Center drilling problem

[SpiritRider]

I am having a problem drilling center of wood blanks. I have checked alignment, vertical and horizontal. The jig is centered on the bit end but WAY off on the other side. I think it might be the bearings on the drill press shaft but I am looking for other possible causes with the brain trust here.

It is a 50 year old Craftsman press. My father did a lot of sanding with it and I think that the side loading has wore it out

 

[monophoto]

You need to describe what you are doing - - -

My guess is that the table on the drill press isn't perpendicular to the axis of the bit - you are drilling a straight hole, but since the axis is tilted, it goes through the blank at an angle. Therefore, the hole will be centered at one end, and off center at the other end. There are many ways to align the table - do a search in YouTube for how-to videos.

By the way, unless you are working with segmented blanks, the hole doesn't have to be centered exactly. The only requirement is that there be enough wood surrounding the hole at both ends for you to turn the blank into a pen body - the portion of the blank that is off-center is going to be turned away.

However, if you are working with segmented blanks, you generally need the hole to be centered over the length of the blank so that the pattern that eventually appears on the surface of the turning will be what you intended for it to be. For example, if you have a blank that is segmented to become a celtic knot, and the hole isn't centered across the full length of the blank, the knot will be distorted toward the off-center end.

 

[SpiritRider]

I would agree with you but acrylic blanks drill perfectly.

 

[jttheclockman]

Better off drilling on the lathe.

 

[monophoto]

I would agree with you but acrylic blanks drill perfectly.

This is new information. I'll say it one more time - you need to describe what you are doing. What kind of jig are you using? What kind of drill bit are you using? Wood or acryllic, and if wood, which timber? Is the bit 'wobbling' as it advances through the wood? How fast are you drilling? Are you clearing swarf?

 

[danhoke]

Agree with John T. Drilling on the lathe is a real problem solver.

 

[KenB259]

I drill on the lathe only. Best advice I can give you and wish I had known about them sooner, is the get a set of stubby center finding bits. Got mine at Harbor Freight and they are good enough. I have not had an off center hole in over a year. Another thing to look into in solving this is simply make sure your blanks are good and square to start with. As pointed out already, it's not so important until you get into segmenting. It's better to instill good habits from the get go, than to break bad habits in the future. I'm not a big fan of brad point bits either, they are not the best for end grain drilling.

 

[duncsuss]

Try sharpening the bit (or get a new one).

 

[dogcatcher]

Pictures

 

[ramaroodle]

You need to describe what you are doing - - -

My guess is that the table on the drill press isn't perpendicular to the axis of the bit - you are drilling a straight hole, but since the axis is tilted, it goes through the blank at an angle.

+1 As long as the blank is perpendicular to the table and the table is perpendicular to the bit.

 

[wolf creek knives]

What type of bit are you using and what species of wood. There's some great ideas here but to say that acrylic drills just fine but not wood blanks makes me wonder about the bit.

 

[howsitwork]

If it were the bearings then the drill bit will cut an oversize hole as it oscillates. So I think, from the information you have given that the bit is suspect . As acrylics have no grain there is much less deflective force as you drill, assuming you drill slowly, clear the chips repeatedly etc. With wood if the flutes get clogged as one side your bit will divert and once it's started to go y ain't going to stop it.

 

[SpiritRider]

I drill with Brad point bits at a medium speed and clear the chips often. Lately I have checked the alignment 4 times in the last 2 months. I have a Penn state center drill jig and their bits.
I don't see wobbles and have it happen with all woods. Maple, walnut bocota

 

[howsitwork]

brad point bits are good in plastic, less so in wood. Try a bullet pint drill instead. These seem to have a more substantial flute construction and although you need to withdraw slightly more frequent to clear the chips they are more rigid and do go straighter, or so i have found .

My guess is the brad point on one side hits harder end grain and pushes slightly over and the other pout is in softer grain but that's pure guesswork. I too have had brad point bits wander in wood

 

[dogcatcher]

Try some jobber bits from a good hardware store.

 

[PaulWitmer]

What type of table is your drill press on? Also, as mentioned in the replies, the table must be perpendicular with the drill bit for accurate results. If there is any wobble or flexing, the drilled hole will have drift off-center. When I first started out, I had a table top drill press which I had set on a "work table", but as drilling began, the table wobbled or "flexed" somewhat and I noticed the same problem (wood and acrylic blanks). When I renovated the shop, the drill press sat on a sturdy table and haven't had an off centered hole since then.

If you don't have the room for a separate drilling station, then you can always drill on the lathe and get that centered hole.

This helped with my situation, but many of the comments above can also address your concerns as well.

Paul

 

[wolf creek knives]

I use ICS drill bits with great success. U.S. made too. I've had problems with brad points following the grain in some woods and the only way I could correct it was switch to these bits and also move to the lathe. The only other option you might try is to oversize your blanks.
Also, you might be drilling at too high of a speed. I drill at a RPM of 575. I resisted using the lathe to drill holes but once I tried it I won't go back. Lots of other great options for lathe work too like the Rick Herrel offset jig.

 

[ramaroodle]

Try some jobber bits from a good hardware store.

