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Lee Roberts
22-06-2008, 11:50 AM
Hi, i have recently recived some center drill bits as recomended by another member, i know what they are and how to use them.

I was just wondering if anyone had any advice or Tip when using them, i have been using them to make nema 23 motor mounts for my cnc machine:

http://www.mycncuk.com/forums/photoplog/images/2/medium/1_DSC05057.JPG

Lee Roberts
22-06-2008, 11:52 AM
Sorry kip i hit the wrong button, kips posts are below:


Be careful when using small ones on hardened steel...they break!

And use a scriber rather than a marker pen as it's better for accuracy and never rely on a piece of metal being "square" when marking out.... :D

Lee Roberts
22-06-2008, 11:57 AM
Yes it did take me a few go's to get the holes right, i managed to get the holes close enuff that i could then file out a small amount so my screws would line up with the motors.

Now i have a template i just use that to make/mark out new plates and so on:

http://www.mycncuk.com/forums/photoplog/images/2/medium/1_DSC05172.JPG

Robin Hewitt
23-06-2008, 01:48 PM
There are some really naff centre drills around, regular PITA when they snap off. I got some cheap, centred 2 holes then lobbed the lot straight in the bin.

Caveat emptor, I've gone back to Plan A, don't use anything but Dormer :D

Lee Roberts
23-06-2008, 01:49 PM
I have a quick bodge/cludge for marking out...Draw the part in CAD and then print it 1:1 and just centre punch through the paper :toot: :D Works a treat ;)

Thanks kip i didnt think of that, i'v downloaded the file ill take a look soon !

Lee Roberts
23-06-2008, 01:55 PM
There are some really naff centre drills around, regular PITA when they snap off. I got some cheap, centred 2 holes then lobbed the lot straight in the bin.

Caveat emptor, I've gone back to Plan A, don't use anything but Dormer :D


I got mine from ebay, dont think they cost much more then 10. I take my time with them and they seem to be ok, now i think just a small drill bit would have more then likly done the trick anyway :)

CM

Robin Hewitt
23-06-2008, 03:20 PM
i managed to get the holes close enuff that i could then file out a small amount so my screws would line up with the motors.

You really need CNC it makes it so easy and everything lines up just perfect. No more swapping centre drill then bit then countersink/bore on every hole :D

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.

Lee Roberts
23-06-2008, 11:23 PM
:) now i can mount my motors, my machine can move/work, guess what i will e making with my machine once its up and running :D

Robin Hewitt
24-06-2008, 12:54 AM
:) now i can mount my motors, my machine can move/work, guess what i will e making with my machine once its up and running :D

First thing I made when I got my mill CNC'd was a suds pump :D

Lee Roberts
24-06-2008, 05:20 PM
First thing I made when I got my mill CNC'd was a suds pump :D

Yea i was thinking i'm gonna need to keep things cool if i'm doing ali cuts ? i was thinking of having a vac to clear the "chips" and my compressor blowing to keep the cutter cool ?

Have you got any pics of your pump?, this cnc stuff is leading me into so many "new area's" of making things so on, i love it i wish i had tuned in at school and gone down this path for a career.

Cheers,
Lee

Robin Hewitt
24-06-2008, 11:55 PM
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
30-06-2008, 12:39 PM
Would be nice to see some pics if you get a chance Robin, will defo come back to this at some point.

Robin Hewitt
06-07-2008, 01:00 AM
FWIW, a picture :D

Lee Roberts
07-07-2008, 08:48 PM
Now that looks KOOL !

Robin Hewitt
08-07-2008, 03:36 PM
Now that looks KOOL !

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

Hogout
14-05-2009, 10:53 AM
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
14-05-2009, 01:56 PM
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 :beer:

Robin

John S
14-05-2009, 02:24 PM
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
14-05-2009, 04:13 PM
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 :rolleyes:

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 :beer:

Robin

Hogout
14-05-2009, 06:34 PM
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.

bogstandard
24-03-2010, 09:38 AM
About the cheapest spot drills in the UK I have found are here. Put a search in for all diameters and go to the bottom of the second page then the third.

http://www.engineeringsupplies.co.uk/drilling-c-160.html?9=172&10=&11=192&12=&13=

They are very good quality, both the Cobalt and Carbide, and if not really abused, should last almost forever. For 20 to 30 you can kit yourself out with a decent range of sizes and angles up to 8mm, over that, as in all places, they get expensive.

I tend to use the 120 degree ones, as that almost matches the standard grind of a normal twist drill of 118 degs. For holes that have a countersink requirement, I use the larger 90 degree ones to do the countersink first, then drill down with a normal drill from that, two ops in one.

Hope this helps

Bogs

alan2525
07-04-2010, 03:12 PM
Caveat emptor, I've gone back to Plan A, don't use anything but Dormer :D

Dormer aren't what they used to be...I picked up a set of drills, made in Mexico of all places. Drilled a hole in a piece of 1/4" mild steel and managed to snap a brand new 10mm drill bit straight in half with just the torque from a cordless drill and in a hand tightened QR chuck too!

That's the first time I've ever managed to break a drill over about 4mm in diameter!

Complete carp!