Wobbler, dunno?

[neksmerj]

Dear Members,

What is this thing called? Recently I saw this jigger mounted up into a mill chuck. Basically it was a centre finder, and when brought down into contact with a centre punch mark, in the work piece, it stopped wobbling when it was exactly centred on the mark.

I want to make one, or at least know what it's called and where I get one. Any clues?

Start typing now, I'm impatient.

Regards,

Ken

[Grahame Collins]

How is this?

http://home.iprimus.com.au/stevor/millingtools1.htm

http://home.iprimus.com.au/stevor/lathetools.htm

Grahame

[tomhowell]

Having looked at Grahame's links in iprimus, that gizmo looks mighty swish & very impressive.

But as an experienced machinist, I can't help but wonder why you'd need it at all if you actually have a centre punch mark on the job?
If you did, why not just use the lathe tool or tailstock centre to set up to the centre punch mark?.
If you used the tool you could scratch the job once you were close & verify that you were centred by ensuring you weren't scribing a circle at all.

As for a milling machine, if you want to line the centre of the spindle with a centre punch mark, why not just turn up a pointer to fit into the mill's taper & do much the same thing?

Are you looking to ensure a super accurate distance between two holes?
Say for some sort of tooling (punch or press tooling), or shaft centre disances for a gear drive?

If you were after that result, I'd suggest centre punching the position of one hole & getting close to that by the pointer I mentioned above.
Lock the table in place X & Y directions (traverse in the flat plane)
Bore your hole to finished size, unlock the table & move in the right direction to the position of you next hole. If you step the distance off with the dial indicator as well, all the more accurate, but using the dials on your mill should suffice.

Obviously you'd need to set the centreline of the two holes up with the axis of travel of the mill table.
Again the ponter comes in handy for this.

Is this any use?
Was the above covering the kind of stuff you want to do?
If not maybe you could fill me in some more?

good luck

Tom

[JTonks]

When I was working as a machinist, if I had something to set up in a 4 jaw chuck to a centre punch hole, I would sharpen a bit of 3mm rod at least 300mm long(usually a welding rod) to a point, mount that in a chuck in the tailstock and engage the point in the centre punch mark.

Spin the 4 jaw chuck, the rod wobbles. You can then either put a dial indicator on the "wobbler" or just do it by eye. Pretty simple and accurate enough for any thing marked out and centre punched.

For accurately positioning holes on the mill, I would put a bit of 10mm bar in the chuck or collets, touch the edge of the job then use the XY table to position the hole, taking into account the diameter of rod.

Hope this is of some use

John

[neksmerj]

Thanks Grahame, Tom & John.

All comments are taken on board. In the finish, I used a "pointed stick" to find the centre punck mark, by eye. It was good enough.

Regards,

Ken