Drill Head for ShopBot?

[chris_ma]

I want to use a ShopBot for drilling holes in thin aluminum. I need the drill head (with drill chuck) to turn about 1000-2000 rpm. ShopBot doesnt have a head for such an application and doesnt have any suggestions. Anyone out there have any ideas? I want to hold the +/-.005" positional accuracy for the holes.

[grandpas@ix.netcom.com]

I use a Milwaukee core drill attached to the z axis. Speed is only 600 rpm. Normally considered a mag drill. it had a steel mounting bracket. You have to rewire to standard plug from control box plug. thakes 5 minutes and their tech support will tell you how. e-mail me off line and i will send you a picture of my set-up. Although I'm drilling hardwoods , it works just fine. Dust collector this week has a bag full of holes.

[stickman]

Is anyone using the Shopbot to Line bore 5mm holes along the entire length of a 96" x 14" cabinet side? Or something along this lines? How long does it take? Do you feel its work the time spent on the machine?

[Brady Watson]

Jay,
Although I haven't used it for cabinet holes, I have used it for drilling lots of 1/8" holes for a long diffuser. If you keep your safe Z height at .2", drilling is very quick and efficient. If you have a spindle, run the RPM down around 5,000. If you run a standard router, you should move a little bit quicker in the Z speed to avoid burning from tool dwell...and don't use a drill bit...since they are not rated for 10,000 RPM.

-Brady

[bleeth]

Jay:
You can get a 5mm straight bit made for cutting and do all your drilling and rabbeting/dadoing and then cut the panel out without a tool change. Definitely worth it.
Dave

[gerald_d]

Brady, where did you see that 5mm drill bits are not rated for 10,000 RPM?

[Brady Watson]

Gerald,
*most* drill bits, unless stub-length, are not rated for speeds over 6,000 RPM. Not sure how things are rated on that side of the lake...but be sure to read the recommended RPM for the tool before assuming that it is good to 10k. Drill bits are made for drills...duh!


5mm end mills of course are a different story...they are shorter and probably exibit less vibration and runout than a standard length drill.

-Brady

[gerald_d]

Brady, I will ignore the condescending part of your reply. Can you please provide a link to an authoritive source for the max speed of drills?

Drills and router bits are made of similar materials. Their resistance to breaking should therefore be similar - and this is also my experience. The chances of breaking both a drill and a router bit increase dramatically with the protrusion length and side-load. Since side-load is absent with drilling, I find that I can allow drills to protrude further out of the collet. However, I am always mindful that a longer protrusion makes a bigger projectile when it might snap - this is no different to using router bits.

The bottom line is that I can see no reason why a router bit should do a better job of drilling than a drill - in fact, my experience tells me that drills do a better job of drilling. (We have to compare apples with apples, and be sure that we are talking of good quality bits from reputable suppliers).

For shallow 5mm holes into MDF I would use this drill (http://www.somta.co.za/dri/151.htm) at over 20,000 RPM. I would like to see where it is recommended that I must keep below 10,000 or 6,000 RPM?

[stickman]

Where is a good source of 5mm bits. I have seen drill point bits for Blum machinery with a 10 mm shank, which converts to 3/8" shank?

MCLS has upcut router bits at 7/32" which is just a little oversized for 5mm.

[mrdovey]

I use my machine as a CNC drill fairly regularly. If/when I don't have a bit of the size I want, I use the next smallest bit that I do have, and move it in a circular or spiral path to cut the hole (I posted an inside -> outside spiral tool path a while back illustrating how I do it.) I've only broken one bit drilling this way; and that happened because I hadn't yet figured out how deep I could cut in a single pass without stressing the bit beyond what it was willing to tolerate.

BTW when my one broken bit snapped, the loose part was left sitting in the partially "drilled" hole.

[harold_weber]

Regarding twist drill recommended speeds for drilling wood:

A quick search uncovered this page from this manufacturer,

michigandrill.com/tech/twist_drills/speeds.php

who says on the above page:

1. recommended surface feet per minute (SFM) when drilling wood ranges from 300 to 400

2. A formula to convert SFM to RPM is: 3.8 times SFM / drill diameter in inches

3. Using this formula, we get for a 5 mm (0.2 inches) drill and 400 SFM a recommended speed of 7600 RPM.

Anyone else have any manufacturer's recommendations they wish to share??

[fleinbach]

I found the following sites containing charts for drill speeds. The first one amazed me. I didn't know there where motors that could spin that fast.

DIAMETER/ RECOMMENDED RPM'S

.001” to .004” / 300,000 to 450,000
.005” to .015” / 65,000 to 150,00
.016” to .030” / 30,00 to 65,000
.031” to .090” / 9,000 to 30,000
1/8” (3.18mm) / 2,500
You need to scrol half way down the page to see the chart
http://www.ukam.com/drilling_recommendations.htm

http://www.lawsonproducts.com/website/main.nsf/html/Products~Literature~Drilling_Speed_Table/File/E-132.pdf

http://www.chipblaster.com/Tech/DrillFS/CastIron.htm

[bruce_clark]

Frank,

Some of the those dental "drills" are 100K+ rpm, and that is why they make that distinct noise.

Also, most of the drills that spin that fast are actually air turbines, not really "motors" in the sense that most people are familiar with. NSK does make some fairly large "air routers" motors that spin 50K+rpm and are quite large in rated HP (~1/4 HP) but require a 10+ HP air compressor to run, so technically, they are pretty inefficient.

Anyways, more that you wanted to know.

Bruce Clark

[bleeth]

Jay: Here's an onsrud you can order that is decently priced and made:
http://www.toolsxp.com/on57-400d.asp

Dave