drill bushings

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refinery mike
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Joined: Sat Jul 02, 2011 1:54 pm

drill bushings

Post by refinery mike » Wed Jan 13, 2016 11:58 pm

If i use a jig, and drill through an appropriate drill bushing. will a standard drill bit produce a round hole. How would such a hole compare to a reamed hole or a bored hole.

spro
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Re: drill bushings

Post by spro » Thu Jan 14, 2016 12:41 am

A drill bushing is a very hard locater and a regular drill needs lubrication to pass it. In the end, it is still drilled hole which didn't wander as much.

Harold_V
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Re: drill bushings

Post by Harold_V » Thu Jan 14, 2016 2:55 am

Pretty much what spro said. Assuming a rigid setup, a bushing will ensure reasonably proper location, and may even restrict the amount of movement that can accompany a twist drill, but it won't guarantee a round or straight hole.

If you have need for a decent hole with proper location, consider building a jig with a liner bushing, in which you can use slip renewable drill bushings. You can go from a twist drill to a reamer to improve the quality of the hole, and it takes but seconds to switch bushings. A shoulder screw prevents rotation of the slip renewable bushings when in use, and locks them in place, so they don't lift when the drill and reamer are extracted. The shoulder screw permits rotation of the bushing (for insertion or removal), so no tools are required in making changes.

Harold
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Carm
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Re: drill bushings

Post by Carm » Thu Jan 14, 2016 3:42 pm

refinery mike wrote:If i use a jig, and drill through an appropriate drill bushing. will a standard drill bit produce a round hole. How would such a hole compare to a reamed hole or a bored hole.
The location will be as accurate as you have placed the bushing, and most accurate if the jig plate is in contact with the work. The drawback to having contact is that chips will wear the bushing sooner than the recommended clearance, which is based on drill size. They are normally Rc60's, so wear is not an immediate thing.
The hole will be round but will not have the finish of boring or reaming. And there is no guarantee that the drill bit won't wander in thicker material though a true center sharp drill won't cause problems in material 1" thick, IME.
An interesting thing with a jig plate is that the plate can be shifted off location a half diameter or less and still drill a new hole at the new location without wandering into the existing hole.
The longer the bushing the straighter the hole but the greater the need for coolant and greater chip wear.
A radial drill can swing into the jig plate locations and hit power feed without locking the column though hitting the bushing with the drill center means game over.

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