How to bisect a piece of round bar

[MadNick]

Hi there,

Ive been pondering this problem.

Say you have a piece of round stock, clamped upright on a milling table. You wish to bisect the bar in order to mill a slot horizontally along the bar.

Say the bar isnt clamped by way of a vice, so you cant come off the inside of the jaws.

How would you do this please?

Nick

[Lew_Merrick_PE]

Nick -- If it isn't clamped in a vise, it is clamped somehow, right?  Otherwise the cutting forces are going to toss it all around!  The thing/set-up clamping your round bar should have a reference surface from which you can measure and adjust your cutter's position, right?

I often have to add Woodruff keyseats to shafts.  I most often mount the shaft on v-blocks that are dialed in on my table (most commonly by setting a precision bar that has been dialed in and then clamping my v-blocks to it) -- which allows me to offset my cutter from the "top" and "side" of the shaft to center my cutter and set my depth of seating cut.  This is the same thing (only different) from what you are looking to do.  ???

[David Jupp]

If precision required isn't high, set up a cutter to just graze the top of the bar (cut a small flat) - if the bar is round the flat will be centred and you can then align your slot cutter to the flat by eye.

If the slot should be along the side - same principal, just graze the bar from the side.

[Fergus OMore]

The crude way is to split it with a pencil and thumb. The next is with a set of jenny leg calipers but the best is to mike the diameter- half it
Make a D Bit( yes, the one that Wongster couldn't fathom) fit it in the mill chuck and zero it in on your x and y axis dials.

You can use a bell punch- I've got one  in my museum for white elephants but who knows where white elephants migrate to.

Incidentally, does anyone know how to retrieve the computer programme- CentreCam using a web cam?

I suspect that my copy is next door to the bell punch

[andyf]

I assume your bar is held in a lathe chuck or similar, so you dont have a reference surface available.  I'm not quite sure what you mean by "bisect the bar to mill a slot horizontally along the bar". Is this going to end up looking like a screw head with a big slot across it?

If so, and if (a) the bar is smallish diameter and (b) you have another piece of the same bar, you could mount the second bit on the mill spindle, bring it down to the piece on the table, and adjust X and Y until you can't feel a ridge at the join. It's surprising how sensitive fingers are, and you can usually get things centred within a thou or so like that. Then lock up the X or Y slide, fit your cutter, and use the other axis to mill the slot.

Andy

[Fergus OMore]

Nick,
        Is this the little spacer on the Kennet?  If so, it is not critical.

Simply put your slot drill in the chuck, touch it, take a reading. Go around to the other side, take a reading and half the difference and get on with the slot. Then  change the cutter- without altering the setting for the wider slot.

It looks more difficult than it is.

Cheers

N

[MadNick]

Thanks Men!

Nick

[mattinker]

Incidentally, does anyone know how to retrieve the computer programme- CentreCam using a web cam?

I suspect that my copy is next door to the bell punch

I did a web search for centrecam and got http://www.miketreth.mistral.co.uk/centrecam.htm Which is the right link for it!

Regards, Matthew