Bridgeport Interact 4 Series 2 to Acorn6 build

[suntravel]

You can also misuse the rigid tapping for honing, just set M3 also for the bottom and you will get a nice cross finish...

Uwe

[richardb15]

I was using the W and Z together just for a trial, yes I could have just used the W for that particular job but it was more a test of me using the machine and the boring programme I wrote.

Yes I do have a chuck mounted Delapena honing tool I could use in the mill but I prefer to use the rigid mandrel on my Speedhone and hold the barrel in my hands, that way I can feel how it is cutting and adjust the pressure with the foot control as it moves into and out of the barrel. It is especially tricky on blind barrels as if you just run a hone down and back out you get a tapered bore as the stones have much more contact time at the exit than at the turnaround, and on two stroke barrels you get more material off around the ports if you don't vary the pressure and time during the hone stroke. Not a problem with a 4 stroke through barrel where you can run the stones out the other end to keep the cutting time consistent.

Speaking of two stroke barrels, here is one bored today on the Bridgeport, a 1920's Scott. A customer job who had a circlip fall out and run between the piston and bore, he thought it was scrapped but I think we've rescued it, will get honed tomorrow then I'll make a pair of new pistons for it:



On other projects I bolted the rotary axis setup onto the machine and when clocking it in realised the axis spindle was bent so my CNC12 messing about time became an exercise in correcting the runouts, but it is now an awful lot better than it was this morning!

[suntravel]

The needle of the dial Indicator is also bend

Uwe

[richardb15]

The needle of the dial Indicator is also bend

Uwe

Err.... that DTI has seen some major action in it's time, at some point I might take the lense off and sort the needle, but all the time its working, well its working so best left alone maybe!

A big milestone today where a lot of small project items came together. getting CAM and post processors sorted, going from 3 linear axis PP files to 2 linear and one rotary, using the robot wrist assy as a rotary axis, and doing some tasty engraving work! I'm well chuffed with the outcome, nice accurate and sharp lines and characters and all done with a cheap Dremel 1.5mm dia ball nose carbide bit! Many thanks to Uwe/Suncatcher for the inspiration for doing this, although I've gone a bit of a different route to get to this.

[richardb15]

Okay, so I've been shamed into fixing the needle on my DTI:


Better after surgery


Back onto the mill it was time to do a job using the newly setup rotary axis. For many years I've always drilled ring stop pins in pistons using a manual quill machine and a dividing head, but it was time to put the Acorn 6 to use, no more manual 2mm bottom puckering drilling for me!



All good, those pistons are for a 1929 Scott and should be back into our customers engine next week. Onto the next project now, a custom big end roller bearing for a 1920's BSA V twin but that will probably be CNC lathe, heat treat then cylindrical grind, no Acorn required.

[CentroidFrog]

Incredible work Richard.
Such a creative solution for a rotary.
Watching those pistons slide so perfectly into that checker was very satisfying.

[suntravel]

Very cool

Nice to follow your project .

Uwe

[richardb15]

The whole driving reason for doing this retrofit with a system capable of two axis rotary and thread milling was to be able to thread inlet and exhaust ports on veteran motorcycle barrels. The local CNC shop who used to machine them for us said no more, volumes are too low and parts to fiddly so they won't machine them any more. 10 years ago they were glad of this work, I guess sometimes people forget where they got here from.

Anyway, after a day of making fixtures and mounts, I have a test barrel set up ready for programming for the port threads!

Inlet port position, this is an internal thread:


Exhaust port position, this is an external thread, with very little clearance to the cooling fins:


The reason for mounting the barrel on the top rather than the bottom is its nearer to the machining area, so more rigid, and I made special mount bungs for the valve caps, they are 1.5" 16TPI so a much better location feature than the 4 5/16" holes in the base flange. For extra mounting I also made a top hat bush and bolt that fixes through the spark plug hole, so 3 strong mount points I hope will ensure good alignment, repeatability and rigidity.

[suntravel]

Very cool. It is always good if you can help yourself.

Uwe

[richardb15]

Time to find out what thread these pre WW1 Triumph barrels were. The company was German owned and some parts including Triumph bicycles were actually made in Germany. Not so British as people think! Anyway this connection meant early Triumphs probably used some German machines or equipment, or at least carried over some of their influence, so everything ended up a mish-mash of bizarre thread sizes. The ports in the top of the barrels are 1.5" 16TPI, but it turns out the inlet port internal thread here:



Any guesses? Nope, I thought not! It is M30 x 0.9 pitch. Yup, really. The only 0.9 pitch I've ever found on anything.

The exhaust is an external thread, any takers for this one?



Still nope! It is M37.5 x 1.0. Now you see why I needed thread milling capability

Off the shelf thread gauges are not so easy to find in those sizes so I figured I'd just use the ISO M6 tolerances at 6g/6H for both and that will get me where I need to be. By setting up the CNC lathe and taking a skim cut with the ID and OD threading tips I can calibrate their diameters then use that to cut the threads with the appropriate major/minor diameters to suit the tolerances for the go and no-go ends of the gauges.

Nogo side of the M30x0.9:


go side of the M30x0.9:


Finished ID and OD gauges:


Now I could screw the thread gauge onto the angled exhaust port, level it up and that will give me the angle. 42.8 degrees......

Yes I had levelled the machine up before doing this.

I think our friends at Triumph had a rubber jig for doing these. I'll check another couple of barrels to be sure then it will be time to do a bit of intercon and hand g code. That will have to wait a week or two while other work gets done though.