Replies

1. 
   gofigure57 | Jan 25, 2009 05:44am | #1

   Sid, saw tooth as in hole saw at 520 rpm?

1. 
   sjscat | Jan 25, 2009 05:46am | #2

   Meaning a Fostner bit with teeth on the outside, not two continuous edges. All of the bits about an inch or more that I have seen are like them.

1. 
   gofigure57 | Jan 25, 2009 05:59am | #5

   Ok , My thinking is to speed up the rpms , make sure the backer board is clamped down tight and watch your plunge pressure.  Test on scrap first.  Hopefully your bit is sharp.

                Tom.

2. 
   kreuzie | Jan 25, 2009 05:51am | #3

   Set the drill press depth stop so that the center spur of the bit just exits the back of the plywood. Flip the plywood over, and using the mark where the spur broke through, center the spur on this small hole and complete boring the hole.

   kreuzie

1. 
   sjscat | Jan 25, 2009 05:56am | #4

   Great idea. Thanks!

3. 
   ring | Jan 25, 2009 09:12am | #6

   The trick of working from both sides will work, but if you've got a lot of drilling to do, this is the type of bit you want:

   http://www.dimarcanada.com/products/product_details.php?familyIDVar=7&pLineIDVar=2&categoryIDVar=88&groupIDVar=295

   David Ring

   http://www.touchwood.co.il/?id=1&lang=e

4. 
   roc | Jan 25, 2009 09:15am | #7

   A bit wasteful but you can sandwitch your good material between sacraficial and clamp it together. That will hold all the fibers down.

   If possible you can stack drill serveral good ones at once with sacraficial on out sides.

   To index them drill a 1/16 pilot on centers then use the smooth part of the bit or a nail or wire etc to align them for clamping. To make them very accurate punch the centers with a little punch before drilling the pilots.

   
   

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   Edited 1/25/2009 1:19 am by roc

5. 
   WillGeorge | Jan 25, 2009 08:15pm | #8

   I have a back up board under the plywood that I am drilling also.

   Then the two boards separated as the drill exited the top board into the sacrificial board. Period! If a clean hole going in, the same should be out...

   I try to use the same wood for each board if possible. Not sure why?

6. 
   DustyGeorge | Jan 26, 2009 07:45am | #9

   Sid,

   Have you tried a circle template and router to cut out your holes?

   George

   You don't stop laughing because you grow old.  You grow old because you stop laughing. - Michael Pritchard
7. 
   USANigel | Jan 26, 2009 07:43pm | #10

   I suspect your thin ply is popping up as you finish the hole. Clamp a piece with slightly larger hole over the top and then drill through. Like a sandwich.

   1/4" is on the thin side to drill from both sides. 

   By the way what you making to need "both sides good"?

   
   

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   Edited 1/26/2009 11:44 am ET by USAnigel

1. 
   sjscat | Jan 27, 2009 11:52pm | #11

   I am making sock blockers. A friend owns a yarn/knitting shop where she sells them. Wet socks are put on over the forms after washing so they can air dry and not shrink.

1. 
   USANigel | Jan 28, 2009 12:17am | #12

   Interesting!

   Got a picture? How many you making? This might change the way of making them.