A Theoretical Question For The Expeienced Users

A Theoretical Question For The Experienced Users

I just got this 9A machine and one of the statements that I keep hearing is, "It's too small".Small is a relative term in my book. So what is too big? What I'm wanting to understand is what is the largest part I would be able to create safely and successfully with a 9A. For example, I doubt I could chuck up a V-8 crankshaft, but I'm thinking that I will be able to make new spindles for changing over an old car from drum to disc brakes.How do I tell what will work?

Bob Leistner said:

I just got this 9A machine and one of the statements that I keep hearing is, "It's too small".Small is a relative term in my book. So what is too big? What I'm wanting to understand is what is the largest part I would be able to create safely and successfully with a 9A. For example, I doubt I could chuck up a V-8 crankshaft, but I'm thinking that I will be able to make new spindles for changing over an old car from drum to disc brakes.How do I tell what will work?

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Tougher question than you might think...

I've no clue what's a "9A". A ( dubious ) OLD rule of thumb was no work on unsupported parts heavier than the "normal" chuck chucked in itself. I've no idea where that comes from and even if it's true. But, with the spindle out or a drawing you could easily run an FEA and figure out max load and once you divide that by 3 you'll have a decent idea what the load ( weight + imbalance ! ) can be. If you're not using the lathe turn the chuck 180 degs every couple of days and always park the carriage right at the other end.

Now that I found the lathe on YT I am confident it'll do fine for making new spindles. I must say I envy you : this would be highly illegal where I am - one is not allowed to manufacture steering/suspension/brake parts and fit them without proper paperwork.... One can however import any kind of abject rubbish from China, India etc etc. But I digress...

How do I tell what will work?

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will it swing over the cross slide if it is long?
Will it swing over the ways if it is short enough to work on end-wise?
Do you have a steady to carry it when it is necessary to work or bore on the end(s) of a long piece that won't fit through the spindle?

For the work you propose, certainly within the range.
It just takes longer on a "small" lathe due to smaller cuts so as not to overcome the HP or rigidity of the given machine.
Learn to sharpen & use HSS. The 9A barely has spindle speeds (nor stiffness/rigidity) that make carbide tools useful. They can be used, but you will fight surface finishes, or alternately, tip chipping with small pos rake tools necessary.

The spindle has to be good, and adjusted correctly to get decent repeatable surface finishes and hit sizes with the precision advisable for
automotive spindles (bearing fits, e.g.) & make single point threading of the ends "easy".

Wherever possible, throw the chucks away, especially the 3 jaw. Learn to work between centers to decrease overhangs on the small lathe spindle bearings, & to make it easy to take parts for other machines (such as autos) on & off for trying; or reversing to work on opposite ends.

smt

If it hasn't been done convert the drive belt to a timing belt. This greatly increases the reliable transmission of torque to the spindle and prevents the slowing down phenomenon. I did mine about a year ago and wonder now why I didn't before. As to what you can turn, anything that'll clear the cross slide and fit between centers. You just have to work more slowly with lighter cuts.

9a's are a small step up from a toy. Sure you can do work on them but they are not meant for heavy work.

Bob Leistner said:

...what is too big? ...

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Does not fit through the door, does not go down the stairs. Requires more electrical power than your location can supply.

Takes up too much room so you can only have that one lathe.....

Where size matters to me is rigidity. One reason a Monarch 12CK is better than a South Bend 13, a 14" clausing etc is the rigidity. Its not just taking a heavy cut, its also vibration.

Tom

I'm not saying that this is true all the time , but sometimes you need to look at it like this .
1 How much does the part cost to buy ?
2 how expreienced al I
3 is this a project that can cause los of limb & or life to myself or others .
4 How experienced am I
5 maybe it does cost alot due to the complextion ( is that a word ) & or the responsibility taken on by the manufacturer of the proiject due to liability .
6 how experienced am I .

sure there are alot of parts that will fit on a 9A & can be made by a 9a , that doesn't mean that they can / should be . I think before you go down the path you should become extremely knowledgeable with the limits of both you & your machine .
there's lot's of ways to fit 10 gallons of crap in a 5 gallon bucket . You must be talking of a pretty small vehicle , a 9" rotor is pretty
small . What is the bed length ? what tooling do you have to start with ?
end of rant
YMMV
animal