Safety in drilling the frame?

At the top of the frame, passing under the seat and just ahead of the upper shock mounts on my '82 KZ750H, there is a cross tube welded between the main upper tubes. Looks to be about 1" OD tubing. Would it weaken the frame to drill a 1/4" hole vertically through the tube near each end? Like this.....

Removing material weakens structure. I would add a cross bar and drill that. (2 cents given)

As related mostly in earlier threads by respected others ---

If going to drill the frame, would make a boss (a thick walled tube that extends through the frame) and braze it to both sides. That would provide strength and support to the frame and keep the hole from cracking. Like the right front engine mount plate bolt holes.

A boss reinforces the frame where it's been drilled.

Done right with quality welding, the frame with boss is stronger than before. The tube goes all the way through, and that's what is meant by a "boss". [Similar to a spacer welded perpendicular through the frame which serves as a passageway or tunnel for a bolt to pass through. Note front motor mount bolted through frame downtube, per factory manufacture.]

Tig welding would probably be better than brazing, but the equipment is more expensive and it requires more skill.

The frame is just mild steel, and the only difficulty drilling is keeping the drill centered.

If feasible for the intended application, brazing a mount to the frame would be better, or adding another crossbar as loco suggested.

Good Luck!

I would not recommend brazing to the frame. Too much of the steel must be heated red hot and you risk softening or dis-tempering too large of an area. welding only. I would never drill into the frame. Cracking is a real possibility.

what are the holes being drilled for?

otakar wrote:

I would not recommend brazing to the frame. Too much of the steel must be heated red hot and you risk softening or dis-tempering too large of an area. welding only. I would never drill into the frame. Cracking is a real possibility.

would never drill into the frame

Yep. Just a gut reaction, but I wouldn't bore a hole of any size into one of my own motorcycle frames for any reason. Being afraid it might weaken the tubing, foster stress cracks, or result in some other weakness sooner or later, due to vibration, etc.

Perhaps jonnybiker said it best:
I guess when the frame tubes start cracking from the new holes out.....you might then see the big effect. Then again....Its your bike, your butt.... go ahead and drill away if you so choose. Would never consider such a thing on any of my machines. just my opinion. jonnybiker


Good Luck!

a hole can actually be used to stop a crack when drilled in the end of the crack.you also have to look at which direction the metal is under a load from,im not saying to swiss cheese youre frame im just saying that drilling a hole is not always a bad thing you guys would really freak out if you were to watch a plumber or electrician blowing holes through floor joists and studs in walls when a wood framed house or building is being thrown up! :woohoo:

I wanted to mount a GPz tail section onto a CSR frame. I could have drilled holes to make it easy but the thought never crossed my mind. I decided to do it with a cold weld.

Here's more

Another

And the last

With due respect I'm not sure comparing a wood framed houses drilled for pipe or wire compares to a metal frame drilling. As stated vibrations and rust are also concerns along with the initial weakening. Great ideas to boss the holes and such if you do need to drill. I have seen cracks in windshields stopped by scribing circles or drilling a hole. Do they do this in metal too?