I need to drill an 8" deep shaft for a floating shelf rod to be inserted. Can this be relied on for this drill depth?

I drilled six inches into Wood and it worked perfect 170 times. Don't see a problem just make sure the guide is clamped down well and don't put too much strain on the drill. I was skeptical myself but the result made a 100% believer out of me.

Doesn't this metal drill guide increase the wear on the drill bits and shorten their lives?

No, not really. The cutting surfaces of the bit are the tip of the flutes, not the sides. There will be some rubbing on the sides of the drill bit and obviously some wear, but it won't affect the diameter of the hole that the drill bit is designed to cut. With the possible exception of wood and cast iron, metal cutting good practice does involve using a cutting lubricant and always the appropriate cutting speed to achieve a design chip removal rate. Using a cutting lubricant would further reduce even the slight side wear of the drill bit due to using this guide. Using too high a cutting speed without a cutting lubricant, and thereby causing the cutting edges to overheat, lose temper and dull, are the primary causes for the cutting edges of the drill bit to wear out faster than they should. HTH

Is the size of this drill guide a true rectangle? Also, is the height of the drill guide the same on both the smallest and largest drill guide holes?

The large hole (3/8" - 1/2") drill guide is a true rectangle of uniform height. The 4 corners of the drill guide are rounded (small radius).

1/2" drill bit doesn't go into the 1/2" hole. Why?5

I don't totally understand your question. 5 what? As far as the bit not fitting into the 1/2 inch hole, I would say you might have a burr on your drill bit keeping it from going into the guide hole. Try another drill bit or use emery paper to smooth down any irregularities on you bit. I tried 2 bits on my drill guide and they both went in. They fit tight with only maybe .001" clearance, but it should be that way for an accurately drilled hole. Or, by some error in the manufacturing, you may have a defective guide. I would suggest using a digital micrometer, and measuring the guide hole on both ends and see what the reading is. Hope this helps.

Manufacturer	Big Gator Tools
Part number	BGRSTD2000DGNP
Item Weight	335 g
Product Dimensions	15.24 x 2.54 x 2.54 cm; 334.52 g
Item model number	BGRSTD2000DGNP
Size	3/8"-1/2" - 9 hole sizes
Color	Silver
Finish	Uncoated
Material	Steel
Item thickness	8 Inches
Item Package Quantity	1
Number Of Pieces	1
Measurement System	English
Batteries Included?	No
Batteries Required?	No

BGRSTD2000DGNP V-Drill Guide, Standard Sizes 3/8" to 1/2"

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