Building the Trent Pinion Mill
It's officially started, so here we go with an official build thread. I'll be keeping this thread up to date as I make progress on the build.
Here's a video for part 1 of the build... for the unfamiliar, this is the building of a tiny horizontal knee mill that is specialized for cutting small steel pinions. I am starting with the castings sold by Hemingway.
I'm making a few deviations from the plans, and in this first video it's mostly me showing the castings and bar stock that came as part of the kit, as well as the drawings/documentation, and also lots of yakking about he project itself and particularly the changes I will be making. There's about 3 minutes at the end of the video with actual work making the first component.
Brilliant, I have one of these to build.
Looking forward to you working out all the fixtures so it makes my build simple
Wow, that looks like a pretty involved project. I look forward to seeing it come together. So is there anything this does that you cannot do on a normal milling machine with a dividing head?
That's a great question!
Originally Posted by pinstripe
No, there is nothing it does that you cannot do on a conventional vertical mill and dividing head. The advantages are all about the efficiency of the work it does, the compact size, and low out-of-pocket money cost. Being a horizontal mill with overarm support for the cutting spindle, it's a convenient configuration, and very rigid for its' minute size.
There are advantages to doing your small work on small machines, and putting aside the cost factor for a moment, if we consider other setups that would be used for cutting small pinions that are about the same size, the closest match as far as compactness would be the Geneva-style watchmakers lathes outfitted with gear cutting attachments, such as those sold with the Vector and Sincere name (I personally own and use a Sincere). Moving on to setups that are a bit larger than the Trent, of course there is the Sherline vertical mill, the Taig vertical mill, then the more robust watchmakers lathes with gear cutting attachments such as the Schaublin 70. There are some very small Sieg benchtop mills as well, but I believe even the smallest of them dwarfs the machines we're talking about here. Another slightly larger option are the wonderful universal mills made by the likes of Aciera, Sixis, and Dixi. There are some other small mills out there, such as the Benchmaster, Rusnok, etc, but again those are all getting into a totally different league as far as size. The bed of the Trent is less than 8" long.
I have a Sieg-based mini mill right now, and if I wanted to buy or build a small dividing head and tailstock for it, it could do this work on it. I have a Hjorth bench lathe with an indexing milling attachment that might first appear to be well suited to this work, but with that arrangement there's no good way to support the work from both ends so it would be totally unsuitable for small pinion cutting (however it would be very well suited to cutting wheels). Neither of those options have a way to support the cutting arbor or spindle from the far end. And both of them are substantially larger, to the point that I wouldn't want to be trying to cut watch-sized pinions on them unless I had to. With the Trent, I'll have a machine I can leave set up to do this work, with a rigid cutting setup and rigid work setup (including convenient surfaces for supporting underneath the work with jacks if necessary), and is small enough for me to feel comfortable cutting pinions that could easily be down to 1mm in diameter.
With the Trent modified for lever and screw feed, it will also have distinct advantages in wheel cutting over many of the other options.
Now when you throw in the money-cost factor it's no comparison. The real cost is my time, and that time wouldn't otherwise be earning me additional money.
I suppose what it all boils down to is that this is a niche machine, and would be quite impractical if I wasn't planning on cutting very small steel pinions pretty often. For occasional pinion cutting, any of the other options would work just fine, and most would also be more versatile for general use.
Part two of the build video series is up, showing manufacture of the knee support and knee support nut. Getting ready to start machining the column casting now, I'm going to spend some time getting the mill into tram as perfect as I can get it first.
Next video on the Trent Pinion Mill build is in the works, but in the meantime here are a few shots of the column casting being machined. The fly cutter got quite a workout! I bought an inexpensive dovetail cutter for this project, knowing it would be a bit of a gamble. My fallback plan was/is to get one of Randy Richard's (that would stall things out a bit until the budget allowed for it), but so far this cheapie is doing a fine job.
Finally got around to making a set of #10-24 screws to attach the column to the base plate. I drilled and tapped the corresponding holes into the bottom of the column as well, and everything ended up being a perfect fit, the shoulders of the screws keep the two parts aligned, with no need for dowel pins. The tapered head screws specified in the drawings would have been a much easier way to provide alignment via the fasteners, but I much prefer the aesthetic of countersunk "cheese head" screws and was up for the challenge. My backup plan, in case I goofed something a bit and had to drill out the shoulder holes for everything to line up, was to fit dowel pins for the alignment.
Here is a pic of the screws, made from O1 drill rod. They still need to be hardened, tempered, and polished, but I used them in rough form as you see here for the trial fitting.
One more set of screws (to hold the knee support to the base plate) to make before I have all the footage I need for the next video.