Pocket Pistol CNC Mill project

I have begun to make parts from “patch’s” design. My project is based on his drawings but had to be changed extensively for them to work on my Sherline CNC Mill.  Arcs had to be added to any parts that called for an inside angle. CNC does not like to cut inner angles. So these were converted to arcs. Then when Cutter Compensation was turned on there were new problems to cure! CNC is not as easy as most people think it is. This is especially true when you have some machine experience, but that is more than 30 years old. These two parts are being cut so that measurements can be checked. They should be ready for production in steel. Still a little bit to fix, such as moving out of the work to plunge. Not a good idea to plunge into steel as I do into aluminum! I have put about 25 hours into coding, so far. I am not using CAD or CAM. All of it is created just in EMC2 (now LinuxCNC) with a text editor(Leafpad). All of the parts have had their outlines completed in G-code. I upgraded from EMC2 2.4.4, that comes in the Sherline Computer to LinuxCNC 2.5.3. This actually solved some of my cutter comp problems. I may eventually bring it up to the current version 2.6.3. The below parts have not been pilot drilled, but the pilot drill G-code has been written and tested.

Sear and Hammer

Sear and Hammer

The Hammer is being prototyped in aluminum. It and the Sear will be cut out of 5/16″ 1018 steel. The hammer above was an earlier test. A couple of unintended cuts had to be solved but looks good now.

Hammer in progress

Hammer in progress

So far so good! Bill of Materials; Aluminum 3/16″ x 4″ x 4″ (side plate) 1/2″ x 4″ x 4″ ( left side (receiver side)) 5/16″ x 3″ x 1″ (trigger)(smallest size available in 5/16″ was 3″ width limited size options this is for the trigger. I am going to reduce a scrap from the frame for the triggers for now) 3/4″ x 1 1/4″ (Barrel shroud) Steel; 5/16″ x 1″ x 3″ (Hammer and Sear) 3/4 x 1 x 1″ (breech block) 5/16″ .223, 1:16″ (26″ long) Barrel Liner (from Numrich, Midway or Brownells) Pins; still to be determined. springs; still to be determined Accuracy Problems; SOLVED; After making these parts I found they were pretty far out of the dimensions that I had coded them with. The length was off by more than -.010 and the width was off by more than-.005. I decided to over the Mill and see if the problem was mechanical. I found that the cross slide was able to twist about +/- .015″. I tightened the X and Y gibs. Then I adjusted backlash. I squared the entire machine and I retested all axis. Adjusted the backlash settings in the .ini. Then I recut the hammer prototype. The hammer was still -.0088″ short and -.0058 under width. So tightening the cross slide made very little difference. The Prototype sear was off undersized also. Something was still wrong. I had upgraded to LinuxCNC 2.5.3 (actually went up to 2.5.4). So I checked what file I was starting from. I found I was starting from the older EMC files instead of the LinuxCNC files. I changed the target locations and created new .ini files. I recut the hammer proto and now I was +.0027 on width and +.0038 on Height. Much better to be oversized than undersized. Then I checked my .ini. file and found that I had not set the backlash settings in yet. NOTE: I cut out the Trigger and it was within .0005″ in length and dead on in height. accuracy is no longer a critical problem! I have not cut a new hammer yet, but I am betting it will be very close to the coded size now. So now I think I have a handle on most of the accuracy issues. Back to working on the code files for all the parts. I have tool radius comp working for the inside trigger guard cuts. The outside frame cuts are the fighting tool comp. I may separate the code for the frame outside from the trigger guard to make it easier to solve the problems. This file has a couple of hundred lines in it to go through right now. Splitting it up will make it easier to see where the problem is. then I might be able to merge them back together later! I should be trying some more cuts this week. Making Progress, Slowly; Making progress, finally tracked down all the small errors in the frame cutout. Cutter comp now on. I made cuts in black nylon to see if my measurements were going to work out. I am using a 1/4″ end mill on the frame.

cutting outline in black nylon

cutting outline in black nylon

Looks pretty good so far. I also placed the pilot holes on the piece. all the hole locations look good except the tang screw. It is off center. I had to guess at this radius. So I have two choices, go back and redo the whole backstrap or re-locate the hole. I think you can guess which one it is going to be!

