I have created some interest in how I checker frames. This will cover 20 LPI checkering.
I started with hand file checkering on 1911 frames back in 1985 and found it took 8 hours, 20 files, and the next day I could not use my hands.
Using my mill to do the same work today, I can checker 8 to 10 frames in two days. The only thing I have worn out are some of the cutters.
This is where a good large mill makes a job well done. I have a 10x54 Jet variable speed vertical mill with square ways, 3 axis DRO and a Hitachi 3ph inverter. If you try this on a table top mill you will eat up cutters and frames. The table top mills are just not good enough to do this kind of work.
Be aware that the fixtures, tooling, and setup will be time consuming, but worth it once your used to doing it this way. Tooling took weeks. First setup took 4 to 6 hour. Today setups take less the an hour. Once the rotory table is set changing frames is about 5 minutes.
Tooling you will need to have plus a good mill:
Mist cooling system for your mill.
A horizontal rotor table with a tail stock with at least a 6" table. (what I am using)
MT2 with 1/2 " hole.
1/2' drill rod at least 6" long
90 degree head with short R-8 arbor.(for the horizontal cuts) I have tryed the chinese imports and they suck. You will have to bit the bullet and get a bridgeport 90 degree head.
Two Iron Angle Plates measuring 3.5x3.0x2.5. for keeping the frames indexed(so they won't move).
One 1/2" 4 flute carbide mill end.
One 4.0x1/8 with 1.0"center hole slotting saw. This will have to go out to a reputable tool sharpener and have the tips recut with a 30 degree angle on each side.
One cobalt 1/2x20 4 fluted bottoming tap. This will also go to your tool cutter and have three of the four flutes removed. The 4th flute will have to be back cut to points so you remove all of the pitch from the cutting flute.
Lots of bolts and square metal for the adapter plate hold downs and for mounting the rotory table and tail stock.
One of the early problems I had to solve was a way to hold the frame from the inside. Holding the frame in a vise type fixture would warp the frame causing all kind of fit problems. This is what the 1/2" drill rod and the MT-2 with 1/2' hole is for. If you mount your rotory table and then install the 1/2" drill rod into the MT-2 adaptor then slide them into the center hole of the rotory table it becomes clear. This is what the front inside of the mag well will center on. Now to hold it in place I built a 2 piece wedge to hold the frame to the 1/2" drill rod. (second picture) This locks the frame, but you still need the angle plates to keep the frame from moving during the cutting phase.
The angle plates I have now have been modified so I don't have to remove the grip screw bushings or the plunger tube that is stacked into the left side of the frame. (a time saver).
As you will see in the pictures the angle plate have been milled to allow the cutter and the mill spindle collet nose to clear the frame. (trigger guards will get eaten up if you don't do this).
The setup
Rotory table must be leveled. Rotory table must be centered 90 degrees to the spindle.
1/2" drill rod must have a counter sink hole in one end for the tail stock to index into.
Install Mt-2 collet and rod into table. Lock MT-2 collet with a threaded bolt to hold rod secure. Slide the tail stock into the end of the 1/2" drill rod end with the counter suck hole. The tail stock can be adjusted to get the drill rod parallel and perpendicular to the spindle.This has to be within 0.001" or your checkering will come out crocked Make sure your tail stock has an indexing block on the bottom to whatever your size your t-slots are. This will make frame changes extreme quick and accurate.
Slide frame onto 1/2" drill rod untill it bottoms out on the indexing bolt. I have a stop bolt (carriage head type) screwed into one of the t slots on the rotory table to help index the frames. Install the wedge devise to lock the frame down onto the rod. Grease the tip of the tail stock and slide the tail stock back into place and lock it down. Adjust the tail stock pressure. Install your angle plates onto the rotory table to keep the frame from twisting.
The actual cutting phase
Vertical cuts first. Lots of coolant. Tap speed 400 to 500 rpm. Lock the tap in good and tight. I bring the spindle all the way up and lock it there. I use the table lift to get to the frame. Depth of cut will be 0.032 to 0.035". I go 0.005 per pass until I get to depth. Then do a 0.000 pass to deburr.
