center drilling using a drill press center device

[Charles]

Ok, guys. I have a center drilling clamp from PSI, I have used for 3+ years. No real problems till now. When I have it centered under the drill bit and push the bit into the grove it is aligned perfectly. Drill press is plumb and pushing straight down. When I place a blank in the jaws and drill; the top hole will be perfectly centered and where the bit exits is off center. I can not figure what is causing this. It is as if the bit is traveling at an angle insted of straight through the material. Any help appreciated. BTW I checked the alignment and tightness of the screws of the vise and tightened all screws and still got an off centered exit hole. Ok, guys what are your thoughts??????

 

[talbot]

Could be you're drilling too quickly and at too high a speed.
Drill speed around 700/800 rpm or slower depending on type of wood or material and drill about 10mm at a time clearing the waste each time.
Also make sure the bit is sharp and of good quality.
regards, Bill

 

[GaryMadore]

IMHO, only 2 things could cause this:

1) The table isn't perfectly perpendicular to the bit; or

2) There is something in your wood (different density) causing the bit to wander.

I have had #2 happen, but the result was usually an oblong (vice crooked) hole, and it's confined to that particular piece of wood.

I *suggest* that your table isn't perfectly perpendicular to the wood - whether that's a table or head issue I cannot say. I learned a lesson, though about using the TLAR* method of alignment while drilling a very expensive (and thus very small (the seller wants to get max # of blanks from a given piece of wood, so they're BARELY 3/4", if that) blank. I now use a machinist's square and check for alignment fore/aft, side/side, and on a couple of diagonals - just to be sure.

An afterthought: Are your table and the bottom of the vice clean? It doesn't take a very sizeable chip to crate an angle.

Cheers!

Gary

*That Looks About Right

 

[BRobbins629]

Try ordering a set of centering bits to start your hole. You can order a set these from places like ENCO for around $5. Takes about 2 minutes longer to drill the hole because of switching bits but for many of us its well worth the effort and though it doesn't guarantee concentricity, it sure helps. It's particulary important when you start to work with segmented blanks.

 

[GaryMadore]

Try ordering a set of centering bits to start your hole. You can order a set these from places like ENCO for around $5. Takes about 2 minutes longer to drill the hole because of switching bits but for many of us its well worth the effort and though it doesn't guarantee concentricity, it sure helps. It's particulary important when you start to work with segmented blanks.

I use brad-points in order to ensure a centred and straight start. I'm not familiar with centering bits - do they do something that brad points (et.al.) do not?

Thanks,

Cheers!

Gary

 

[Charles]

Thanks for the responses. Well it could be a table issue. I noticed that when I tighten the collar on the drill press the table rises slightly. Speed is not an issue. I have drilled everything from bullets to acrylic to alumalite to wood at different speeds of course, so I feel confident I am not melting or pushing/burning through the blank. Also, I hold the blank up in the vise. I don't let them rest on the bottom. Could that be a cause?? I thought the grooved plates would hold it plumb if the plates were plumb. I have a tight area with the vise mounted to the drill press table, so a square to check alignment has a hard time fitting and can't get next to blank. I will double check the squareness of the table to the bit. Sometimes I drill blanks prior to squaring the bottom so thats when I let them ride in the groove. Does this make a difference? My press has gotten a lot of use and I wondered if I might need a new one. Again thanks for the ideas.

 

[KenV]

I find that tramming the drill press table from time to time is necessary. The tramming is done with a piece of rod or wire (I like 3/32 welding rod bent into a streached "Z" shape with one end of the "Z" in the drill chuck and the other end pulled down to just clear the table. Turn the chuck and use a feeler gage to measure any change. Perfect setup has the same space all around the circle.

I made a discovery on my drill press when I pulled the end of the rod back up a couple of inches and moved the quill down that far --- the quill alignment was not matching the table alignment with the quill retracted.

Once trued up, the work to get it aligned does have the effect of causing me to avoid horsing things with the drill press that could cause missed alignment to come back into the workload.

