Figured you guys would like a picture update. Got all of the prep work done Saturday. Ran into a major snag yesterday, but un-snagged it. Details below!
Pre-processed and tagged the racks Saturday. Everyone looks good.
You'll see my machining setup below. I do racks on an original Bridgeport Vertical Milling machine, we have two with 2HP 2J variable speed heads. They're great machines. About 2600lbs each of ancient technology, completely manual with no digital anything. Tried a small DRO once and decided I'll keep using the dials until I'm ready for a real Digital readout system.
Both Bridgeports were made in 1950 according to their serial numbers. One was treated pretty rough before I bought it, with about 10% life left on it. The other has seen far less use, with probably 75% of its lifespan still ahead of it. Guys that can run these professionally are (literally) a dying breed, and get a ton of respect from me. Although I plan to eventually get a CNC mill, I'm going to keep these, and keep them maintained. These two machines will easily outlive me, and are something I hope to pass down to my boy when the time comes. Along with the knowledge to use them. Never know when you'll need it.
I've always used the worn mill for the racks out of convenience, so I wouldn't have to change around the setup a lot. It's 70 year old with shot head bearings and still cuts extremely accurate for anything meant to go on a Yerf Dog. With that said though, I've known since I got the machine that I need to rebuild the head sooner or later. It runs great, but you can hear the old worn bearings are on their last breath.
Well!!!! After starting on the first cut yesterday, I heard a new noise from the head and decided that later is "now", and that I don't want to use it anymore until I do the rebuild. Just don't want to risk damage. This meant several hours transferring everything over to the "newer" mill, indicating it all properly and setting it straight. Plus wiping down and re-oiling the newer mill as well.
Using the indicator to line up the vise.
Using the dial indicator again on the rack. I cut the extended flat at this step. Using the indicator is critical to getting perfectly flat and true cut. (There is no such thing as perfect, but you know what I mean). It measures down to the thousandth of an inch. Properly indicating and adjusting the part in the vise/fixtures is one of the most time consuming parts of machining each rack, but is the most important step to making sure your extra teeth work and last without binding.
Alright now let's complete that cut...
Notice the area pointed to in red, this is a particular point of pride for me. That what I'm going for and why I spend so much time making sure it's properly indicated... there is practically zero angle and the height difference between the new cut and the existing shoulder right next to it is literally the thickness of the layer of grease.
Before, I always used to reposition the rack in the vise and indicate it again to cut the flat on the other side. TIME CONSUMING! This time I tried something new. Planned ahead when positioning the first time, and so that I'd be able to do the second cut without repositioning or indicating a second time. I was concerned about lack of rigidity/support and also about how far off "true" the second surface might be since it's 3" away from the zero'd surface, but neither turned out to an issue.
There was slight amount of twist in the rack (either in the steel from use, or from my positioning), you can see it in the second cut. The amount of twist was minimal. Just about the thickness of the grease layer. Much less than the thickness of a fingernail. Well within tolerance. I'm super excited to be able to skip that step from now on.
Zeroing the tailstock now... this just gives us a 90 degree vertical surface to mount our rack.
And finally what all this entire process is about.... cutting teeth! This is a true gear cutter, mounted on a custom arbor + R8 collet setup I machined in 2014 or so specifically for cutting Yerf Dog racks. Lots of trial and error and $$$ to figure this one out.
See that witness mark highlighted in red? That means success! It's not a tool mark, it's a line of grease from the pinion gear inside of the rack. If I see that line, I know that the rack travels fully on the new teeth.
I'll be continuing to machine racks the rest of the week in the evenings. I'm doing all of our shipping and customer service now myself, so balancing everything is key. I'll post smaller updates as racks ship out. Thanks guys!
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