Setting up Portass PD5 lathe

[Rowan Sylvester-BradleyParticipant @rowansylvester-bradley37244]

I’m trying to set up a Portass PD5 lathe for some turning jobs. The probelm I have is that the tool height seems to be much higher than the axis of the lathe, which means that I could never face off or part off a workpiece. Here are some photos:

Rear View                                                                    Front View

The problem that I’ve got is that if from the bed of the lathe I add the thickness of the saddle, and then the cross slide. and then the compound slide, and then the tool holder (a new cuneiform quick release toolholder I bought form China) even it its lowest position, as you can see in the picture, the tool height is well above the centre line of the lathe. What am I doing wrong? Even with the old original tool holder, it’s difficult to get the tool low enough even without any shims at all under it.

Thank you – Rowan

[Peter Cook 6Participant @petercook6]

All the pictures of Portas PD5 (and other Portas lathes) on Lathes.co.uk show the tools clamped directly on to the topslide with suitable shims. I can’t see you having the headroom to use a QTP on top of the topslide.

If you want to use the QTP (and don’t need to turn tapers), one option may be to remove the topslide and attach the QTP to one of the T slots in the cross slide assuming there is sufficient control of he cross slide traverse towards and away from the headstock.

[Howard LewisParticipant @howardlewis46836]

Your problem is probably that the QCTP is too big for the lathe. It would originally have only had a simple clamp for the cutting tool.  QCTPs had probably not been invented when the Portass was first made.

Have a look at the “Lathes UK” website, to see pictures and to learn more about your machine.

Simce most tool holders are hard, it might not be possible to mill the bottom of the holder to lower the tool.

You may be better with the original tool clamp, or a four way toolpost that gives a lower tool height

Using smaller shank, or section, tools might help, but at the expense of rigidity (A 1/4″ toolbit is 2.37 times stiffer than a 3/16″, so use the largest section toolbits that you can)

If you lack a four way post, it would be possible to make one, by laminating pieces of flat steel

Two larger squares for the top and bottom and a smaller piece for the middle section. The bottom, ideally, will position the tool so that the cutting edge is at centre height (or needs the minimum of shimming for this)

The middle piece will need to be slightly thicker that the largest tool that will sit at centre height.

The top section needs to be thick enough to withstdtand the loads imposed when the tool clampiong screws are tightened, so needs to be as thick as possible

The three pieces can be held together by three countersunk screws, (They can be inserted from the bottom, to be invisible.) whilst the fourth position can be used for a dowel (With four holes in the cross slide to ensure the toolpost is square to the axis of the lathe.

In that way, as the toolpost is rotated around the central pillar and clamp, the dowel will ensure that it is square to the lathe axis.

To keep things as prototype as possible, BSF screws (Or BA if you can get them) should be used. Try not to mix Metric on an old Imperial machine!

HTH

Howard

[Clive FosterParticipant @clivefoster55965]

Rowan

The PD5 is a final update of the Portass S design and shares many of its fundamental dimensions. My first lathe was a Portass S so I can confirm Peters comment that it was built to use (small) tooling clamped directly to the topside. Very dim memory (it wa almost 60 years ago) suggests that even 3/8″ square tooling needed a bit taken off the top to get down to centre height. Absolutely no chance of getting tools on centre height with a tool post on top of the topside.

It came with some tooling but I’m blowed if I can remember anything behind a “thats optimistic” feeling over what was provided as an alleged parting off tool. Hacksaw and subsequent facing had to do whilst I saved for something better.

Peters suggestion of mounting the toolholder on the cross slide either direct or via block suitably sized to get your preferred tool size on centre height is the sensible option. Given an occasional bit of creative thinking its fairly rare to absolutely need a topside for work of the classes generally done on machines of this general type and style.

Howards method of making four way tool post is good, although I’ve always felt interchangeable two way blocks are a better option. Way back I did make some four ways basically to Howards method albeit using aluminium alloy for the centre portion as not only being easier to tap but also in stock in an appropriate size. Unfortunately the idea is likely to be impractical on your machine due to the base ending up so thin that it will likely bend if removed from the machine with the tool clamped down. I reckon 3/8″ – 8 mm is about the minimum safe thickness for the base. Which is probably not vastly different from the current situation.

It might be possible to make holders taking 1/4″ or 3/16″ (can that size still be got) square HSS bits pointing upwards at around 10 degrees as in an Armstrong holder. The up tilt means that the tool tip height can be set by sliding the tool in and out so the slot can be a snug fit maximising the base thickness. But that sort of thing needs access to milling machine to carve the thing from solid. I did a couple for a pal which worked well enough but was unconvinced that the effort was worthwhile. But he wanted a lathe to say he had a lathe so the amount of use they were going to get was minimal!

Clive

[PeteParticipant @pete41194]

Without some actual numbers about just how high the tool tip is currently above the head stocks center line it’s difficult to recommend anything. Safest and making the least permanent changes to the lathe would be Peter Cooks thought about attaching your qctp directly to the cross slide. Although it looks like that may also need a metal block under the qctp to then position it roughly at the correct elevation and allow the last fine adjustments to be done using the tool holders.

The top slides upper face appears like it could be re-machined to help lower the qctp. But I’m somewhat adverse to making permanent lathe changes by machining since once the metal is removed it’s gone for good. Machining a bit off the bottom of each tool holder and using smaller cutting tools would further help.

