Aligning drill press

[coleman10]

Okay, I’ve tried this a dozen times and either something isn’t right with my head or something isn’t right with this drill press.

I’m trying to drill a hole down the center of a 1” wooden ball. Seems easy enough. Clamp a piece of wood to the table, drill a hole into the wood with a Forstner bit, set the ball into the hole, drill the hole into the ball with the bit I want, a 3/8” bit in this case. Every time I do this, the damned thing is off center. I put a dowel into the ball and roll it on a flat surface and it wobbles up and down. Argh. I’ve placed a combination square against the table and the bit and it looks great. Checked it on all four sides. I just don’t get it. Am I missing something very obvious here?

Thanks, guys.

 

[The Cobbler]

is your table square to the bit? put a pc of coat hanger bent in a z shape , raise the table so the bottom tail just clears the table, rotate the drill chuck and see that the tail of the coat hanger is equal distance to the table
is the ball moving on you as you drill, causing the hole to wander off ?

 

[coleman10]

is your table square to the bit? put a pc of coat hanger bent in a z shape , raise the table so the bottom tail just clears the table, rotate the drill chuck and see that the tail of the coat hanger is equal distance to the table
is the ball moving on you as you drill, causing the hole to wander off ?

Coat hanger and full sized square both check out. The ball is definitely not moving. The wood is securely clamped. It’s almost as if the bit is hitting it off to the side. Imagine a bicycle wheel with the hub off center. Roll the wheel and the hub will spin around the center - up, down, up, down. This doesn’t make sense.

 

[tarbellb]

How are you finding top dead center on the ball?

Might try putting some chalk on a flat table, then place the ball carefully down to mark it?

 

[cannuck]

Your centering plan is a good one....IF the wooden ball is actually round. That would be the first thing you need to do - check it for being true. If it is, you should use a center drill first to locate the hole without bit wandering. Same goes for your jigging hole at the bottom - start it with center drill so the bit doesn't wander off. Make sure you jig plate is well clamped. Not sure how you are clamping the round ball, but just make sure that doesn't move the jig plate. Before center drilling the hole in the ball, put a flat piece of material (1/8 aluminum or similar) under the bit and when you push the center drill into it, it should be parallel to the table in both axes. If you want to be REALLY accurate: once you have a round ball clamped in the middle, put a dead center into the drill chuck and push into the ball to make a center punch mark, then center drill that at high speed and very light feed.

I think you have the right idea and approach, just need to be super careful about what you are doing, now you are doing it and what you are working with. Being genuinely **** you would be surprised just how precise even the simplest tools and setup can be made to work.

 

[GreyOwl]

Try sanding a flat spot on the ball before drilling so the drill bit doesn’t wander when starting. Also use a small bit to make a pilot hole before going to the final size.

 

[coleman10]

I’m going to read your very helpful responses tomorrow when I have time over the weekend to try things out. I just came back in from testing it out again and I noticed while bending down to look at the way the drill bit was hitting the ball, if I don’t take it veeerrry slowly, the bit moved off to the side ever so slightly. Even when I drilled one suuuuuper slowly, it was still off. Then I decided to measure another ball. It’s supposed to be 1”, but its measurements varied from .982 to .9625. I’m not sure that’s enough to make a big difference, but it’s something. I did notice that the 3/8” bit went right down to the center of the hole made by the forstner bit.

All I know is my balls wobble.

 

[larry_g]

Can you pay attention to the grain in the ball? I would assume that the grain would want to guide the bit some. If you can see the grain then drill so that you are drilling across the grain perpendicularly.

Also how big is your forstener bit? Try something in the 3/4 to 7/8" range so that the ball sits on the rim of the hole.

lg

 

[coleman10]

Can you pay attention to the grain in the ball? I would assume that the grain would want to guide the bit some. If you can see the grain then drill so that you are drilling across the grain perpendicularly.

Also how big is your forstener bit? Try something in the 3/4 to 7/8" range so that the ball sits on the rim of the hole.

lg

The grain is a good suggestion. I’ll try that, too. Using a 7/8” forstner. It holds the ball very well.

 

[Cruzan80]

Either sanding a flat spot, or spot drill it first. Otherwise, you are asking the 3/8 bit to stay straight on a surface designed to deflect.

 

[coleman10]

Yep. Greyowl and Cannuk suggested the same. I’ll try the sanding first to check for improvement and then try it with the pilot hole. I think with everyone’s suggestions, I’m on the right track.

Thanks, everyone!

 

[RTM]

Someone previous mentioned creating the flat spot for drilling steel balls for a vise handle, so I agree with all those who said so. The created it on a sander. I would worry about grain, but make sure it will work well in your usage too, not just for drilling.

 

[ez-duzit]

One sure way to get the hole centered in the ball would be to chuck the ball in a lathe and bore it.

 

[cannuck]

yes, grain would be a big concern (I am not a wood guy, so appologize for not mentioning). Whey you make you locating hole, I strongly suspect the the sharp edge of the hole will collapse a bit more on the parallel grain sides vs. the end grain size. To eliminate that variable, I would stay with the same forstner bit but use a 45 degree countersink to make a much more rigid support for the ball than the tiny point of the sharp edge of drilled hole.

