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).
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.
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.
Nice, I do have a couple of questions. Could you show a couple pictures of the setup in stages? The 90 degree head? The only horizontal heads I've seen have a holder that keeps it perpendicular to the table. Instead of having a high dollar cobalt tap sent to a tool grinder for an extra expense, do you think a 60 degree double angle cutter would work? I really like the way this sets up and that you could do all the verticles for several frames first, then switch the cutter and do the horizontals.
I have not seen a double angle carbide cutter that has a 0.5 diameter. Most are larger and this mean you can't get the vertical lines up as high as needed. Second thing is the double angle cutters only cut a single line. With the tap setup you always have your next line started which helps you index to the next line. On 1911's it is not that important. But when you have to checker a wide frame, like a para, you need this indexing to help you set up for the next line to cut.
As for the pictures, give me a day or two. I have a setup in the mill right now that I can't move until the parts are done. All the pictures I have right now are to large for this website to except. I have to reset the camera from 1600X1200 down to 640x480 for the pictures to get uploaded. This really suck on showing details.
OK, I didn't think about the 3/4 cutter not getting up far enough. I guess that this same set up would work for a Caspian widebody frame also? You could always email the pics to me, I can load them on photobucket and embed them here? My day job is kind of tech related, so those things keep me busy.
Thanks again for taking the time to share.
That's a very interesting writeup, rzap. Thanks for taking the time to share.
No need rzap, simply load your photos into PC Paint and then save them to JPG format. That will compress them to a size the website will except. They will still be very good photos. Microsoft Windows comes standard with Paint.
Originally Posted by rzap
Thanks for the offer to post the large pictures I have guys. I really need to get some better shots of the fixtures, tooling and the setup process. Tomorrow.
To do a para or caspian frame, I still use the original setup. I have some delron or aluminum spacers that go into the mag well area (one on each side) to keep the frame true to the fixture. Also the 90 degree side plates have to be moved further out. Both frames are wide. This is where the tap cutter setup comes into play. You do the vertical serrations on the front flat first, then when you do the radius cuts you use the degree wheel of the rotory table.
I have checkered both, and they come out really looking good.
If 20 LPI is to course, you can use the same setup to do 40 LPI checkering. The only difference is on the four fluted tap you grind every other flute to give you a 40 LPI cutter. Your rotory table movement goes from 7 degrees to 3.5 degrees. Your horizontal lines are cut at 0.025" spacing for 40 LPI, instead of 0.050" for 20 LPI. Depth of cut is 0.016 to 0.018" for 40 LPI.
One other thing I forgot to mention. I still keep checkering files around to deburr the checkering the mill just did. Some people want there hand to bleed checkering. Others don't want it this aggressive. Glass beading the checkering will keep it distinctive but not bloody.
I have also made a fixture to checker main spring housings. These are quick to do compared to a frame.
Other uses for tap cutters. When I install a boMar rear sight I can use a 50LPI tap to line the back of the slide to match the lines on the Bomar rear blade. Front sights can be lined. Checker large mag release buttons. Checker fronts of trigger guards. Line the top of flat top slides. I have made a cutter to do Gold Cup slides (with side reliefs)that I have added a comp to.
OK Rzap, we might really need to talk. I have had the same idea for using taps in the past, but not really being a machinist I could not wrap my head around what to ask for or how to grind them.
RZap, I see you live in Dallas. I hope you made it through the bad weather OK.
A lot of damage to buildings and houses where the tornados touched down. But no one died.
I was not in the path of there destruction.
As for making taps into cutters, They have to be 4 flute, HSS or colbalt, and no spiral taps. Carbide taps don't like the interrupted cutting and will break teeth off with time. Water and a bench grinder with a good flat/straight stone is how I originally started making the tooling I needed. Today I have a tool grinder, diamond and CB wheels, and good oil based cutting fluid to make the tools. Don't let the taps discolor when your grinding them or they loose there hardness. Take your time when making the cutters.
I have entertained the idea of using an Acme thread tap to make square cuts, but have never tried it yet.
Any chance of getting a link to one? I searched MSC, but only found spiral taps.
These guy's prices are great. Thanks for the link.
Originally Posted by rzap
67cuda, you are welcome.
I am showing you pictures of the taps I have back cut for the purpose of machining lines.
The 20 LPI tap has a few worn teeth, but it has checkered 10 frames. The nice thing about tap cutting is if you wear out an area you just turn the head down 0.050 to the next cutter.
The small tap is 56LPI and this is the tap I use to line the back of front sights, and the back of slides to match the bomar lining. Enjoy!
Cool, is there someone you sent them to (including the slitting saw) to grind them? I could grind off the extra flutes, but I'm not so sure about the angles.
Find a local tool sharpener service. Bring a drill or mill end to them to test how good they are first.
I have had places I have tried give me back blue tipped tools. Not good.
If you get back a great looking tool bit, then they usually know what there doing.
Once you find a good sharpener, Bring in your taps and the pictures I posted. Let them know what your doing and what you want. They can usually get it done for you in quick order.
If they can resharpen carbide mill ends they have the right setup to do the taps and the slitting saws.
Get a tool and cutter grinder with coolant. and learn to do them yourself.
Tool & Cutter Grinders | MSCDirect.com
I am using option 2.
I also have a gorton tool grinder that I got used and rebuilt. It was a lot cheaper and takes up less floor space. $250 verses $3,000. But the MSC grinder works so much better. CBN wheels give the best results.
Cobalt taps work the best, but there getting harder to find these days.
Stay away from home depot taps. Not sure who is making them but they don't last.
And no one makes a 30LPI tap. Eventually I am going to have to make a 30 LPI cutter.
Now what I really want is a 4 flute zero pitch tap. There would be no back cutting necessary, and the cutter would have 4 cutting flutes instead of one. This would make it much faster on doing the cuts.
What about using a threadmill?
I have never used a Thread mill, but it looks like you will have to contend with some of the same issues as with tap modifications. On a 4 flute straight Thread mill, 3 of the 4 flutes need to go. You will have to back cut the 4th flute to get rid of the pitch. You will have to watch out for spindle interference with the part you are cutting as these look to be shorter then taps. I would stay away from the carbide ones. my experience with carbide shows that it does not like interrupted cutting.