10 Years of Mini Lathe Ownership: Pros, Cons, Modifications and Improvements

for anyone looking to buy a lathe you need to ask yourself why you need one maybe you want to repair antique pocket watches maybe you want to make custom parts for your project car or maybe you want to make bits for your radio controlled aircraft whatever you're up to you'll need a machine that's suited both to the task in hand and your experience in using one but what if you don't really know what you need because you just want to try your hand at turning metal with no bigger picture or goal Beyond learning the craft of running a lathe I did some research pretty much every resource out there pours scorn on the Chinese minithe the Mantra by big and by old is the Bedrock on which every hobby machine shop is built and once I've learned that advice isn't without Merit I took it with a pinch of salt I've been the owner and regular user of the same minithe for 10 years and I'm about to spend the next half hour reviewing my experience explaining exping what you get for your money and detailing a few modifications that I've made I'll apologize in advance if it gets a bit long and rambling but it turns out I've got quite a bit to say I'll address the buy big and buy all things separately first buy big aside from the logistics of getting a huge lump of cast iron from where it is to where it needs to be I have real reservations about big machines in novice hands careless use of a minithe can certainly spoil your afternoon but you're unlikely to sustain life changing injuries I winse when I see posts like finally got my first lathe home and there's a picture of a fourton monster with a 20 horsepower motor my little half kilowatt machine weighs just 42 kg and once you can lift it you wouldn't want to carry it far in a small Workshop that has to fulfill many roles this can be a real Advantage but there is definitely a significant tradeoff in performance for reduced size and weight and you need to remember that it's easier to make small parts on a big lathe than it is to make big Parts on a small lathe it all depends on what you're trying to do second buy old if you're not a season lathe user you're not going to be able to tell the difference between a well-maintained machine that's a bit grubby and one that's seen years of abuse but has had a Fresh coat of paint if you're not careful you may end up with a complex and expensive restoration project that you don't have the experience or facilities to complete minithe spares are inexpensive readily available and to a great extent interchangeable and that can't always be said for parts for machines dating from the second world war machines classed as minil lathes come in many different sizes one of the more common is the 7-in swing type like mine and they come in various bed lengths this one is 14 in and for what it's worth I wouldn't go for one of the shorter ones the seven is the maximum diameter in inches that will physically spin without hitting the bed it's not really an indication of the size of work that can be reasonably carried out a job of that size won't fit directly in the Chuck and even if you do manage to mount it your tooling won't come far enough back to get onto the edge and you won't be able to move the saddle under the work to reach the left hand side realistically diameters of 3 and 1/2 to 4 in are what you're looking at the 14 is the size in inches measured between centers though with my particular centers I only get about 13 and you have to factor in that by the time you've got a Chuck on one end and a Chuck on the other and maybe a drill bit there's only a hands width of space available for the thing you're working on all the 7in lathes that I've seen appear to be built from the same castings only the color of the paint seems to change I don't know if they come from the same Foundry or the clones from different places but there's not a lot to choose between them those from reputable suppliers do seem to be better finished cleaned and set up though the machine most often comes with a 75 or 100 mm chuck mine has the larger of the two and it attaches with slightly fiddly studs and nuts sometimes I think an even larger chuck would be better better still though anything bigger might not clear the bed when the Jaws are wound out the headstock is three Moss taper and is barded through 20 mm so stock slightly under that size will pass right through the tail stock is two M and this one has a lever action lock from what I've seen the simpler not operated type is more common it's quick and easy to operate but needs careful adjustment to strike a balance between being able to slide freely when released and grip adequately when locked the machine is driven from a 550 W DC motor via a tooth belt this one is brushed though the new ones seem to be moving towards being brushless it's variable speed and reversible without messing around with belt changes or back gears the speed control isn't perfect and it tends to overcompensate when it's on the load in other words it gets faster the harder it's p pushed there are pots on the driver that might need a tweak but I've only ever been able to make things worse with them it's got a tack disc but why it only drives a display instead of being part of a closed loop control is a mystery I can cut metric threads and with the addition of a 63 to gear it'll make a good approximation to Imperial mini lathes often come with plastic change gears which some people are absolutely appalled at I don't understand why though plastic