Controlling large diameter Forstner

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Forum topic by JCantin posted 06-25-2010 10:11 PM 1882 views 0 times favorited 11 replies Add to Favorites Watch
View JCantin's profile


179 posts in 3652 days

06-25-2010 10:11 PM

Topic tags/keywords: forstner drill press

I bought the 3” individual Forstner bit from Rockler to drill some recesses in hardwood for hockey puck displays.

I adjusted the belts on my 16 1/2” Delta drill press down to 250 rpm. The workpiece is held against the fence and a stop block. When I start drilling the bit doesn’t really cut, it freezes and the spindle stops turning.

Have I got a problem with the drill press? Or is the bit just not good enough quality?

The DP is new to me but came to me well used. It’s worked fine otherwise with smaller diam bits in both HW and SW.

11 replies so far

View TheWoodNerd's profile


291 posts in 3432 days

#1 posted 06-25-2010 10:13 PM

Is the belt slipping? You might just need to tighten it.

-- The Wood Nerd --

View JCantin's profile


179 posts in 3652 days

#2 posted 06-25-2010 10:30 PM

The belt is slipping. I’m not sure if the tension lever is doing anything. On low RPM there seems to be a lot of tension to take up between the center and rear (motor) pulley and that’s the one that is slipping. Would I normally see the pulley move when moving the tension lever? I guess another possibility is the belt is just old and slack.

View PurpLev's profile


8548 posts in 3888 days

#3 posted 06-25-2010 10:36 PM

yes, as you are pulling on the tensioning lever the pully is visibly moving backwards (or forward if you are releasing the tension).

-- ㊍ When in doubt - There is no doubt - Go the safer route.

View TheWoodNerd's profile


291 posts in 3432 days

#4 posted 06-26-2010 02:34 AM

Hard to say without seeing how the tensioning lever works. But generally, yes, the motor/pulley should shift visibly when the tensioning mechanism is tightened/loosened.

Look for a way to adjust the mechanism, it may be out of whack. Another possibility is that at some point the belt was replaced with one not quite the right size, i.e. it’s just a little too long.

-- The Wood Nerd --

View JCantin's profile


179 posts in 3652 days

#5 posted 06-26-2010 01:22 PM

Guess I will have to take a look under the hood. Thanks.

View docholladay's profile


1287 posts in 3299 days

#6 posted 06-26-2010 01:52 PM

I believe everyone else has pretty much hit the nail on the head. It’s pretty obvious that the belt slipping is the problem. This could be, the belt is worn, the belt is the wrong size, the tensioning mechanism is not getting the belt tight enough. On my drill press, the tensioning mechanism has a “spring” that should keep it tight enough, but I always have to help it a little and it fortunately has a lock bolt that holds it in place to keep it tight. The spring isn’t strong enough by itself.

-- Hey, woodworking ain't brain surgery. Just do something and keep trying till you get it. Doc

View Jeff Roberts's profile

Jeff Roberts

35 posts in 3545 days

#7 posted 06-26-2010 02:11 PM

I have a Craftsman where the chuck will slip at the morse taper. The solution is to clean both surfaces and tap it back in place.

-- Jeff, Dayton, OH

View Kent Shepherd's profile

Kent Shepherd

2718 posts in 3526 days

#8 posted 06-26-2010 07:43 PM

I agree, something is probably slipping, either the belt or the chuck.

When that is taken care of, I would consider starting with a smaller diameter bit, and working up to the final finished size. I was drilling into Bubinga end grain with a 2 1/8” Forstner bit. It would hardly drill it (brand new bit). I tried starting with a 3/4” bit and working up to the final size and had no trouble at all. It was well worth the extra time. Since I had the piece clamped to the drill press table, there was no additional set-up. Each bit remained centered.


View richgreer's profile


4541 posts in 3314 days

#9 posted 06-26-2010 09:35 PM

Whenever I need to drill a large hole with a forstner bit, I clamp the piece securely in place and drill in steps. First I drill a 1’ hole, then a 1.5” hole, then a 2” hole, etc. until I get up to the size desired.

Drilling a 3” hole without going through the steps puts a lot of stress on your drill, especially if you are drilling a very hard wood. I have used my technique to drill a 3” hole into Padauk (a very hard wood).

One more thing – sometimes, I start with the largest bit just to help position the piece before clamping. Then I will only scratch the surface with that bit to know exactly where the hole will eventually be.

-- Rich, Cedar Rapids, IA - I'm a woodworker. I don't create beauty, I reveal it.

View wch's profile


45 posts in 3198 days

#10 posted 06-26-2010 10:57 PM

It’s possible that your bit needs sharpening. I bought a set from Rockler and they weren’t very sharp, but after a little work with a small needle file, they cut much better. In the future I may get small diamond hones to make them even sharper.

View jusfine's profile


2422 posts in 3166 days

#11 posted 06-27-2010 01:06 AM

If you are going to replace your belt, look into the link-belt system. Hard to go wrong with them for sizing, and your machine will run with less vibration.

If your spindle stops, it is the drill press problem, not the bit.

-- Randy "You are judged as much by the questions you ask as the answers you give..."

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