Scott H
Cast Iron
- Joined
- Dec 2, 2001
- Location
- Covington, VA
Will the hole finish be better or worse using a spade drill vs. a twist drill?
Thanks,
Scott
Thanks,
Scott
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Hole finish with spade vs. twist drill
- Thread starter Scott H
- Start date
- Replies 2
- Views 4,321
jkilroy
Diamond
- Joined
- Jul 23, 2004
- Location
- Vicksburg, MS
I have only had one experience where I could directly compare, and I make this part fairly often. Using the exact same machine drilling the same size hole in the same material (aluminum) I would say the finish of the spade was slightly better. Both the regular bit and the spade holder have MT3 shanks. The regular drill is a quality new US made drill and the spade holder and insert are Allied products, both uncoated. I am drilling a 7/8 through hole 3" deep into 6061. I used speed/feed info off of the Allied site for the spade and MHB for the drill.
precisionworks
Diamond
- Joined
- Apr 20, 2005
- Location
- Benton, IL USA
Quite a bit of info on the AMEC site, click here.
If you're drilling from the solid, if your setup is rigid, if your machine is tight & well adjusted, spade drills produce better finished holes & straighter holes than twist drills. In larger sizes, they are the least expensive way to make a hole. It's easy to find huge inserts, 4" and larger, on eBay for $30, click here.
Spade drills are primarily center-guided. Even after the point penetrates to full diameter, there is no 'body' to guide the drill, as there is with a twist drill. Twist drills will tolerate gawdawful sloppy setups - once the point makes full diameter, the body/flutes provide support to keep the point going straight, more or less.
All things being equal, the spade drill will produce a better hole finish.
--------------
Barry Milton
If you're drilling from the solid, if your setup is rigid, if your machine is tight & well adjusted, spade drills produce better finished holes & straighter holes than twist drills. In larger sizes, they are the least expensive way to make a hole. It's easy to find huge inserts, 4" and larger, on eBay for $30, click here.
Spade drills are primarily center-guided. Even after the point penetrates to full diameter, there is no 'body' to guide the drill, as there is with a twist drill. Twist drills will tolerate gawdawful sloppy setups - once the point makes full diameter, the body/flutes provide support to keep the point going straight, more or less.
All things being equal, the spade drill will produce a better hole finish.
--------------
Barry Milton
