Lathe machining sequence

[Gary Clarke 4Participant @garyclarke4]

Evening All!

I am trying to make a 2 inch od by 7- 16ths wide bearing cap. The cap has to be threaded 20TPI on the OD. The 2 faces have to be smooth, one has 2 recesses for a pin spanner to turn the bearing cap

I need 2 bearing caps.

I have a lathe (monarch 10ee 1943 vintage) in my garage but have hardly any experience with it. I have a 2.5 inch 1018 steel bar which is 18 inches long for material.

Question is.. how should I machine the bearing caps.. one at a time or both together, part off each and then finish the faces.

I am assuming the threading on the od would be done first.. but maybe that would limit the way to grip the parts when doing the rest of the machining.

Can anyone suggest a machining sequence for me please..

[Gary Clarke 4Participant @garyclarke4]

[Gary Clarke 4Participant @garyclarke4]

I forgot to mention that the lathe has a 3 jaw chuck and no collets. I have a fixed steady and live center. Carbide insert tooling including threading tooling.

I probably sound like a crazy guy but I have only used the lathe for some basic ops but my issue is workholding and machining the faces..

I apologize for the choppiness of the post and odd punctuation. My keyboard keeps moving all the special chars around and doesn't match what the keys indicate. I cannot locate the question mark, apostrophes etc.. however we will leave that issue till later!

thanks (from Canada)

[HopperParticipant @hopper]

As with the removal of feline epidermis, there is more than one way to do it.

One way would be to hold the job in the three-jaw (no need for collets).

Machine OD to 1.995" for long enough to make two caps, plus extra for parting and machining. Face the end. Bore the centre out to size.

Cut your thread

Part off the first one.

Face the end.

Part off second one.

Parted surface could be cleaned up by holding the cap in the three jaw chuck with some brass shim to protect the thread.

Cut pin spanner notches in the surface that was parted off — the other one is going to be more square to the thread and should push against the bearing.

[Pete RimmerParticipant @peterimmer30576]

Hi Gary,

I would follow Hopper's suggestion to the letter.

The only thing I will add is add a healthy runoff groove for the threading if you're a novice, and if your lathe has ELSR, use it! certainly make use of the built in threading stop.

If you can't do it – it won't be the lathe's fault! The 10EE is a lovely machine.

Pete,

[Gary Clarke 4Participant @garyclarke4]

Many thanks to both of you! Hopper that is exactly what I was looking for. Your suggestion on which face should be the bearing face is something I had not thought about at all.. should I cut off a chunk off the 18 inch bar to start or is there a better way considering the bar will not fit in the headstock bore? If so, how long should this chunk be?

much appreciated!
Gary

[JasonBModerator @jasonb]

I would certainly not follow hoppers suggestion as you could end up putting an 18" long bit of steel in a chuck and then try to turn and then part off at the end.

Saw it into a safe length first eg enough to hold in the full depth of the jaws + 2 x job length = 2x parting + 4 x finish cuts + a bit

[HopperParticipant @hopper]

I was assuming your 2" bar would fit through the spindle of the Monarch. Long time (45-plus years) since I used a Monarch. Must be a bigger lathe in my memory than in reality. (Or I was smaller?)

If not, follow Jason's suggestion.

If you can't cut the bar easily, you could hold one end in the chuck and put the fixed steady a few inches in from the far end and machine the few inches sticking past the steady in the same manner. Standard procedure on smaller lathes such as Myford and Drummond with spindle bore like a mouse's ear'ole. You could even part off the piece you want to work with first in this manner, as per Jason's sizing formula and then follow the above steps.

[JasonBModerator @jasonb]

It's 2,5" bar

[Pete RimmerParticipant @peterimmer30576]

The lathe won't pass the bar through the spindle bore the best you can get is about 1-3/8". You'll have to cut the stock down to less than about 4-5" long if you're going to part 2.5". The 10EE is very stout for it's class but it's still only a d1-3 camlock spindle and will chatter if you part with too much overhang.

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