when drilling a stock for pillars, how large a drill bit compared to the pillar being used. for example drill a hole 9/16 for a 1/2 pillar. And the next question. What is the best way to determine the final height of the pillars? any tips or what I should be looking for. What is the most efficient way to cut pillars to final height?
There is lots of info about how to install pillars but not much on a few details I am looking for.
Thanks
Depends. Many ways to skin a cat and I have tried several with equally good results. Keep it distortion free and understand the concept (instead of just following some prescription blindly) and a number of ways will produce a similar outcome. Anybody telling you there is just one way is really telling you they have only tried one way. Or worse, they've compared the theories on paper and picked one based on feel.
In the end you just want a precision molded mirror image of the action in the stock, and you want to prevent the stock material from compressing when you repeatedly loosen and bolt together the nut (the action), the washer (the bottom metal) and the screw (the action screw).
You can do poured pillars, pillars touching the action, pillars covered by bedding material, two-part adjustable pillars, pillars poured in two parts, whatever. Do it right and it doesn't matter. Just think about consistency: Will everything sit the same way every time and will it stay in place when firing?
The way I currently do it, I leave the pillars covered on the action side, and long on the bottom metal side. This way I really only need to care about screw to pillar side clearance when installing the pillars. Topside alignment will be achieved with bedding material forming a 100% fit (regardless of receiver contour, heat treatment induced distortion etc.) , and bottomside I will mill the pillars for a good bottom metal fit.
When I'm working on a rifle that already has a good inletting job, alignment is ok, waterline is correct, etc. , I use quick epoxy putty pads to retain level, and action screw holes to retain alignment.
With release agent (Kiwi) applied, I assemble the rifle with two pads of epoxy putty in the barrel channel, one pad at the chamber area and another at the fore end tip. After the epoxy has hardened, I have my reference for level.
Since I now have my reference in the barrel channel, I can just go to town on the inlet. I make some 1/8" of clearance for the bedding material.
I produce my pillars by cutting threaded rod to length, followed by drilling them slightly oversize for the action screws. I used to cut "locking lugs" (as seen in the picture) to prevent the pillars from turning, but I don't do that anymore, in practice it just doesn't happen so it was overkill.
Two alternative methods for the pillar holes, one not better than the other. I have tried both.
1. I make the holes in the stock slightly small for the pillars and thread the pillars in (kind of tapping really). If the original action holes were well aligned, screw to pillar clearance will be guaranteed. Or,
2. I make the pillar holes slightly oversize. Thread a pair of headless screws (painter's tape applied to the screws until the pillars are a tight fit) into the action. Apply 5-minute liquid epoxy on the outside of the pillars and set the barreled action in the stock. Eyeball and adjust for final alignment (since the oversized pillar holes allow for slight adjustment) before the epoxy cures.
I open up existing action screw holes with a custom reamer I made, with a long 1/4" solid pilot to follow the existing holes.
So now the pillars are in place. I plug the pillar holes with a couple of wooden dowel pins to prevent bedding material from running into the holes. The headless screws in the action will push these pins through the pillar holes and onto the table or floor when I lay the action into the bedding later.
Next the usual preparation for bedding. Clay, release agent, tape, zipties, clamps, acetone, q-tips, etc. 24 hours later I have a precision mold of the action in the stock.
