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Trouble Maker
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I was wondering about having some of my bolts on my V "gun drilled". Gun drilling is hollowing out the length of a bolt. I have a set of axle shafts for a 2 1/2 ton Rockwell axle that I had gun drilled. It makes them lighter and I'm told stronger because there is now 2 shear planes. Any thoughts? Anyone on here capable of doing this? Would the bolts need to be heat treated afterwards? Thanks. Jim
 

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Sharks-Parts
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check with Ron Cooper....
 

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I was wondering about having some of my bolts on my V "gun drilled". Gun drilling is hollowing out the length of a bolt. I have a set of axle shafts for a 2 1/2 ton Rockwell axle that I had gun drilled. It makes them lighter and I'm told stronger because there is now 2 shear planes. Any thoughts? Anyone on here capable of doing this? Would the bolts need to be heat treated afterwards? Thanks. Jim
I couldn't resist. I know you asked for a machinist or an engineer. I could not see this being stronger despite the shear factor mentioned. The mere fact that you are losing mass by hollowing out the center tells me that this would weaken the material. I guess you could temper and quench the materials to improve the strength but I would still be skeptical.
 

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I couldn't resist. I know you asked for a machinist or an engineer. I could not see this being stronger despite the shear factor mentioned. The mere fact that you are losing mass by hollowing out the center tells me that this would weaken the material. I guess you could temper and quench the materials to improve the strength but I would still be skeptical.
Gun drilling bolts is an old racing trick to lighten the bike. Hollow titanium bolts are what serious road racers use. The strength of the bolt is in the outer diameter. The inner material contributes very little of the strength. A large diameter hollow bolt or axle is stronger than a smaller diameter solid one.
I don't know enough about the material used in Harley Davidson bolts to make any judgement on what drilling the stock bolts will do to their strength. How much of the diameter is drilled out (remaining wall thickness) and how parallel to the length of the bolt they are drilled (very big if) will affect strength.
 

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What's the purpose in drilling a bolt? Losing half a pound of steel on a 700lb motorcycle equals no difference. The stock bolts are strong enough, I think...
 

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Gun drilling bolts is an old racing trick to lighten the bike. Hollow titanium bolts are what serious road racers use. The strength of the bolt is in the outer diameter. The inner material contributes very little of the strength. A large diameter hollow bolt or axle is stronger than a smaller diameter solid one.
I don't know enough about the material used in Harley Davidson bolts to make any judgement on what drilling the stock bolts will do to their strength. How much of the diameter is drilled out (remaining wall thickness) and how parallel to the length of the bolt they are drilled (very big if) will affect strength.
In one respect, you say that the strength of the bolt is in the outer diameter but your last statement says that the remaining wall thickness will affect strength! I'm confused...

I know that a hollow shaft of the same material is not as strong as a solid one... I believe that was his question.

Not trying to be a [email protected] just pointing out how I see it.
 

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In one respect, you say that the strength of the bolt is in the outer diameter but your last statement says that the remaining wall thickness will affect strength! I'm confused...

I know that a hollow shaft of the same material is not as strong as a solid one... I believe that was his question.

Not trying to be a [email protected] just pointing out how I see it.
I understand. The strength of a shaft is proportional to it's diameter. Since the diameter of the hole or hollow portion is less than that of the outer diameter of the shaft but the proportion is not a straight line relationship, the material that was in the hollow portion contributed little to the strength of the shaft. I have included a link to some of the math involved.
In general the comparison is that for equal weight shafts, the larger diameter of the hollow shaft gives it superior strength to the smaller diameter solid shaft. For equal diameters, the solid shaft is stronger, but at a considerable weight penalty. With most vehicle fasteners, the necessary strength is derived from the outside diameter of the fastener (surface area of the thread becomes the determining factor when applying a torque), so the inner material is really surplus, but making hollow bolts is quite a bit more expensive than making solid bolts so manufacturing costs become the deciding factor, unless you are racing.

http://www.engineeringtoolbox.com/torsion-shafts-d_947.html

Here is an interesting discussion of solid vs hollow shafting for mixer drives.

http://www.sharpemixers.com/Shafting.htm
 

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I know that a hollow shaft of the same material is not as strong as a solid one...
This is true and not true at the same time, a hollow shaft is strong in some directions then a solid shaft. I could if I really wanted to run a FEA test on it and show you but it is to time consuming and I am just to lazy to do any more FEA work then absolutely necessary. I already have to do to much for work without bringing my hobby into it....

That being said because you question is to vague, because you never ask which bolts. There is no yes or no answer. I am sure that it would be ok in some instances and not ok in others but with that being said I would guess you would probably not lose any appreciable weight on our bikes with the bolts that could be substituted with gun drilled ones and if you decide to experiment with it I would not want to do it with the factory bolts, as just about everyone I have dealt with on my bike has been a non-hardened POS and I wouldn't want to risk breakage of the factory bolt machined down.
 

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I understand. The strength of a shaft is proportional to it's diameter. Since the diameter of the hole or hollow portion is less than that of the outer diameter of the shaft but the proportion is not a straight line relationship, the material that was in the hollow portion contributed little to the strength of the shaft. I have included a link to some of the math involved.
In general the comparison is that for equal weight shafts, the larger diameter of the hollow shaft gives it superior strength to the smaller diameter solid shaft. For equal diameters, the solid shaft is stronger, but at a considerable weight penalty. With most vehicle fasteners, the necessary strength is derived from the outside diameter of the fastener (surface area of the thread becomes the determining factor when applying a torque), so the inner material is really surplus, but making hollow bolts is quite a bit more expensive than making solid bolts so manufacturing costs become the deciding factor, unless you are racing.

http://www.engineeringtoolbox.com/torsion-shafts-d_947.html

Here is an interesting discussion of solid vs hollow shafting for mixer drives.

http://www.sharpemixers.com/Shafting.htm
Thanks for the material Philthy!
 