runs just fine they're quiet aren't needy for lubrication and provide a weak length might save a mistake turning into a disaster in all honesty I can count on both hands the number of times I've needed to single point thread as Taps and dieses cover most of the sizes I use regularly I've used it to cut a variety of aluminium Alloys mile Steels stainless steel cast iron various brasses copper bronze titanium engineering Plastics and even wood within reason if you can spin it you can cut it that said it's really best suited to softer materials and if you're planning to mainly use steel a 7x14 minithe might not be with the best choice by way of an example for this job I needed to machine the end of some 20 mm 304 stainless steel on a larger machine I'd imagine one or two roughing passes and a finishing cut would probably get me from the 20 mm OD down to 10 mil on my machine half a millimet depth of cut was about as hard as I wanted to push it which means nine passes to take out the bulk and a couple more lighter cuts to hit the final size if time's money this is a serious consideration but for me and a lot of other hobbyists it doesn't make a lot of difference if it's finished in the next 30 minutes or the next 30 days they didn't turn out bad in the end though one operation I know many minithe users have problems with is parting off locking the carriage the compound slide and working as close to the Chuck as possible all help but success has always been more luck than judgment I've tried a bunch of different high-speed steel blades and these are just the ones that frustration didn't send to the scrap bin I've experimented with different widths angles and reliefs but i' fail almost every time flipping the tool and running the spindle backwards sometimes helps but even that's a bit hit and miss that all changed when I picked up a grooving tool from the Doncaster model engineering show which used mgmn 150 1.5 mm wide carbide tips it was an absolute GameChanger well it wasn't until it broke this is the replacement and it isn't as nicely made but it still does the job I can only fully part a bar up to about 30 mm in diameter but it can still put a decent Groove in larger stock that can then be completed with a haaw I like it so much I've already got a spare on hand should this one fail one or two things to remember are make sure the tool is square to the work don't just eyeball it set it against the choke even a small error will make it wander offline second it will complain if you run it dry a little cutting oil goes a long way and third third once you're making chips keep the feed going it's much easier to keep it cutting than to start it cutting in the first place once it doesn't absolutely guarantee success it works more often than not for what it's worth I'd stick with this type of insert which has little to no back rake these more hook shaped ones tend to be pulled into the work and haven't been all that useful I'll say one last thing about tooling high-speed steel is your friend put freehand grinding your tools on a bog standard bench grind that can seem like a tall order when YouTube is your only tutor doing it well is an art form but doing it barely adequately isn't all that hard and if you've a Dremel and a diamond needle file to help with the fiddly bits so much the better indexable carbide tools can be had cheaply and seem like the answer to getting going as quickly as possible but I'd say they're not always the best choice for the minithe carbide is hard and durable but it's often not sharp so large cutting pressures and good rigidity are needed to get it under the surface of the material and making chips that said I found the inserts designed for aluminium work well these are sharp relatively speaking and are fine with light cuts and most materials using them in ways that they weren't designed for means they are prone to chipping but with two three or four useful edges per insert they still can be quite economical to use a quick note about accuracy you can make accurate Parts with an inaccurate machine but it takes a bit more effort I can generally cut a diameter to 01 mm but it can take a little while to get it spot on what I was going to say next is that I can only maintain the accuracy of diameter over a very short distance because I know full well I've scrapped Parts in the past for being tapered to illustrate my point I set up a length of aluminum rod with a live Center in the tail stock I wasted the middle to leave two shoulders about 130 mm apart I took a light cut at the tail stock end and measure the diameter so we've got 20 21 22 23 2420 21 nine then without adjusting the crossline I took the same cut at the headstock end and then measured that to fully expecting a difference of somewhere between 0.1 and2 mm we've got 20 21 22 23 2420 21 22 3 the difference is 4 1,000 of a millimeter now I'm not pretending that this is typical or even repeatable but that's what I got on the day with no special preparation or camera trickery measuring down to single figure microns is is really beyond my capability but I think it shows that on a good day with a following wind a minithe doesn't have to be terrible the alignment of the head stalk and tail stalk bed twist cutting forces and many other factors come into play my unheated Workshop can be below zero in Winter and over 30 in summer so there are built-in limitations before I even switch anything on for a while I got lost down the improve accuracy rabbit hole but it began to spoil my enjoyment a bit so I let sleeping