Boring for real now. Fingers crossed it all comes good in the end!
A few passes with the fly cutter to come down to width. The CNC really comes into it’s own hrre. I wrote some basic GCODE to run the cutter across the job with a slow feed. The cutter is slightly narrower than the area to be cut, so it needs to move and make another pass.
So, basic GCODE does a slow pass on the Y, then a rapid move away and across on the X. Another slow pass back on the Y, finishing with a rapid move back to the start. I’m not 100% on my calibration with the Z axis, so I put the cut on manual by raising the knee.
Like hybrid – which saves me time and is easy to use. And the bonus is that unlike a conventional power feed, I don’t have to watch it like a hawk as it moves to a safe place and stops. 🙂
At some point I’ll sort out controlling the spindle motor. A job for Ron!
Now I’m happy with my boring setup, I’m working on the big end for real. Setting up the rod on the Bridgeport is probably the hardest part, as it takes ages to get everything straight and level.
The Mk I eyeball isn’t accurate enough, so it’s a job for Uncle Ernie’s clock. One of a few things of his I still have. The rod is a bit thick at the bottom so will need finishing to the bearing width. I’ll aim for the same bore diameter as the bearing is a good fit in the test piece.
A bit nerve racking as a lot of work has gone in so far, and it’s so easy to muck things up – especially bore diameters!!
With the trial bore completed, measured and measured again, I thought I’d try pressing it in. I put the bearing in the freezer over night, and warmed up the ally in the oven.
The bearing went in very easily and grabbed itself tight when everything came to a constant room temperature. The bearing is reassuring tight, but still runs freely – I’m happy with that. Even Bob said well done!
Onto the rod itself next for the final article. When I’ve got somewhere near I’ll press the bearing out of the test piece. (Or saw it out). As long as I can reliably repeat the process, I’ll have a finished rod 🙂
So far, so good – although it’s a slow process. Getting to grips with a new boring tool and machine takes a while. The tools seem to be working well, I’m getting a lovely finish on the finest feed and the bore size corresponds to the graduation marks.
I’m starting to hate aluminium swarf though, it gets everywhere! I can only take a 25 thou cut, so opening the bore from half an inch to 80mm (3.149") is going to take a while. And when I’ve finished?
Start again on the real job, the conrod!!
I have a couple of weeks off work, still during lockdown so I’m hoping to get some time in the shed. One job I’ve been putting off is boring the big end of the conrod.
A lot of work has gone into it so far, mostly by Bob, so I don’t want to mess it up and have to start again. I’m using the Bridgeport as it has a power feed to the quill.
The rod is too big to turn on the lathe, so boring from the top is the best option. I’ve setup a test piece so I can check out the boring tools that came with the mill.
A good result would be to get the bearing pressed in before I have to start work again. Stay safe everyone 🙂
Here’s a youtube video of the CNC conversion on the Bridgeport. Saves me a load of typing!
I decided not to motorize the handle that lifts the knee. I’d need an enormous motor for starters, and stepper motors don’t go much over 4nm. The weight of the table, cross slide etc. presents the first problem.
The second issue is the handle driving the knee, which exits at an angle (not perpendicular) with no end cap on it. The mill would have to be accurately drilled and tapped, in situ, to mount the motor. Lots of problems to overcome.
Instead I’m driving the quill to achieve my Z axis. I’m limited to 4" of CNC travel, which should be enough. I can also manually drive the Knee. I went for the largest pulley to get the most torque and steps per mm.
Mounting the motor for the Z was a bit of a faff, but I’m there now. Just a case of calibration and fine tuning now 🙂
I rescued 16 plastic boxes from work before Christmas during an office clearout. They were destined for the bin!
Just the right size to mount three microstep motor drivers in and an Arduino running GRBL. Neat!
The more observant will notice the Z axis controller is wired. These drivers will fry themselves without a load from a motor, so yes, the Z axis is also done!
Great progress in the garage last week, mostly due to a week off work and a lockdown in place. I have both motors mounted for the X and Y axis, microstep controllers in a tidy box and a working 2-axis solution!!
I still have to calibrate it all and fine tune it, work out the backlash and see whether I can program that in too. But so far I’m really pleased. I’ll see if I can post a video to YouTube and link it here.
As always, whenever there’s good progress there’s still much to do. But I’m very happy to have come this far!