Home lathe precision question

nnam

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For good home lathe, whether US made or others. Home, I meant things most of us have, not from some special lab. Good meaning average like new quality. It is abit hard for me to say.

So, what kind of precision can it do? Can it do piston pin level fitting? I don't know what the gap is actually. But things like that, or injector plunger. All very smooth and tight fitting, would a decent home machinist lathe with a person who has good skill, but not god like-can do anything type, be able to do it?

I am sure some super high quality lathe can do it, but maybe it is not a lathe thing? Maybe they need to precision grind it, something like centerless or something of that sort.
 
Great question!
Definitely watching this thread.


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There is accuracy and consistency.

Both are more in control of the operator than the machine.

A good operator can make good parts with a bad machine as they can compensate for machine faults.

The items you describe often are ground on grinding machines as they are beyond general lathe work.

A better machine is capable of better work by a skilled operator.

Many great things can be made on lousy machines but it takes a lot more work and effort.

Out L&S can peel off A 0.375 chip at 7 inch diameter without busting a sweat and the carriage controls setup for production allow many same cuts to be made.

Same tasks on the 14.5 SB take many passes and great care to repeat.

Your workspace limits the overall size and that limits the selection of models.

Your budget limits the selection past that.

Many decent for hobby machines as well as others that sgg123 one like but are not desirable.

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A lathe would be the wrong tool for piston pins, at least the final fit. Piston pins are centerless ground, and the pin bores are honed. Final clearance is in the 0.0003'' range, but that does depend on the spec for a particular engine. Piston pins today are probably held to +/- 0.00005'' or better for the final tolerance. Injector plungers are also ground, and the bores are honed. Final fit on those is around + 0.0002'' You just can't achieve the needed surface finish with a single point tool. You could use a tool post grinder to achieve the needed finish and final size.

Your average home manual lathe of reasonably quality can probably repeat to +/- 0.0001 or better, but this does depend on the skill of the operator. Notice I said ''repeat'' rather than ''accurate to'', the accuracy is dependant on the operator also.
 
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Many decent for hobby machines as well as others that sgg123 one like but are not desirable.
I don't understand what you mean here. Can you elaborate?
 
A
 
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Asian imports and precision are not synomonous


Actually Your statement is probably fairly accurate for most Chinese made machines, but the majority of Taiwanese machines are a much higher quality and usually quite suitable as tool room equipment. Also Japanese machines are as good as any and I expect South Korean is pretty good also.
 
A lathe, any lathe, is not suitable for piston pin, lifter internals or that type of operation. For the average "home type" lathe to repeat and hold .0005 especially over any length I would say is remarkable............Bob
 
This is how I generally see it. In a manual world mill and lathe work will get you .0005-.001 accuracy. Grinding will get you .0001-.0005. Their are ALOT of variables involved machine, operator, knowledge, capability of accurate measurements. Modern cnc will hold half thou or better repeatable.
 
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