Posts: 2,596
Threads: 99
Joined: Dec 2014
Location: Michigan
What don't you understand about the gearbox?
Posts: 968
Threads: 67
Joined: Apr 2015
Location: Australia
I'm going to make some semi-educated guesses that I hope may help. There are a few controls on the apron of the lathe, presumably one of them is to engage the 'half-nuts' for threading (this uses the big acme thread on the leadscrew), one will be to engage the power feed in either longitudinal or cross feed (probably driven by a keyway in the leadscrew that operates a gear set in the apron).
Presumably there is also a moveable gear, probably at the back of the headstock, the 'sliding gear' that can either be 'in' or 'out'. The photo on the web page shows a lever on the headstock above the threading gearbox, I'll assume that is for the 'sliding gear'.
The chart on the gearbox is set out in columns which correspond to a position for the bottom selector lever directly below that column. The rows obviously refer to the position A, B or C of the lever on top of the gearbox.
The big numbers are threads-per-inch you will cut when using the half-nuts (on the apron) with the gearbox levers in each position. The small numbers are the distance the tool will move along the work when using the power feed,
e.g. sliding gear 'out', top lever in position A and bottom lever all the way to the left, will give you 32 threads per inch if you're screwcutting using the half-nuts, or will advance the cut .007" per revolution if using the longitudinal power feed, .014" per revolution in cross feed i.e. facing.
That's probably as clear as mud; have a look at some threading videos on youtube (I highly recommend an obscure youtube channel called 'Tom's Techniques') that will demystify the threading process and put your gearbox arrangements into some context. Have a play with the levers, particularly the ones on the apron, and see what each one does.
Lathe (n); a machine tool used in the production of milling machine components.
Milling Machine (n); a machine tool used in the production of lathe components.
Posts: 17
Threads: 3
Joined: Dec 2016
Location: Scotland
Power feeds I understand and what all the levers on the Apron do. It was the figures on the plate of the gearbox I wasn't sure about . But thanks for the explanation I now understand a bit more . I'll have a tinker with them . I'll download a chart from somewhere.
Posts: 17
Threads: 3
Joined: Dec 2016
Location: Scotland
(12-04-2016, 03:08 AM)Vinny Wrote: What don't you understand about the gearbox?
Whre to postion each lever for a certain thread . looks like I have to find a 127tooth gear for metric threads .
Posts: 4,683
Threads: 93
Joined: Feb 2012
Location: Perth, Australia
(12-05-2016, 02:37 AM)Seanlogie Wrote: (12-04-2016, 03:08 AM)Vinny Wrote: What don't you understand about the gearbox?
Whre to postion each lever for a certain thread...
As Pete said, you simply match the position of the two levers in your picture to the corresponding position on the chart. For example, to cut a 13 tpi thread, position the top lever to position B and line up the bottom lever with the column on the chart that reads "13" (second from the right). It is that straight forward.
When cutting a thread, I like to take a scratch pass. I'll apply some ink to the part that I am threading (using a sharpie) and set the tool so it only just scratches the surface. Then I make a single pass and make sure that the scratch lines up with the corresponding thread on my thread gauge.
This is more important when using change gears but I'd do it just the same to make sure I don't wreck a part by making a silly mistake.
Hunting American dentists since 2015.
Posts: 17
Threads: 3
Joined: Dec 2016
Location: Scotland
12-05-2016, 01:22 PM
(This post was last modified: 12-05-2016, 01:27 PM by Seanlogie.)
When explained it's a bit obvious and now i feel like a dork
. Think I was trying to read something into what wasn't there ,over think it so to speak .So am i right in saying i need a 127 tooth gear to cut metric threads .... I can hear you all going .... here we go again lol .
Thank you .
Sean
Posts: 2,324
Threads: 271
Joined: Jun 2014
Location: La Libertad, Philippines
Here are a couple of resources:
How to Run a Lathe by South Bend. Goggle the book as there are many ways to obtain the pdf. Unfortunately many/most require a purchase.
Machinery Repairman 3 and 2
http://eric.ed.gov/?id=ED203130 this one is free
Also look for YouTube resources. Tom's Techniques are among the best, if not the best.
BTW, welcome aboard.
Posts: 8,739
Threads: 313
Joined: Feb 2012
Location: Arizona/Minnesota
The following 1 user Likes EdK's post:
Seanlogie (12-06-2016)
(12-05-2016, 01:22 PM)Seanlogie Wrote: i feel like a dork
Sean,
You've got company. That's my normal mode.
Ed
Posts: 17
Threads: 3
Joined: Dec 2016
Location: Scotland
My crosslide has a 10tpi and a 1/2 shaft . to make a thread I'd have to set the QC gearbox up as follows
Sliding gear in
A
And 3rd slot
San
