Thread: How to hold a disk for machining

I need to hold a 200mm disk and machine both sides - one side flat and the other like in the photo. Another will be made with the male projection for the circular registration.

I will get the blank disks laser cut 205 by 16mm from plate and can have a few spot holes done to help in set up.

I have a 12 by 36 lathe and the faceplate is the only thing big enough to hold it.

What is the best way to fit this up to machine the face and edge and also any tricks to remounting on the opposite face to machine that flat?

I don't mind a couple of tapped holes in the part if this makes it easier.

Thanks

I would think if you could Tap at least 2 holes the more the better,depending on what your face plate is like would be the easiest set up in your situation.
Would go for a 12mm fine thread or 1/2"UNF.

Would have some parrallel packers to put between your job and Face Plate when you turn it over.

I would initially find the Centre and scribe a Diameter to set up to if you might be concerned about the concentricity of the plate after being cut,other wise just set it up the best you can to the OD,you have 5mm to play with.

Would Face first and turn the OD till it was cutting all the way around.
Then remove and mount back up to your Face Plate using the machined OD to set up to.

You would need to make sure your packers give you enough clearence to Drill and Bore your centre hole if the Face Plates centre hole is not big enough.

Now should only be a matter of finish machine to size.

pipeclay's method would be the easiest, but if you didn't have a face plate or your faceplate was not big enough or if the job couldn't have holes drilled in it etc, another way would be to tack a short length of 60 - 75 dia pipe ( or bar, pipe just makes it easier to bore the id) to one side and grab that in the 4 jaw. then do all the turning you need on the front, also if possible face a little bit of the back face.
(boring bar with removable HSS bit, held parallel to spindle but on the side of the toolpost closest to the front of the machine. grind up a left hand bit and fit to bar so it cuts the back face.)
Once thats all done grind the tacks away and remove the pipe. If your four jaw is big enough , reverse the jaws and set the job up to face the unturned face. You can set up to the small bit of the back face that you turned in the first setup.
If your 4 jaw is not big enough you can turn a stub mandrel that your plate would just fit on, drilled and tapped in the centre for a bolt and use a tapered bung with a bolt to hold the plate for the final facing cuts. (the bung is so you can pull the plate up tight on the mandrel and still take a full facing cut)
I have used this method to make an adapter to fit old style VW wheels with the large PCD to a modern wheel balancer so that the wheels could be balanced.

regards

bollie7

I recently did something similar whilst making a dividing plate



I did most of the work on the faceplate with a 19mm plywood disk mounted on it, with another smaller plywood disk putting pressure on it via the live centre in the tailstock.

Thanks appreciate the advice.

Fred
I give up, what is the tool hanging on the wall behind the lathe. Top right of pic. Its green, with a handle on it, looks like it is fairly large in Dia.?

I'm guessing its some sort of wood working tool, but I have no idea what.

regards
bollie7

My first thought was to make a mandrel and bolt the disc to that, seeing as you want a hole in the centre anyway. You then just hold the mandrel in the chuck and machine away.

Sterob

Thanks Steve,
I'll more than likely go with the faceplate but have changed my material to aluminum now. It is for a swivel so I can run a high speed spindle as well as small milling head (X2). The steel was going to add too much weight so I'll try ally first. I have some 25mm plate and 40mm plate to choose from.
I am thinking of cutting the disk on a rotary table on the mill first before I go to the lathe.