 

[Charles]

Thanks for the responses. Well it could be a table issue. I noticed that when I tighten the collar on the drill press the table rises slightly. Speed is not an issue. I have drilled everything from bullets to acrylic to alumalite to wood at different speeds of course, so I feel confident I am not melting or pushing/burning through the blank. Also, I hold the blank up in the vise. I don't let them rest on the bottom. Could that be a cause?? I thought the grooved plates would hold it plumb if the plates were plumb. I have a tight area with the vise mounted to the drill press table, so a square to check alignment has a hard time fitting and can't get next to blank. I will double check the squareness of the table to the bit. Sometimes I drill blanks prior to squaring the bottom so thats when I let them ride in the groove. Does this make a difference? My press has gotten a lot of use and I wondered if I might need a new one. Again thanks for the ideas.

 

[hilltopper46]

Also make sure the bit is sharp and of good quality.
regards, Bill

I read this about 1000 times until I finally got smart. I can't believe how my drilling has improved since I got my Drill Doctor out of the cabinet and spent a bunch of time with it.

A dull brad point bit wanders much worse tha a sharp conventional bit. The conventional bit is better if ground with a split point.

 

[jimwill48]

Could be your blank is not perfectly square. Mine will do that if not. Doesn't really matter if its off a tiny bit and leaves plenty of wood thickness. The oter cause might be drill speed and feed. Drill to fast and the bit tends to wander a bit (follows the wood grain).

James

 

[marcruby]

One thing I do once a week is check the perpendicularity of the press to the table. I use one of those electronic angle finders and put a half inch drill in the cuts. Now zero on the table and check the drill. Or vice versa. Make sure the press is set up as if you would be drilling.

Marc

 

[scotti158]

Dial Indicator

I've got a dial indicator and mount that I put in the chuck and then turn it by hand around the table. It will show you in a hurry if the table is off and by how much. I try to get it within .010" front to back and side to side. If you do this, make sure you unplug the drill press. If you accidently turn it on, it really messes up that indicator.

 

[LEAP]

One of the things I found early on was that my vise had some give to it. when drilling the vise jaws would tip just a bit and cause the hole to come out the bottom off center. Now I always put a small block beneath the blank so that the blank is pressing on the base of my vise not putting the pressure on the Jaws. I've continued doing this with my PH designs vise.

 

[Sabaharr]

OK, here is my 2 cents. I agree that the most likely prooblem is the table being off plumb. You might also check that everything is tight and in good alignment with your blank vise. Also try a new bit to eliminate the possibility of a dull bit or one that wonders when slightly heated from drilling friction. If this is happening with several types of blanks, different woods, acrylic, whatever, then the problem is definately equipment. Since you could visually confirm that the chuch is turning straighe by the vise not wobbling then it has to be one of the parts I mentioned. Table, bit, vise are the suspects in that order.

 

[bubbatd]

I was having the same problem. New bit new vice aligned the table still doing it. Found that the quill of the drill press was moving as I lowered to drill. Took it out and cleaned the taper inside and out and made sure the chuck was seated well. That took care of the problem for me.

 

[Manny]

It could be the it

I bought a new set of bits from Harbor Freight. Noticed I am exiting off center now. Here is a good way to tell if its the bit.


Mark a center line in your blank and load it into your vise. With the press off lower the bit and align it to the center point of the blank. Manually turn the drill press mandrel so that the bit spins slowly. Watch the tip spin. If the drill bit is centered and straight you won't get any wobble and it's likely the table alignment. If the bit wobbles its either the bit itself (need to test with a new high quality bit to be sure) Or there is something going on with the mandrel or chuck.

I just put a high quality bit in my press and I am exiting on center now. That's what I get for buying cheap I guess.

Manny

 

[ldb2000]

Are you tightening your table lock clamp . If your not your table won't be level and you can get off center holes . A cheap drill press , like my ryobi , comes with a very flimsy table and will flex if you use too much pressure while drilling . Switch to drilling on the lathe and most of your problems will go away .