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Steve Middleton
10-23-2014, 09:41 PM
I have a Shop Fox 12x36 lathe at 2 yes old. STANDARD thereads no problem but metric threads no success. Have studied the manual, etc but nothing seems to work. Today I switched back to stanDard threads and things are fine. Any help will be appreciated.

Don Young
10-23-2014, 10:03 PM
I don't know about your manual but the gear setups are often not real clear. If your problem is wrong thread pitches you might check this carefully. Generally, for metric threads the top (spindle) gear meshes with a 127 tooth gear and the bottom (gearbox) gear meshes with another gear on the same shaft as the 127 tooth gear. This gear is often a 120 tooth one, but that can vary.

If wrong thread pitch is your problem and the above doesn't help, a good clear picture of your gear chart will help. If not, you need to be more specific as to just what kind of problems you are having.

Jim Hubbell
10-23-2014, 10:55 PM
If the problem is wrong pitch, re study the gear chain setup.
If the problem is split threads, the problem is loss of sync. do to opening the half nuts during the threading operation.

The Artful Bodger
10-23-2014, 10:59 PM
Be aware too that you probably cannot use the threading dial when cutting metric threads.

Paul Alciatore
10-24-2014, 12:22 AM
We could give better advise if we knew more about how the threading process is failing? Questions:

1. After just one pass, is the metric pitch OK or wrong? If wrong, which way; too coarse or to fine?

2. If you get the correct pitch on the first pass, does the second pass follow that initial cut properly? Or does the tool cut a second path?

3. If both of the above are OK, then what is going wrong?

loose nut
10-24-2014, 10:54 AM
Simple solution. Don't use metric threads, they are one of the devils devices.

Alistair Hosie
10-24-2014, 04:42 PM
I have the exact opposite problem. My lathe is set up with an automatic gearbox, set at the moment and ever since I bought it and had it set up with the aid of my old pal Fred,for metric all sizes.I can though, quickly change it as I have been led to believe.* though never actually tried* by changing some gears, which I have they come with the lathe when I bought it.There has been really no occasion for me to cut imperial threads since I bought the 10-24 Smart and Brown lathe the newer variable speed model , but it is nice to know I could if I needed to.
Most things I do I can usually work out to get them done metrically as very little imperial stuff crosses my door. You guys are the best. Alistair

Peter.
10-24-2014, 04:54 PM
I have a Shop Fox 12x36 lathe at 2 yes old. STANDARD thereads no problem but metric threads no success. Have studied the manual, etc but nothing seems to work. Today I switched back to stanDard threads and things are fine. Any help will be appreciated.

If you're using the thread dial to spot when to close half-nuts, it'll chew up the metric threads every time.

Juergenwt
10-24-2014, 05:02 PM
If your lathe has a inch lead screw and a inch thread dial you must keep the half nut engaged from start to finish when cutting metric threads. Reverse the compound by putting the lathe electric motor in reverse.

lakeside53
10-24-2014, 07:44 PM
If your lathe has a inch lead screw and a inch thread dial you must keep the half nut engaged from start to finish when cutting metric threads. Reverse the compound by putting the lathe electric motor in reverse.


And of course, withdraw tooling when reversing or the backlash trashes the thread.

Steve Middleton
10-24-2014, 09:42 PM
Thanks for all the comments. Have a sizeable display of failures but not giving up. Not dis engaging the half nuts, not trying to use thread dial, but pitch isn't correct. Most likely the operator's fault but have to figure out why. Update tomorrow.

oldtiffie
10-24-2014, 11:21 PM
I have a metric lathe with a threading dial that will cover most metric pitches - and virtually none of the "inch" pitches.

The use of the lathe for either or both metric and inch screw-threading is best addressed by leaving the lead-screw half-nuts engaged for both metric and inch screw-cutting on both metric and inch lathes - and forget all about when to engage the half nuts and forget all about the threading dial as well.

Once you get used to setting the gear-train you are cruising.

krutch
10-25-2014, 02:04 PM
Most of my lathe threading is done on my Clausing/Colchester 8000 Series lathe. It has reversing spindle by start/shutoff lever. Makes it a breeze to thread and I keep half nuts closed through both mm and in. threading. Just have to slow down the spindle if doing "to-shoulder" work. Long length threads take time during the reverse mode but not waiting for the dial takes the guessing game out of the equation.

GadgetBuilder
10-25-2014, 02:49 PM
There is a way to use the inch thread dial for metric threading but it differs slightly from how it is used for imperial threading on an inch lathe, see: https://www.youtube.com/watch?v=HXt4TWa382Q
Might help when threading to a shoulder.

John

The Artful Bodger
10-25-2014, 03:02 PM
Steve, can you post some photos? Pictures of the gear train, the position of the levers and the threading charts on your lathe would be very helpful.

John

Steve Middleton
11-20-2014, 01:31 PM
Steve, can you post some photos? Pictures of the gear train, the position of the levers and the threading charts on your lathe would be very helpful.

JohnI got it sorted out finally. Operator error as you might suspect. I did not fully grasp the change gears. Once I got it through my head things worked as they should. Thanks to all for your help!

Paul Alciatore
11-20-2014, 01:42 PM
Glad to hear that.

Happy Chips!