After a loooong delay due to moving house, I finally got the rebuilt lathe set up and running (an article on the rebuild is here).
I can see that owning a lathe is a hobby in itself: I am busy with projects to improve and modify the lathe, the projects I bought the lathe for (rocket parts) have been put on hold temporarily. It is all the more tempting to spend time modifying the lathe because it can make its own parts – this is immensely pleasing and addictive.
This was my first time using a lathe. If this is also your first time, I can highly recommend Harold Halls’ excellent book: Lathework: A Complete Course. Harold also has a website stuffed with useful information.
Top tips for beginners:
- install a thrust bearing at the handle end (right end) of the leadscrew
- make a height gauge for setting tool height – getting tool height correct really makes a difference
- buy some HSS blanks and grind your own tools – I find they work better than the bought ones
- don’t try parting off (or: do try and see for yourself) – use a hacksaw instead
- use cutting fluid
- adjust your gibs – run the top and cross-slides through their full travel when adjusting (to avoid seizing up or going loose during a cut)
Attaching the BFE65 mill head to the lathe
My summary: don’t do it, unless you really have to. If you do have to, limit yourself to small pieces and light cuts.
While I do love my little lathe, it is not the most rigid of machines – this is largely down to its small mass. If you have the BFE mill head you have the option of milling on the lathe. However, I had a lot of trouble milling with any accuracy on the lathe – all my pieces were either not square or had a terrible surface finish. Being new to all this I didn’t really know what the problem was…
When I finally got my dedicated KT mill table set up the difference was very noticeable. If you do have the BFE mill head I would highly recommend setting it up on a dedicate mill table.
Before I fitted the thrust bearing to the leadscrew, the handle was such a pain to turn that I used the powerfeed whenever possible. After several hours use the changewheel that is mounted on the end of the leadscrew seized on its shaft.
There is something hypnotic about the leadscrew handle turning all by itself – I know it is not in fact “magic” as my Nauty son exclaimed, but there is something about it…
I suspect that this had something to do with me fiddling with the play on the leadscrew handle, in an attempt to get it to move more freely.
Be careful when adjusting the play on the leadscrew handle: if you leave too much play on the handle end, the whole leadscrew will move to the left when using powerfeed and the changewheel gears (attached to the motor end of the leadscrew) will rub or crash.
This happened to me a couple of times, and I suspect this is what caused the changewheel to seize. This crashing will not happen if you fit the thrust bearing to the leadscrew handle end.
Below is the diagram for the manual – the ‘bush’ (part 4) rotates on the ‘wheel stud’ (part 2). I know I had greased this up pretty well during the rebuild as it had already galled when I was reassembling it. However, this is steel-to-steel contact and is intolerant of kak-handed baboons like me.
I scratched my head for a while trying to work out how to get the bush off the shaft, as I didn’t want to damage the small plastic gear. In the end I cut a washer in half and filed a sharpish edge onto it, then put it in a vice to close it up. If you look closely, there is a small “v” between the gear-end of the bush and the nut-end of the shaft – where opposite sides of the “v” are the metal of the bush and the shaft. This got the bush moving, some taps with a centre-punch got it out completely.
Split the washer, file a sharpish edge on it, and squeeze in vice as shown above.
I had some brass bushes that I had stripped off old photocopiers that I thought could be made to fit, and would at least be better than the existing steel-on-steel arrangement. These had a 6mm bore and 9mm OD. I figured I could turn the shaft down to 7mm and drill out the original bush, then machine the brass bushes to size. Bear in mind I have never done anything like this before…
Brass bush. Kate Bush.
The drilling out of the new brass bushes went OK (my first machining of brass), as did the drilling of the original bush (use cutting fluid). And, after a couple of mishaps (see below section on tools) I managed to get the shaft turned down to around 7mm, and (ahem) press-fitted the new bushes. I was VERY pleased with myself.
I then put the shaft with new bushes into the lathe and attempted to turn the bushes down to just smaller than the new drilled-out bore of the original bush. I got most of the way, then I guess the heat of the machining caused them to expand, because soon enough they were just rotating on the shaft.
I test-fitted the original bush – it went over the shaft with brass bushes, but did not turn freely. When I pulled it apart again, the brass bushes were stuck in the bore of the original bush. So, I put the shaft back in the lathe and skimmed it – put at all back together and it turns really smoothly. Result.
It is hugely satisfying to repair parts like this – this is one of the reasons I wanted a lathe in the first place. I have a lot to learn but I went to bed a very happy man that night.
