   LEEROY WISNER
;LAST MACHINE:     BRIDGEPORT MILL #1
;CODE:                       Fanuc Mill Configuration, G CODE, MODAL, ABSOLUTE X & Y,
; INCREMENTAL I, & J, RPM & COOLANT PROGRAMMED, R RADIUS CODES COMPATIBLE
; H# =HEIGHT COMP, D# =DIA COMP
; Z MOVES ARE COMPATIBLE WITH COMP CODES
;
;MACHINE/CONTROLS:   BRIDGEPORT-CENTROID 39+ CNC7 VERSION 8.10
;
;CUTTER LIST:
;T1 =  H1= 0.0        D1=0.0 REF. SETTING HEIGHT TOOL (ELEC. EDGE FINDER) .500 OFF MATERIAL
;T3 =  H3=-2.905   D3=.390 DIA COMP, 3/8" TIN R/F                                        1200 RPM W/MC
;T5 =  H5= 3.333   D5=.750 DIA COMP, 3/4" ROUGHER END MILL                  500 RPM W/MC
;T4 =  H4=-2.765   D4=.248 DIA COMP, 1/4" CARBIDE,                                    2000 RPM W/MC
;T6 =  H6=-2.650   D6= 0.0 DIA COMP, 1/16 X 1" WOODRUFF                          800 RPM W/MC
;T2 =  H2=-1.111   D2= 0.0 DIA COMP, 3/32" .094 DIA DRILL                          2600 RPM W/MC
;T21= H21=-2.161 D21=0.0 DIA COMP, #2, .221 DIA DRILL                            2600 RPM W/MC
;T7 =  H7=-2.765   D7=.125 DIA COMP, 1/8" CARBIDE                                     2800 RPM W/MC
;T8 =  H8=-3.259   D8=5.00 DIA COMP, 3/32" X 5" SLITTING SAW                   225 RPM W/MC
;
;SETUP INFORMATION:
;X0.0 = +2.00 FROM RH EDGE OF MATERIAL
;Y0.0 = +.525 FROM BACK EDGE OF MATERIAL
;Z0.0 = TOP OF MATERIAL
;MATERIAL STOP:      LH SIDE
;VISE JAW STEP:       .150 DEEP
;
;SPECIAL INSTRUCTIONS:
;2ND OP,  SERRATE SPUR IN SPECIAL FIXTURE IN VERTICAL MILL, USING SPECIAL TOOL
;3RD OP, MILL SEAR NOTCHES TO MATCH SAMPLE, USING SPECIAL FIXTURE & 60 DEGREE CUTTER
;
;NOTES:
;FINISHED PART TO BE .278 AT SPUR & THICKNESS OF THIN PART TO BE .142 MAX
;T6 WOODRUFF CUTS TO BE CENTERED IN THIN SECTION
;DEBURR & SLIGHTLY COUNTERSINK PIN HOLES BEFORE CASE HARDENING
;MAKE RETRACTING SPRING OF .026 DIA. WIRE TO MATCH ORIGINAL CONFIGURATION
:PINS MADE OF 3/32" MILD STEEL WELDING ROD & RIVETED INTO HAMMER
;
;MATERIAL:              1018 CRS 3/8" X 1 3/8" CUT TO 2.580" OAL
;HEAT TREAT:          CASE HARDEN 1675 DF 1 HR, LET COOL TO 1450,
;                                       WATER QUENCH, =.010 PENETRATION DEPTH
;DRAW:                     675 DF 3 HRS, REDRAW AT 500 DF 3 HRS,
;                                      CHUNK OF WOOD ENCLOSED IN CRUCIBLE TO KEEP FROM SCALING
;ROCKWELL C:       42C
;FINISH:                    AS DRAWN
;
;CNC RUN TIME:
;CENTROID PROJECTED TIME 8.34 MIN, ACTUAL LOAD TO LOAD 10.34 MIN
;
;PROGRAM STARTS HERE:
;
G90
G0 X3.0 Y-2.0
T3 M06                                      ;T3 3/8" HS TIN R/F .390 DIA COMP
M03 S1200
G0 X2.300 Y1.00
G43 H3 M25
M07
G0 Z.100
G1 Z-.370 F30.
G41 D3