Experience has taught me that 1911 front straps are not straight. I use the 1/2" carbide mill end to get all the bumps out of the front of the frame. I also change the radius under the trigger guard. This gets you a higher grip on the gun and also perfect checkering.
Once this is done you can start cutting your vertical serrations using the modified 1/2x20 tap. Each line will be cut 7 degrees to the right or the left of your center line cut for 20 LPI checkering. This means that you will change the rotory table +-7 degrees for each new line. Where to stop the last line is up to you. (note: Usually this will be a 42 or 49 degrees) But make a note of where you stop on each side. You will need this information for where to stop the horizontal cuts. As you get close to depth you will notice that you have already started your next line(s). This will help you judge where to stop your last line. Do one side first the go back and get the other side. At this point the frames begin to look really good.(see picture)
When I have multiple frames to do, I do all the vertical cuts first then switch to the next frame and repeat as neccessary.
Horizontal cuts
Setup Change: Lots of coolant.
Remove the tap cutter, drop the table down, unlock the spindle, drop it down to install the 90 degree angle head. Center the head with an indicator. Lock down the head. Raise the spindle up until it bottoms out and lock it there. 90 Degree head must be parallel to the frame.(bed table). Install short R-8 spindle, install the 4x1/8" slotting saw blade.
RPM of saw blade 325 to 375 RPM (or you will dull the teeth) Each cut will be 0.050" apart. Depth of cut 0.032 to 0.035". Again I only go 0.005 to 0.10 per pass. I start at the bottom of the frame.
I usually line up the first cut with the recessed part of the the lower mag well area. No sharp points or half cut checkering this way. (second picture)
Now you need those number of where you stopped your vertical cuts(42 or 49 degrees).
This is how far you will turn the rotory table for the horizontal lines. Cut each line to depth before moving onto the next one. Work your way up the frame and stop when you get to the top of your vertical lines.
If all went well you have a checkered frame.
I am sure you all have lots of questions. I will answer them as best I can.
Thanks for the interest guys.
I started with hand file checkering on 1911 frames back in 1985 and found it took 8 hours, 20 files, and the next day I could not use my hands.
Using my mill to do the same work today, I can checker 8 to 10 frames in two days. The only thing I have worn out are some of the cutters.
This is where a good large mill makes a job well done. I have a 10x54 Jet variable speed vertical mill with square ways, 3 axis DRO and a Hitachi 3ph inverter. If you try this on a table top mill you will eat up cutters and frames. The table top mills are just not good enough to do this kind of work.
Be aware that the fixtures, tooling, and setup will be time consuming, but worth it once your used to doing it this way. Tooling took weeks. First setup took 4 to 6 hour. Today setups take less the an hour. Once the rotory table is set changing frames is about 5 minutes.
Tooling you will need to have plus a good mill:
Mist cooling system for your mill.
A horizontal rotor table with a tail stock with at least a 6" table. (what I am using)
MT2 with 1/2 " hole.
1/2' drill rod at least 6" long
90 degree head with short R-8 arbor.(for the horizontal cuts) I have tryed the chinese imports and they suck. You will have to bit the bullet and get a bridgeport 90 degree head.
Two Iron Angle Plates measuring 3.5x3.0x2.5. for keeping the frames indexed(so they won't move).
One 1/2" 4 flute carbide mill end.
One 4.0x1/8 with 1.0"center hole slotting saw. This will have to go out to a reputable tool sharpener and have the tips recut with a 30 degree angle on each side.
One cobalt 1/2x20 4 fluted bottoming tap. This will also go to your tool cutter and have three of the four flutes removed. The 4th flute will have to be back cut to points so you remove all of the pitch from the cutting flute.
Lots of bolts and square metal for the adapter plate hold downs and for mounting the rotory table and tail stock.
