T.D.S. 1/1G B.L. Threading

[Liore]

Hello,
I am new to this forum and joined to get some thread advice

I have a TDS1/1G B.L lathe, the lathe was given to me as a gift about 12 years ago and so far I have used it a lot for my collectible car and motorcycle.
Recently, I had a need to make thread and the subject really fascinates me I tried to understand the gears table on the lathe
part of the understanding process was through this forum, but I had a small gap in my understanding of which gear is actually being replaced
It should be noted that the lathe was given to me without spare wheels but I will get what is required

For the sake of explanation, I tried to make 1.5 mm pitch thread. I understood from the table that I need to put the handle and the counter on 1 ,64 gear must be installed and right turn
I understood that the wheel in the picture should be replaced with a 64 wheel, at first glance I don't think there is room for this wheel. What am I missing?

I would appreciate any help and assistance

Lior

[mynewviceroy]

Bit hard to see from your picture (or the picture you found?), but my (old) Viceroy (imperial) had this arrangement:

Gear Arangement.jpg (69.41 KiB) Viewed 5737 times

On the bit where it says 54T 18T there are 2 sliders which allow the gears to move on a slider so smaller gears move closer, bigger gears move further away, and the whole arrangement moves on an axis to ensure alignment.

Is your lathe metric or imperial? If imperial, you'll need a 127T gear to do metric threads from recollection, search on here for 127T and I'm sure you'll find lots of threads etc.

Different lathe (my current one!), (still at TDS1) different gear arrangement (not engaged)

IMG_20230719_181744.jpg (737.83 KiB) Viewed 5737 times

[richardb]

There are quite a few versions of the lathe, mine is a late metric one with a gear box.
If you have similar you will see from the thread chart plate to get a pitch of 1.5 you need to select the following :-

Quad sliding gears (nurled end that pushes gears in and out to select course/fine feeds) needs to be pushed 'In'
Top lever move to 'Right'
Selector dial lever to position 1 and sliding lever also to 1

Stud gear is 'D' which is 24 tooth.

From my understanding the Stud gear is the outer one of the cluster you pointed to in red, the inner is an idler. The top 4 gears in your pic are the drive from the headstock, the two reversing direction gears and an idler.
If you have a metric lathe you may be lucky and find that the stud gear is already a 'D' 24t ?

If you have a similar lathe and its still not clear I can upload some pics that might help.
I do find the instructions quite difficult ay times especially as i don't use all thefunctions enough to remember (age ?)

[DavidB]

For metric cutting with an inch leadscrew or vice versa you only need a 127 tooth gear if you require an exact conversion. There are some other gear combinations which will give a very close approximation which is good enough for most practical purposes and should fit in the standard gear train, you'll have to look up what the combinations are. There are also some spreadsheets about I understand that will help you work out a good combination for the pitch you're aiming for. I haven't the need to look up this information as my Harrison M300 will natively cut common inch and metric threads, I presume it has one of the close approximation gear sets built in.

An important thing to remember is that when cutting metric threads with an inch leadscrew or vice versa you cannot use the thread indicator but instead have to keep the half nuts engaged throughout and reverse the lathe to get back to the start to do a new cut.

[LesT]

There was a topic from a few years back which included a spreadsheet which
simplified the process of screwcutting imperial with a metric leadscrew,
its here:
viewtopic.php?t=1061

Regards,

Les.T.