Portass gear setup

[Chris HollingsworthParticipant @chrishollingsworth76581]

I’ve got all gears except a couple just wondering does anyone have the gear setup for the portass model s

[Chris HollingsworthParticipant @chrishollingsworth76581]

How to setup portass gears

[BazyleParticipant @bazyle]

Perhaps a slightly longer post explaining your problem would help. The pictures on Lathes.co.uk are pretty clear about the setup.

[Clive FosterParticipant @clivefoster55965]

As far as I'm aware there were never any specific threading gear set up tables produced for the smaller Portass lathes. I think I found a sufficiently close listing in either Newnes Engineers manual or the Caxton equivalent back when I had my S type. Dreadnaught versions usually had a brass plate on the stand. No idea if this was also appropriate to the smaller ones. I have feeling that the Zyto list may also work.

If its a model S its likely that not all the valid permutations can be accommodated on the banjo. Fairly sure that some set-ups need the banjo swung in front of the headstock rather than the usual position behind. Mine came with a single slot banjo which was very limiting. Two slots are more normal, some variation in patterns and size which may or may not make a difference in the real world.

Clive.

[Chris HollingsworthParticipant @chrishollingsworth76581]

I have just ordered the book the amature lathe to try and help I’ve had a look at the lathe website as well as emailed Tony but not had a reply. I can olny find 1 up picture of the gears. You are right it has a single banjo that is moved behind or in front depending on how you want to took to travel

[Brian WoodParticipant @brianwood45127]

Hello Chris,

I might be able to help you.

If you can give me some basic information, such as leadscrew pitch, a list of the gears you do have and whether or not you are able to arrange them in compound on the banjo I should be able to work out some set ups for you for the standard imperial thread pitches at least.

Send me a PM

Regards

Brian

[Clive FosterParticipant @clivefoster55965]

Chris

I'd take Brian up on his offer. There is a threading gear table in "The Amateurs Lathe" but it includes spindle gear changes. I think your spindle gear is effectively fixed as none of the others will fit. On reflection I think mine may have been the earlier XL. It would do all reasonable Whitworth threads but not much else.

Factory pictures of the S on Tonys site show the gears set up for lowest feed rate. its how mine normally lived.

Clive.

[Chris HollingsworthParticipant @chrishollingsworth76581]

I’ve emailed Brian hopefully he can help

[MuzzerParticipant @muzzer]

I think a lot of it will come down to what gears you actually possess. My Portass S has only a part set (like most machines this age, I expect), so when you come to cutting threads, it's going to be a question of either you have the correct gears or you don't. True enough, you'll need some gear tables if you don't know how to do the sums but many of the gears have no likely use, given their tooth count.

I managed some threading on mine. IIRC, the leadscrew is something like 8TPI and I think I managed to thread 24TPI (??) for a Jacob's chuck but that was a triumph against adversity rather than an easy event. I also managed to thread a faceplate at one point. You may be better off just buying some taps and dies….

Best thing is perhaps to select the biggest and smallest gears in your set so you can get the lowest feed rate – then you can get an approximation of "power" feed on the leadscrew.

Murray

[Chris HollingsworthParticipant @chrishollingsworth76581]

Thanks murray Brian is trying to help me out with the gears at the mo. What do you mean biggest and smallest does all the small ones go faster than all big gears

[MuzzerParticipant @muzzer]

Use the smallest gear to drive the largest, pair that largest gear alongside the next smallest and use that to drive the next largest gear on the end of the leadscrew. That will then give you the finest feed you can achieve. Probably won't be very fine but the best you can do.

I take it you have the various collars, keys etc for mounting the gears on the spindle, banjo, leadscrew etc?

Some photos of mine in my album. This would be back in the late 1970s when I bought it as a youngster (£14) and had just done it up.

Murray

[Howard LewisParticipant @howardlewis46836]

If you know what pitches you will want to cut, and knowing the leadscrew pitch, you can calculate which gears you will need. (Since the Portass is likely to be an Imperial pitch, if you want to cut Metric, you will need, ideally a 127T, but a 63T would probably produce an acceptable degree of error.

Cue for someone to give other possible combinations that would suffice.

Probably a stupid question.

Since it is unlikely that any missing gears will be easily obtainable, but could you, or some kind friend not make make the missing ones?

(Currently, am SLOWLY working on producing some 100T Mod 1 gears for a mini lathe. Inspired by Stub Mandrel's file to 3D print some)

The drawback is likely to be the cost of gear cutters, (if not already available) or that the lathe uses gears with some strange DP (Presumably OLD, so predating use of metric Module gears)

The other problem may be cutting the keyway for intermediate "compound" set ups, but lacking slotting facilities, some judicious drilling and filling out of the corners may solve that.

Howard

[MuzzerParticipant @muzzer]

They are straightforward DP gears – I forget the pitch but the issue is that they have a (presumably) unique bore and keyway, so a PITA to make a set. Certainly not Myford or Drummond – and why would they be back then (pre-1920). From what I recall, 63T was not present and a 127T wouldn't even fit in the space available. These were in the Sooper Adept mould, so I doubt anyone would even have thought to cut metric on them in those days.

I once found some mating gears in a scrap yard but machining them down to the right width on the little machine would have lost me the will to live. The obvious solution is to get another lathe – and keep this one obviously!

Murray

[Clive FosterParticipant @clivefoster55965]

14 squidlits. For a Portass S!

The man saw you coming Murray.

Mine was a couple of pints and a pack (or two) of Players back around 1974. Maybe another pack of Players, or some other brand tho', for a drop front writing cabinet full of useful, semi-useful, bleugh and WTH stuff. 63 tooth gear, but only one 20, too which I specifically recall as it bugged me for a couple of decades as not being able to find out what it was for. Broken bearing to cap at the chuck end too. So I learned to weld. My re-decoration was in black and red. Dad said "looks like a ….. traction engine." Traded up to a Pools Special, via bed'n breakfasting a  pair of round bed Drummonds (objectively nearly as Yuk in machine tool terms) with no regrets. First step on the long workshop equipment journey.

Re-sizing and re-keywaying gears isn't too tricky. If the hole is undersize drill a hole just smaller than the keyway in the right place before opening up the bore. Few strokes with a baby file to square it out and job done. Fit doesn't have to be amazingly good. Or give up on the key altogether and drill holes for drive pins. need a simple jig, basically two holes, to get everything in the right place. Rollers from a defunct needle roller bearing do fin as pins. nails cut short work fine too but have to be the good old type. Modern ones tend to be less than round and easily bent.

If the hole is too big make an insert with the right bore and keyway. Loctite and dutch key to hold it in. A dutch key is a grub screw or similar fitted a tapped hole set central on the join between the two parts. Probably not needful if the loctite is properly applied but a mechanical connection always feels more positive.

Agree that thinning down gears on such a small lathe is um "tedious".

Clive.

Edited By Clive Foster on 07/09/2017 13:27:50

Edited By Clive Foster on 07/09/2017 13:28:56

[BazyleParticipant @bazyle]

This is a good opportunity to try making gears as changewheels do not need to be very precise nor strong. So you can use aluminium and plastic or Tufnol. Obviously plastic is a rather wide spectrum so not something brittle like Perspex nor squidgy like HDPE. The tooth form does not need to be precise either, just the right kind of size so read up about 'DP' measure your existing gears (it will be an even number between 12 and 20) and then search for how to make a simple gear cutter.

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