Deep Hole Drilling In Aluminum

[Fabrickator]

I would use a stubby screw machine drill to go as deep as possible using my dual-air blower to keep the chips cleared and minimize overheating. Then I would switch to a jobber drill to complete the hole if needed. Always best to keep the drill as short as possible and chips clear to prevent wandering.
Another trick I use on deep drilling to use my QCTP/compound to apply a very slight side load to the bit itself. to keep it running true.

I made a dual-nozzle chip air blower (w/regulator) to keep the 2 flutes cleared.

 

[Round in circles]

This I find fascinating and perplexing at the same time, correct me if I am wrong.
You machined tools and fixtures to make a part as accurate as possible then the last operation is eyeballing the hole position with a rule, what am I missing?

On my work piece , I couldn't get it in the lathe to bore the four inch dimension , as the piece was far too long & I don't have a milling attachment or a crutch pad to do it , so I had to resort to the old Mk 1 eyeball old way . I did try using the cross slide with the compound removed but it wouldn't play for me .

 

[Wreck™Wreck]

You can drill the depth of the hole regardless of the travel of the quill in the tail stock. It is a bit of a pain, but drill what the stroke is, then you will have to slide the tail stock up a bit and lock it with the drill in the part. The one thing you will need to do is advance the drill a bit, then unlock the tail stock and slide it back to clear the chips, then slide it back up, lock it down and drill. Repeating as needed to get the hole through.

I do a repeat part several times per month, 9/16 hole through 12" of 440 Stainless linear shafting, the surface is cased and ground the ends and center are not. I position the carriage so that after retracting the tail stock (by sliding it down the ways) and clearing the chips one may just push is back in without the risk of driving the drill into the bottom of the hole, works a charm, advance the carriage when you run out of tail stock travel.

In the past my employer has considered purchasing gun drill tooling for this type of work, I do not see this happening in my lifetime however.

 

[Paul in OKC]

Gun drills are nice. We have one we use regularly at the shop. Run as small as 3/16, and up to 1 1/4". The small bits scream at up to 4k rpm and 2 IPM feed. Drills great.

 

[prasad]

Guys,

I went ahead and drilled the deep hole with a 1/4" parabolic flute drill. The hole came out great. Thank you all for your advice. I have one question on my experience in drilling with the parabolic flute drill. I did the drilling operation on my 9x19 lathe in small steps, withdrawing the bit frequently to clear chips and to spray WD40 into the hole. I noticed one odd behavior. The chips appeared to come out in spiral form only from one of the flutes of the drill bit. The other flute did have some accumulation but not as much as the first flute. I felt that only one cutting edge was properly cutting. Could this be due to drill bit faulty or defective construction? The drill bit is of unknown make and was bought from an ebay seller.

Thank you again for your comments and advice.

Prasad

 

[prasad]

Get yourself a parabolic flute drill, this will work a charm in high D/L ratio holes in aluminum, use a spotting drill rather then a center drill to start. this should give you a fairly straight hole then ream or bore as needed.

Hi Wreck, I did it with a parabolic flute drill. The hole came out good. Offset at the other end was under .005". Exactly as you said. However I noticed that only one cutting edge of the bit was producing spiral shaped chips. The second cutting edge did produce some chips though. Could the drill bit be faulty/defective?

Thanks
Prasad

 

[janvanruth]

the drill was not properly ground
but as the result is fine i would say dont change a winning team

 

[Wreck™Wreck]

Hi Wreck, I did it with a parabolic flute drill. The hole came out good. Offset at the other end was under .005". Exactly as you said. However I noticed that only one cutting edge of the bit was producing spiral shaped chips. The second cutting edge did produce some chips though. Could the drill bit be faulty/defective?

Thanks
Prasad

This is not uncommon when using conservative feed rates, push the drill harder. Do a test for your own education, chuck a piece of aluminum, spot drill it and then drill as you normally would, do this again with another test specimen but crank the tail stock wheel fast enough where you are afraid of breaking the drill, you will then see 2 chips coming off of the bit.

If one were to purchase a drill from a highly reputable manufacturer, Guhring for example, it would be likely that you would observe the same chip formation at less then optimal feeds, this does not mean that the tool is "not ground properly", you simply may be using it incorrectly.

Last week, Warner & Swasey # 5 turret lathe, 1 1/4" twist drill straight through 1018 steel parts 1 5/8" thick, no center drill or spotting drill, no pilot hole just ran the drill in and let it find it's own center and eat, accuracy was not important as they were later bored in a CNC lathe to 1 1/2" +.010 - .000". 44 parts at less than 40 seconds each actual drilling time. 1:45 from chucking to finished hole, it took longer to change parts then the actual machining time. I bored soft jaws with a step in them to hold the part because that much feed rate with a drill will push the part right through hard chuck jaws, even with a 15" chuck. A large W & S Turret is a powerful machine make no mistake about that.