Portass Lathe - Finally at home!

[bieomax]

eeek, the threads expanded just a little since my last visit, sooooo much reading to do 

[Ajohn]

I thought it was worth straying a bit on this thread Richard because lots of people want lathes and it can be a bit of a mine field.

The Raglans are very capable machines. In respect to ME10's the floor standing boxfords with the drive in the cabinet have several advantages but I needed rear drive :-) otherwise I would have lost a cupboard and would have to remove an unused sink. There is storage space under the sink too.

My Boxford came with the 127T gear and many people want them but really for the majority of things it's best to google screw cutting conversion gears as I mentioned earlier. What I did though is use a spread sheet to see what I could do with the gears I had. It turned out that Boxford used one needed for some of the common metric threads as a spacer so I just needed one other. The pitch error is small enough not to matter. I have used these as it's quicker than changing the whole gear chain and looking at a massive table of set ups for precise pitches that will still really not be exact any way for a number of reasons.

I always use imperial threads when I can as the screw cutting indicator can be used on all of the ones I am likely to cut. The machine has to be stopped and run backwards for metric threads to keep the tool in sync with the thread that is being cut. There are other ways but the time between cuts can get enormous. The same is true when cutting metric threads on a metric lathe other than some which have a certain relationship to the pitch of the lead screw.  The boxford metric lathes have 2 gears on the indicator to help with this but it can still be a problem. Colchester did an extremely complicated one that could cope with lots of metric pitches but the time between cuts could still be enormous so when it's a problem people still use the screw cutting indicator after a fashion. ie

Engage screw cutting and cut along the thread.

At the end of the thread note the screw cutting indicator position and disengage screw cutting.

Wind out the tool, stop the lathe and select reverse

When the indicator shows the same position re engage the screw cutting

Allow the tool to run back to the start position and stop the lathe

Set the cut and then take it with the lathe running in the usual direction.

Repeat etc.

This is why some metric lathes don't have screw cutting indicators - other than working up to a shoulder which is pretty easy done as above they don't offer much help. Some pitches can just be engaged and disengaged providing they have a certain relationship to the pitch of the lead screw. More can be done with a screw cutting indicator, some don't benefit from one at all other than for use as a disengage re engage indicator as above. I did think that the ISO people might sort this out but while they have rationalised the range of metric pitches they don't seem to have. There were myriads of them. Imperial managed with 3 basic styles, fine and coarse with tpi suitable for use with screw cutting indicators. Then BA for instance which seems to be metric based (127 tooth gear) and perhaps the equivalent of metric fine.  I suspect that the American fine screw pitches may be more sensible in this respect but maybe not.

John

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[SnakeyJ]

No worries John and Richard on broadening this out - this is one of the best things about SGL, people willing to spend the time sharing their own experience to help educate and inform.    Only hope in some areas I can return some of this experience to point someone else in the right direction!

[Ajohn]

I'v had a mad moment. Making small things such a m2 thrumb screws for microscopes on a Boxford isn't much fun. I've meant to do something about this for  some time. Nosing around I came across a Pultra 1750 complete with all of it's collets that seems to be in fine condition. I'm off shortly for a few days so no time to take a photo. It's neatly mounted on a small cabinet that just fits by the side of the miller but needs wheeling out to use. It's on castors!

There are some details about them here

http://www.lathes.co.uk/pultra/

Everything is scaled down from a full sized lathe on this type including feeds so they are ideal for making smaller parts. Max rpm is around 5,000 which again helps.

 However I suspect I have made all of the microscope bits I need to  . However I'm wondering how I could make some thread chasing gear for certain telescope bits.

John

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[SnakeyJ]

I'v had a mad moment. Making small things such a m2 thrumb screws for microscopes on a Boxford isn't much fun. I've meant to do something about this for  some time. Nosing around I came across a Pultra 1750 complete with all of it's collets that seems to be in fine condition. I'm off shortly for a few days so no time to take a photo. It's neatly mounted on a small cabinet that just fits by the side of the miller but needs wheeling out to use. It's on castors!

There are some details about them here

http://www.lathes.co.uk/pultra/

Everything is scaled down from a full sized lathe on this type including feeds so they are ideal for making smaller parts. Max rpm is around 5,000 which again helps.

 However I suspect I have made all of the microscope bits I need to  . However I'm wondering how I could make some thread chasing gear for certain telescope bits.

John

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Nice acquisition John, they look rather good from the descriptions/images on lathes.co.uk - look forward to seeing the pictures

I've also had a moment of madness and am off up country to pick up another Portass lathe (Dreadnought) - I don't intend to keep two (as the misses might skin me!), but will keep the best bits and sell on the rest.     I really like the cast iron stand with sump, might be useful with a decent flywheel!

