Newbie help hole boring

[spluppit]

If you have a 4 jaw chuck use it! You have a lot of extension from the chuck this will do you no favours at all. A 4 jaw will give you a LOT more rigidity. It's hard for anyone to categorically say what is the problem without being in front of the machine once all the basics have been covered. It may well be you are just reaching the limit of rigidity of the machine with the work length you have. The machine will have a limit like all machines.

I would do as has been suggested and use a hss boring bar you do not need to buy anything, they are easy to make. You can use a bit of mild steel with a drilled and reamed hole in the end set at 45 deg or 90 deg for a through hole and a grub screw, insert a bit of Hss and grind with a decent amount of top rake as you having problems, i would suggest about 20 deg to start. High rake will help in this situation as it reduces the shear load. This kind of home made bar works very well in difficult situation and works in a contrary fashion to the reasons explained about rigidity. I do not agree a solid carbide boring bar will help on a manual machine. As long as the bar is strong enough to do the job and resist the cutting force and being mild steel this means it has properties to absorb shock because mild steel En3b or even En1a these material are ductile, ductile materials absorb shock and dampen and all you guys know what that means to a machine tool. Harder materials tend to and will resonate more.

This sounds crazy i know but logic dictates this when you think about it. There is not a comparison using these kind of carbide tools on small machines compared to what carbide is generally designed for which is pressure cutting. This works fantastically on the right machines but not all, and manual not being one of them generally speaking when problems are arising such as you are experiencing now. It's the wrong tool for the job on a baby machine..... as you are probably working out or will soon find out.

You also need to learn how to grind tools if you own a small lathe and you don't know how. It's a vital skill you can not be without. Plenty of advice is available on that subject.... but its often overly complicated on the internet. A properly ground tool with no honing or stoning will give a very good finish if done correctly.

Good luck.