preventing fine drill bits from drifting

[goodtime7]

In keeping with the thread concerning repairing pin holes, etc   I have had the mis-adventure of drilling pin holes with fine drill bits, and ending up with them drifting off line.   This has happened even when I have using a "spike type" drilling guide.   The bit lines up with the spike before and after drilling.  The bits have been high quality and sharp.   I suspect that I should be drilling slower, possibly with higher drill bit speed?   Any other thoughts or ideas?  thanks......

[frogwalking]

The way to prevent this is to drill from each side to the middle.  If you have a drillpress and the sides of the stock blank are parallel to each other this is actually not difficult.  I didn't believe it until I tried.  The key to making this work is getting the measurement right (and the sides of the blank being parallel.)  My current build had 24 each 1/16 inch holes drilled, half from each side.  22 hit right on, and the other two are close enough.  I didn't try to drill through the metal, but just marked it and drilled it out of the rifle.  (The barrel is held to the stock with keys).   I drilled the trigger retaining pins all the way through and yes, the bit wandered a little. 

[huntinguy]

By fine, I take it you mean small diameter drills.
General rule of thumb is no more than one drill diameter of depth per peck. I have found half a diameter works better.

[B Shipman]

If being on a perfect line matters, as when you're running a molding line down the forestock, I drill from both sides with a bit smaller drill then ream the hole, then drill with thecorrect size drill. Then drill thru the tab of the underlug.

Wedges are a matter of driling 3 holes side by side and cleaning out the material in between and suqaring the corners.

[B Shipman]

If you want to go straight thru in one shot make sure the bottom side is square, run the drill fast and go slow backing off frequently cleaning any woood out of the flutes.

[Richard Snyder]

I find it useful while using a drill press or mill/drillpress to very lightly lower the bit onto the surface with the motor off and watch for a very slight deflection of the drill bit in any axis, and then carefully make corrections.  Then repeat the same with the motor running.  If the drill bit deflects even slightly initially, it is likely to continue off axis.

[Curt Larsen]

I still use one of Tom Snyder's or Dave Rase's drill jigs.  I locate my pin positions on each side of the stock and use a pin drill with a 1/16" bit and drill by hand on each side.  The holes intersect in the middle as they should.  The only problem with this method is that your fingers get a bit tired.  I use this same tool for lining up my tang bolts and trigger plate pilot holes although using a 3/32" bushing that I asked Tom Snyder to make for me.
Curt

[Acer Saccharum]

The smaller the bit, the more flexible it is. Drills like .02 0o .031 will flex considerably, and tend to follow the grain of the wood. For 1/16 pin holes, I use a 1/16 right from the start, and have little trouble with wandering. If drilling on a sloped surface, I do a spot location drilling with the tip of a combined drill/countersink then switch to my 1/16 drill.

[smylee grouch]

I have had some luck using an awl to poke start a hole before using the drill.

[T*O*F]

Spot your holes on either side with an icepick or scribe using a small square to keep them straight.  You should be able to push them in 1/4" or so to give a straight hole with some side support to continue with your drill.

[flehto]

I just clamp the stock/bbl assembly in a very accurate vise w/ the top bbl flat against the permanent jaw. A parallel at the muzzle end makes things horizontal. This is all done on a reinforeced 3/4" plywood which is bolted to the DP table and accommodates drilling all the bbl lug or RR pipe holes in one setup.

Accurate layouts of the holes are made and an awl makes the dimple for starting the drill. I use 1/16 dia music wire for all the pins in my builds and only use a 1/16 drill. First I "eyeball" the drill point alignment w/ the "dimple" w/ the spindle on and drill to a depth of approx. 1/16".....then the workpiece is moved by hand so there's no "skating" of the drill.  A spindle speed of 1350 RPM is used and a sharp 1/16 drill w/ light force and constant chip clearing  starts the drilling until the drill contacts the tab and then even lighter force gets through the tab and the drilling continues until the drill breaks through on the opposite side.

Have bought "hardware store drill bits" that have bent shanks and wrongly sharpened "points".... the cutting clearance isn't sufficient so that the "heel" hits first. So, I check all drills for these "mistakes".

After the layouts are made, the total drilling time for 4 holes is approx. 15-20 mins. The clamping of the ass'y and RR pipes  , etc is for another topic.

The holes all are straight and go where intended.....Fred



 

[Dphariss]

In keeping with the thread concerning repairing pin holes, etc   I have had the mis-adventure of drilling pin holes with fine drill bits, and ending up with them drifting off line.   This has happened even when I have using a "spike type" drilling guide.   The bit lines up with the spike before and after drilling.  The bits have been high quality and sharp.   I suspect that I should be drilling slower, possibly with higher drill bit speed?   Any other thoughts or ideas?  thanks......

Start the hole with a CENTER DRILL. MAKE SURE THE BITS ARE SHARP I.E. NEW. Run at highest speed. Drill slow and clear chips every 1/8" or so.  I don't drill holes this small though stocks. If you are drilling through a metal part such as an underlug/rod pipe. Stop when the metal is marked by the drill. Remove the part, drill the hole at the mark, reinstall and finish drilling the hole, or finish drilling the hole then reinstall. Best to use 1/16 holes or larger. This will end some problems.
It is also important to watch the runout of the chuck on the drill press. Run out can make static marking of the drill start point inaccurate. IE put the "center" off center if this is used to indicate the start point of of the hole. This is why the center drill works better. They come in a variety of sizes.
Oh! Don't by taps and drills for precision work at the hardware store or lumberyard. Buy QUALITY tools and avoid imports from the Commies and the third world.
USA or European are best Japan is good too. China etc, = junk.
Dan

[P.W.Berkuta]

The previously mentioned methods all work when the moon & stars are aligned "just right" -- I think it was Mike Brooks that said that you also have to hold your tongue to the right of the corner of your mouth and griped by your front teeth with just slight pressure to "steer" the drill bit on a true path !

[jerrywh]

 When you start the hole chuck the drill bit up very short. Only leave about 1/4" or less of the bit extending out of the chuck. Once you have the hole started to that depth then proceed as described by Bill Shipman. This will give you a guide hole. I also drill from both sides in this manner.

[PPatch]

After careful measurement I prick or punch at the correct location on the stock (each side) then use a finger drill for the first eighth inch or so and finally switch to a power drill going first one side then the other. I do not drill through the metal, that I do in a separate operation. For me hand starting slowly with the finger drill gives me total control. I use the same method for starting butt plate screws.

dave

[Steve-In]

Also use stub length drills to get the holes started straight.  Less drill length usually equals less drill bending.

[flehto]

To expedite the drilling, I use 1/16 drills full length so they don't have to be re-chucked to drill through. Wood is soft compared to metal and although center drills and "stubby" drill bits  would be OK w/ metal parts, they don't flex when first contacting the "dimple" in wood.....so the location could be off  from the start because these 2 types of drills won't "pull" the heavy workpiece into alignment and will start to drill irrespective of the "dimple".

Evidently many have problems w/ drilling straight holes and holes that are  accurately located.....so the  use of drill jigs , etc.  Nothing wrong in using   them, but there are easier, faster and more accurate ways to do it.....Fred