I started making one for a 1 1/8'' hole I need to drill in a piece of 6061-T6 aluminum. Trepanning drills have a few interesting features I wanted to try: less power needed to drill a big hole, less chips made and a core left for other projects, and less time used for drilling the hole.
I used an old Morse #3 dead center I had as the shank, I annealed the end and made 5/8''-18 NF threads, 3/4'' in length. There's a shoulder 1/8'' long and 3/4'' OD to center the drill body, and an Oring to seal if I ever use coolant or air. BTW the grey-ish color is due to tungsten disulphide dry powder burnished on the parts.
The body is made from a piece of an Iscar 1 1/4'' boring bar (4140 steel?), turned down to 1.075'' and drilled with a 13/16'' twist drill, with the front end @ 1.100''. Total body length is 6 7/8'', with a maximum (inside) depth of cut of 5 3/4''. The core left should be 0.775''-0.780'' OD. The base is threaded the same 5/8''-18 NF as the shank, and I left 1'' of the original flats for ease of unscrewing the body. The flutes have been cut using a 1/2'' HSS end mill, they are 0.075'' deep and 0.050'' off the center line of the tool. I actually followed Bob Sterne's tutorial on making a reamer to cut the flutes
.I still need to machine flats on the shank for a box end wrench, make a cutting tooth blank out of HSS, also cut the teeth seats in the front end of the body. Then it'lll be nickel/silver soldering the teeth and grinding them to final shape. I'd need to know about the angles if anyone has some advice? I know I need to grind relief angles, but what would be good angles for aluminum?
BTW I designed my tool based on the work of this great British fellow:
https://www.youtube.com/watch?v=pAactI93w6U
| Attachments: |
|
TD_1.JPG [ 80.78 KiB | Viewed 1109 times ] |
|
TD_2.JPG [ 84.65 KiB | Viewed 1109 times ] |
|
TD_3.JPG [ 23.06 KiB | Viewed 1109 times ] |
. No stores open in my area for the week-end, need to wait for Monday. More to come