    

[SnakeyJ]

Another option. There's a Portass Dreadnought for sale on Ebay at the moment: http://www.ebay.co.uk/itm/Portass-Dreadnought-Metal-Turning-Lathe-on-stand-with-extras-/121634829808?pt=LH_DefaultDomain_3&hash=item1c520035f0

It has several backplates and accessories with it. Why not buy that, select the accessories you want from both lathes then sell the rest on. I have picked up changewheels and chucks for my lathe that way and still passed on a well equipped lathe.

Richard

Thanks Richard - I did get this in the end after another buyer withdrew!

[RLWP]

Thanks Richard - I did get this in the end after another buyer withdrew!

Exciting! That cast iron base looks like a good buy in itself.

Now you have two Portassises, you could breed them

Richard

[martin_h]

All this talk takes me back to my engineering days, like many I was a tool room apprentice for Crawford Collets, so I used to make tooling etc to make the collets that a lot of you may now use!

[bieomax]

You'll have to let us know what your putting up off of the second one.

[Ajohn]

If I had 2 Portass lathes I would rig both up some how and adjust and try them to see which one was best. Grade 400 wet and dry plus paraffin will make short work of the rust on the bed. Maybe a grade coarser for some things. Cast iron is so hard the chances of removing a significant amount are slight. Chucks can be hard to clean up fully.

John

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[SnakeyJ]

All assembled and working beautifully - just need to get some wire wool to start cleaning this up, but mechanically this looks to be in good and tight condition.   There were lots of included bits 'n bobs and a huge collection of tool steel in various shapes/states.

The three morse taper drills, milling bit? and centre were unexpected extras.

Excuse the mess behind, but cleaning this up in my cabling unit to keep things sweet at home.

I'll post some more pictures up once it's all cleaned.

[SnakeyJ]

Best laid plans and a destinct lack of foresight/imagination on my part!  The dreadnaught has a bigger spindle and so the back plates and faceplate are too big for my PD5    

This leaves a slight dilemma - The Dreadnaught is potentially the better of the two, (bigger, longer bed, heavier and better equipped), though it's footprint is much the same with the stand I made for the PD5.    It is currently missing the back gear spindle and wheels, which I think were sacrificed to fit the V belt counter shafts.       Assuming they are the same pitch as the change wheels, I have the 25T and 65T gears for this and can machine up a new shaft and come up with a better way of mounting the counter shaft.      

I think I should take John's advice and try out both machines for accuracy.    The PD5 is clean and neat and should be easy to sell on if the Dreadnaught performs better!

I'm going to test out the washing soda and reverse electrolysis method of rust removal for some of the tooling and change wheels and will give the bed a gentle rub down with the parafin and wet 'n dry or wire wool.

[Ajohn]

I'd be interested in exactly what the washing soda rust removal process is and how well it works. Others may be too. 

In the past I have had chucks that have a sort of brown patina rather than rust. It's almost shiny. I think it's caused by soluble oil coolants. I leave that alone also just plain discolouration. I've used paraffin and a kitchen type scotch scouring pad to just get the crud off the later.

Paraffin helps because most lathes have been well oiled at some point in their life. Theory has it that some soaks into cast iron so some rust can be simply lifted off with wet and dry. I suspect it's more a case of it acting as a lubricant and preventing the  wet and dry from clogging up.

Some of the gearing that forms the back gear is often part of the pulley. I believe that lathes.co.uk can supply flat belt if some one wants to keep that. There may be other sources. An inverter can be used to slow lathes down but there is  risk of burning the motor out if this is done with higher loads for long periods.

Most lathes come with the slides set loose. In order to produce the best work that they can this isn't ideal. The best way to set them on the cross and compound slide is to remove the lead screw and then adjust until there is slight resistance when pushing the slides by hand. It's also possible to do this by detecting a slight increase in resistance at the handles with the lead screws in. Most older lathes will show signs of wear usually going too tight as the cross slide is wound further out. Sometimes it's possible to fix this by adjusting the gib strips in stages where they pass over the dovetail they are running over - hard to explain but the dovetail might be 3in long and the slide a lot longer than that so the gib strips can be set with the tool wound right in, half out and fully out. If a lathe looked promising tested and adjusted via the handles like that I would strip it down, clean it up and use some slide way oil when putting it back together.

