Drillcent Centering Jig

[William Young]

I got my centering jig yesterday and so far , I am not overly impressed with it. Some holes come out dead centre top and bottom while some are centre on the top and off quite a bit on the bottom. So I spent best part of an hour meticulously setting my 16 speed drill press 90 degrees to the table with my dial guage with magnetic base. So that is not the problem.

One thing I did find out though is that some of the blanks that I bought are not square, (one side a little wider than the other and also , some even vary in size a little from one end to the other.

So I am thinking that I should set either my table saw or bandsaw to the smallest part of one end of my smallest one and run them through once and then again with a quarter turn to make it perfectly square and uniform from one end to the other. Is this a common practice or did I just get some blanks that were off square.

Before I try shaving my bought blanks down to square, I will try making some out of some scrap wood that are perfectly square and try the jig again.

So far, the most impressive thing I have found about the jig is that it is a very safe way to hold them compared to other ways that I had tried so just for that one feature , I will probably keep it.
W.Y.

 

[Old Griz]

Even with a centering jig it is not unusual to get some drill bit drifting... it is caused by the grain of the wood. The bit will actually bend a little to follow the grain even though the jig is holding the blank perfectly perpendicular to the bit...
The best way to lessen the drift is to drill no more than 1/2" at a time and clear the bit and then start again another 1/2" until you are all the way through... and even then you may see a little drift..
The type of bit used is also a factor.. I only use Fisch Vortex bits and bullet head (pilot head) bits.. I have found the parabolic bits want to pull the bit into the blank and drill too fast... even though they have better chip clearing ability.. I get more bit drift with them than the Vortex bits..
I have not found the blanks not being perfectly square to be deciding factor.. as long as they are the same size top to bottom and not tapered in any way..

 

[bjackman]

Will,
It seems to me you could spend/waste a lot of time trying to get everything your blanks square.
When drilling blanks I have two requirements.
1. I always try to start drilling both blanks from the ends that will touch each other,and start each blank in about the same spot so the grain will have a pretty close match when I assemble the pen.
2. As long as the remaining wood at the end of the blank exceeds the diameter of whatever kit's bushing I will be using, I dont really care where it ends up.

I drilled for a long time using a gate type jig that I made when I first started turning pens. Looks about like the ones many places sell for about 15 bucks, but it's always nice to start out with some of your own tools/jigs.
I "adjusted" the angled slot in the jig a little by sanding it, so that it actually drills pretty darn straight and accurate.
I still use it sometimes, but am _very_ pleased with the Paul Huffman vise I use now. I won it at the rendezvous in the speed turning contest, so I did not buy it, but he sells them in small numbers as he makes them.

So the bottom line? If you have enough wood at the end of the blank to cover your bushings, don't worry.

 

[William Young]

Thanks Bill J;
That was kinda the way I was looking at it. Most of the wood is going to be removed anyway. At worst it just causes a wobble when the lathe is first turned on before turning but a couple light touches with the gouge brings it to a uniform size pretty quick. . I was just curious about other peoples experience with that when using the same jig and the same run of the mill drill bits like me and probably most others that are just starting into this great hobby. .
W.Y.

 

[Bev Polmanteer]

I use the drilling center vise on page 45 of the PSI catalog and love it. The dumb little thing under it is what I started out on. It is now burried somewhere in the 'never used again' pile.It never matters if the blanks are a little off square cause as Bill J said, as long as there is enough to clear the bushing that's all that matters. I even use it with the round acrylic blanks and it works great.

 

[William Young]

Thanks Bev;
That is the same one that I got just yesterday.The one at the top of the page .
Sure glad I didn't choose the one that you *burried the dumb little never to be used again thing* [] [] [] [)]
W.Y.

 

[Daniel]

AN easier way to get a tapered blank to square in the jig better is to use a shim at the narrower edge. I have a home made blank vise that I am able to do this with. Just about anything that causes the narrow edge to be thickend to match the wider end works. folded paper. wood chips,(not shavings) match book covers, auto feeler gauges. it helps to get the hole straighter. but perfectly straight is not necessary. also working with very small pieces in a table saw is dangerous so be carful. there are push blocks made for them though. also I have found that the cuts my table saw make on things like a single blank are not very accurate.

 

[jrc]

I use a gate jig to drill blanks, on the gate I have two sheet rock screws when closed it pierces into the blank to hold it more firmly. None of my blanks are ever the same size. I use a bullet tip drill bit and I think it drills straighter than others I have used. The jig I have loosely clamped on my drill press table where I can quickly move it to set it for each blank. I've drilled about 10,000 blanks with it and it's fast and easy to use and cost me $1.29 for the hinge.

 

[Paul Downes]

I also use a hinged drill jig and have found that bullet point drills seem to work best. Some of the brad point drills are sharpened wrong. I found that the brad point doesn't always cut wood and actually was acting like a wedge similar to a rotary splitting wedge used for splitting wood. I resharpened those drills to a conventional point and usually split grind the point to eliminate as much pressure as possible. 2 things will cause a blank to split. Woods have different densities and lubricity characteristics. You may have to back the drill out every 1/4 " on some woods. I always have a consumable backer underneath each blank I drill. I have lots of scrap mdf to use for this. If you don't use a backer there is the risk of splitting the blank when the drill breaks through the bottom.

 

[tipusnr]

White oak from old shipping crates make a great backing board as well.

 

[Guest]

I use a machinist vice with an insert that looks like a gate jig.
It's a block of western red ceadar with two V's cut out on opposing edges.
Don't tell anyone but I don't use a backer board.No blow outs.I cut my blanks long enough to make up for it if it did.
Some times I will rough out a blank to see the grain.The jig holds irregular shaped blanks well.