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Shaggy, I am referring to a shear configuration same material under the same test... We never ever use hollow shafts in our applications and our shafts are always in a direct shear. We are also always looking to save weight as well. We have multi-million dollar R&D department and I would assume that they would explore this option. I am referring to from 1/2T to 800T loads.
 

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You are3 correct in strictly a side load shear application a solid shaft will be stronger... Knowing what you do for a living I highly doubt any fastner you have on one of you set ups would benefit from a hollow tube vs a solid shaft no argument there. but please
800T my sons play with weights that small....:stilpoke:

Here is a real lift

 

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Kind of a hard thing to discuss without knowing what fasteners you are talking about. All fasteners have some tensile load on them simply by tightening them. However, some fasteners are then also put in shear loads (axles come to mind).

I'd say a general rule would be if there's no shear load applied, it would be fairly safe if you get the wall thickness correct. However, if there is a shear load then just leave em alone.

But I don't know much. :)
 

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Take no offense but I fancy myself an expert in the school of hardknocks relative to drilled out bolts. Just so happens this past weekend I was installing the road rod lower bracket. 4 bolts 10mm1.5 thread 50mm stainless. I found myself in the unenviable position of a cross thread , tried everything to get her loose NFL! soooooooo sheared head off and started drilling 1st pilot hole then larger one to accommodate extractor. Well the extractor is hard as hell but the drilled out bolt was fuken harder! Sheard that bitch off too. Had to walk away cuz I got no drill bit hard enough to get the extractor out so I had a long talk with Pepe ( lopez )

So I can speak to the relative shearing strength of a drilled bolt its all in the threads. Lesson learned keep your tap and die set handy!
 

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Trouble Maker
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Discussion Starter #14
Any or all bolts that I can possibly do. Thanks Jim
 

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Buy American!
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Just Ride

There's a lot of weight to be lost on these bikes if you have the machine shop to do it. You will probably want to start with the unsprung weight (axles, swing arm, wheels, tires, rear sprocket, brake brackets, etc.), then move on to rotational mass reduction in the transmission.

I'm sure that you could lighten the frame by a considerable amount if you can smartly drill dimple and grind in hidden low-stress areas.

Another place to look is in the engine cases. You could mill out pockets in the oil pan and easily lose 2 lbs of aluminum there. But if you expand the pan inside, you'll then have to replace it with 3 lbs of oil. Drat.

Keep track of the weight reductions, but be careful not to turn your bike into swiss cheese. All in all, I don't expect to see you lose 25 lbs in the process, but knock yourself out and prove me wrong.

You're greatest weight savings have already been met when you changed your stock exhaust.
 

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What's the purpose in drilling a bolt? Losing half a pound of steel on a 700lb motorcycle equals no difference.

There's a lot of weight to be lost on these bikes...start with the unsprung weight (axles, swing arm, wheels, tires, rear sprocket, brake brackets, etc.), then move on to rotational mass reduction in the transmission.

You're greatest weight savings have already been met when you changed your stock exhaust.
You'll spend a lot of money and time trying to save a pound by drilling the bolts.

Lighter wheels and exhaust are easy and will make a difference.
 

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Dare to Dream
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I do not have an "engineering" opinion to give, but its funny this thread should come up, because I also have a Triumph Daytona 675, and I recently installed riser bars on it to bring the riding position a little easier on the back. And I had to remove the top triple clamp to do it, and I noticed that the steering stem nut is aluminum and weighs nothing, and the aluminum steering stem shaft is hollow. I was thinking, wow they went to extremes to lighten this bike at Triumph, and it only weighs like 370 pounds. I have seen alot of hollow bolts on performance bikes I have owned in the past also. But my V Rod I cant imagine those kind of fasteners on, you may as well just redesign a lighter frame first, then lighten it ground up with the small amount you would gain with nuts and hollow bolts. Its just not a light bike overall. I myself would have an easier time losing weight than my V rod, and I only weigh 190 pounds.
 

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Trouble Maker
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Discussion Starter #18
I am not looking for super #'s. Just any help I can get. I already have the V&H Indy pipe which helped alot. I removed my front Reactor wheel which was 10 lbs. Heavier than the stock "F" wheel. I am looking to Sharkey for some lightweight wheel goodies and composite brakes. Carbon Fiber wheels are highly wanted but not in my near financial future...lol. We chase the dream anyway we can. Jim
 

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You are3 correct in strictly a side load shear application a solid shaft will be stronger... Knowing what you do for a living I highly doubt any fastner you have on one of you set ups would benefit from a hollow tube vs a solid shaft no argument there. but please
800T my sons play with weights that small....:stilpoke:

Here is a real lift

Show off! :D
 

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Instead of dickin around with drilling axles and bolts and all ( though the axles are hefty ill give u that) save your money and have a chromoly frame made up. Have you ever picked up a bare frame? I replaced my wheels with stock R1 wheels. Cheap, look good and very light compared to the dx boat anchors. But if your gonna go the full extent, dont forget the steering stem, that little things got some heft to it!! Good luck man, I know where your comin from. Check out my thread with the R1 vrod. I lost a ton of weight without spending a fortune. Id rather have a 400# 125hp bike than a 650# 200hp bike.
 
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