G01 X 1.982 Y.734 F30.
X 1.885 Y.340 F5.                      ;ROUGHING PASS
X 1.864 Y.244
G02 X 1.849 Y.228 I-.020 J.004
G03 X 1.686 Y-.124 I.063 J-.244
G02 X 1.681 Y-.698 I-.412 J-.284
X1.617 Y-0.542 I.135 J.147
 ;G03 X 1.444 Y-.132 I-.519 J.023   ;BYPASS SEAR NOTCHES
 ;G01 X 1.358 Y-.047
 ;G03 X 1.235 Y-.068 I-.061 J-.016
G03 X 1.568 Y-.299 I-.519 J.023
G01 X 1.355 Y-.220 ;POINT
X1.196 Y-.343
G02 X 1.097 Y-.604 I-1.209 J.310
X1.068 Y-.611 I-.018 J.009
G01 X.767 Y-.400
G03 X.542 Y-.408 I-.107 J-.153
G01 X.530 Y-.415
G02 X.249 Y-.361 I-.118 J.145
G03 X.037 Y-.257 I-.170 J-.078
G01 X-.352 Y-.336
X-.354 Y-.337
G02 X-.416 Y-.262 I.393 J.385
G01 X-.558 Y-.076
X-.518 Y.199
X-.466 Y.267
G02 X.403 Y.278 I.442 J-.583
G03 X 1.300 Y.457 I.365 J.507
G01 X 1.374 Y.446
X1.382 Y.412
X1.698 Y.367
X1.704 Y.398
X1.86 Y.376
G02 X1.885 Y.340 I-.004 J-.030
G01 X1.952 Y.144 F20.

M05
M09
G40
G49 M25
G0 X3.00 Y-2.00
T5 M06                                        ;T5 --USE BACK GEARS-- 3/4" ROUGHER END MILL
M03 S500
M07
G0 X2.500 Y1.00
G43 H5 M25
G0 Z0.0
G1 Z-.145 F30.
G42 D5

G01 X1.982 Y.664 F30.              ;MILL TOP SURFACE
X1.433 Y.115 F2.5
X-.302 Y-.318
G41
X.974 Y-.617
X1.266 Y-.427
G02 X2.076 Y.521 I1.696 J-.629

M05
M09
G40
G49 M25
G0 X3.00 Y-2.00                        ;SHIFT BACK TO HI SPEED SPINDLE
T4 M06                                       ;T4 1/4" CARBIDE .248 DIA COMP
M03 S2000
M07
G0 X2.200 Y1.00
G43 H4 M25
G0 Z0.0
G1 Z-.300 F30.
G41 D4

G01 X 1.982 Y.734 F30.
X1.885 Y.340 F8.                        ;FINISH PASS
X1.864 Y.244
G02 X 1.849 Y.228 I-.020 J.004
G03 X 1.686 Y-.124 I.063 J-.244
G02 X 1.681 Y-.698 I-.412 J-.284
G02 X1.617 Y-.542 I.135 J.147
G03 X1.444 Y-.132 I-.519 J.023
G01 X1.297 Y-.063
X1.223 Y-.210
G02 X1.097 Y-.604 I-1.235 J.176
X1.068 Y-.611 I-.018 J.009
G01 X.767 Y-.400
G03 X.542 Y-.408 I-.107 J-.153
G01 X .530 Y-.415
G02 X .249 Y-.361 I-.118 J.145
G03 X .037 Y-.257 I-.170 J-.078
G01 X-.352 Y-.336
X-.357 Y-.337
G02 X-.432 Y-.096 I.364 J.247
G01 X-.472 Y-.106
G02 X-.458 Y.018 I.434 J.017
G01 X-.501 Y.156
G02 X-.466 Y.267 I.539 J-.108
G01 X-.435 Y .376
G02 X.403 Y.278 I.442 J-.583
G03 X1.300 Y.457 I.365 J.507
G01 X1.374 Y.446
X1.382 Y.412
X1.698 Y.367
X1.704 Y.398
X1.86 Y.376
G02 X1.885 Y.340 I-.004 J-.030
G01 X1.952 Y.144 F20.

