Threads; Lining up slot in heads

OK...you all have seen it before...

Example; a recent cover of Precision Shooting had a double rifle/shotgun on the cover and all the slots in the screws were in the same position.

Is this because he/she torqued them differently to achieve this look or is there something simple I am not aware of?

Anymouse,
I heard one trick was to make the head extra thick, then torque the screw to the correct level and mark the screw. Remake the head so you cut the slots to line up.

There are other ways to do the same thing, just don't remember the others right now.

Thanks,
Paul

There is no trick to this; it is simply a matter of tightening the screw, determining how much more it needs to be turned to index correctly and then removing the correct amount from the underside of the head so it will index correctly.

Jim has it right for most of the screw alignment jobs done.

To align the screw slots you must know the thread that is used and have an accurate (maybe just a good eye) way of knowing how far off the slot is.

So if your screw has 32 threads per inch, one full turn will move the screw 0.03125 inches.

If your slot is 45 degrees from being true you would divide this by 8 to tell you that you would need to machiine off 0.00390625" or just a smidgon off0.004" of an inch, this about as close as I could get it. better stop short and try it several times to get it right. It also helps to establish a line on the gun that you will true to.

It takes time and effort to get it right which is why it is done. The closer you can measure the off angle of the slot and the cut that you make does the trick.

Being a little off on something like this sometimes looks worse than being way off. Aligned slots are a true challenge but on the right firearm well worth the effort. I do like to have a taller head so that when they are properly torqued and aligned then I can finish the tops to be flush with the sideplates of the gun.

Eagle

Eagle,

Two questions:

1.) what is the formula to get movement if TPI is known? E.g. 32 tpi; 1 turn = 0.03125"

2.) if the screw is not bottoming out...Stop! I figured this part out.

So there is only one question.

Thanks!

Anymouse

If the screw is 32 threads per inch then one turn moves it in one 1/32 of and inch or .0325". 40 Tpi = 1/40 of an inch per turn or .025". And so on.

bandhmo said:

If the screw is 32 threads per inch then one turn moves it in one 1/32 of and inch or .0325". 40 Tpi = 1/40 of an inch per turn or .025". And so on.

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I think that should be .03125" ( half of a sixteenth, .0625).

I use a protractor to determine how much to turn the screw. If you need to turn it 45 degrees, divide .03125 by 360 deg = .0000868 x 45 = .0039". You need to take off about .004" from the back of the screw. This method can also be used to orient a barrel to an action if you need to align the sights correctly. SImply level the action and with a protractor with a bubble, measure the amount of turn needed.

Perhaps a bit easier than removing material from under the screw head would be to deepen the counterbore/countersink, especially if you are only talking a few thousands of an inch. the counterbore or countersink tool could be held in a tap wrench or pin vise. Getting the screw head slots all going in the same direction is called timing the screws.

I don't like cutting on a part I can't replace to fit a replaceable screw.

Eagle

Chuck the screw in a drill press with the head a little below the end of the jaws. Turn on the drill press and hols a knife edge file against the head. Try and repeat, try and repeat. After a while you get a good idea of how much to take off without going too far.

If you are making new screws then you can have a long head and cut the the slot after the head has been trimmed to length, as mentioend in the first post.

Yes, you can deepen the counter sink, but I would never do that. Screws are cheap. Actions are expensive (and much harder!!!). Stick to the screws.

It sounds real cool to take off metal down to the hundred thousandth at some funky angle, but in practice it is not so easy to do. Also remember that your tool is between the screw head and lathe chuck/collet/whatever. And you first must have a good way to hole the screw where the head sticks out and the screw will not tighten as you cut. You really need to be turning with your compound, as your Z axis on the lathe has the poorest and most coarse motion control. This means the compound needs to be swung to csome funky angle that you must first accurately measure on the screw. Try this on a lot of old European and English shotguns and get back to me on how consistent and easy to measure the angles are!!! The drill press method is faster and just as accurate if you know what you are doing. It does not take much practice to figure out how to do it.

