Portass Lathe - Finally at home!

[jetstream]

Jake-great lathe & an excellent project,I'm envious!

[SnakeyJ]

Thanks Gerry,

Really enjoying this project and hope to be producing some useful output in the not too distant - It's been 30 years since I last used a lathe at school, so much to learn and lots of good metal to be turned to chips in the process!

Still given three weeks of either full moon or cloud, it is at least a diversion that can be enjoyed in any weather    Hope you are fairing better over in Canada with the new VX10 getting good use this new moon.

Jake

[SnakeyJ]

Turned up my first bits of brass this evening, making some adaptors for the oil cups - bit of a custom fit for each oiling point!    Ground my first HSS tools for brass and steel, which seem to work quite nicely and give a nice finish.

I also turned some longer 12mm steel bar, though think this shows some run out over 5" - so things may not be quite true.   However, I shall build and steel face a new bench top and shim/remount the lathe properly before trying to trace this down.

There is some slip in the motor belt which definitely needs to be replaced pronto.    Also a fair bit of backlash evident when changing direction on the top slide, but don't think there's any adjustment I can do here.    I also need another 1/32" shim to raise the tool height to centre for facing.

Overall very pleased, not at all noisy and was cutting quite nicely on both steel and brass at top speed.

[SnakeyJ]

As I was lacking the materials for my obsy door, I started preping for the improved lathe stand.

The original table was inadequately supported and banana shaped in the middle.    I removed the lathe and table last night, which was quite a job with the old war wound playing up!    The base should be quite adequate and has two angle iron supports welded in to the top to take the cross pieces supporting the table.     I have cut 8 cross pieces (from decent seasoned timber) to replace the original two and will cover this with a double layer of 18mm OSB, then skin with steel sheet (side door from an old network rack).    I have a couple of 1" wide steel plate strips that will be screwed down on top to provide the bolt down points for the lathe, or alternatively some heavy square washers.    I'll also put some earth bonding in between the four mounting bolts and the cabinet as I feel it should all be grounded properly.

It would be nice to have a self draining top, though this is way too much work at the moment - so I will probably make up a long aluminium tray to slide in between the two mounting positions.   This should catch the worst of the lube and swarf and help keep things tidy.

I've started cutting the steel and OSB this evening, but had to stop due to noise - hopefully I can get the bench top completed tomorrow, but here's a quick picture of stage 1:

Who knows might even knock the dent out of the door!   Thinking I will mount the switching on the stand top left and perhaps add a kill switch to the right - which should allow me to shut off with either arm in a panic.

[SnakeyJ]

I've cut and glued the two layers of 18mm OSB for the work top quite easilly, but really struggled cutting the steel facing for the worktop out of an old network cabinet door.   My tin snips cut well enough, but getting sufficient clearence to use them makes the work slow and painfull.

I managed to cut about 2/3 of this last night over a couple of hours, but had to give up when the blisters burst.     A jigsaw or grinder would make short work, but not allowed to make too much noise in the evenings.    I'll percivere tonight and wear gloves to try and prevent more blisters or cuts from the edges.

I've cut out to allow a 30mm fold over the edges, so that I can screw along the edge to avoid fastenings in the top surface - however, I think getting a neat fold along the edges (1120 x 600mm) is going to be quite difficult without access to a big sheet bender.    Perhaps I can do something with sash cramps and timber, or a block of wood and the trusty 4lb precision adjusting tool?    Open to advice if anyone has suitable experience.

[SnakeyJ]

Hmmm, perhaps I can improvise a bending brake with some angle iron and G clamps...     The sheet is 1.2mm, so shouldn't be too difficult to do.

[SnakeyJ]

Using whats to hand I have 6' of unistrut and two G Clamps - Oh and some gloves for my soft southern hands

I'll post the results later.

[SnakeyJ]

Not got as far as intended, but did finally win the argument and get the sheet cut to size - an absolute pig of a job, but got there in the end.

I'll leave the bending until tomorrow night when my usual zen like calm has returned

[SnakeyJ]

Bench top completed, took rather longer than planned but pleased with the end result.

I've positioned and drilled the holes for mounting the lathe, but now find my bolts aren't long enough!   Another quick trip to my local fastening suppliers tomorrow morning to get these and some bolts for the mount

I'm considering options with the bench grinder at the moment - would quite like to mount this and a metal vice on the bench, but don't want to clutter the surface too much.,.

[Bizibilder]

Nice bench, Jake.  But keep that grinder away from the lathe - grinding dust is the worst thing there is for slideways and machine tools!