The full outline plus trigger cuts and the pilot holes.

The full outline plus trigger cuts and the pilot holes.

I cut the outline first. Then I merged the trigger cutout code back into the file. Then I ran the pilot holes to help see the scale. You really get a feel for how small this design is with the outline at size. I can get maybe one finger on the grip! Patch must have some small hands. Mine are not that big either. It truly is a pocket pistol. So next up is the internal cuts for the FCG parts. These should be easy compared to the frame outline and hammer. Trigger is still acting up, I’ll get it whipped into shape soon too! After patting myself on the back so hard I dislocated my shoulder, the dang thing is backwards. Or it was I have fixed it now but have to wrestle with the tool comp again. Have it fixed tomorrow, then I can move on! I must be learning something! I took me less than 5 minutes to cure the tool comp issues. I will have to try cutting it again. Then setup the cuts for the FCG cuts! Moving along again! With some of the figures left out of Patches drawings there are some of my measurements that are different from his. The drawings are still very very useful. They give you about 85%+ of what is needed to finish this project. More importantly they give you a good starting place to drawing and building your own project! The important parts like the FCG are complete. I am going to have to try to get my measurements into Corel so there are complete plans, one of these days. Do not ever think that I am nocking Patch on his design plans. They accomplish the task he set for them, a starting place for HIS project. I am very glad that he posted his plans as it gave me a starting point and the impetus to start my own project. Using his plans got me started months ahead of where I would really be at right now! Thank you Patch!

A shot of the frame in the Controller window

A shot of the frame in the Controller window

Thought some of you might like a screenshot of the frame in the controller program. This is after the flip, with tool radius comp on. That is why the trigger guard looks small and the Frame looks fat. Those are the actual cut paths with a 1/4″ end mill. Some minor changes were needed on the frame. Ready to cut now. 10/22/14 Most of the work on the breech block is done. Side of breach block needs finishing. Double checked most of the files for proper cut depths. Writing notes in the plans for CNC file run orders. The frame outside is ready to cut. Side plate is ready to cut. Need to finish the FCG cuts then incorporate into the frame cuts file. Hammer and sear are ready for pilot drilling and to be cut out. Trigger ready to be cut. 10/27/14 Making lots of progress on the CNC front. Ran a virtual cut on the frame last night. It took 196+ minutes to finish. I found several errors and fixed them. Reordered the cutting sequence so the outside cut is last. was not happy with the clearing cuts inside the frame so re-plotted those today. Ran some test cuts and found I could cut .015″ instead of .010″ per cut that should reduce cut time by 64 minutes overall. Code for Side Plate, Hammer, Sear and trigger are ready to cut. Breech block is 90% done only needs side cuts completed. Barrel shroud is only about 50% complete so far. I probably will not finish it until the frame has been cut. Trigger dimensions were dead on! Getting very close to cutting some REAL chips. I have made several test cuts in Nylon 4″ X 4″ x 1/4″ to test frame cuts. Trigger cutouts just finished in 14 minutes instead of 26 minutes.

screen shot of final, I hope, virtual run.

screen shot of final, I hope, virtual run.

10/28/14 Finished all of the frame today. Had some areas that were not being cleared of metal but now fixed. 100% done. Tang hole relocated to fit the Tang radius. So frame pilot drilling is 100% also. Frame Side Plate ready to cut and to be pilot drilled. Hammer is 100% done. Sear is done, pilot hole for pivot done but the spring hole is not done. May leave this to be hand drilled as it is not critical. Breech block length wise cuts done. Side pilots and angle cut mostly done. Will have to radius the bottom breech block to fit radius in frame. Barrel shroud outline cuts drawn. I am leaving this until the frame and breech block are cut out. This is in case the Barrel shroud lengths needs adjusting to the frame and breech block. I need to order a Barrel Liner here soon. Getting very close to cutting it all out. I have 2 4″ X 4″ X 1/2″ Aluminum already cut. I have the 3/16″ but need to be cut to 4″ X 4″. All the metal is in fact here, just needs cutting to final lengths. need to figure some of the fixtures still. 11/11/14

3 piece frame fixture

3 piece frame fixture

I continued to have problems getting the metal in flat on my mill. So I took the time to build a fixture to hold the work flat and tight. It has a fixed jaw, tightened to the table. A floating jaw and then there is the tensioning block. The block has an under cut to hold the floating jaw, it tightens down to the table also. The angled screw is used to put in the final tension.