 

[ez-duzit]

...use a 45 degree countersink to make a much more rigid support for the ball than the tiny point of the sharp edge of drilled hole.

You must mean 90-degree. 82-degree is most common.

 

[cannuck]

You must mean 90-degree.

Yes, 90 degree INCLUDED angle. Thanks for catching that.

 

[cannuck]

One sure way to get the hole centered in the ball would be to chuck the ball in a lathe and bore it.

I would worry about differential compression of the wood with respect to grain in a 3 jaw.

 

[64C10]

Have you verified that your drill chuck runs true? I’ve seen Jacobs chucks out by as much as .005” out of the box.

Another possibility is that your bit isn’t true - try drilling the opposite side of one of your rejects with a different bit and see if there’s a change in the offset.

Also check for deflection in the quill - some presses have an ungodly amount of movement.

 

[seber]

Honestly a center drill should solve this problem without sanding.

 

[jbfsr]

How about an end mill instead of a drill bit. Just a thought.

 

[coleman10]

Results are in…

It just so happened that the next ball I grabbed from the bag had a flat spot on it. I dropped it in the hole, and drilled it slowly at high speed, and stuck on the dowel. It was perfectly centered. Awesome.

Next test: I took a small bit and drilled a very shallow pilot hole, just enough to keep the bit from deflecting. I drilled that one out and…. Perfectly centered. I put the first and second on each of the dowel and rolled it. Beautiful. No up and down, just a nice, level roll.

I’ve been holding these things steady with my fingers and they get pretty hot while drilling. I’ll have to invest in a clamp for this.

Guys, seriously, thank you all for your suggestions and help. I knew that the brain trust here at GJ would have the answer.

 

[coleman10]

How about an end mill instead of a drill bit. Just a thought.

I had to look up what that was. Not sure that would work. If the end is flat, not sure sure how it would bore into the rounded surface. It would work with a flat are for sure.

 

[RoninB4]

How about an end mill instead of a drill bit. Just a thought.

End mill in drill press chuck is not a good work habit and will wander, even if center cutting type. Sorta works (not very well in drill press) if 75% of hole size already removed. End mill in collet/holder works as it should (vertical/horizontal milling machine).

 

[Thirdyfivepickup]

Results are in…

It just so happened that the next ball I grabbed from the bag had a flat spot on it. I dropped it in the hole, and drilled it slowly at high speed, and stuck on the dowel. It was perfectly centered. Awesome.

Next test: I took a small bit and drilled a very shallow pilot hole, just enough to keep the bit from deflecting. I drilled that one out and…. Perfectly centered. I put the first and second on each of the dowel and rolled it. Beautiful. No up and down, just a nice, level roll.

I’ve been holding these things steady with my fingers and they get pretty hot while drilling. I’ll have to invest in a clamp for this.

Guys, seriously, thank you all for your suggestions and help. I knew that the brain trust here at GJ would have the answer.

Isn't this place great? I've never stumped the Garage Journal...

 

[coleman10]

One quick add here. I bought a stubby, brad point, 3/8" drill bit. The total length of the bit including the brad point is 1 1/4". Very little room, if any, for flexing and going off course. Even drilling into an unsanded ball gives a great result. I'll still sand off one side just to make sure it has a nice, flat surface to start with, but I think the stubby bit is the way to go as it's even more accurate.

Anyway, just wanted to share.

 

[cannuck]

One quick add here. I bought a stubby, brad point, 3/8" drill bit. The total length of the bit including the brad point is 1 1/4". Very little room, if any, for flexing and going off course. Even drilling into an unsanded ball gives a great result. I'll still sand off one side just to make sure it has a nice, flat surface to start with, but I think the stubby bit is the way to go as it's even more accurate.

Anyway, just wanted to share.

As I think I wrote at the start of the thread: instead of ruining the ball trying to sand a flat on one spot and guessing where 180 degrees apart is: CLAMP a piece of wood onto the table. hole saw a hole into it. DO NOT REMOVE CLAMPS. place the ball in the appropriate size hole (diameter to keep ball from touching table) Remove hole saw and put your brad point into the check. It will be perfectly centered over the ball IF the ball is round. Drill your hole.

 

[coleman10]

As I think I wrote at the start of the thread: instead of ruining the ball trying to sand a flat on one spot and guessing where 180 degrees apart is: CLAMP a piece of wood onto the table. hole saw a hole into it. DO NOT REMOVE CLAMPS. place the ball in the appropriate size hole (diameter to keep ball from touching table) Remove hole saw and put your brad point into the check. It will be perfectly centered over the ball IF the ball is round. Drill your hole.

Yes, that is exactly what I was, and am, doing. The problem was that the bit was still being deflected and going off center. The flat spot helps with that and works perfectly fine in conjunction with the seat/hole drilled with a forstner bit. The stubby bit prevents much of the deflection since it’s a fairly thick bit and very short, so there is little give in it.

 

[cannuck]

Yes, that is exactly what I was, and am, doing. The problem was that the bit was still being deflected and going off center. The flat spot helps with that and works perfectly fine in conjunction with the seat/hole drilled with a forstner bit. The stubby bit prevents much of the deflection since it’s a fairly thick bit and very short, so there is little give in it.

which is why you use a center drill first to locate pilot. center drills are extremely short - for obvious reasons