Anyone ever turn down a boring bar?

Back to the original question. My lathe came with a set of boring bars from 3/16 OD to 7/16 OD. They use a 1/8 round HSS tool bit. The set included two small v blocks that fit the lantern tool post that came with the lathe. I have only used the 7/16 OD boring bar. It has a lot of spring. And I mean a lot of spring. For example if I try to take a .010 cut with the 7/16 BB the actual cut is .005, maybe .006. The smallest hole I have been able to slip the 7/16 BB into is 5/8 ID. I don't have a 9/16 drill. It might fit into a 9/16 ID hole. It won't fit in a 1/2 ID hole. Based on my very limited experience I think that you could clean up a drilled hole taking very light cuts. Remember that a drill cuts a slightly larger hole than the size of the drill. Back to your 9/16 example you would probably need to drill a 1/2 or maybe 17/32 hole to end up with a 9/16 hole.

X2 on the 4 way tool post holder. Also the norman style qctp was designed in either the late 1800's or early 1900's. That's still pretty old school.


A .010 cut should be fine with a 7/16 bar. How much stick out do you have. To get that much spring I would suspect one of a few possible problems. Not enough clearance, a cutter that is not sharp, too big a radius, cutter not on centre line, Too much stick out, poorly supported and clamped bar. Have you checked all these things. Some photos might help.
 
Hi and welcome to the forum.

I was gifted a bunch of reamers so I didn't have to spend the $$ on them. I don't think I would want to trade them for boring bars though, two different tools. Yes it is possible to get very precise hole sizes with a boring bar, but a reamer does it in one pass. I would think reamers are sufficiently "old school" and would have been used back in the day as it were.

I would highly recommend the OP find the lathe he is planning on working with and try for one that comes with some tooling included. Once we know what machine you're talking about and the particular job involved it's much easier to give solid advice. I've found that adding a variable speed motor and QCTP have made my 100-year-old lathe far more functional and I'm pretty sure that the original owner would have agreed. I use both carbide and HSS tools and find that each has their place, also many things we think of as modern do go back quite a while.

I love watching Roy Underhill in "The Woodwright's Shop" on PBS and marvel at some of the things people were able to do hundreds of years ago. Modern blacksmiths practice many ancient arts with metal as well, and I know we have a few members who operate line shaft shops so there's plenty of "old school" knowledge still out there.

Get yourself some "old iron" and start making chips....


Cheers,

John
 
Thanks for all of the advice. It's appreciated!

I'm still using a imaginary 9" south bend until I can source one. Lol There's what looks like a Heavy 10 for sale near me but that's it for now. https://rochester.craigslist.org/tls/d/mumford-metal-lathe/7043653695.html

For those that have not looked at a piece of merchandise far away in a craigs list ad, be aware that the sellers usually misrepresent the condition and don't care what so every if you have to travel a long ways. My own policy is I won't travel far to look at some thing because I wasted enough time and gas to build the stereotype that craigs list sellers are liars.Lol.

As far as bench grinders go I was trying to find a 6" that has a narrow motor and good rests on it that is priced for the home shop. The issue here is that all of the 6" I can find that have a narrow motor housing are under 1/2 hp. Here's a dayton that is a 8" and does not look massive. https://www.grainger.com/product/DAYTON-8-Bench-Grinder-467L84 Seeing the 8" Delta in person at lowes was intimidating. Lol. If my 4 1/2" hand held grinder will take a lot of metal off pretty fast ,why do I need a 3/4 bench grinder? Dewalt has a 6" with good specs but the motor housing is big. I'll keep searching the net though. I'll most likely get the dayton because its about as heavy as a 1/2 hp 6".
 
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A boring bar should take whatever cut is dialed in . You're L over D is the limiting factor when it comes to spring in the bar . The problem with very small bars lies within the SSPM , as most smaller lathes aren't capable of 10,000 rpm .
 
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