I'm not picky. I have 2 or 3 bits that I spent waaaay too much on at Rockler because of their odd size but otherwise I use Harbor Freight bits and never really have a problem. I used to use the lathe and still do occasionally but it's a bit of a PITA and in reality, I can drill 4 times as many blanks on the drill press in the same amount of time and I can dribble DNA into the hole to keep the bit and blank cool especially in acrylics.

A little difference happens all the time so no big deal. If the blank is square to the bit and the bit is square to the table the bit would have to be visibly wobbling for it to be the problem IMHO. If everything else is square and you're starting in the center of the blank up top It should be pretty close to dead center out of the bottom.

Only thing left is whatever you're using to clamp the blank. When the blank is clamped is it still square to the bit?

 

[sorcerertd]

I drill on the lathe only. Best advice I can give you and wish I had known about them sooner, is the get a set of stubby center finding bits. Got mine at Harbor Freight and they are good enough. I have not had an off center hole in over a year.

Ken, are you talking about the hinge bits that are used to center the pilot hole? I've had my share of off center holes, so I'd certainly give them a try.

 

[duncsuss]

Not hinge bits - these:

Center Drill Countersink Set, 5 Piece

Amazing deals on this 5Pc Center Drill Countersink Set at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

 

[sorcerertd]

Not hinge bits - these:

Center Drill Countersink Set, 5 Piece

Amazing deals on this 5Pc Center Drill Countersink Set at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

Ah, the one that says "drill accurate lathe centers" in the description. That makes sense. Thanks!

 

[KenB259]

Not hinge bits - these:

Center Drill Countersink Set, 5 Piece

Amazing deals on this 5Pc Center Drill Countersink Set at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

Yes these are the exact ones I have. Get them, you will not be sorry. I use the biggest one 99 percent of the time. Do not use them with brad point bits though.


Sent from my iPhone using Penturners.org mobile app

 

[darrin1200]

If everything else checks out and it drills well in acrylic, then I suspect the wood grain. Quite often, drills can be pulled slightly off center by the grain in the wood. The only cure I found for this is a good sharp bit. The next critical part is starting straight. This is accomplished with either the center bits mentioned above or by using a split point in the bit.

I solved all these issues with my purchase of a Drill Doctor 750X. There are many that say this is not needed if you just learn to sharpen. Personally, after 26 years in a hands on tech trade, I couldn't sharpen a drill bit to save my life. Since I got the drill doctor, I sharpen my bits often and have pretty well eliminated the wandering bit issues.

I don't say completely, because I still get wandering due to heat if I become impatient in a particularly dense piece of wood. If the bit over heats, it can actually bend oh so slightly, and cause great nightmares. Once cool it goes back to normal. Dmkt

Good luck with your drilling adventures.

 

[KenB259]

If everything else checks out and it drills well in acrylic, then I suspect the wood grain. Quite often, drills can be pulled slightly off center by the grain in the wood. The only cure I found for this is a good sharp bit. The next critical part is starting straight. This is accomplished with either the center bits mentioned above or by using a split point in the bit.

I solved all these issues with my purchase of a Drill Doctor 750X. There are many that say this is not needed if you just learn to sharpen. Personally, after 26 years in a hands on tech trade, I couldn't sharpen a drill bit to save my life. Since I got the drill doctor, I sharpen my bits often and have pretty well eliminated the wandering bit issues.

I don't say completely, because I still get wandering due to heat if I become impatient in a particularly dense piece of wood. If the bit over heats, it can actually bend oh so slightly, and cause great nightmares. Once cool it goes back to normal. Dmkt

Good luck with your drilling adventures.

I agree on the drill doctor, works great and I love mine.

 

[RobS]

Agree with the wood grain.

I have seen this multiple times, even on the metal lathe, with wood, that is spot drilled, then drilled with a stub drill, then when i use a brad point, the brad point follows the grain.

 

[howsitwork]

I'm not picky. I have 2 or 3 bits that I spent waaaay too much on at Rockler because of their odd size but otherwise I use Harbor Freight bits and never really have a problem. I used to use the lathe and still do occasionally but it's a bit of a PITA and in reality, I can drill 4 times as many blanks on the drill press in the same amount of time and I can dribble DNA into the hole to keep the bit and blank cool especially in acrylics.

A little difference happens all the time so no big deal. If the blank is square to the bit and the bit is square to the table the bit would have to be visibly wobbling for it to be the problem IMHO. If everything else is square and you're starting in the center of the blank up top It should be pretty close to dead center out of the bottom.

Only thing left is whatever you're using to clamp the blank. When the blank is clamped is it still square to the bit?

Andy

I am hoping DNA stands for De Natured Alcohol not your DNA ie blood ?

I've tried a few things as lubricant but never deliberately bled into a hole. ??? I'd worry it might attract vampires or mothers in law to the workshop ???

 

[howsitwork]

Ken

for interest you can get long series centre drills which would go all the way through if lifted clear VERY frequently to clear the chips . Available over here from MCS They are very rigid and go where you point them.

 

[SpiritRider]

Thanks everyone,

I switched to regular bits for wood and it has helped, I don't have to worry about drilling out the side of the blank. So far, after the change, none of them have been so far off that I can't use it.