The installed bush. If you look closely at about 1 o’clock on the shaft, you will see evidence of my kak-handedness.
After some research, I found that online consensus was that small lathes were not rigid enough for carbide tools. So I bought a set of HSS tools to get me started.
I had loads of problems with these tools – they kept digging into the work. No doubt my inexperience had a big part to play, but the very sharp tips galled/dragged on ally and tended to dig in (same on EN3B steel).
That sharp tip just kept digging in… but the long edge nearest the camera gave a very nice finish (when it didn’t dig in…).
I did have some success facing with the tool with the long blade, when it worked it gave a really nice finish.
Difficult to get a decent shot, but a very nice finish even close-up.
In the end I spent a few quid on 3/8″ HSS tool blanks, and ground my own tools with rounded tips. This was pretty easy to do after watching a few YouTube instructional videos, these two in particular:
- tubalcain – this guy has an extensive series of very helpful videos
- ProjectsInMetal – I like this guy’s delivery, and he makes it simple
My grinding wheel is probably too coarse, and my grinding definitely needs practice, however despite this these tools work very well. The grinding does not take long and is well worthwhile to better understand how these little things manage to cut steel.
The rounded tips make such a difference, I think also the larger cross-section of the blanks (3/8″ vs 1/4″ for the bought tools) made a difference – my home-ground tools seem more rigid. The stock toolpost will hold up to 1/2″ and I would be tempted to grind some tools from 1/2″blanks.
Tool height gauge
If you search on YouTube for instructional videos for lathe beginners, you will see people blithely whizzing their toolpost over to the tip of the tailstock to set the tool height. This doesn’t work on the MD65, mostly due to the combined annoyances of the four bolts for the top-slide (which you can’t get to without removing the tool holder…), and the supremely annoying pinch bolt / push bolt arrangement on the tailstock.
I made this tool height gauge while practicing facing, drilling and tapping. It’s a bit crap because the washer is not perfectly horizontal, but I just put a mark on it so I know where to measure from.
It’s a round of steel, faced both sides and with an M4 tapped hole in the middle. That’s M4 threaded rod that I had hanging around, plus a couple of nuts and washers.
Blehgh! Grrr! Aaaargh!
These are some of the sounds I made to accompany the screeching from the lathe during my attempts to part off. The concept is so appealing: make something and then just zip it off. Easy as pie.
It doesn’t work like that.
I even bought a special (very cute) parting off tool. In the end, every time, it was easier to use the hacksaw and face the cut end.
The problem is rigidity – small lathes don’t have this like big ones do. Online research suggests a tool-post that is bolted direct to the cross-slide, and/or a rear-mounted toolpost (as in, on the other side of the work) will help. This may be the most challenging type of cut to make on a small lathe – I will tackle this when I have a bit more experience, and in the meantime just use the hacksaw.
The steady is done and in operation!
All the good stuff is here.
Update November 2016 – the new toolpost is made and in use, here is the write-up.
I dunno about anyone else, but the set up of the toolpost and top-slide is my biggest gripe with the MD65. Especially the four bolts securing the top-slide:
- often you can’t get to the back ones without removing the tool holder – meaning it can be a pain to change the angle of the tool
- the front one can interfere with the top-slide gib locking screw
- most of the time only two of the four bolts can be installed…
I have used the top-slide, but most of the time it’s just locked. I am planning a central post style toolpost that bolts directly to the cross-slide. Something like the one explained here.
Other planned upgrades / improvements
I am trying to focus on rockets, and not get too diverted by the lathe. However the following improvements are already in progress… I will post more detailed info when each project is complete and working (don’t hold your breath).
Treadmill DC motor
Ranking just below the C3 8mm ballscrew, this treadmill was my second-best eBay buy of 2013. £30 and 10 minutes down the road. Popped out during my lunch break, it (just) fit in the back of my car. I hid it from Mrs Naut under a sheet, and over the course of the next week disassembled it from the back of my car without anyone being the wiser, secreting the various parts in the garage and even under the bed. The console even had a little TV on it.
Size-wise it’s a perfect fit. There is loads of great info online about using the driver (the big circuit board in the photo). I would also add a tacho to the lathe spindle when installing this.
I have not done much besides making this test-bed and getting the bits needed for a control circuit. Just need to wire up the circuit and make sure the motor is alive, then take it from there.
Leadscrew stepper conversion
Ahh the long-cherished dream of CNC…
Update March 2017 – I have created a page for this project here.