dogs lie so long as I can make parts that I'm happy with then it's accurate enough remember these things that I touched on earlier where it matters they are all the same to within about 20 microns which is much tighter than the job call for but I've answered the challenge so that's more or less what my mini lath is your mileage may vary on the face of it it's really versatile for its footprint but remember it's built to a price to make it really rigid and really accurate would make it larger heavier and much more expensive there are already plenty of lathes out there that take all these boxes if this is important to you and you've the space and Pockets deep enough you're welcome to look at one of those instead when you like tinkering but don't have a bigger overarching hobby of which the lathe is only a small part fiddling with the lathe becomes a perfectly good hobby in itself I've made a number of changes that have improved the machine to my personal taste these range from the trivial to the more involved in no particular order here are some of them I replace the cap head screws on the end cover with nled knobs so I can get inside without tools it's it's worth mentioning that the end of the headstock spindle is directly above the change gears and the swar has a tendency to fall out of the end and directly onto the gears below if the job doesn't need to poke out of the end I generally keep a foam plug in there to help keep the wheels clean early on the little intermediate shaft between these two gears broke it appears to be made from cined floor sweepings or something similar though it's getting a bit worn now the brass replacement that I made has done really well probably the first thing every new owner does is fit a cover to the apron gearbox as without one it soon collects swarf and gets crunchy in there mine is made from an offcut of f fr4 fiberglass sheet as it's what I had lying around at the time once we're looking at the Saddle I made an aluminium cover to keep the worst of the chips from sticking to the lead screw this fairly horrible joint is made with those low temperature aluminium soldering brazing welding call them whatever you like rods on mine there's enough insulated space behind the power supply to accommodate it but take care they may not all be the same the plastic apron hand wheel broke so I made a replacement from an aluminium disc with a steel boss pressed into it I don't really get on with these button Oilers so I've replaced many of them with cup Oilers I have more confidence that a useful amount of oil is delivered with these the tail stock end of the lead screw is easily accessible but with the cover fitted there's no easy way to reach the headstock end to lubricate it so I added a small small Reservoir that directs a little oil down a tube to where it's needed there's a little gutter that catches any oil that drips out and directs it to the chip tray rather than it just running all over the inside of the end cover after spending some time on cardboard AED design I made brackets to mount a scrap digital caliper to the tail stock and a clamp to attach it to the quill with this I can zero as I touch off and keep an eye on the depth this works really well and I would definitely recommend adding one I've added miniature thrust and ball races here here and here where previously there was lots of poorly fitting metal to metal contact I soon got sick of fiddling with spaces so I replaced the standard four-way tool post with a quick change type the first one I got was an all aluminium Affair and although it was easy to swap tools some of the holders were really sloppy so there was little repeatability when dropping the tools onto the post later on I replaced it with a steel 250 tr0 type and it's a thousand times better I've ordered additional holders as I've gone along and each one has been a good fit on the post I've had to slightly modify one or two to get Center Height but that's no big deal just one last thing on tool posts I didn't use the supplied screw to fit them as the constant tightening would eventually wear the threads in the top slide instead I glued a stud in place and if the top of this wears it's an easy swap the lathe used to sit on horrible rubber feet being really close together made it prone to wobbling to and fro when turning the hand wheels it's not really an accuracy thing but it did look odd on camera so I made a pair of Steel Outriggers with adjustable feet that made it much more stable but without taking up any more room on the bench early on I began to lose my temper with the saddle adjustment as supplied a couple of strips sit beneath the saddle and contact the underside of the bed each strip has five holes two are threaded M5 and the other three are M6 clearance the 3 M6 es pull the strip towards the saddle and the 2 m5s work against them applying tension to hold everything in place the idea is that by balancing the torque on all the screws the strip can be made to barely but fully contact the underside of the bed along its full length but it was a disaster it was incredibly fiddly to set up and it would soon work loose and the whole thing would need repeating I replaced the strips with quarin thick brass plates the Nylock nuts were profiled with a form tool to give a kind of rolling pivot action that is adjustable from the top top they work a bit like a toolmaker clamp whereby the Jaws can be set just slightly off and then brought fully into parallel contact with a screw which on the lathe can be locked in position at the