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Mr Fixit
12-09-2013, 04:00 PM
Hello Group,
I need help in setting up a 4"x1/4" disk that I have trued up on the lathe and drilled a 1-1/2" hole in the center ( the largest I have ) after using a 3/8" bolt hole as my first setup. I need to bore a 2" hole in the center and feel the hole saw and my setup in the drill press is not as centered as it could be, so I need to reference the outside edge of the disk. In setting up the 4 jaw chuck where do I measure and adjust a the same time? I have U Tube 4 jaw setups and get the idea for stock in the center but where do I go for the OD of my disk?

Tx Mr fixit for the family
Chris ☺

Richard P Wilson
12-09-2013, 04:08 PM
Why not use the reverse jaws in the 3 jaw? It should be accurate to around .002", loads better than the drill press/hole saw set up you mentioned, and there is no need indicate the OD of the plate when setting up.

Richard

basalt
12-09-2013, 04:18 PM
You can use the outside of each jaw, or go beside each jaw using a dial indicator. After centering you could go to any 3 or 4 spots on the OD of the disk and if they are equal you are centered.
Alternatively, you can just grab the disk in the 4 jaw, put the dial indicator in the drill chuck with the point in between the jaws--then tap the chuck around until it is centred beneath the drill spindle and clamp it down. The work doesn't have to be exactly centred in the chuck just don't bore thru into the jaws or the chuck.

jlevie
12-09-2013, 06:17 PM
You can use the outside of each jaw, or go beside each jaw using a dial indicator.
It would be better, and more accurate, to use the inside of jaws as they are touching the disk. You'll want to use a Test Indicator for this.

By now you have probably figured out that you are making the part backwards. The rough blank should have been put in the 4 jaw and bored. Then the rim trued. I'd turn a stepped plug with the minor diameter 0.0002" or so less than the bore and friction drive the plate.

Jaakko Fagerlund
12-09-2013, 06:23 PM
Grab from the outside diameter so that a few mm's are left out of the jaws so you can put a DTI on it to get it centered.

Edit to add: When you first mount it, tap it into axial alignment first with the DTI against the disc face.

Mr Fixit
12-09-2013, 09:32 PM
Richard, I tried that but my 3 jaw is not big enough to accommodate it the jaws fell out. Jlevie you are correct I did do it backwards but I had to because it was cut from a larger sheet of steel with a torch fun you say not quite round.Jaakko I did as you suggested on the face and it worked ok, but I then was not comfortable with so little holding it in the jaw's so I used my 1" dial indicator and lifted the plunger as each jaw passed, this let me get it dialed right in.

Tx for all the suggestions
Mr fixit for the family
Chris ☺

jlevie
12-09-2013, 10:36 PM
Jlevie you are correct I did do it backwards but I had to because it was cut from a larger sheet of steel with a torch fun you say not quite round.
The out of round doesn't matter with a 4 jaw chuck. Well if not approximating a circle, you go the the grinder and make it so. Scribe a circle of the desired diameter on the plate and adjust the chuck until that runs visually true. Then bore and so forth.