Pm 1228-vf-lb Lathe Preparations

[Franko]

The thread chasing dial arrived yesterday. It attaches to two little holes on the left side of the saddle that were plugged with set screws. It didn't come with attaching bolts or any instructions what so ever. The bolts were 5mm. I had to purchase 50mm bolts and cut them down to about 45mm.
Other than having to modify a couple bolts, the installation went easily.

I have absolutely no idea how to operate it. Matt sent me some instructions.
As near as I can tell, it says to do all imperial threading from zero on the dial.
For metric threads the dial won't work without the other gear it didn't come with.

 

[Muskt]

Franko, here is my recommendation for use of the threading dial.

Remove it from the lathe and carry it to the nearest swamp. Close your eyes very tightly and turn around about 3 revolutions and with your eyes still closed, throw the dial as far as possible and do not open your eyes for at least 2 minutes, then go home hand have an adult beverage.

Seriously, unless you have lots of extra brain cells to spare, just leave the half nuts engaged and reverse the lathe (after backing out the crossfeed). That way, whether imperial or metric, you will never go wrong.

Here is a link to a very old book from "The Southbend Lathe Company" on my site. I am not sure if it is applicable to you machine, but check page 15.

http://www.akpilot.net/How To Cut Threads/How To Cut Threads.pdf

Best to you,
Jerry in Delaware

 

[John Hasler]

That lathe has a 10TPI leadscrew?

 

[Franko]

John, the manual and my ruler says it has an 8 TPI leadscrew.

Franko, here is my recommendation for use of the threading dial.
...
Best to you,
Jerry in Delaware

Jerry, thanks for the book.
I've never used a thread chasing dial. All the threads I've cut have been by reversing out of the cut. I thought maybe I should give using one a shot. But, that little bit of info that Matt sent me is confusing me. Or, maybe not. I've watched several videos by guys who knew way too much about thread chasing. I was under the impression that different pitch threads had to be started a different marks on the dial depending on the pitch of the lead screw and pitch to be cut. On a certain group of threads, any mark on the dial will work. But, maybe the one number they all have in common is zero.

I have a threading project that I was hoping to use the dial. I'm cutting an external thread to match a part that is already threaded internally. The only way I have to check the thread progress is with the original piece. It is about 8 inches long and I'm going to need to clear the saddle that far back in order to determine when to stop cutting.

In my experience, at the end of the process, it takes several test fits and running the slide that far back with half-nut engaged could be a little overly tedious.

Typical of the rest of the manual, the grammar seems nonsensical and is difficult to interpret.

If I'm translating correctly, I think it says not to engage the half-nut while the lathe is turning. I can only assume from the so-called instructions that I'm supposed to manually rotate the lathe until the chasing dial is on zero, then engage the half-nut. That's not how I've seed it done.

 

[JimDawson]

This assumes that you have an imperial lead screw and are cutting imperial threads, or metric and metric.

Normally if I start on a number, I stick with that number for the rest of the operation. It does not matter what number you start with for any thread. There are some TPIs that you could pick up any number during the operation, and some TPIs that would require that you use opposing numbers. I can't remember the different combinations. Starting at even/odd or even between numbers makes no difference as long as the rest of the operation is continued with that position.

You may need to adjust the threading dial so the numbers line up correctly with the half-nut engagement point.

I think the manual is a bad translation from the original language. I have never seen a lathe that it was not acceptable to engage the half-nuts while turning. If you engage on the numbers, there is no load on anything during the engagement.

If you are cutting metric threads with an imperial lead or vice versa, then you would not want to disengage the half-nuts until the operation is complete.

 

[ronboult]

Hi Franko
Jim above gives good advice. A thread chasing dial is either metric or imperial. A metric dial works with a metric leadscrew to cut metric threads. An imperial dial works with an imperial leadscrew to cut imperial threads. While you can cut metric threads on a imperial lathe (using a 127 tooth gear) you can't use the thread dial easily. There is a way and I will try to dig out the Web address that shows you how. I have it stashed away somewhere. Its quite ingenious and simple when you know how.

