HNLD

[mynewviceroy]

Hi All,

Happy New Lathe Day (HNLD) to me!! Well, I say 'new' lathe, but it's actually rather old.

I've just bought myself a Viceroy TDS 1 S and am now trying to find out as much about it as I can. I've already had a good read of the forum and many thread etc - I've found the manual for the TDS range but still have lots more to find out. If anyone can shed any history on tis particular lathe, I'd be very grateful.

One thing I'd like some help with is the gear selection for thread cutting. I didn't get a set of gears with the lathe, so I'll either need to pick up individual ones bit by bit, or see if I can find a set (at a reasonable price) somewhere etc.



The gears are (from top to bottom)
38T on the spindle (stud gear?)
ignore forward/reverse cogs, they drive
38T (at rear - not visible) 36T on front (less teeth than the 38 gear behind but larger diameter?) driving
56T with 18T on front (one piece gear, not 2 separate gears) driving
100T onto leadscrew (screw gear?)

The question is - what TPI is this generating please? Can I arrange these any differently to get different TPIs?

[Andy B]

Hi ?? (you didn't give us your name)
Welcome to the forum.
If my maths is right, you'll be able to cut 66.67 tpi - or about 0.015" per rev which is a heavy roughing feedrate.

Your screw thread chart shows you all the gears you'll need to cut a standard range of imperial threads; I don't think there is a lot else you can do with what you've got as you're already at the lowest possible reduction.

The 100T gear you have may have been pinched from a Boxford at some point...

Andy

[mynewviceroy]

Thanks Andy - sorry - it's Phil

How is that figure calculated please? I've found various online calculators but not much makes sense to me (at the moment....)

I have a 3D printer so maybe I can print myself some new gears and see how they hold up under the stress of screw cutting (if I ever do any...)

[Andy B]

Hi Phil,
Think of the calc as 2 different bits.
First, the overall gear ratio, which is the product of the gear pairs, i.e. 36/54 x 18/100 = 0.12
So the leadscrew rotates by 0.12 of a turn for each rotation of the spindle.

Now take the leadscrew, which is 8tpi.
Every turn of the leadscrew moves the carriage by 1/8" (0.125").

Putting the two together we get 0.125 x 0.12 gives us 0.015" feed per spindle rev, and tpi = 1/feed = 1/0.015 = 66.67

Plastic change gears are now quite common, so definitely worth a try 3D printing them for occasional use.

Andy

[mynewviceroy]

Many thanks Andy, that helps a lot, but (and there is always a but), what does the 38T/36T gear arrangement do? I understand that the spindle gear is 38T, the feed direction gears then transfer the drive to the 38T gear to the rear of the pair, but that gear then drives (via the shaft and keyway) the 36T gear visible in the picture.

If I wanted to cut a 20TPI thread, I can see this on Fig 2, so where would I put my (to be bought/made etc) gears? I need a 16T and 40T - I believe the 80T just transfers the drive so if there is physical space I can use (?) the 100T I already have in here?

Does the 16T replace the 36T I currently have and the 40T replace my 100T? I'll need to look again at the vertical alignment as I'm sure the 36T is currently 1 gear width away from the 100T and I don't recollect a removable spacer boss inboard of the 100T.
Cheers!

Edited to add:

Reversing the maths, if I want 20TPI, that's a feed of 1/20 = 0.05
leadscrew is 0.125", so I need a leadscrew rotation of 0.05/0.125 = 0.4
0.4 is also 16/40 (as per the chart) - so that all checks out which is great, but it's just making sure I understand the interaction of the 38T / 16T arrangement and making sure I can get the necessary vertical alignment of the gears.

[Andy B]

Hi Phil,
You can ignore the 38T spindle gear to reverse idlers to 38T - all that does is give you a 1:1 reversing arrangement, so the shaft with the second 38T on it is your 'stud' shaft - i.e. the input to the reduction train.

Yes, you're right that the 'stud gear' as indicated on the charts is currently the 36T, and you'd swap that for a 16T (or 24T or 32T) according to the desired thread pitch, and right again that for the 'Fig.2' pitches the idler could be the 100T if it will fit.
If there isn't currently a separate spacer behind the 100T gear then you'll probably need one to pack out to the nut - either machined or 3D printed.

My lathe has a gearbox, so different set-up - but I think all the necessary drawings should be posted here somewhere.

Andy

[mynewviceroy]

Brilliant! Many thanks for helping to clear this up for me - much appreciated.

I've found some 3D print gears via Thingiverse but I just need to check my current shaft dimensions - I think it's 9/16" shaft - then learn how to print in PETG (I've only used PLA so far) - don't really want to mess with ABS and heated enclosures etc.

Start small and build big - hopefully the way to do it!

[Andy B]

The parts list is on page 49 of this download - https://www.denfordata.com/downloads/fo ... imised.pdf.

Some of the drawings are in here - https://www.denfordata.com/downloads/fo ... 0scans.pdf

2 spacing bushes ML105/113 required for a full set.

[mynewviceroy]

Thanks!

Turns out there is a spacer behind the 100T gear, so it can go backwards so as to align with the Fig 2 chart (if I had the gears). I can't use the 100T in place of the 56T/18T (where the 80T is shown) as the shaft diameters are different - so I'd either have to turn a bush (not a problem as long as I can find some suitable material - bronze / oilite maybe?) or not go that route and just see what gears I can pick up or print. 100T is a 9/16" with keyway, the 56T/18T is larger (forgot to measure it) and no keyway. In the parts list you linked me to, the 80T change wheel and gears (ML105/133 and 134) both have a 9/16 bore so what has probably happened is that the shaft I have has been changed to suit the 56T/18T, so it's a new shaft I need to make rather than trying to make the gears fit. I just need to hunt down its name and then the drawing for it (or make it up as I go along based on the existing one and a 9/16" shaft).

Thanks for the parts list and drawings file - much appreciated.

[DavidB]

Phil,

If you haven't come across it already you might want to try the free 3D modeller Freecad for Windows/Mac/Linux https://www.freecad.org/ as it has a gears workbench add on so you can create various types of gears. You'd need to add a cylinder to represent your shaft and subtract it from the gear blank and export it as a STL file for use by your preferred slicer. I'm no expert with it but have used it for a number of simple models and gears. It's still in development but worth a try.

[mynewviceroy]

Thanks David,

I wasn't aware of that website so I'll give it a look. I've created gears using this website - https://evolventdesign.com/pages/gear-stl-generator, though it is metric so I've had to adapt imperial sizes to the nearest metric size the website can handle, or re-jig them later in post processing. I've generated a 32T, printed it in PLA this evening, so I'll try to find time tomorrow to see if it fits / meshes / works and go from there. I have access to the Home use Fusion 360 - I've not looked to see if there is a gear creator module in that yet. Adding a cylinder and keyway shouldn't be too much of an issue hopefully - I've been using Tinkercad for this sort of thing so even if I can't manage it through FreeCAD, I know I can do it through Tinkercad.