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Discussion in 'CNC IN THE HOME SHOP' started by jbolt, Aug 21, 2016.
Looks great, nice work.
Jbolt, sorry i was in a bit of a hurry when I typed my message. How did you go about modeling the pocket in the chassis for the receiver to sit in? How did you correct the rear tang area since it was off the first time? I'm trying to get a accurate model of a Remington 700 but I do not have the correct tooling just yet to be confident in my measurements
The inlay is straight forward with the receiver being round. The size of pockets for the trigger, safety & bolt release were done by measuring the receiver/trigger and also one of the Bell Carlson stocks I have. Since I am using a box magazine I just used the magazine dimensions with some clearance for fit and measured its location on how it fits against the receiver.
For the tang area the error was in my favor so material removal was necessary. The rear tang is not flat but has a slight radius to match a typical hunting style stock. I didn't bother with that since it is not important for this build.
I have not fully modeled the receiver. Because I am not trying to make a receiver all I need is the relevant dimensions to do the inlay.
I couldn't find a check valve locally that would work and it was a week lead time to order one so I rolled my own. Works great!. I posted a quick build thread on that if anyone is interested.
With the coolant system operational I was able to finish the last op on the barrel guard mount. The 2-1/2" flute 3/8" end mill chatters like crazy no matter what I try. Maybe solid carbide would be better but since this project is getting painted I can live with it. It just adds some handwork. The slots will be done on the 4th axis. The last photo is the fixture parts.
For those deep cuts I have used a reduced shank carbide end mill. Various sizes are available. I have used the 3/8" with the flute length of 5/8" and the shank is something like .370. It takes a few steps down for deep pockets or in your case, outside profile. Then a finish pass of .005 pretty much removes all tooling marks. Also make sure you only have the tool sticking out of the holder the min. required. I purchased these from Maritool in Woodale, IL (they have an online store.)
Thanks vertcnc. I figured there was something like that. I'm familiar with Maritool. Of course now I have done all the deep stuff on this project.
Watching for more very nice build. What's your finish weight target. About seven pounds I'm guessing.
The stock or the whole rifle?
A little more work completed. I got the 4th axis completed and running but the first motor I used was too long. I had to put a sorter stepper motor and coupler so it would clear the new enclosure so I could use the flood coolant. It also took a while to get the Mach3 post modified correctly for the 4th axis.
This is the vent slots on the barrel guard mount. To index in HSMWorks I had to create an individual tool path for each slot. That's just a matter of duplicating the first tool path and editing it for the correct orientation and contour of the next slot.
I decided error on the side of caution and run a test part before committing the actual part to the last operation on the 4th axis which I am still getting used to. I turned a piece of stock the same diameter as the finished part and set the offsets for the actual part so if it was successful then the actual part can be ran with no other setup needed other than orientating the part in the 3-jaw.
Success! (and no the chuck key was not in during the machining)
Here is the actual part mounted in the fixture in the 3-jaw ready to machine.
That was the last operation for this part so it is now completed.
Beautiful piece of machining!
Thanks Tom. There is definitely room for improvement. I'm still discovering the appropriate tools for certain jobs.
I desperately need to fix the backlash in the system that has creeped in over the last two years. Not so bad for one off parts but it really shows with the multi faced assemblies. The double ball nuts seem to be the way to go.
Well it was bound to happen sometime. I scrapped my first part. I started on the barrel guard and I think I was a little too optimistic about my setup.
Here is the CAD.
Here is the guard modeled in the fixture.
Here is the turned guard blank ready for machining.
The guard is mounted between a plate that is attached to the rotary axis and a plug that rides on the tail stock taper. A threaded rod is between the plate and plug to hold the guard under compression. The guard at the plate end is tapered and is very thin. There was not enough surface area to properly grab the face of the plate.
In addition my lead in speed was too fast, the lead length and lead radius were too small.
The end result.
I remade the plug that is pressed into the plate with a larger OD that is a press fit into the guard. On the tail stock end I drilled out the center of the plug and made a Chicago bolt to go through the plug. The bolt head is counter-bored for the tail stock. This gives me greater clamping pressure.
I also decided to not turn the OD and taper yet to leave a greater clamping surface.
Here is the revised fixture.
Ready to try again as soon as I tweak some of the g-code.
Things went pretty well today. I learned a few things but overall I'm happy with the result.
First op was to cut the flats on eight sides. I'm glad I modeled the fixture in solidworks. I caught a cut interference with the button head cap screws that hold the fixture to the rotary axis. I was able to change the lead out to avoid it.
Next was drilling the holes.
Next is milling the slots.
Next is the chamfer on the slots. I was getting some chatter out at the tail-stock end. At first I thought it might be because as the slots were being cut the torsional rigidity was being compromised allowing that end to twist a little. Turned out the tail-stock was not tight. Oversight on my part.
Final op on the 4th axis is the front contour. I couldn't figure out how to do this tool path in HSMWorks so I used Aspire for the CAM. I added some additional screws to keep the end plug from rotating in the part during cutting.
Off to the lathe to turn the final OD and rear taper.
Completed part ready for final deburing.
Awesome work Jay. You make this look easy.
It doesn't feel easy sometimes. It has been a lot of fun though and I'm learning a lot.
Here is the picatinny rail.
My original 3D model of the receiver was not correct so I had to spend some time drawing one with enough correct details to finish the picatinny rail model. I searched the interweb for dimensions of the radius of the rear bridge where the rear scope mount sits. It also sits lower than the front. Everyone I found was different and varied a lot so I figured out a way to measure it using a TDI in my drill press and a machine vise on a X Y table.
By zeroing the TDI on the center-line of the receiver and moving a measured amount right and left I could plot the radius. Height gauge was used to measure the offset.
Here is the old (left) and new (right) 3D model.
Machining of the picatinny rail. It was machined from 1" x 2" stock. The CAM was done with the model inserted into a model of the stock to set the coordinate origins for the top & bottom operations. The full rail is 22.2" long which exceeds my table travel so it was made in two pieces. The main piece shown here is 16.2" long
The bottom was done first. For the top operations the part can be held by the machined sides under the bevel and still have room for the cutting tools.
The rail has a built in 25 MOA slope when installed so all the bottom finishing operations were 3D tool paths.
After 3D adaptive roughing with a 0.5" 4 flute roughing end mill.
After the 3D horizontal profiling wth a 0.5" 2 flute ball end mill. Step over on the radius-ed areas that contact the receiver were done with a 0.012" step over. The balance was done with a 0.04" step over just because I like the look. When installed it is mostly hidden. The sides and bevel were done with a 0.375: drill mill.
Test fit on the receiver. Perfect! Unfortunately there is a shadow at the base so it does not show well in the picture.
Now the top.
Before I can drill the mounting screw holes in the picatinny rail I need to assemble the hand guard and double check the measurement from the receiver mount holes to the drilled holes in the guard just in case of error creep.
The guard is pressed onto the guard mount and they need to be indexed to each other. To do this I made a jig to hold the guard mount so that the flat on the guard could be used for indexing.
Here is the stock partially assembled to do final measurements for the scope rail.
You do very nice work Jay, your extra effort in detailing and posting is inspirational. Keep it coming!
All I can say is, WOW!