rear of the saddle the arrangement is similar with an additional piece of square steel for the adjustment screws I can take no credit for this idea there's a link in the description to Brian's Workshop where the plans can be found onto the compound slide on my leg the compound an angle is locked and unlocked by spinning back the compound slide to reveal a pair of screws the first problem is it's really slow to do and then when you decide actually I think I'll add another few degrees it all has to be wound off and back on again second and even more annoying access to the screws needs the slide to be Unwound almost its full length of travel and there's a tendency for the lead screw to come out of the nut and sometimes for the Gib to fall out and then the whole thing needs reassembling my plan was to add a couple of holes under the tool poost so the screws could be accessed without winding the slide all the way back but there was a problem imagine the compound slide is turned all the way around and we take a slice through here working from the bottom up we've got the saddle the cross slide and the cross slide Gib sat on top of that is the compound base the compound slide and the compound Gib I've not drawn the tool poost but that sits on top of everything a stepped steel disc sits in a big hole in the top of the Cross slide and clamps to the compound slide with two M6 capad screws my plan was to drill down directly above the screws to be able to access them without having to wind the slide all the way back but that would risk breaking the compound Gip there's not a lot to it and removing 3/4 of its thickness would likely leave it weak so I blanked the existing counter board 6 mm holes in the compound base with brass plugs and redrill them with smaller 4mm holes that were further apart drilling from above now would mean that some material would still need to be removed from the compound Gib but it wasn't nearly as severe the steel disc couldn't accommodate two 4 mm holes on 35 mm centers so I made a new larger disc from brass but of course the big hole in the cross slide now wasn't big enough so I made it even larger on the mill I was concerned about removing more material from what already looked like a fairly fragile piece of cast iron but this was 5 years ago and touch wood it's not broken yet the holes are positioned so that when these two surfaces line up the screw heads can be accessed by swinging the tool post to one side and dropping in a 3mm Allen key all told it works really well and now use the compound quite often whereas before I'd avoid it at all costs another shortcoming of the lathe is that there's no way of knowing how far The Carriage is moved it's easy enough to Mark the working machine up to the line but if you need any sort of accuracy there's only really the dial indicator option once this works well all mine only have 10 mm of travel and they're a pretty bulky thing to fit into the space available on a small lathe without getting in the way of the job or the machine itself some people have managed to fit proper glass scale Dr but there's limited real estate available to attach them and then there's the wires to run somewhere and you need to fix a display to something I took a different approach by making a brass clamping box and attaching a cheap digital caliper to it the other end picks up on the holes meant for the thread indicator which I've never used and this gives close to 150 mm of measurable travel if I need to bring in the tail stock or move the carriage it just slides out of the way and when clamped I can zero it and take a measurement it works surprisingly well though it was only a prototype and I wish I'd used a slightly better quality caliper about 2 years in frustration got the better of me and I had to rebuild the tail stock as supplied it was just about useless the base appears to a machine with a bread knife it just doesn't sit on the ways correctly every time the tail stock was moved it would clamp in a slightly different off-axis position when a drill bit is off center it becomes a boring bar which makes for massively oversized holes in hindsight instead of blaming myself for using it wrongly or convincing myself that that's as good as you get for the money I should have sent it back and asked for a replacement instead I persevered with it long Beyond where any warranty might have covered me until I threw in the towel and had to go at remaking it I ordered up a 1in thick slice of 4in square meite and machined it as best I could I soon discovered the inverted V of the bed isn't quite 90° and even with my finest improvised work holding I had great difficulty in cutting a matching angle so I deliberately cut it oversized to fit brass inserts that would be both easier to make and cheaper to scrap if anything went wrong plus although the bed is meant to be hardened I didn't really want to put it to the test and in my mind at least brass to iron would be more forgiving than iron to iron the inserts are retained with a couple of pins and the gaps between the brass and iron are filled with metall loaded epoxy the original base allowed a small amount of angular adjustment by screws bearing against this block it was such a pain to set up again once it had been touched I did away with this feature Al together once it's been set up true the new design is essentially fixed it took an awful lot of trial and error to get the height right but I think I got it pretty close in the end the central fixing screw on each side is hollow to allow a little oil