Bantam thread cutting set-up?

[Rob Thomas 4Participant @robthomas4]

[Rob Thomas 4Participant @robthomas4]

[David George 1Participant @davidgeorge1]

What a shame it is sooooo rusty. Never mind it will clean up and it can be put back in to service with a lot of hard work.

David

[EmgeeParticipant @emgee]

Lot of work there, OK if you have plenty of spare time and a lot of cleaning materials.

Emgee

[BazParticipant @baz89810]

Must be me being thick as usual but all I see is a picture of a Bantam 800, is there a question or some statement of some sort to go with it.

[Nick WheelerParticipant @nickwheeler]

Posted by David George 1 on 09/08/2020 14:51:29:

What a shame it is sooooo rusty. Never mind it will clean up and it can be put back in to service with a lot of hard work.

Is it? 1/2hr with some degreaser and fine Scotchbrite, and another few minutes lubricating it should make it both usable and tidy looking.

[Rob Thomas 4Participant @robthomas4]

Sorry Gentlemen, not familiar with the posting method on this forum, pushed the wrong button!

Here's my lockdown efforts, my first lathe.

The bed way valleys are quite pitted but the bearing surfaces appear OK and the Eagle gearbox was badly mashed and some of the cog teeth needed dressing with a file. I've got the feed drive to work but it's noisy at high revs.

My question is when setting up for screw cutting do the driver and driven cogs run on different cogs of the compound idler(120T/127T). I appologise, I'm finding the user manual quite difficult to understand.

Edited By Rob Thomas 4 on 09/08/2020 17:56:29

[DC31kParticipant @dc31k]

Posted by Rob Thomas 4 on 09/08/2020 17:50:54:

My question is when setting up for screw cutting do the driver and driven cogs run on different cogs of the compound idler(120T/127T).

I am assuming it is a native imperial machine (i.e. 4tpi leadscrew).

When screwcutting imperial threads, you use only one of the 120/127 pair. It is used only as an idler gear so does not change the ratio. Thus either one of the two is OK to use.

When screwcutting metric threads, you need to use both gears as a compound gear. This provides the necessary imperial to metric conversion factor.

[Howard LewisParticipant @howardlewis46836]

If the Leadscrew is Imperial pitch, for Imperial threads, it does not matter whether you use the 120, or the 127 as an Idle.

Ditto, if the Ladscrew is Metric.pitch.

BUT

If the Leadscrew is Imperial pitch and you wish to cut a Metric thread, then you will need to drive

Mandrel /Tumbler reverse to 120T / 127T to Gearbox Say 8 tpi, so 3.175 mm x 120/127 = 3

If the Leadscrew is Metric and you wish to cut an Imperial thread,

Mandrel/Tumbler Reverse to 127, 120T to Gearbox 3 x 127 / 120 + 3.175 mm ( 0.125 = 8 tpi )

In each case the Driver and Driven gears need to be chosen to suit the ratio chosen in the Norton gearbox, for the required thread pitch.

HTH

Howard

[EmgeeParticipant @emgee]

Rob

Blimey, you cleaned that up pretty quickly !!!

Did the gear selector chart on the gearbox cover clean up OK so it is all readable ?
If it did you can see the gear selector positions which will suit the threads and feed rates in that band.

Emgee

[Pete RimmerParticipant @peterimmer30576]

You say it's an Eagle that makes it a Metric machine. You use the compound for inch thread, but use the 127 as an idler for metric I believe.

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