Cutting a perfect circle out of square steel

[Ulma Doctor]

there is this kind of tool:

 

[caster]

Depending how accurate you need to be, here is how I center in a 4 jaw. I find the center of my work piece and center punch it. I mount and eyeball center it in the 4 jaw. I mount a drill chuck on the tail stock and place a wiggler in it. I bring the tail stock close to the work so the wiggler can touch the center punched ding. I then use an indicator touching the wiggler and center the work by centering the wiggler. This can bring you within a thou. So how accurate do you need to be?

Caster

 

[little_sparky]

Depending how accurate you need to be, here is how I center in a 4 jaw. I find the center of my work piece and center punch it. I mount and eyeball center it in the 4 jaw. I mount a drill chuck on the tail stock and place a wiggler in it. I bring the tail stock close to the work so the wiggler can touch the center punched ding. I then use an indicator touching the wiggler and center the work by centering the wiggler. This can bring you within a thou. So how accurate do you need to be?

Caster

It is for a wheel hub, so I want as little wobble as I can, but I reckon my wheels or axle or something will be out more than that so that method should be just fine I think, maybe even more than fine, could almost call it perfect! Thank you for your answer Caster

Little_sparky

 

[kd4gij]

If you don't have a band saw. You could layout the circle then chain drill around the outside and rough cut it with a jigsaw. Then drill center and mount on an arbor and turn in the lathe.

 

[kwoodhands]

Hello all,

I was just wondering how I would go about cutting out some perfect circles from about 10-15mm thick cold rolled mild steel. I have a fair few basic tools, like all hand tools and grinders and a lathe but I don't have a mill or CNC machine.

The purpose for this is for a hub I am creating to put onto a custom made axle and wheels.

Here is a link to my thread about creating and strengthening the wheels/axle, and page 2 has a drawing of how I am thinking of doing the set-up, although I will post pics very soon,
http://www.hobby-machinist.com/showthread.php/31010-Beefing-up-an-axle-what-methods-could-i-use

Thanks, little_sparky

Find center and bore slightly with a spotting or center drill. Mount on face plate with spacers. Install a center in the tailstock. Bring center up to center hole and move the work so the center pushes against the bored hole. This will aid in centering the stock. Clamp the work to the face plate in areas away from the trepanned cut.
Back the tail stock off and install a parting tool in the tool holder. Lock the saddle and locate exact perimeter of the cut.
Now you can begin parting the circle. If the work needs any holes ,then add a temporary bolt in the piece to keep it from falling out after the trepanned cut is done.
Go slow and use plenty of oil. If the perimeter has to be within .001 or closer then it would pay to trepan a few thousands oversize and the turn to exact dimension the usual way.
For me this is easier and faster than interrupted cuts.
mike

 

[larry4406]

About 7 years ago I built a rotisserie for my car body. I need to make indexing spindles. I did not have lathe at that time. I drilled center holes thru the plate, tapped a piece of steel for a spindle bolt for the stock to spin on, used a cutting torch that was bolted down, and cut the discs like a phonograph.