Derek,

I'll explain in detail:

'na tveva' = 'but not'
'tappaccayaa' = ta.m + paccayaa (Ablative), 'on that account'
'na tveva tappaccayaa' = 'but on account on that ... not'

You wrote: 'oil-clean sword'
I would propose 'oil-washed', or taking in account that boiling in
special oils is an ancient method for keeping iron from staining,
'oil-bleached' or something like this.

Moving right along now ...

Aarocayaami vo, bhikkhave, pa.tivedayaami vo, bhikkhave, yathaa
etadeva tassa vara.m dussiilassa …pe… kasambujaatassa ya.m balavaa
puriso ti.nhaaya sattiyaa teladhotaaya paccorasmi.m pahareyya.

Ta.m kissa hetu? Tatonidanañhi so, bhikkhave, mara.na.m vaa
nigaccheyya mara.namatta.m vaa dukkha.m, na tveva tappaccayaa kaayassa
bhedaa para.m mara.naa apaaya.m duggati.m vinipaata.m niraya.m
upapajjeyya.

Yañca kho so, bhikkhave, dussiilo …pe… kasambujaato
khattiyamahaasalana.m vaa brahma.namahaasaalaana.m vaa
gahapatimahaasaalaana.m vaa añjalikamma.m saadiyati, tañhi tassa,
bhikkhave, hoti diigharatta.m ahitaaya dukkhaaya kaayassa bhedaa
para.m mara.naa apaaya.m duggati.m vinipaata.m niraya.m upapajjati.

Let me tell you, monks, let me answer you, monks, that it better for a
person, immoral, wicked, unclean and suspect in conduct, secretive in
deeds, not a contemplative though claiming to be one, not leading the
holy life though claiming to do so, inwardly rotten, oozing with
desire, filthy by nature, if a strong man were to strike with a sharp,
oil-bleached sword in the nether-quarters.

Why so? For, monks, because of that he would suffer death,
or death-like agony, but on account of that, on the break-up of the body
after death, he won't be reborn in a place of woe, a realm of misery,
a state of punishment, a purgatory.

And monks, for such a person, immoral, wicked, unclean and suspect in
conduct, secretive in deeds, not a contemplative though claiming to be
one, not leading the holy life though claiming to do so, inwardly
rotten, oozing with desire, filthy by nature, who makes a salutation
[wai or namaste gesture] to rich kshatriyas, or rich brahmins, or rich
householders, for him, monks, there is a long-term harm and suffering,
and on the break-up of the body after death, he is reborn in a place
of woe, a realm of misery, a state of punishment, a purgatory.

Metta,
Dimitry