Center Drill Bits

[Robin Hewitt]

Have you got any pics of your pump

I have the working drawing if that's any good, the pump is up at my shop.

That's a 40mm impeller, (I just happenned to have some 40mm diam polyurethane)

I drive it with a DC motor through a variable voltage regulator, that way I get to adjust the flow using a pot on the front of the machine. Works good :D

[Lee Roberts]

Would be nice to see some pics if you get a chance Robin, will defo come back to this at some point.

[Robin Hewitt]

FWIW, a picture :D

[Lee Roberts]

Now that looks KOOL !

[Robin Hewitt]

Now that looks KOOL !

Maybe that's why it's called koolant? :D

[Hogout]

I draw everything with AutoCad, convert the milling to G code and overlay the .dxf file on the cut file. Then I can use the "Move to hole" feature which puts me on the hole nearest the mouse.

Hi Robin,

Can you share some more info on this process?

Cheers.

[Robin Hewitt]

Can you share some more info on this process?

It's home brewed software that pumps Gcode out to the parallel port as steps.

It is a bit simple minded when it comes to arcs and you have to boot DOS so it has full control of the timer interrupt, but you are welcome to a copy if insane enough

Robin

[John S]

Forget centre drills, they are a throwback to earlier days and were designed for putting in the support holes for centres on lathes, hence the name.

No commercial CNC shop would dream of using centre drills today, instead using what are called NC spotting drills.

These are very stiff short fluted drills that will start a hole off without wander and not break like the flimsy centre drills.

Nearly the same results can be obtained using a good quality stub drill.

John S.

[Robin Hewitt]

Forget centre drills,

And avoid "UK Drills" on ebay.

I bought £30 worth of cheap Jobbers bits, the first two I tried broke almost instantaneously, the rest followed them quickly in to the bin

Hi Kip

My Z axis is delayed. First I'm remaking my standoffs for the milling table. The previous set was too clever, interchangeable bolt holes in different sizes. I soon lost precision.

This time I'm making 20 in 5 different threads, all cut from the same 3/4" thick steel bar and all 3/4" thick

Robin

[Hogout]

Forget centre drills, they are a throwback to earlier days...... instead using what are called NC spotting drills.

John,

I have looked at the webpages of the usual suspects but none mention 'spotting drills' only centre drills. Do you have a source?

Cheers.