If your qctp is what would be referred to as an AXA sized tool post and holders, it may be too large for your lathe. There is one smaller and designated as an OXA. Although I don’t know how well those standard tool post designations and sizes match up with the Asian copies.

[Nigel Graham 2Participant @nigelgraham2]

I agree with everyone else: I am afraid you are trying to use tooling not designed for the lathe. I don’t know the centre-height of that lathe but that QCTP looks as if it would be too big on a Myford 7.

Don’t go and try modifying the lathe to suit incorrrectly-chosen tools. No-one stocks putting-on tools for when you find you should not have done that. Worse, apart from the question of spoiling the machine’s original form, cutting the slide surface down will weaken the slide.

 

There is available, and I own, a very basic, commercially-available, small [Fairly-]Quick Change Tool Post that works by a spring action in the block itself. It works, sort of. It fits my EW 2.5″ lathe, sort of;  so might fit the Portass if used with 1/4″ square tools, but it’s crude and rather disappointing to use.

Four-way tool-posts have long been common on these little machines – indeed even very large industrial lathes can still be supplied with their own versions, which have an indexing arrangement to ensure rapid, repeatable tool-cycling.

As Howard suggests they are not difficult to make, and if you use mild-steel plates held by 4 (or more) countersunk screws, 1/4″ / 6mm thickness is fine provided you use tools of appropriate bar size. I’d be inclined to use 8 screws of modest size, e.g M6 for a 2.5″ – 3″ square tool-post: 4 near the core block’s corners, the others in line with them and midway between them.

Note that the tooling still needs headroom for height-adjustment shims.

 

Further to Clive’s suggestion I long ago made a few, simple Armstrong-principle tool holders for my EW lathe (with “clog” tool-clamp as your Portass would normally have), and without needing the milling-machine I did not own at the time.

They are simply short lengths of square mild-steel bar drilled to hold bits ground from 1/4″ dia round HSS. My source of tool material is typically broken or worn out centre-drills, FC3 milling-cutters and the like! They are gripped in the holders by grub-screws in tapped cross-holes.

To make them on the lathe that will use them, select stock of thickness 2 X the lathe’s centre-height above the tool clamping surface on the top slide. Cut blanks of length a bit over the top-slide width.

Hold the blanks on the top-slide by the normal tool-clamp, drill the bit holes and grub-screw holes from the headstock.

For angles to give height-adjustment or some lateral access needs such as boring recesses, working close to the chuck and left-hand tooling, set the blank in azimuth by an adjustable-square.

The ends are not critical. Simply file the sawn surfaces to neatness.

 

I used one only today, though on a Myford lathe, with a weeny bit of 1/4″ shank diameter, to bore out a hole too small for my normal tooling.

 

If you want some repeatability with this system, make a set of blanks a bit over-long. Counter-sink screw a thin steel strip along the flank that will face the headstock, and insert a simple pin protruding below the bar’s overhanging rear end. The strip extends deeper than the bar so acts as a location and orientation rebate over the top-slide’s end edge. The pin is the back-stop against the outer flank of the side. The strip and pin depths naturally need account for any height-adjusting shims, if you use those rather than the slope-adjustment method.

 

[Clive FosterParticipant @clivefoster55965]

Worth looking into the small indexable insert tooling made for the mini and micro lathes taking standard ISO tooling inserts for mounting on the topside. Either the  1/4″ – 6mm or 3/16″ – 8 mm size ought to fit, 3/8″ – 10 mm will probably be too large. HSS parting tool systems can be found in 6 mm and 8 mm nominal shank sizes. For example this one from Amazon probably comes with a normal folks lifetime supply of blades

https://www.amazon.co.uk/Factory-Parting-Holder-Blades-Lathes/dp/B07KZNCG1C/ref=asc_df_B07KZNCG1C?mcid=b9b1a594c31c34b38f89ea2306807cc6&tag=googshopuk-21&linkCode=df0&hvadid=696351256518&hvpos=&hvnetw=g&hvrand=18285601843783087798&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1006666&hvtargid=pla-1149332690049&hvocijid=18285601843783087798-B07KZNCG1C-&hvexpln=0&gad_source=1&th=1

Inevitably fragile tho’.

For tool position repeatability make a square plate of similar thickness with shank size cutouts maybe half to three quarters of the side length on two sides at 90°. Pin the plate to the topside to fix it in rotation. When changing tools push the new tool firmly against the side and back of the cut out before clamping the top plate down to hold it in place. With care the variation in tip position between changes will be of the order of a thou or two, maybe less. I’d do two sets of cut outs, one longer than the other, giving the option of working with more or less tool stick out as best suits the current job. Add more holes in the plate for the location pin so you can work with the topslide at different angles. Certainly have one for 90° and another for 45°. Others as needed. If you need a shim to bring the tool tip up to centre height it can go permanently under the plate.

The plate system would work well with Nigels round bit toolholder too. I’d probably modify the concept by drilling right through and add pusher screw working from the back to set projection. But I have some small round HSS toolbits about 2 1/2″ long in the “what can I do with these” box which would work well.

Realistically, as you already have the QC toolpost, removing the topside for most work using the QC post directly mounted to the cross slide is your best option. If nothing else it allows the use of larger parting tools and boring bars with vastly greater rigidity and corresponding ease of use. For the occasional jobs when you do need the topside, short tapers mostly, a basic square shank HSS tool and shims will be workable. Nigels idea will be more convenient in use but whether the gain is worth the work for occasional use may be open to question. Still use the alignment plate on the topslide tho’.

Clive

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