After considerable consideration I have decided to abandon the compound scale application. The real benefit to a compound scale would only be used on a limited basis but the cable would always be hanging out there waiting for something bad to happen. I had considered rotating the scale 90º (facing down) and placing it on the left hand side well above the gib lock but then I would have a cable draped across the dial full time with a fairly big loop to allow rotation of the compound. What I do use a lot like most of you is the tailstock. This machine has 6" graduations but travels a bit further. I started taking measurements and designing a bracket system that would allow the application of the third scale on the tailstock (TS) quill.
The scale would be fitted to the front side of the TS. I would have liked to use the rear but the two clamp levers don't provide enough clearance for this. I used some angle block to determine the angle of the TS body and set up the mill head accordingly and face milled the profile needed to bring the scale plumb. I feel by doing this it will make things easier to align the quill clamp arm to the scale leaving only lateral adjustment to set the air gap between the readhead and scale.
I set the X/Y in absolute and took readings prior to adjusting the nod. I had never had the opportunity to use the mill with the nod adjusted in the past as I was always able to set the work piece to the desired angle and go from there. The bar stock I was profiling would have required some creative clamping and it was much easier and safer to set the angle on the mill head. The initial readings using the co-axieal indicator was used to set the mill head back to neutral. I also used another dial indicator to double check the table as well. By setting the absolute, meant I was checking the same area for reset.
The set up.
I then milled a channel for the scale to to nest in.
The thicker top portion of the scale bracket can be drilled/tapped for a cover if needed. The scale face is now vertical.
A close up side by side. The holes in the bracket will be slotted after transfer punching. I find it easier and more precise than trying to find the center of a slot when working alone.
So this design will make the readhead dynamic and the scale static. I did consider mounting the readhead to the TS body and scale to the quill bracket but felt this would be more secure and cleaner. The cable will loop around the back of the TS below the quill crank dial. I plan on incorporating travel stops into the arms by milling profiles into the male/female tracks. The stock for both scale and readhead brackets are .625" x 1.5" aluminum rectangular bar stock I already had. The quill arm profile will fit over the scale and have clearance to ride along the top and bottom portions of the scale bracket. At least thats the plan. The quill arm will have a pocket milled for the readhead to nest in with two threaded mounting holes. The lateral adjustment will come from the connection (two counter bored/slotted holes between the arm and quill bracket.
I need to finish up the quill clamp bracket and mount it prior to final design of the readhead arm.
Cut a piece of 1/2" x 3"x 6" from some flat bar I had and laid out for boring the quill diameter of 2.046". The rear if the clamp will be drilled/tapped for a single countersunk Allen head cap screw. The cold saw will provide the .120" wide slit. I bored the quill hole .004" oversize for a decent slip fit. I figured the slit provided would give enough to clamp up well.
Used the largest annular cutter I had to save time. Working with aluminum is so much nicer with the soft chips and the nice surface finish comes easy.
Most of the machining to this point had been dry with an occasional shot of WD-40 on final passes.
Annular speed was 325 RPM.
With the 1.8125" hole provided the boring operation went quick. Boring was done at 250 RPM using a carbide tipped cutter.
The surface finish was very nice.
A super spacer rotary was set up next to the vice to cut the radius profiles. The end mill used was a three flute 7/16" at 1500 RPM.
I did use plenty of WD-40 and low PSI shop air for this operation. I also took no more than .040" DOC since the chuck was gripping the bore with just enough clamp force to prevent marring. Also used .125" parallels to set clearance between the work piece and top of jaws.
Having a long table saves time from having to remove the vice and re-tramming for the following operations. I had slight chatter but not surprising due to the setup.
Using the co-axeal indicator to find center. I really like this instrument. My wife and son gave it to me for Christmas two years ago. I use it often and it beats getting an ugly sweater for Christmas
With the center located, the X/Y absolute where set once again. The protoTrak system really helps and with a return to absolute button it makes it easy for me to keep track. This mill is capable of milling the entire bracket without the use of this setup but I'm still learning the CNC functions and mostly machine via commands by inputing numbers for power feed rates and jog. Honestly, manual milling forces me to get creative and use more of my pee brain.
I do appreciate the potential of this machine and will probably hire a tutor to come in and teach me how to use this machine to it full potential.
I'm a metal fabricator first and a novice machinist second.
Once set to center, the cutters offset or compensation was set moving the X feed (locked X/Y on the table), the piece was rotated to both starting/end points for each cut taking notes on where the degree pointer where before the fist cut was made . The final .020" clean up pass provided a real nice finish seen here.
pretty happy with the results so far.
The setup. I'm gonna need to save up for one of these rotary tools. Mark's (mksj) been kind, trusting and generous with me. Rest assured, when he gets it back it will be clean and serviced like it was never used.
I also got the Y scale cover cut and installed. The compact scale looks/fits nice. To cut the cover I used a cheap electric hand shear from HF along the bottom length. The cover is extremely soft but too thick for hand shears.
The clearance between the readhead bracket and cover is just under 1/16".
I would like to thank everyone who chimed in on the compound. I take your time seriously and ask
opinions from those who care about helping.
That said, thanks again, I'm learning everyday so your time was not wasted.
In the end I will use the TS DRO way more than compound vector/summing and the proximity carriage stop also plays an important role in precise depth stop.
No shop time today, I have to sit in class all day for a recertification, I'll be day dreaming about what I could be doing in the shop.....I mean learning prehospital trauma management (PHTLS) ...again. You know you'r old when this is the ninth recertification for this course. The state/ fire department requires nine different certs (every two years) to work as a medic. Oh well, at least they pay me to learn on my time off.
Thanks for looking and Turn and Burn!
Stay safe out there.
Paco
