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Do we need a spot drill before U drill?
- Thread starter M Code
- Start date
- Replies 6
- Views 1,549
CAMasochism
Stainless
- Joined
- Jun 6, 2019
- Location
- DFW, Texas
If you are going in with a long drill (x6D or more) it's usually recommended to use a shorter drill to create a pilot hole. However for 5xD and shorter you don't need anything. Though this can change per manufacturer recommendations.
MaxPrairie
Hot Rolled
- Joined
- Jul 9, 2015
In general, yes. Unless it is a 5xD carbide. Also depends on material, hole size, hole depth, hole tolerance, location tolerance.....etc
CAMasochism
Stainless
- Joined
- Jun 6, 2019
- Location
- DFW, Texas
I think he's referring to a U-drill and not a letter U drill. If it's a letter U then he should clarify and yes you would want a spot unless it was a screw machine length or carbide drill.
Orange Vise
Titanium
- Joined
- Feb 10, 2012
- Location
- California
Not needed and not desirable anyway.
Even with two inserts, they're effectively single flute and wouldn't follow a spotted hole. The center insert is usually designed to guide it in straight.
Even with two inserts, they're effectively single flute and wouldn't follow a spotted hole. The center insert is usually designed to guide it in straight.
Orange Vise
Titanium
- Joined
- Feb 10, 2012
- Location
- California
+1 on this.
If you have a long drill and don't want to spend money on a second, shorter drill, you can use an endmill and helical bore a starter hole about 1/2" deep.
