Turning thin material question

[Schmitz08]

Hi everybody. I have a question for you that may be simple but gives me (as a beginner) some problems. I am currently working on a 3/4 inch flywheel for a small steam engine. After turning it on my 7x14 inch lathe I took it out of the chuck to drill an off centre hole. Now I want to make some adjustments but can't get it squared in my chuck again (see attachment). It always seems to wobble a bit.

Do you have some suggestions or tips? How do you get it perpendicular?

Thank you for your comments.

Greetings from Holland

Hans

 

[cl350rr]

place a couple of square HSS tool blanks (or some other square, flat object) across the chuck behind the piece you are trying to grip. tighten the chuck while pressing in on the flywheel to keep it square. remove the tool blanks when the chuck has the flywheel securely and before you turn on the lathe. I keep a couple of each size of HSS tool blanks around on the bench just for this purpose.

HSS: High Speed Steel

HH

R

 

[Tin Falcon]

If the faces are parallel you may be able to place parallels behind the part to get it square. Remove them before turning on the lathe.
the more accurate way is to indicate in the face. Use a dial test indicator against the face. Snug up the chuck. Tap the face with a soft face hammer to push down the high side. an Aluminum wedge behind the part and a little tap to bring up the low spots.
Tin Falcon

 

[Schmitz08]

Thank you for your replies. I tried to get it square by using the method with the parallels, but it did not work to well. The backside of the flywheel has a little bump in the middle so the wheel does not drag. That makes getting it square more difficult.

It is quite a small piece so I have to place it on the far ends (tips) of the chuck jaws. It's kind of difficult to get it firmly gripped without damaging the workpiece. I also want it protruding a bit so I do not touch the jaws with my cutting tool when I'm facing the part, leaving even less material to grab. Do you use other methods to hold small parts? May with a thorn or something?

Hans

 

[Tin Falcon]

what is the head stock taper of your lathe if it has a 3MT taper you can get a collet adapter and a 3c pot chuck. another option i a chuck with soft jaws.
pot chucks and soft jaws are designed to be machined to fit your parts.
here is what a pot chuck looks like

Tin
PS now I see you have a 7 x14 . Littlemachineshop.com in the US has collet adapters.
Tools for cheap, has pot chucks
http://cgi.ebay.com/NEW-3C-3-STEP-POT-COLLET-CHUCK-SOUTH-BEND-9-LATHE-/400119405488?pt=LH_DefaultDomain_0&hash=item5d28f99bb0


POI place a set of shims in the slots of the chuck tighten it down then machine to size.

 

[Peter.]

For this I use a small bearing fixed to a piece of flat bar held in my toolpost. Bring it up to the work so that the bearing rolls against the face of your flywheel. A little bit of pressure against the face of the work and it will run true.

You could even use the back-end of your insert tool holder if you only grip the flywheel very lighty, it shouldn't mark it.

 

[mklotz]

Another effective solution to problems like this is a chuck spider. I described the one I built in this thread...

http://www.homemodelenginemachinist.com/index.php?topic=1235.msg8925#msg8925

 

[Ken I]

I normally grip the work very lightly in the chuck and run the lathe in reverse and bring a carbide cutter to bear against it (nice and square to the job and gently does it) this squares it up nicely.

It doesn't cut - just rubs - and doesn't mark the work. Sometimes you need to further tighten the chuck and repeat.

Then fully tighten the chuck.

In Peter's post earlies he suggests much the same thing using a roller or the butt end of a tool shank - all these methods work.

Ken

 

[SBWHART]

You can fix a back stop in the chuck face the back stop off square first then press the work up hard against it face it off or do what's required it can't help coming out correct, like this

Another way is to get hold of some soft jaws for your chuck bore a small step take the work and away you go.


Stew

 

[Schmitz08]

Thank you very much for all of your tips and tricks. I will try them all and select the best suited.
I'm glad so many people are willing to help a beginner like me. It's a great hobby! ;D

Happy new year everyone.

Hans