[bambuko]

Vice would be fine on the bench if you really want it there? but grinder I would keep well away from a lathe bed - you don't want it ruined by the grinding grit?

[SnakeyJ]

Sage advice Roger & Bambuko - Thanks

[bambuko]

And another thing... think carefully before "bolting" your lathe down to the bench - the only result of which will be bent/twisted bed.

You will find interweb full of theories about keeping the bed level (ie straight, since it doesn't have to be level to be straight).

My lathe (of similar size) just stands on the bench without being secured to it - never had any problems   with this arrangement.

[SnakeyJ]

Thanks Bambuko - I have finally finished the bench and got it back in to the correct position with an OSB offcut providing splash back protection to the newly repaired wall behind.   I've taken advice on board re not mounting the grinder.   I have dropped some bolts through the bench to stop the lathe walking around, but these are just finger tightened so as not to cause any distortion to the lathe bed.    I will knock up a test bar to have a look at the alignment/run out over the length of the bed properly to make sure I'm not turning long tapers on any extended work

I've had to raise the feet on boards as the floor surface is very bumpy!     I will mount a small metal work vice on the rh end of the bench facing the right hand wall, but will make another stand for my bench drill and grinder!

Now ready to start learning on some small projects and have a good play with the screw cutting.    As I haven't got a face plate I may by one of the the blank castings and see if I can machine this up, but need to practice the screw cutting first and probably source a few change wheels.

[Gina]

Looking very good   I want one

[SnakeyJ]

Looking very good   I want one

Be warned, it's another money hole hobby - the lathes are quite cheap, but it's all the extra tooling that sends the overdraft soaring

Lots of fun though and will be nice to machine up some one off parts for the projects as my skills improve (hopefully)!

[SnakeyJ]

Having failed to find any Portass change gears, I decided to give the Myford ones a try and brought a single 63T one from RDG.    Sadly, although the shaft and key dimensions are correct the Myford gears have a finer pitch on their gear wheels

I guess this does leave the option of purchasing an entire set of Myford gears, though I would also have to change the tumbler reverse gears to match.     Alternatively I will have to look around harder for some more of the Portass ones!

[Bizibilder]

No need to go to that expense!  Just buy the gears you need for the threads you are going to cut.  If you make an adapter you can mount a gear on the headstock and pick off from there.  If your leadscrew is 8tpi (I'm guessing) then 20 tooth on the headstock and 80 on the leadscrew will give you 8/4 32 tpi a forty tooth for the leadscrew adds 8/2 16tpi etc (You can use any "spare" gears as the idlers between the ones you are using.  If you buy a 60 tooth (lots of useful factors) gear you can make a dividing head and machine all your own gears!!  

[SnakeyJ]

No need to go to that expense!  Just buy the gears you need for the threads you are going to cut.  If you make an adapter you can mount a gear on the headstock and pick off from there.  If your leadscrew is 8tpi (I'm guessing) then 20 tooth on the headstock and 80 on the leadscrew will give you 8/4 32 tpi a forty tooth for the leadscrew adds 8/2 16tpi etc (You can use any "spare" gears as the idlers between the ones you are using.  If you buy a 60 tooth (lots of useful factors) gear you can make a dividing head and machine all your own gears!!  

Roger - excellent thought on this, my brain had completely overlooked this!   I could get a couple of longer keyed studs to cluster the original Portass gears to the newer Myfords and this will save replacing the headstock and tumbler gears - brilliant and many thanks!

I shall look up the dividing head and machining my own gears, though may have to do lots of practice to machine to this level of precision.

[Bizibilder]

If you make a dividing plate and use that on a worm and 60 tooth gear any errors in your dividing are reduced by 1/60.  Make a second generation plate and it will be spot on!!

[bieomax]

Sorry to dredge up an oldish thread, but how are you doing with your lathe? And thread cutting? As ive just picked up a portass dreadnought and trying to find out more about it / using it. This thread has so far been invaluable

Mark.

[Gina]

Proper job

[Ajohn]

There are some cheap gear hob cutters on ebay at the moment. I went for one from the Ukraine or somewhere similar rather than the Chinese ones, 1 MOD as it's close to 8 tpi for worm wheels. There are others, some from the UK in various sizes. I believe people have used plastic gears for screw cutting as well.  Another option might be modifying gears that are for the many smaller chinese lathes really but do take care to make the central hole central. Too much run out will lead to grief.

Interesting thread. People always get wrapped up with 127  teeth gears on imperial lathes when really there is no need to especially on finer threads. This  for instance is settings for an imperial boxford with gearbox.