Anyway to get you started you can engage the half nuts with the lathe started -no problem. If the thread dial is installed correctly the half nuts will engage cleanly as the thread dial passes zero. You just wait until the thread dial reads zero then engage. When you reach the end of the thread cut disengage the half nuts. You can leave the lathe running. Wind the carriage back to before the start of the thread, put on some extra cut and then engage the half nuts when the thread dial again reads zero. Note the when the half nuts are disengaged the thread dial keeps turning so you can choose when to engage.

Actually you can use any number on the dial to start the thread as long as you use the same number for subsequent cuts.

Depending on the number of divisions on your dial ( and I think the TPI of your leadscrew) you can use other numbers for subsequent cuts. Which number can be used for a particular thread depends on the tpi of the thread you are cutting and the number of divisions on the thread dial. I am sure there are others on this website that can give you the combinations for Odd and Even tpi threads with your leadscrew and thread dial. While my lathe is metric it has a chart on the headstock that tell you what number to use for a particular pitch thread.
I just counted the divisions on your thread dial and I think there are 20. That is a very odd number, most dials that I have seen have 4, 6, 8 or 12.
In the first instance until you work it out just stick to the same number for each cut and it will work. Being able to start on other numbers for some threads just makes cutting quicker.
Good luck
Ron

Edit
Franko here is the Youtube video by Tom Lipton ( Oxtools) that shows how to use a thread dial to make metric threads on an Imperial leadscrew lathe

 

[Dale Aune]

Franko G0773 lathe/mill combo looks like the same lathe. Not variable speed though. It looks like a Sieg c10. Maybe the owners manual on Grizzlys site would be of help to you.

 

[Franko]

Hi Franko
... Anyway to get you started you can engage the half nuts with the lathe started -no problem. If the thread dial is installed correctly the half nuts will engage cleanly as the thread dial passes zero. You just wait until the thread dial reads zero then engage. When you reach the end of the thread cut disengage the half nuts. You can leave the lathe running. Wind the carriage back to before the start of the thread, put on some extra cut and then engage the half nuts when the thread dial again reads zero. Note the when the half nuts are disengaged the thread dial keeps turning so you can choose when to engage.

Actually you can use any number on the dial to start the thread as long as you use the same number for subsequent cuts.

Good luck
Ron

Edit
Franko here is the Youtube video by Tom Lipton ( Oxtools) that shows how to use a thread dial to make metric threads on an Imperial leadscrew lathe

Thanks Ron, that's useful information.
I've attempted engaging the half-nut while it is running, but about half the time there is a little snag and it engages a little off the mark. It won't hit the zero exactly even when it isn't running.

Franko G0773 lathe/mill combo looks like the same lathe. Not variable speed though. It looks like a Sieg c10. Maybe the owners manual on Grizzlys site would be of help to you.

Great snooping, Dale. Thanks, that's full of lots of useful information.
All of the Grizzly manuals I've seen seem to be very well made.

 

[markknx]

Franko,
Not sure if someone else pointed this out but before you put the tool holders in the mill to find out if they are hardened try a file test, it won't cost you an end mill. The file will be fine also.
Mark

 

[ronboult]

Franko
A correct size shim between the thread dial and the carriage should cause the half nuts to close directly on one of the lines. Even so if you have the correct thread dial with the correct gear for an 8tpi leadscrew the half nuts should engage at exactly the same point on the dial every time- same distance from zero. If not there is a problem with the dial. Does the dial mount on a pivot so it can easily be disengaged without total removal? If so do you do you have the dial gear snugged up to the lead screw so there is no play? Given that your dial has 20 divisions this seem quite strange for a 8tpi leadscrew.
Hope you sort it out because a correctly functioning thread dial makes threadcutting easy & quick
Ron