M05
M09
G40
G49 M25
G0 X3.00 Y-2.00
T6 M06                                       ;T6 1/16" X 1 WOODRUFF, NO CUTTER COMP
M03 S800
M07
G0 X-.103 Y1.00
G43 H6 M25
G0 Z0.0
G1 Z-.245 F30.
  ;G41 D6                                     ;COMP OFF

X.103 Y.638 F3.                          ;STOP POINT FOR 1/16' X 1' WOODRUFF
Y1.00 F20.                                   ;BACK OUT
 Z.400 F60.                                  ;RAISE UP FOR CLEARANCE
X.326 Y-1.100
 Z-.245                                         ;DOWN
X.326 Y-.675 F3.                        ;STOP POINT
X.326 Y-1.00 F20.                      ;BACK OUT

M05
M09
G40
G49 M25                                      ;PECK DRILL PROGRAM
G0 X2.0 Y1.0
T2 M06                                        ;T2 .094 DIA DRILL
M03 S2600
G43 H2 M25
D2
M07
G83 X.033 Y.258 R-.100 Z-.320 Q.250 F2.5     ;PIN HOLES
X.376 Y-.329 R-.100 Z-.320 Q.250 F2.5
X1.297 Y-.063 R-.100 Z-.320 Q.075 F2.5         ;CLEARANCE HOLE FOR 1/8" CUTTER UNDER SPUR
M05
G80

M09
G40
G49 M25                                     ;PECK DRILL PROGRAM
G0 X3.0 Y1.50
T21 M06                                      ;T21 #2, .221 DIA DRILL
M03 S2600
G43 H21 M25
D2
M07
G83 X0.0 Y0.0 R-.100 Z-.350 Q.260 F2.5       ;CENTER PIVOT HOLE
M05
G80

M09
G40
G49 M25
G0 X3.00 Y-2.00
T7 M06                                         ;T7 1/8" CARBIDE .125 DIA COMP
M03 S2800
M07
G0 X1.350 Y-.500
G43 H7 M25
G0 Z0.0
G1 Z-.290 F30.
G41 D7

X1.462 Y-.265 F30.
X1.444 Y-.132 F3.
X1.358 Y-.047                            ;CLEAN UP UNDER HAMMER SPUR CORNER
G03 X1.235 Y-.068 I-.061 J-.016
G02 X1.097 Y-.604 I-1.248 J.035
X1.068 Y-.611 I-.018 J.009
G01 X.974 Y-.617
X-.286 Y-.439 F40.
X-.357 Y-.337 F5.
G02 X-.432 Y-.096 I.364 J.247
G01 X-.472 Y-.106                     ;FULL COCK LOCATION
G02 X-.458 Y.018 I.434 J.017
G01 X-.501 Y.156                      ;SAFETY REBOUND LOCATION
G02 X-.466 Y.267 I.539 J-.108
G01 X-.435 Y .376
 ;X-.336 Y-.355 F5.
 ;G02 X-.416 Y-.262 I.375 J.403
 ;G01 X-.436 Y-.129
 ;X-.471 Y-.142
 ;G02 X-.477 Y.031 I.231 J.095
 ;G01 X-.506 Y.126
 ;G02 X-.466 Y.267 I.544 J-.078
G01 X-.435 Y.376 F20.
X.103 Y.638 F40.
X1.363 Y.498
X1.363 Y.498 F5.
X1.382 Y.412                              ;CLEAN UP RECESS OF HAMMER AT FIRING PIN INDENT
X1.698 Y.367
X1.715 Y.447 F20.

M05
M09
G40
G49 M25
G0 X4.500 Y-2.00
T8 M06                                        ;T8 --USE BACK GEARS-- 3/32" X 5.0 SLITTING SAW
M03 S225
M07
G0 X4.0 Y-2.0
G43 H8
G0 Z0.0
G01 Z-.375 F40.
 ;G41 D8                                       ;CUTTER COMP OFF

G01 X4.060 Y-1.910 F30.
G01 X.685 F2.5                           ;SAW OFF PART

M05
M09
G40
G49 M25
G0 X3.0 Y2.0
M02                                              ;PROGRAM END

 

In the photos below show usage of a 3/8" roughing cutter being used to hog out excess material, then a 1/4" carbide cutter will be used to finish the periphery of the part to size.  Different size drills are used to put the desired holes in.   A 1/16" X 1" Woodruff saw is used to slot the mainspring plunger pivot and the retracting spring slot. 