So here are a couple of other ways to skin the cat. Try them all out and figure out which you like best. If you come up with a different way to do it, then please share it here!

Some gun screws that you may like to time are rather short. Chucking the threaded end in a drill press SECURELY and trying to file the underside of the screw head may next to impossible or at least very difficult. While I certainly agree with working on the least expensive part first, I would not have a problem with removing a few grand from a countersunk or counter bored hole if it would be expediant. Making a new screw as suggested by gunbuilder is the best way, especially if there is a total refinish as well. The screw can be timed and then polished in place to match the contour of the parent part.

Gazz said:

Some gun screws that you may like to time are rather short. Chucking the threaded end in a drill press SECURELY and trying to file the underside of the screw head may next to impossible or at least very difficult. While I certainly agree with working on the least expensive part first, I would not have a problem with removing a few grand from a countersunk or counter bored hole if it would be expediant. Making a new screw as suggested by gunbuilder is the best way, especially if there is a total refinish as well. The screw can be timed and then polished in place to match the contour of the parent part.

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All well and good but we don't always have the counterbore for the part.

I chuck up the screw in my 3-jaw and leave it out with about an eight inch clearance between the head and chuck jaws. I have a small tool I use with the lathe in reverse and touch the tool to the back side of the screw head. I put a dial indicator, on a mag base, on the lathe bed and against the carriage, move the required amount and cut.

Properly "timed" screws stop on the threads not with the head. This lessens the possibility of the screws being over torqued and compressing the wood, along with other bad things.
h2o

Who said anything about wood?
James

J. Randall said:

Who said anything about wood?
James

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James,
Not all screws are in the action alone. Tang screws go through the wood. On a high end gun/rifle ALL screws are timed. Even the ones inside that are not visible.
h2o

h2oboy said:

Properly "timed" screws stop on the threads not with the head. This lessens the possibility of the screws being over torqued and compressing the wood, along with other bad things.
h2o

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I'll raise the BS flag on that one. What the hell do you mean by that?

Jim Kobe said:

I'll raise the BS flag on that one. What the hell do you mean by that?

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Jim,
You can call BS all you want, but its true. Maybe I should have said "Quality" guns not high end. On a H&H, Purdey, or Boss the head of the screw does not time the screw. The threads time the screw. I believe Michael McIntosh wrote about this somewhere, but I do not remember where. Maybe in Shooting Sportsman. I learned this when I was in Austria. Think about it, It makes sense.
h2o

H2O, guess what ? I knew guns had wood on them and they are sometimes fastened on with screws, and on high end guns they are usually timed. It was just my way of saying I thought most everyone else was talking about metal. I am kind of like Jim, I think I still need some convincing as to the method you described.
James

h2oboy said:

Jim,
You can call BS all you want, but its true. Maybe I should have said "Quality" guns not high end. On a H&H, Purdey, or Boss the head of the screw does not time the screw. The threads time the screw. I believe Michael McIntosh wrote about this somewhere, but I do not remember where. Maybe in Shooting Sportsman. I learned this when I was in Austria. Think about it, It makes sense.
h2o

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If that were the case, why have a head on a screw at all? For looks? How in the hell would you hold the side plates on a high grade shotgun or rifle? What does the head do, in your opinion?

J. Randall said:

H2O, guess what ? I knew guns had wood on them and they are sometimes fastened on with screws, and on high end guns they are usually timed. It was just my way of saying I thought most everyone else was talking about metal. I am kind of like Jim, I think I still need some convincing as to the method you described.
James

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James,
I was not implying you did not know guns had stocks. I am a pretty blunt person and I say what I think. It was not my intention to insult you. But when you talk about timing screws, it is all scews. Not just some. What differance does it make if it is in wood or metal? Its still the same. That is why I answered the way I did.
h2o