Headstock bearings are a pain. Some spindles just run in cast iron, split on one side with a pinch bolt. The castings sometimes crack when these are adjusted. Other have phos bronze bearings. Some of those are tapered with a nut on one side which pulls them into the taper to close them up and  another one on the other end to lock the setting up - it's important to slacken that one off before adjusting the other. It's possible to make new bearings as well. The outside diameters need to be correct, taper too if there is one. The inside bore is made a few thou undersized and then fitted to the spindle by hand. A scraper or maybe an adjustable reamer. Some lathes use taper roller bearings etc. Unless they are really bad and even then it's best to just adjust them as lathe precision bearings are very expensive. I've found heat the best way of adjusting these - they should warm up a fair amount after the lathe has been running for say 20min at medium speed. The bearings themselves might be running at around 100C so the castings around them will warm up noticeably.

If thing have to be loose on a lathe, wear etc the best answer when a good finish is wanted is heavier cuts and a very even feed. How heavy is TBD but people shouldn't be afraid of trying say 1 to 2 mm or even more. Much depends on the feed rate but basically the net effect needs to load the loose parts of the lathe sufficiently to force them home and keep them there. Another approach is to just keep running the same cut until no more metal is removed. This works well on some. If all else fails it's files and emery cloth etc but the lathe needs running at a low speed when a file is used. In my experience Chinese lathes are different largely down to the cast iron they use. It can also be very difficult to correct any built in errors. 

John

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[SnakeyJ]

Cheers John, much useful information in there and it will take a couple of reads to fully sink in. The headstock bearings on the portass lathes are two part phosphor bronze, which I'm told are factory shimmed - presumably between the headstock casting and bearing, to run true and parallel with the bed. I've been previously advised to leave well alone, as I don't have the tools and experience to refit these with any accuracy - doubtless good advice, but perhaps one day I can recruit a local engineer to assist. However, there's no appreciable play in the headstock spindle and I shall do some test cuts to look at the extent of the taper it produces. I don't have any long projects in mind, other than a back gear spindle.

[SnakeyJ]

I'd be interested in exactly what the washing soda rust removal process is and how well it works. Others may be too. 

John

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I stumbled across this recently, but have yet to try this myself - http://myweb.tiscali.co.uk/andyspatch/rust.htm and at http://www.instructables.com/id/Electrolytic-Rust-Removal-aka-Magic/

This one is also quite interesting - http://www.frets.com/HomeShopTech/QuickTricks/RustRemoval/rustremoval.html

I will get some washing soda tomorrow and have a little experiment to see how this looks myself, but potentially a lot less messy than the wire brush or emery cloth.    I'll post the results up in a new thread in the DIY section.

[RLWP]

The easiest method of rust removal I have found is a strong solution of citric acid with a dash of washing up liquid. As it is lemon juice, I'm happy to dilute it and put it down the drain afterwards. Hot water, acid, washing up liquid into a bucket, followed by rusty items. Leave for a day

Citric acid is cheap off t'internet

Richard

[Ajohn]

There is or maybe was now a man in B'ham who rubbed something on rust on lathes and over a period of time it just flaked off leaving nice shiny metal. He wouldn't tell anyone what he used. He seemed to rub a bit of what ever it was on now and again. Rust remover works well but the metal discolours rapidly afterwards. Some one on the telly derusted a square by cutting a potato in half and rubbing it on the rust. Slow but it does work,

Lathes with shimmed bearing caps often have no shims left to remove. Myford ML7's  use this sort of set up originally with white metal bearings but they later supplied phosphor bronze - the 1st batch had way to much excess metal that needed scraping out and don't I know it. They refused to supply the more sensible ones they later supplied unless I just paid for another set. No way at £80 odd a set.

The way these types are initially made is pretty simple. The bearing housings are only truly round when a certain size of shim is fitted under the caps. They make the bearing shells so  accurately that they will come out correctly when fitted or maybe a few may need a tiny bit of hand scraping. When the bearing has worn the general idea is that a little bit of the shim thickness is removed to close the bearings up and they are then scraped to fit the spindle correctly. A razor sharp 3 square (triangular) scraper is used to do the scraping. The fit is judged with engineers blue - an incredibly thin layer, so thin it's not that easy to judge the high spots that need scraping down. It can be done in 2 halves. Lower shells first checking for fit and that the spindle is level and aligned with the bed using a DTI. Then the top shells just for fit.

They have been using laminated shims for this sort of thing for some time. The idea is that changes can be made by peeling small thicknesses off. To honest I have found it easier to buy shim material and select thickness to suite.