One of the early problems I had to solve was a way to hold the frame from the inside. Holding the frame in a vise type fixture would warp the frame causing all kind of fit problems. This is what the 1/2" drill rod and the MT-2 with 1/2' hole is for. If you mount your rotory table and then install the 1/2" drill rod into the MT-2 adaptor then slide them into the center hole of the rotory table it becomes clear. This is what the front inside of the mag well will center on. Now to hold it in place I built a 2 piece wedge to hold the frame to the 1/2" drill rod. (second picture) This locks the frame, but you still need the angle plates to keep the frame from moving during the cutting phase.
The angle plates I have now have been modified so I don't have to remove the grip screw bushings or the plunger tube that is stacked into the left side of the frame. (a time saver).
As you will see in the pictures the angle plate have been milled to allow the cutter and the mill spindle collet nose to clear the frame. (trigger guards will get eaten up if you don't do this).
The setup
Rotory table must be leveled. Rotory table must be centered 90 degrees to the spindle.
1/2" drill rod must have a counter sink hole in one end for the tail stock to index into.
Install Mt-2 collet and rod into table. Lock MT-2 collet with a threaded bolt to hold rod secure. Slide the tail stock into the end of the 1/2" drill rod end with the counter suck hole. The tail stock can be adjusted to get the drill rod parallel and perpendicular to the spindle.This has to be within 0.001" or your checkering will come out crocked Make sure your tail stock has an indexing block on the bottom to whatever your size your t-slots are. This will make frame changes extreme quick and accurate.
Slide frame onto 1/2" drill rod untill it bottoms out on the indexing bolt. I have a stop bolt (carriage head type) screwed into one of the t slots on the rotory table to help index the frames. Install the wedge devise to lock the frame down onto the rod. Grease the tip of the tail stock and slide the tail stock back into place and lock it down. Adjust the tail stock pressure. Install your angle plates onto the rotory table to keep the frame from twisting.
The actual cutting phase
Vertical cuts first. Lots of coolant. Tap speed 400 to 500 rpm. Lock the tap in good and tight. I bring the spindle all the way up and lock it there. I use the table lift to get to the frame. Depth of cut will be 0.032 to 0.035". I go 0.005 per pass until I get to depth. Then do a 0.000 pass to deburr.
Experience has taught me that 1911 front straps are not straight. I use the 1/2" carbide mill end to get all the bumps out of the front of the frame. I also change the radius under the trigger guard. This gets you a higher grip on the gun and also perfect checkering.
Once this is done you can start cutting your vertical serrations using the modified 1/2x20 tap. Each line will be cut 7 degrees to the right or the left of your center line cut for 20 LPI checkering. This means that you will change the rotory table +-7 degrees for each new line. Where to stop the last line is up to you. (note: Usually this will be a 42 or 49 degrees) But make a note of where you stop on each side. You will need this information for where to stop the horizontal cuts. As you get close to depth you will notice that you have already started your next line(s). This will help you judge where to stop your last line. Do one side first the go back and get the other side. At this point the frames begin to look really good.(see picture)
When I have multiple frames to do, I do all the vertical cuts first then switch to the next frame and repeat as neccessary.
Horizontal cuts
Setup Change: Lots of coolant.
Remove the tap cutter, drop the table down, unlock the spindle, drop it down to install the 90 degree angle head. Center the head with an indicator. Lock down the head. Raise the spindle up until it bottoms out and lock it there. 90 Degree head must be parallel to the frame.(bed table). Install short R-8 spindle, install the 4x1/8" slotting saw blade.
RPM of saw blade 325 to 375 RPM (or you will dull the teeth) Each cut will be 0.050" apart. Depth of cut 0.032 to 0.035". Again I only go 0.005 to 0.10 per pass. I start at the bottom of the frame.
I usually line up the first cut with the recessed part of the the lower mag well area. No sharp points or half cut checkering this way. (second picture)
Now you need those number of where you stopped your vertical cuts(42 or 49 degrees).
This is how far you will turn the rotory table for the horizontal lines. Cut each line to depth before moving onto the next one. Work your way up the frame and stop when you get to the top of your vertical lines.
If all went well you have a checkered frame.
I am sure you all have lots of questions. I will answer them as best I can.
Thanks for the interest guys.