3/8" rougher being used to hog off outside Drilling the pivot hole, note the plunger slot is already done

Shown below is a 1/8" carbide cutter doing the final sear and retract locations, (which need to be final cut later).    And the 3/32" x 5" saw parting off the part.    Note the coolant nozzle on all these pictures.

Here is the 1/8" carbide being used to get into the corners that the larger cutters could not reach Sawing off the part, note you will see the mist coolant nozzle on all of these pictures

The machined part needs to be bandsanded to remove burrs or irregularities from the previous machining, or saw off operations.  Now the part goes into a special fixture in a 6" vise on a Bridgeport type manual vertical milling machine to do the sear and safety notches.  On the left below you will see both RH and LH hammers placed in the fixture (to save time and for more support).  They are placed on a drill bit the same size as used to drill the pivot hole to give a basis for placement of the parts.  The 1/8" pin seen is a stop for the sear notch cut.  There is another pin hole to the right  that is used in cutting the safety notch.

On the RH photo below is the serration operation on the hammer spur.   Here a 3/8" x 24 TPI tap was modified, by removing 3 of the 4 flutes, heated red and bent to the shape of the hammer spur, quenched, then it was re-heat treated.   Now again both hammers were placed in the edge of the same fixture, but using a different locating hole.  In this instance, the part positioning was placed so the bottom rear of the wider section of the spur lays against the LH edge of the fixture jaw.   Both are then clamped in place and the modified tap is ran back and forth in a Y direction to cut the serrations.  This serrating cutter is moved in approx. .005 per pass to prolong cutter life.

Cutting the sear notches Serrating the hammer spur

Below are shown the original but reblued hammer on the left, with a sample unfinished setup part next to it.   These setup parts are critical to save for the next person who may make another run of these parts at some later date.   To the right you see both the RH & LH hammers before being heat treated. 

The case hardened part was then manually flame annealed (softened) at the two pin holes because with them being so thin on the sides, the thought was that when riveting if they were left hard, the side lips may become broken off. 

In the right hand picture the parts have been case hardened and drawn.   You can see the plunger pivot pin has been added on the rear, along with the rebound spring placed around it's retention pin before riveting of the pins in place.

Original & reproduced unfinished parts The finished reproduced products

The CNC milling machines shown and used in these operations are retrofitted old Bridgeport solid ram milling machines.  The electronics of the original machines are long obsolete and were somewhat cumbersome by modern standards.   Some machinery dealers purchase these non running obsolete machines from large shops, strip them down, retrofit with newer modern servo motors and electronics, utilizing a PC computer to run the unit.  Cost for one of these rebuilt machines usually runs between $25,000 and $30,000 not including a $500 vise or any cutter holders which run $100 each (of which 9 were used on this operation).  This particular machine shown and used here was retrofitted using Centroid controls.

In reassembling these hammers in the frame, the coil mainsprings ride over a long screw that comes in from the rear of the frame and screws into the plunger head that rests in the slot & over the hammer's rear pivot pin.  This firearm is designed to have the retracting hammer (that rebounds by the attached spring), to go back to the safety notch immediately after the gun is fired.  To do this the mainspring plunger needs to be screwed into the plunger head so that the spring is captivated slightly shorter than when fully forward.   This is to pull the hammer away from the firing pin so that the gun will not fire when loaded IF the firing pin is held forward by an improperly adjusted hammer.  The hammer hits the firing pin hard enough by inertia & then bounces away from the firing pin to this safety notch.  Adjustment of this rod needs to be screwed in until there is about 1/16" slack when the hammer is all the way forward.

On this part, there is a fine line between the hammer rebounding away from the firing pin, allowing it to drop into the safety notch and the trigger sear point.  So you can see that the part has to be made precise and final fitting to be done in a manner that ensures safety.


Copyright © 2006 - 2015  LeeRoy Wisner  All Rights Reserved

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Originated 05-11-0206  Last updated 12-17-2014
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