3/8" x 4" Forstner Bit Extension
Forstner bit extensions solve one of the major problems with forstner Bits -- their limited depth capacity. This extension fits WoodRiver forstner bits only that have 3/8" diameter shanks.Features: • Designed for use with WoodRiver forstner bits only• Extension adds 4” to length of...
• Designed for use with WoodRiver forstner bits only
• Extension adds 4” to length of forstner bit
• Socket accepts forstner bits with 3/8” diameter shanks
• Forstner bit held in extension socket with two set screws
• 3/8” diameter drive shank allows use of multiple extensions
Difficult to use for less than 7/8” or 22 mm bit
Works well enough, but the set screws sit proud of the surface of the collar, making it impossible to use for less than a 3/4 inch bit. To use for bits 7/8” or smaller you first need to mill a flat spot on the shaft of the bit, then file the set screws down so they’ll clear the sides of the hole you are trying to drill. If you file the set screws down to use a 3/4 inch bit without milling the flat spot on the bit shaft then there won’t be enough of the hole for the Allen wrench left to reliably tighten the set screws.
description is WRONG, expect 3 inches
I bought both the 3/8 and 1/2 x 4 inch extensions, I found upon arrival that the description is WRONG on both of them. the OVERALL length is 4 inches. you can expect only 3 inches of added length to your bit. sadly woodcraft doesn't offer a 6 inch extension
Set Screw Problem Can Be Modified
I read the review that said the extension was useless on a 3/4" bit because of the set screw length. I bought one anyway because I need to drill 3/4" holes. I found that you can file the set screws down flush with the tool and they still do the job just fine.
Inset screws too long
I got this extender to make longer holes with a 3/4" Forstner bit - I figured since it was 3/4" diameter, it would work with my 3/4" Forstner bit. I figured wrong. The set screws protrude about a 16th" making it useless for 3/4" holes. Should work well with 7/8" or 1" bits. Sturdy construction and good precision. My only regret is that they don't spell out what size bits it will work with.
Good solid extender when needed.
Critical When You Need IT
As a turner, one needs to drill holes deep in a spindle project, like a pepper mill. On a Midi Lathe, there isn't the space to just use a long bit extender. I bought 2 of these extensions. Drill in to the depth of the extension. Add a second 4" extension and drill to that depth. Go to the 10" extension and your done.
Attachment end a little large if drilling smaller size holes.