Thread: question about hercus 9a metric options

Hi All,

We (Dad and I) recently inherited a Hercus 9A along with a whole load of spares, gears and tools.

In mix are a set of metric gears (see attached), which I think are complete. There is also the 127/100 gear.

I want to convert this into a metric lathe and there seems to be a few ways to achieve that (thread cutting). I am assuming the lead screw is imperial, as is the dial indicator.

I am after some clarification on what I would need. For example, if I install the metric gears in the gearbox, I don't think I need the 127/100 gear. Do I need a new thread dial? I have seen a metric thread dial, but does that need metric lead screw? I think cutting metric threads is my main reason for doing all this. I am thinking of putting DRO on it (or at least a cheap diy version), leaving just the compound screw requiring a metric replacement.

I have also decided to replace the felts and repaint it. Is standard automotive enamel ok?

Any help appreciated.


[ just saw its a 1947 model]

I think you may be a little confused in what you think you can do.

To convert you lathe from Imperial to Metric the way you have mentioned above, you would to change the gearbox and leads crew to Metric as well as change the Change Gears to the Metric gears required.

If you do this that will eliminate the need for the 127/100 transposing gear.
You will not be able to use your existing gear box.

You will also have to change the thread chasing dial.

If you wanted to change it over costs would be around the$700/$800 roughly.

In my opinion you would be better off leaving it as it is and just use the transposing gear you have and the change gears equiped to cut the Metric threads that you require.

You probably won't be able to use the existing chasing dial to often but can Allways wire the motor for reverse if capable or purchase one that is for much less than the semi conversion cost.

In regards to the changing of the cross slide and compound screws and nuts, if you are going to rig up some form of DRO it won't matter,even without a DRO if you do the Imperial to Metric conversion that will work fine.

Looking at the photos of the gears quite a few of them appear to be idlers ( the ones without a key ).

These gears along with the ones with key ways are not suitable for the gear box , they are far to large.

Justin
I have a Hercus 260 Lathe Imperial.
Perhaps I am a bit older than you, however I like to work in imperial.
Sometime back, I got Pipeclay, to make me a set of Metric gears, for screwcutting metric threads.
I still use the original chasing dial, but leave the half nuts engaged on the leadscrew, & reverse spindle rotation, at end of cut, saddle then moves back along bed, then toolbit is fed in for next cut.
Hope this makes sense.
The above works well for me.
Bruce

Originally Posted by Abratool

I still use the original chasing dial, but leave the half nuts engaged on the leadscrew, & reverse spindle rotation, at end of cut, saddle then moves back along bed, then toolbit is fed in for next cut.
Bruce

I may be wrong or plain stupid, but my understanding of the chasing dial is that it is used to ensure that the half nuts engage the leadscrew at an appropriate point so that the tool runs in the partly cut thread, and does not create a randomly positioned additional thread start.

Once the half nuts engage, and the carriage is controlled by the leadscrew, the chasing dial should not rotate as the carriage is driven. Therefore the chasing dial is redundant and irrelevant if you need to keep half nuts engaged and reverse the spindle to return for the next cut.

Originally Posted by malb

Once the half nuts engage, and the carriage is controlled by the leadscrew, the chasing dial should not rotate as the carriage is driven. Therefore the chasing dial is redundant and irrelevant if you need to keep half nuts engaged and reverse the spindle to return for the next cut.

That is correct, the chasing dial is irrelevant. I think Bruce probably just misspoke (typed? ).

Vernon
Yes.
Bruce

Hi Justin, not sure about the change gears, Ihave a full set for metric and imperial but have an imperial quick changegearbox so I'm not sure how I could be certain of what metric thread I wouldcut if I wanted to change the gears. I'm sure though somehow the change gearswould allow for an imperial lead screw and make that allowance. I am blessedbecause I have two 9" hercus machines so I don't have to change anythingother then walking to the other lathe. When I cut threads I don't use thethread dial indicator, I leave the half nut engaged and use the motor forwardreverse switch but being careful to move the cutting tool away from the job onthe reverse. Looking at to idler gears that drive the gearbox forward/reversein one of you photos it looks to me if it could be off a southbend lathe, however I'm no expert.
Stephen