What Size Lathe Do I Need?
As a hobby, I rebuild and modify automotive cylinder heads. I'm looking to buy a lathe to make custom valve seat inserts and various jigs and fixtures for my vertical mill and head and block surfacer.
I suspect a small bench lathe can easily handle reducing the OD and enlarging the ID of valve seat inserts up to 2.25" or 2.50" OD?
However, I want to make some fixtures that would use short pieces (4" or 5" long) of 2" solid bar stock that would need to be faced, bored, or reduced slightly. So my question is, would a 9" or 10" bench lathe do the job? What about belt drive vs gear? I can't justify spending a lot of money but want to make sure I buy something that will do the job.
Your input and suggestions are appreciated.
Without opening a can of worms on brand and size; As long as your lathe has a 6" chuck, you should be able to handle 2.5" stock with no problems. Be aware that 2.5" stock will not go through the chuck but you can "clamp" it.
I can get 2.5" stock chucked-up in my 4" but I have to change the jaws and use the "steps" with a live center and/or a rest. It's no big deal just an extra step(s) on the small lathe. I do like the small lathe for valve inserts, guides, etc. Also... You do know that you can get insert stock from the local auto machine shops, don't you? Saves having to bore and cut expensive solid stock.
CCWKEN, yes, I do know you can buy manufactured seat ring inserts. In fact, that's how I would customize the size. I'd take an insert a little larger and cut it down to the desired fit.
If I wanted to make a special size by taking solid stock and boring the center, would a 9" or 10" lathe have the power and ability to do that?
What about internal threading?
I believe the 10" lathes would suit your needs quite well. A 10x24 lathe is a nice size lathe for a small shop or for home shop use and they are not real expensive. In the Tech. school that I attended, we had two 10" South Bends and all of the class projects were completed on those lathes as well as the larger lathes that were available. Both lathes were belt drive, one was a "V" belt drive bench model and one was a flat belt drive floor model. The difference between using a 10" lathe and say the 15" lathe that I preferred was speed. You are not going to cut as much metal as fast on the smaller lathe. As far as internal threading, there won't be any difference since you are not taking any heavy cuts when threading.
I will say that if you could swing it, a 12" lathe will give you a larger hole through the spindle and will accommodate 5C collets.
You should have no problems with a 9 or 10" swing lathe. I do most of my "fine" work on a HF 7x10. Before I got other equipment, I was even boring babbitt ROD bearings with it. (Old engines)
The larger the machine, the more you'll find to do with it, so plan ahead and get the largest you can afford or fit into the space. My third lathe will have at least a 14" swing.
The biggest and finest equipment won't make up for poor craftsmanship. Master your tools and you can do anything.
The larger the machine, the larger the bearings, the larger the chuck the more runout (error) you can expect. Why toolroom lathes are not that large I suspect.
Especially a cheaper machine or one that runs in babbit or bushings. I have saw a few you could lift the chuck 1/4".. (shot out)
I have this perfect lathe for you, a 24" cincinnatti model, only weighs ten tons or so. You can chuck car wheels in it.
Actually, my old leblond w/10" chuck sounds like you described you want for valve inserts. But I ain't giving it up for love or money. I ain't got the only one they made thou. I paid $700 for it.
Anytime you even come near anything automotive the size of the lathe aoutmatically jumps to 17" so you can machine clutches and flywheels. You can do anything on a 17" lathe as accurately as any 6" or 10" lathe.
I used to hold 0.0005" on a 48" American (yeah, I know, but it was a 100mm bearing bore is a large out of balance part).
So my advice to anyone is get as large a lathe capable of 1500 RPM as you can fit in your shop. You'll never regret owning a lathe a bit larger than you actually need but too small a lathe is always too small and leads to fits of frustration where stuff gets broken.
Thanks for the input everyone.
I was originally thinking about buying a new grizzley 9"x19" or 11"x26"(they call it light duty) or a Jet 9"x20". But based on your comments and reviewing some archive messages on lathes, they might not be a good choice. A older american made lathe in the 10" or 11" range may make the most sense if I can find one in good shape.
If anyone disagrees with my conclusion, please speak up.
Forrest Addy has given you the best advice you are going to get on this subject. You can do the small job on a large lathe far better than you can do the big job on a machine too small. Forrest, the 48" American I ran years ago was at Portsmouth Naval Yards.