Thread Cutting Gears on Seig / Axminster SC2

[Steve MParticipant @stevem]

Morning,

I'm sure this question will win the 'National stupid question of the year award' however..

Today I want to have my first turning/threading an M12 bolt with a 2mm pitch on the above lathe.

I'm new to machining and brought my first lathe in December. So still trying to find my feet.

I've read about how to thread and also watched some videos on the difference methods so now want to have a go.

The only thing that I can't get my head around is manual for the lathe it states mounting points A, B,C, D which you attached the gears to which gives you the pitch in a certain combination. What I don't understand when you take the gear box cover off it which mounting point is A, B, C D as they are not labelled.

Once I know where, a, b, c and D are I can mount the gears in right place and crack on.

Kindest Steve

[Steve MParticipant @stevem]

[Martin ConnellyParticipant @martinconnelly55370]

I think this is similar to the Grizzly g9866 lathe. Their manual is quite clear so have a look at pages 26 and 27.

Martin C

[JourneymanParticipant @journeyman]

Can't answer your specific question regarding gear placement for the SC2 but would note that an M12 thread is normally 1.75mm pitch

John

[Steve MParticipant @stevem]

Posted by Martin Connelly on 16/01/2021 09:18:33:

I think this is similar to the Grizzly g9866 lathe. Their manual is quite clear so have a look at pages 26 and 27.

Martin C

Thanks a lot Martin that is it! Kindest

[Steve MParticipant @stevem]

Posted by Journeyman on 16/01/2021 09:19:43:

Can't answer your specific question regarding gear placement for the SC2 but would note that an M12 thread is normally 1.75mm pitch

John

Thanks John

[Howard LewisParticipant @howardlewis46836]

Whether you cut a 1.75 mm or 2 mm pitch thread, you are cutting a thread which is coarser than the 1.5 mm pitch Leadscrew. This will impose a greater than normal load on the plastic Chagewheels, and probably on the motor. Being an SC2 it will have a brushless motor, and so lack the Hi / Lo gear option of the earlier C2 with brushed motor.

The thread will be fairly deep (1.01735 mm ) so the final cuts will impose quite a load.

I would advocate making up a Mandrel Handle for this kind of work.

It will enable you to deliver the torque needed, without stressing the motor and drive, and you can control the speed, so that it is below the minimum that is possible with powered drive.

(As an aside, the motor will be rotating slowly, whilst delivering a lot of torques, so will not have sufficient air flow for adequate cooling, if the job takes anything other than a short time.

This is not to suggest that the motor will not be reliable, but why risk overheating it?

Also, if the thread runs up a shoulder, a mandrel Handle may very well allow you to stop rotation more accurately than depending on the motor and gear train coming to a halt. You can save damaging the tools that way!

HTH

Howard

[HopperParticipant @hopper]

This really handy calculator LINK has clear pictures showing what gear is what on a mini lathe.

Make sure you fill out the bottom part of the page to suit your lathe before hitting the calculate button to find what gears to use. Then fill in the pitch you want at the top and hit the Calculate button and the pic and information will appear. Easy peasy.

Edited By Hopper on 16/01/2021 11:21:52

[Howard LewisParticipant @howardlewis46836]

As an afterthought, don't forget to mesh the gears with a little backlash. This will prevent wear and probably noise.

Just trap a piece of paper between each mesh as you set it. You are looking for paper about 0.003" (0.075 mm ) thick.

The backlash should not affect accuracy, since you will only be cutting in one direction, and so the backlash will always be taken out in that direction.

FWIW, I start setting the backlash from the Leadscrew and work back towards the mandrel, so that the Banjo sets the backlash for the final mesh.

Howard

[Steve MParticipant @stevem]

Thanks everyone for your comments and help. I really appreciate it. Thanks steve

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