Countersink

[MogulTx]

Guys,

I need to do a countersink in 6061 aluminum. I am going to be limited in the way it is cut and the bits I can use, because it will be such a dense material. I don't know how to do it... I thought maybe I would do a 2 rail sweep, but I don't know how I can ensure I get the exact angle and depth. ( I have to admit that I do a fair amount of 2D, but not 3D- so I am a bit stumped..

Can one of you folks give me an idea of how to attack the programming for this?

I have to do a countersink that is .35" diameter at the surface, descending at an angle for the screw head down to .21" inner diameter. (...need to check depth to calculate exact angle). I have end mills, so I may have to clean up manually after cutting- which I am fine with. My smallest appropriate end mill is 1/16". I do have some ball nose, but I don't know that they would be appropriate for aluminum.

I will also go out and search for tutorials...


Thanks for any suggestions...

Monty

[MogulTx]

Did not find programming suggestions or tutorials on Vectric or CNC Zone... So I am back asking for ideas with you folks.

If I can figure out how to make a flat bottom cone of the size I am looking for and to place it directly at the position for the screw, then I could cut it with some form of pocketing tool path, couldn't I? Use a very small percent overlap and pocket it out?

Thanks,

Monty

[zeykr]

Pauls countersink Gadget works well: http://paulrowntree.weebly.com/gadgets.html

[MogulTx]

Thank you Ken.

After a few hours of work, I have figured out through trial and error, how to create a counter sink. I have NOT figured out how to limit the Z nor to put in a ramp-in. on the 3D roughing path. I could cheat and set my Z height such that I never contacted more than .02" of aluminum in any one pass, I guess... That would technically work, but would be very inefficient.

I will go look at the PDF that details Paul's Counter sink widget. That may be just the ticket for me... ( I appreciate your letting me know about that!)

Best Regards,

Monty

[maverickx50]

Most all C'Sinks are at specific "Standard" included angles. Although there are a number of different angles used and available. I have a couple of suggestions. If you only occasionally need to C'Sink then buy a appropriate angle unit and use a drill press as a secondary operation. In thin material where the C-Sink goes all the way to the bottom I recommend drilling an undersized hole, C'Sinking to the correct top (large) diameter then drilling to the final smaller bottom diameter. This will greatly reduce the bulge/burr you will get in this process. If this is more than an occasional process requirement for you consider adding an air drill attachment to your router. Consider a teardrop shaped C'Sink. They have a single edge cutting shape and often do a much cleaner cut with out the typical chatter you see from other styles, They all are available in varying sizes and included angles.

[MogulTx]

Frederick,

Your observations and assessment are, of course, quite correct. I have been looking it over and over and can not justify needing to do it on the ShopBot- But I need to push my boundaries on the machine.

For this one project, I will make exactly two countersunk holes.... I don't need to do it on the ShopBot...

Thanks very much for your suggestions. (Helps me to remember the old "keep it simple" maxim)

Monty

[donek]

Why would you not just use a countersink drill bit. Seems like an awful lot of trouble when there is already a tool designed for the job. As they say, "there's no substitute for the right tool."
metric - 90 deg
http://www.amazon.com/Countersinks-Single-Flute-Individual-Sizes/dp/B0067BW31U/ref=sr_1_32?ie=UTF8&qid=1419720183&sr=8-32&keywords=90deg+countersink
US - 82 deg
http://www.amazon.com/Timberline-608-753-Titanium-Coated-Countersink/dp/B001UTSYWG/ref=sr_1_1?ie=UTF8&qid=1419720244&sr=8-1&keywords=82deg+countersink

[adrianm]

The angle varies according to the fixing being used. 82, 90 and 100 degrees are the most common.

The beauty of Paul's gadget and the pre-gadget way that I set it up (http://forum.vectric.com/viewtopic.php?p=70140#p70140) is that it uses a standard end-mill and the top of the screw can be totally recessed if needed in the same operation.

[MogulTx]

I have to admit. I went ahead and ran it in the 6061 aluminum, using a 3D milling file that I created using Aspire 4.5. I was concerned about the bit not being able to take the side load so I falsely zeroed it above the surface so that it would only impact the deepest .02" of the file. I then moved the Z lower with each pass. It worked like a charm. ( File was really short so it was no inconvenience to do it like that.)

It turned out fantastically well and I am tickled. I would do it again.

I DID blow up to 1/16" bits doing a very small pocketed area. I was using down cut bits and should have been using upcut spirals for aluminum. I have reprogrammed and set the depth of pass on the pocketing such that it will work well when I get the new 1/16" bits.... (I am looking to pocket the car's model name into some handles that I am making... the first prototype looks really darn good... will get the name into it when I get the new bits!) It is a 45 year old car and there were only 587 built in 1970... so, NOS handles would be nearly impossible to find and would also be costly. So a custom handle seemed like a great idea!

Thanks for your input everyone! I will post some pics once I can get the new bits and do the additional work that needs to be done!

Gosh I love this machine.

[Kromet International]

I would start off with a smaller diameter, measure the diameter with digital calipers, than do the trig to figure out the depth required or draw it in cad.

[Brady Watson]

95% of the time you can get away with using a standard sink. SAE is 82 deg; Metric 90 deg. Unless you are doing aerospace work (like kitchen cabinets for NASA), you'll use either one of the two. ;)

MA Ford makes the best coutersink bits. I get mind from ObergBrothers.net

Gadget is pretty sweet...however, in the name of simplicity it makes more sense, with less code, to just use a drill strategy with low pass depth and let the sink do the work...but that's just how I roll. Find what works best for YOU.

-B