Spade Drills ?

[M. Anderson]

Looking for some advice on spade drills.

 

Does anyone use these?

 

How are they at "opening up" holes, or is that a big No-No with them?

 

What I have is a very large quantity (1000's) of some round spacer looking parts for re-work.

 

They have a .644 to .650 hole already through them, parts are 4 inches long. Material is 1018, and appears to have been DOM for ID size.

 

The customer is switching over to a 18 mm bolt and wants the hole opened up to 18.1 mm/(.713) to 18.3 mm/(.720).

 

I am looking for something other than boring with a boring bar. (.500 bar going 4" deep may have rigidity issues)

 

I was thinking about a .718 spade drill but have never used one, nor do I know how they work on re-drilling existing holes.

 

What would be your recommendation?

 

Thanks for any input,

 

Mark

[Alter Ego]

A lot of times the spade drill catalog will show things like maximum suggested pre-hole size. A lot of times you will experience some pretty serious vibration in cases where the pre-hole is very large. You might want to consider an extra-long endmill with the flutes relieved; you only need the thing to cut on the end so have somebody chuck it up on the shank and grind the flutes .030 under, just leaving .250 or something down the end to support the cutting edge. Since you're only doing this to clear for a screw, you could always butch it and bore 2.125 deep and flip the thing around and finish it from the other side.

[heavychevy2155]

What about a 23/32 three flute counterboring tool, feed the crap out of it to break the chip. They are cheep so buy 4 of them, change out if it gets dull and off to the races again.

[Bruce Caulley]

Use a core drill. They are designed for exactly this application.

 

Bruce

[Quickmike]

I've heard about core drills before. I've never used one though. Are there any formulas or rules of thumb as far as what sizes to start and end with.

[Bruce Caulley]

I think most 3 flute core drills will actually drill a hole in solid material, but they really perform with a pre-existing hole. Allignment isn't critical either as they are mainly used in drilling out pre "cored" holes in castings.

 

Bruce

[Mgrenier]

+1 to core drills.

 

In our experience here, spade drills will not work properly when you have a pre-drilles hole. The tool needs to cut in the center to eliminate vibration.

 

Hope that helps,

[M. Anderson]

See, knew I could count on you guys!

 

Thanks for the info, I was afraid of using a "Spade Drill" for this, I have never used one, now I know not to use them in this application.

 

Never heard of a "Core Drill" before, and then someone sends me a PDF from Precision Twist drill.

 

quote:

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REMEMBER...

1. Opening up holes with two flute drills is no guarantee that the finished hole will be round and chatter free.

2. If pre-drilled or cored holes must be enlarged, the most efficient and safe method is with a core drill. It will insure round holes to size and at up to double the feed rate.

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I actualy liked the other ideas also, thanks guys, but if these drills are made for this.... Well...

 

This is what I love about this place!

 

World wide help for all!!

 

Thanks guys, I will order one of these today!

 

Later,

 

Mark

[Müřlıń®]

I used HSS Spade drills on the big engine lathe I ran for years.

 

I would take a 1" twist drill and drill a hole down 6" or so using a 24" cheeter bar on my tailstock and muscle the material out of High nickle steel.

 

Then I would slap in a 2.5" spade drill and take that same 2', cheater bar and gouge on it!!!

 

I could drill a 6" deep hole in short order and not spend 1500 bucks on tooling either

 

But it takes horsepower to do that.....but I could drill holes with hand sharpened spades all day long for nutin'

 

todays mills, it is better to finess the material out of the hole....but it costs.....

 

Spades work all right as long as you are taking at least 1/8" per side so they can pressure up and keep the chatter out..

[elbro]

Why not bore this in a lathe. Could be bored in one pass.

[Bpin]

Graflex makes a two bladed boring tool called a twin bore. great tool, easy to adjust,holds size.

[chris m]

quote:

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Why not bore this in a lathe. Could be bored in one pass

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8X Diameter is a big overhang for a boring bar

[elbro]

I have bored longer with no problems. You will need a heavy metal or carbide bar.