Sear cut from 1018 steel

Sear cut from 1018 steel

Hammer in steel

Hammer in steel

So I have cut out a couple of sears and a couple of hammers in 1018 steel. I am not very happy with the cut finish. I do not expect it to be a mirror finish, but the pebbled surface it has now is pretty bad. I think part of the problem is the small cutter flexing. It is a 1/8″ end mill. I am trying to figure out if setting the spindle speed higher or slower will improve the finish. One hammer was ruined when it let loose. The double sided tape I was trying was just too wimpy to hold it through the last of the cut.   rough finish A picture of the rough finish I am talking about! It is worse on the back and the radiuses. 12/19/14 Well I made a new fixture for cutting the frame and side plates. The frame came out very good, nice machined finish. Cut time was 101.4 minutes. The cut depth was increased to .020″. Enco No. 1 “Lubricoolant” was used by dabbing onto the tool during cutting. This really helped the finish. Slowing down a bit to “F7″ helped also. Still some “burr” issues, blades of metal left where they are not supposed to be, but much better this time. I will work some of them out of the code but others are on the edges so will just be part of the regular de-burring! frame done I fly cut both sides of the work first. I really only need to cut the side that mates to the Side plate. So here are a few more pictures. ready to cut she is a cuttin outside cut trigger cut out next So a couple of side plates are needed next! 3/14/15 Completed the side plates and they were both off, so I had to make them again. Completed a third frame with no events so now we have two pistols that are on their way to being completed. Finished most of the second pistols parts in the last couple of weeks. The three Barrel shrouds have been drilled for the Barrel Liner. So finally making some good progress. frame still needs a lot of de-burring and shaping.

frame/side plate joined, drilled and tapped

frame/side plate joined, drilled and tapped

You will see a plastic trigger in the picture, just underneath the Aluminum part. Received a Printrbot 3D, Simple Metal with heated bed, printer today. I drew the trigger in Google Sketchup. I was surprised it took me less than an hour to get a completed drawing. After using CURA (3d printer software) to convert the .dea file into g-code file, I printed it out in Repetier (another 3D program). Fits in the frame but is a bit proud of the rails. The trigger pin will not fit through the slot. Some dummy made the slot .125″ and the pin is 1/8″ too. It will take less than ten minutes to redraw it and make the changes. Another twenty minutes to print it out. I may be able to edit it to fix it, but so far that is harder than redrawing it! I was very surprised at how easy Sketchup was to use after I figured out how to enter lengths by hand.

The PLA (plastic) is a lot tougher than I thought it was. But it will melt in hot water. I will buy some ABS Filament when I have the Machine reasonably figured out.

So lots of fitting still to do but getting somewhere after all these months.

4/2/15 update

Pocket Pistol

Barrel shrouds are done and the barrels are ready to be put in. all the holes have been drilled and reamed to size. Barrel latch has been figured out. Firing pin still needs to be done.

3D printer

As for the little side project in plastic; I have been fighting with warping so finally turned off the heated bed and am using blue painters tape. todays print of the frame came out ok but still a little tweaking of the temperatures is needed. Some bubbling on the inside of the side plate. Still a bit of misalignment in the back-strap but better than it was before. Getting some experience with Sketchup. Still not much luck at converting the drawings to G-code for my mill but still working at it. These are in PLA so far. I have not decided if on material yet, but ABS might be better.

3D printed pocket pistol frame

3D printed pocket pistol frame

I will do a little sanding then drill the holes to size. Then try some of the metal parts in it for fit.

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