Shopsmith Forums

I am an experienced woodwooker but I am having a beginner's problem. I made a jig to hold a pen blank on the table for horizontal drilling. The table is a perfect 90 degrees to the shaft. I centered the brad point bit in the chuck to hit the center of the blank. Table locked, fence locked, height locked. I plunged the drill bit into the blank very slowly, pulling it back many times to remove the chips. The hole through on the opposiste side was not even close to center. With the bit firmly chucked, set-up checked for accuracy and securely tightened, what caused the bit to wonder off course?

My original thought was that the horizontal drilling was more accurate for this type of drilling. I really did not want to have to go to drill press mode with a centering jig or vice. The only thing I can think of is that the 7m drill bit that came with my mandrel to fit a Shopsmith is quite long and with the pressure of entering a hardwood blank may have caused it to flex. Any ideas?

First, I guess I might verify using soft wood (balsa or maybe bass) that my jig was producing the results I expected. If the jig is accurate then you can presume "that" specific bit in hardwood is probably the problem.

Though I did think about using the horizontal drill mode, I never did try using it. I used the drill press mode until I bought a 4 jaw chuck and now mount the blank in the chuck and advance it on the drill bit in the tail stock instead. Works MUCH better for acrylic blanks.

When using the drill press mode I did have problems with really hard exotic woods and would first drill a very small hole as a pilot for the brad bit (read that on another site and tried it). It did not work great, but did help occasionally (though probably a results of more care than a remedy).

If you find that the jig using soft woods give good results , then I might suggest using a Colt or Gorilla bit. They are more expensive, but give excellent results.

Just my 2 cents,

Ben

Drilling end grain of hardwoods like oak is sometimes frustrating. The best type bit for drilling end grain is a spade bit. They run truer through end grain than brad points.

I had a shopsmith M5 and it did a great job on horizontal holes up to 9 inches deep and 3/8 holes. Then it start squealing awefull. I never found out why it did that. I purchased a 510 same problem and it would not drill straight and actually drilled into the table. I made sure it 90 degrees and parallel. Maybe end grain and or belt slipping? Anyone with clarification please post for us.
Tom

This may be a good place to interject this question.

How well does a forstner bit do in.... say oak endgrain?

Obviously, for drilling pen stock, that wouldn't be an option because of size.

kashman wrote:I am an experienced woodwooker but I am having a beginner's problem. I made a jig to hold a pen blank on the table for horizontal drilling. The table is a perfect 90 degrees to the shaft. I centered the brad point bit in the chuck to hit the center of the blank. Table locked, fence locked, height locked. I plunged the drill bit into the blank very slowly, pulling it back many times to remove the chips. The hole through on the opposiste side was not even close to center. With the bit firmly chucked, set-up checked for accuracy and securely tightened, what caused the bit to wonder off course?

My original thought was that the horizontal drilling was more accurate for this type of drilling. I really did not want to have to go to drill press mode with a centering jig or vice. The only thing I can think of is that the 7m drill bit that came with my mandrel to fit a Shopsmith is quite long and with the pressure of entering a hardwood blank may have caused it to flex. Any ideas?

I would check chuck and drill runout to minimize that possibility.

Maybe drill half way from one end and then drill from the other end.

Are the growth rings on the stock straight thru the entire length?

Is the bit real sharp?

Just throwin some thoughts out there.

I have this problem all the time so I learned to just make my square stock a little larger to account for the hole on the other end not coming out centered. At least it won't be too close to the side of the block and it all comes out in the wash once you turn it on the lathe. And yes, a sharp bit is a must and plunge it as fast as you can otherwise it will burn the inside of the hole and squeals a lot.

fredsheldon wrote:I have this problem all the time so I learned to just make my square stock a little larger to account for the hole on the other end not coming out centered. At least it won't be too close to the side of the block and it all comes out in the wash once you turn it on the lathe. And yes, a sharp bit is a must and plunge it as fast as you can otherwise it will burn the inside of the hole and squeals a lot.

Just wondering about the sqealing. What if you try a little JPW on the bit for lubrication? Pull the bit out often and add more JPW. And what spindle speed do you use?

I know when cutting metal, it's best to use a cutting oil and slower speeds.

You are NOT alone. People have spent hundreds of dollars trying to solve this problem. (And have not solved the problem, this happens to even the most proficient wood workers)

True center line drilling of pen blanks is a perennial problem.

There are many reasons for this.
First and foremost, the drill bit likes to follow the grain.
Second, the longer pen drilling brill bits will flex and follow the hole.

Other problems that cause out of alignment drilling
Drilling too fast. (Forcing the bit through the material)
Poor alignment of stock in drilling rig.
Blank shifting during drilling.
Runout of the either the bit or chuck.
Bits not sharp especially not evenly sharp. If one side of the bit is sharper than the other you will have trouble drilling straight long holes.

Fixes:
As suggested check for runout issues.
Ensure the blanks are held firmly for the entire length of the drill run.
Drill slowly and make sure the bit remains cool.
Use sharp bits. Spade and forstner bits definitely cut more true than twist bits. The problem here is the smaller diameter and close tolerances for installing the tube. Use regular twist bits that are sharp (Jobbers). If using brad point bits, make sure the cutting spurs are sharp.

Another option is to step drill using regular twist bits and remove small amounts of material with each pass.

Yet another option: Drill using the lathe. I use either my scroll chuck (for square stock) or my Collet chuck (for round stock.) to hold and turn the blank, and a tail stock mounted drill chuck. Of course use sharp bits, advance slowly, and even step drilling sometimes. This method is not a cure all but I have gotten much better results then drill press jigs. (YMMV)

Finally, don't worry about it. (As long as you have enough meat on the blank to turn once mounted on the lathe.) Square the ends of the blank to the hole and your pen will come out great. I use a tail stock mounted drill chuck to hold appropriate sized rods to ensure the hole is square and then mount a sanding disc to remove stock from the ends until the ends are square to the hole.

I think that Terry has it right. If the cutting faces of the drill bit are not ground to the same angle the bit will wander and go off center. I have a complete drill index, fractional, decimal and number and when I use a new one I always run across the Drill Doctor first. I don't think I ever found one that was sharpened symmetrically right out of the holder. Also I have found that by increasing the bit speed and taking very small cuts generally about 1/4 inch at a time and withdrawing the bit to clear the material I get much better results.
The oily woods will squeal (bocote) is one. I would not recommend using any lubricant such as Johnson's wax because it may leave some residue in the hole which you may not get out and it would interfers with any adhesives holding power. Accept the squeal and don't lube.
Bill V