to be running from time to time this was back in 2016 I might do it slightly differently now but that said it's worked near perfectly and is a massive improvement over how it arrived the final modification I'll mention is to the Cross slide with this I increased the length of the hand wheeel boss which allowed me to increase the cross slide travel by 15 mm I added bearings where previously there were none and I replaced a weirdly graduated dial with one that made sense I'll say no more about this one as I did a separate film on the subject that already has a bit more detail when I have the time and inclination there are still a number of things I'd like to have a look at from day one I'd planed to fit an eccentric Bush to improve the engagement of the apron gears it wouldn't take long but my project list always grows faster than I can tick jobs off as well as a variable speed control the lathe has a two-speed gearbox fast and insane from experience I know that I rarely go over about 650 RPM which is about half a turn on the knob it seems like it would make sense to try and adjust the ratio to slow the spindle down and improve torque and low gear whilst retaining the higher speed option if I ever need it another small thing is there's just a tiny bit of rotation in the saddle and being driven from the front encourages it to twist when changing direction on external coats this tends to move the tool off the work when moving from left to right which if anything is an advantage the problem is with internal coats where the same movement tends to dig the tool into the work it's something I've grown used to and I get around it either by winding the cut off a little before returning or sometimes just releasing the tool as relocking the post is pretty repeatable but obviously it would be better if it didn't do it at all the next thing I'll mention is that facing Cuts can be significant dished now I plan to illustrate the severity of this by cleaning up a piece of 3-in aluminium but much like my it turns taper demonstration on the day it actually performed okay I think it knows we're watching and it's on its best behavior anyhow perhaps something's moved or perhaps something's worn in either way if it doesn't get any worse than this I can live with it I've never liked the sloppy fit or engagement of the change Wheels it doesn't stop it working but there's definitely room for improvement many of these machines leave the factory with plain bearings in the headstock I'm not sure what's in mine but I've noticed the surface finish has dropped off a bit taper races might be the best option but there isn't a direct equivalent and with only one lathe once it's in pieces my options for making parts to make different bearings fit are a bit limited I've had angular contact bearings which are a straight swap on standby for a while I just need to get around to fitting them I've not decided whether or not to make a film about that one yet okay I promise I'm nearly done just one last thing the only way to advance The Carriage is with the apron hand wheeel the hand wheel turns a 24 to gear which drives a 54 Toth gear which is attached to an 11 to pinion that meshes with the rack I'm not sure if this is 1.25 module or 20 DP actually that's probably not important the upshot is that one turn on the hand wheel advances The Carriage by a little over 19 mm this works fine and it's much more controllable and sensitive than you might imagine unless I'm trying to make a nice continuous finish pass that is the size and location of the hand wheel make it tricky to drive smoothly from hand to hand even with the handle removed different gearing or adding a motor are both possibilities but I reckon fitting a hand wheel to the end of the lead screw might be the way to go though it would need to be done in such a way that it didn't interfere with a cover that I put over the machine when it's not in use a Yorkshire winter can be pretty dank and miserable and although it's watertight my worksh shop is uninsulated and unheated to protect the lathe from condensation it lives in a heated plywood box that doubles up as a bench the heater is three resistors in series driven from 20 volts ac by an electronic thermostat for safety it also has an over temperature cutout backed up by a non-resettable thermal fuse should anything go wrong in the depths of winter this holds the interior of the Box a few degrees above ambient so any moisture in the air tends to find something else to ruin it works very well and have a variation on the theme on the milling machine and in the cutter cupboard a apologies that was a bit off topic so I guess after all that the burning question is if you've a lathe shaped hole in your life should you fill it with a Chinese minithe the answer is yes and no 10 years ago spending 500 quid on something I couldn't say with any confidence that I really needed was a bit of an extravagance but I don't regret buying it for a second it served me well I've made plenty of stuff and I've learned loads I've no plans to get rid of it you can do a lot more with a mini lathe than you can with no lathe at all that said if it were to fail catastrophically I would probably be looking for something a little larger a little heavier and possibly a little older we'll see what the future brings thanks for watching I hope to see you next time

Channel: The Recreational Machinist

Views: 308,907

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Id: GfJSxWOEP44

Length: 28min 43sec (1723 seconds)

Published: Sun Oct 29 2023