After I did my ML7 my father told me that some people used to make things that allowed them to bore new bearings from the lathe bed. the tool being turned by hand. Ok as very little material has to be removed. He did this sort of thing early in his career - I found his scraper after he died. It's size was around 1/3 of what it originally was due to sharpening. He must have done a lot of it. The sides of the scraper should ideally be hollow ground. Some people have ground them from a 3 square file being careful not to over heat it and wreck the temper. They should be hardened and tempered to a very pale straw.

John

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[SnakeyJ]

I've got the cast iron faceplate dipped for my first experiment in reverse electrolysis.    The anode is gently bubbling hydrogen and the rust on the submerged surface is blackening.    Only running for an hour so far, but will have another look mid afternoon and have a cleanup and inspection before swapping this around.

[bieomax]

Are you going to repaint any of it? If so what are you going to use?

[Ajohn]

Here is the Pultra, complete with it's built in work lamp - just to show what mad moments are all about.

 The smallest collet seem to be for work that is 0.4mm dia. The centre height is 50mm but it also came with rising blocks that will lift that to 90mm. As I was allowed to use a lathe at work if I wanted my first lathe at home was a Peatol better known as a Taig in the US. That has a centre height of around 56mm and it is surprising what can be made even with a lathe that small. The biggest problem is the need for a lot of stub drills as the centre distances are rather low. It's also easy to cover one with swarf to a point where it's hard to see what's going on underneath it all. The Peatol was extremely accurate all round when I bought it but over time the heads bend and they start turning a taper rather than trully round work. I'm hoping this one wont have that problem but now have the joys of carefully adjusting everything and hoping that I don't come across some bad fixes applied by previous owners. It dates from around 1955 and was owned by an instrument maker. No problem there but I worry a little about what his son may have done while "restoring" it.

This lathe uses phos bronze bearings, probably on a hardened spindle in this case. Might be worth mentioning that most people reckon that SAE 32 hydraulic fluid is the correct lubricant to use with both bronze and cast iron bearings.  The Pultra has small oil reservoirs. On many lathes a small drop should be added to the bearings each time the lathe is used. 

The bench drill behind it came with it. 3 speed going from 4 to 8 thousand rpm.  I bit fast for anything over 1mm dia and even that might be too fast. It seems it can be used as a sort of surface grinder when fitted with a suitable grinding point.  Have to see. That could be useful.

PS The sweet tin has all of my Boxford gears in it. The tidy up is still on going.  My PC speakers are a bit bigger than usual too.

John

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[SnakeyJ]

Are you going to repaint any of it? If so what are you going to use?

Mark,

I will paint it up again provided it cuts nicely.   Once of the smooth Hamerites would probably do well enought, though I will probably use a two part engine paint, probably applied by brush  - not sure what colours, something classic would be nice, but likely whatever is on offer at the time     I think the best approach is to key the surface in with some emery cloth and then give it a good clean up with a degreasing agent before painting.     Where its easy to strip bits, I might give them a quick blast back with a sand blaster.

[SnakeyJ]

Here is the Pultra, complete with it's built in work lamp - just to show what mad moments are all about.

John

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That looks amazing John, it looks beautifully made and a wonderful collection of collets and tiny tooling.   You should retire to Switzerland and be turning out Rolex watches with that little beauty

[RLWP]

That is a beautiful lathe, John

Craftmaster do a Myford grey paint which is very reliable. Hammerite smooth paints are very variable

Richard

[SnakeyJ]

That is a beautiful lathe, John

Craftmaster do a Myford grey paint which is very reliable. Hammerite smooth paints are very variable

Richard

Thanks for that Richard - not cheap, but half the price of the Myford genuine paint - http://www.ebay.co.uk/itm/MYFORD-GREY-TOUCH-UP-PAINT-DIRECT-FROM-MYFORD-LTD-GREY-/191176062123?_trksid=p2141725.m3641.l6368

The grey would be a more original colour for my Portass, but I was quite fond of the green and red on my PD5.

[Ajohn]

I understands some people have used paint that will pop up if ebay is searched for military paint. Machinery paint will bring up more as well but it tends to be more expensive.

Ideally under that there needs to be a good coat of a suitable high build primer. The layer of that on some lathes which I assume were just cast in ordinary sand is often pretty thick.

Personally I would just clean up what's there. A few chips add to the charm. Repaint if lots are missing - many home repaint jobs viewed from close up don't look very good. It takes a lot of work to get things smooth enough for a glossy finish.

 I just found the thread on the end my Pultra's spindle. Hidden under a screw on cover that in turn is covered by a pull off one. I can now look at fitting it with Taig chucks. That will allow me to get 1/2" bar through the spindle. A fair bit more than the Taig will accept. It's about the same as the Taig when the collet draw bar is used.

John

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