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Making a trepanning drill
https://www.airgunforum.ca/forums/topic89480.html
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Author:  airmec [ Sun Sep 12, 2021 5:11 am ]
Post subject:  Making a trepanning drill

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 8).

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

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Author:  YepYep [ Sun Sep 12, 2021 6:54 am ]
Post subject:  Re: Making a trepanning drill

Looks good and understand the idea~ great job!

Author:  Headdamage [ Sun Sep 12, 2021 3:23 pm ]
Post subject:  Re: Making a trepanning drill

That makes more sense, I was wondering why someone would be asking about cranial surgery ;)

Author:  notec [ Sun Sep 12, 2021 8:24 pm ]
Post subject:  Re: Making a trepanning drill

There is no better feeling than making a tool instead of buying one. Great job!!

Author:  ricksplace [ Mon Sep 13, 2021 4:25 am ]
Post subject:  Re: Making a trepanning drill

notec wrote:
There is no better feeling than making a tool instead of buying one. Great job!!

Home shop machinists often spend more time making esoteric tools than actually using them.
I made a ball turning attachment for my South Bend. After messing around with it learning how to use it, I think I used it once for a job. Making a complex tool is often more rewarding than using it!
Beautiful work, as usual.

Author:  notec [ Mon Sep 13, 2021 2:52 pm ]
Post subject:  Re: Making a trepanning drill

ricksplace wrote:
notec wrote:
There is no better feeling than making a tool instead of buying one. Great job!!

Home shop machinists often spend more time making esoteric tools than actually using them.
I made a ball turning attachment for my South Bend. After messing around with it learning how to use it, I think I used it once for a job. Making a complex tool is often more rewarding than using it!
Beautiful work, as usual.



LOL my shop is full of one time use only tools that I have made over the years........as can be seen by the amount of rust on them :mrgreen:

Author:  airmec [ Sat Sep 18, 2021 3:14 pm ]
Post subject:  Re: Making a trepanning drill

Thank you guys!

Did some progress: I ground the teeth blank, machined the teeth pockets in the drill's head (12° angle), cut two 5/16'' long teeth and had one set-up for soldering, only to see I ran out of O2 for my small torch :hsmash . No stores open in my area for the week-end, need to wait for Monday. More to come 8) .

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