What people don't realise is that screw cutting isn't that accurate anyway and several 0.001mm pitch errors don't matter over shorter distances, that's why nuts tend to be about as deep as the diameter of the thread. Odd thing about these boxford gear settings is that one of the gears needed is generally already on the machine unless some one has removed it. Googling screw cutting conversion gears will also come up with some ratio's that don't involve a 127 tooth gear, even one that Myford have used.

Personally if it's something for myself I always cut imperial as all of the usual pitches can be cut without having to reverse the lathe - few can in the metric series. If the rest of something needs to be metric so be it. I just work in imperial.

I've had several lathes and noted the not as good as Myford comment earlier on. In many cases down to the design their machines do not wear very well at all. Even the headstock bearings on Super 7's need really close adjustment to maintain the performance they can have. Bed wear on them is a disaster. ML7's are worse due to the headstock bearings - they really do need looking after and replacing at some point. A lot depends on how accurate parts need to be but unfortunately I was initially trained as a toolmaker like many others that started off at the  same company and I  expect what I used then.  Boxfords wear in a lot more sensible fashion. It sometimes  surprises me how cheap they can be even with chucks and bits and pieces. Floor standing apart from the ME10 but one of those really may have only been used lightly by a model engineer. Some lathes will have been used 8 hrs a day 5 1/2 days a week what ever make is bought so what happens when they wear is pretty important. Often Boxfords just need the headstock bearings and slides adjusted and the head tightened down - some people remove them to aid moving them around due to weight - all it takes to tighten them down properly is a bent spanner.

I finally found a milling machine I am happy with too. A Dore Westbury. 2 morse but not a problem as I use ordinary 2 morse collets to hold larger cutters and the spindle is stiff enough as is the rest of the machine compared with smaller Chinese machines. These will have been made by model engineers often to very high standards.

Rust - I've spent some time hanging around a used machine tool suppliers. They use paraffin and 400 grade wet and dry. Sounds drastic but cast iron is hard stuff. A kitchen scotch cloth type scouring pad will often get the worst off as well.

 I upset some people as I am rather opinionated or come across like that - tough but I have bought several lathes and a couple of milling machines in the past. Opinionated - no not really but I do spout what I think.

John

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[bieomax]

Thanks for the info John, its all handy

[Ajohn]

Being fair to Myford the ML and Speed 10 should be a decent smaller lathe. These use a dovetail bed which has it's own problems but is better than beds formed by 2 oblong bars etc providing it's not worn too much. Easily checked by tightening them up by the head stock and seeing if it can still be moved all along the bed. These Myford's use taper roller bearings so easy to change or adjust. The other type of Myford beds have to be shimmed up but shims can not be used to  take up any wear as the bed will just be too tight some where or the other.

Explaining a bit more as this applies to any lathe the Boxford and others use prismatic beds.  The saddle*  on this type run along to upward pointing triangles, sometimes just one at the front. The mating part in the saddle is usually much longer than other types so the area to resist wear is much greater and the shape itself resists movement under cutting loads. The ends often go past the head and the tailstock at the extremes of travel making them even longer on some models. Some run the tailstock along it's own prism - unlikely to ever wear out and will remain as accurate as it was made within reason.

The length to width ratio of the guides is important as well. Say a piece of 25mm bar is waggled about passing though a 0.1 mm oversized hole that is 25mm deep. It will waggle by so many degrees. If it passed through  hole that was 250mm deep it would waggle by around 1/10 of the amount.  The basic idea on lathes is usually referred to as the narrow guides principle. The Myford 7's try to use this by running on the front rail but another factor comes into it as well - cutting forces have to push the saddle hard up against it for it to work and they haven't designed that in very well. Really the bed needs to wider. There is also a lot of mass to move if there is any clearance - the prismatic beds are always in direct contact. Dovetail beds take a lot of the force on the top of them which helps but some is also taken on the rear slopped edge so can have the same problem as the usual Myford bed.

Headstock bearings are a pain. They can be a reason for a lathe only giving a decent finish when heavier cuts are taken and also usually explain why the same cut setting keeps removing metal. I notice that the Portass on here uses split phos bronze bearings - not a bad idea at all as a new set could be made on the lathe if needed and then scraped in. The worst ones just run in cast iron split on one side and tightened with a bolt on the side with the split. When fully tightened the castings often split. Lathe bearings always tend to wear oval due to tension from the belts and cutting forces so this sort of adjustment only helps rather than cures unless there is very little wear.

*The part that moves back and forth on the bed carrying the cross slide and compound slide.

John

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