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markopolo 11-26-2007 10:52 PM

Drill holes in the frame ? ?
I've done a Google search but haven't found much. Is it ok to drill holes in the chassis frame?

I'll try use existing holes if possible. I want to mount this battery holder.

I'm open to all ideas. Actually, I want to mount two of them. A group 24 battery fits in the holder.

markopolo 11-26-2007 11:46 PM

I did find this in the GM Body Builders Guide:


G/H VAN (GMT 610) 5 PAGE
Section 2 Frame

Hole drilling, welding, modifications, or alterations to the frame assembly are the responsibility of persons performing these operations. These same individuals assume complete responsibility for frame assembly, reliability, performance after alterations and compliance to applicable FMVSS requirements.

The following procedures and specific precautionary instructions are recommended for proper installation of special bodies and/or equipment on GM frames. Failure to follow these recommendations could result in serious damage to the basic vehicle.

New soft mount provisions for RV and Commercial bodies (vehicles 03/32 YFI). Locations found on the reference pages 38 - 40 in the Body Builders Manual.

Do not drill holes in frame flanges:
Within 20 mm (0.75 in.) of radius tangent and 25 mm (1.0 in.) of raw edge.
Larger than 12 mm (0.50 in.).
Closer to each other than twice the hole diameter.

NOTE: The frame flanges holes recommendations might be affected by the soft mount provisions/locations.

Holes to mount brackets, supports, and out-riggers must be drilled in the vertical side web with the following restrictions:
Material between edge of hole and inside of upper or lower flange must not be less than 37 mm (1.50 in.) for low carbon steel
(36,000 PSI yield).
The minimum edge distance between any two (2) holes must be larger than twice the diameter of the larger hole.
No holes should exceed 20 mm (0.75 in.) in diameter.
All holes should be drilled in the frame using appropriate drilling practice and safety precautions.
and this:


Shear Plate Attachments
Attachments of shear plates should be accomplished by using existing manufacturing holes already available. When additional holes are required for shear plate attachment, they should be no larger than 20 mm (0.75 in.) in diameter. Holes are to be drilled no closer than 63.5 mm (2.5 in.) apart. For holes drilled forward of the rear axle, centers are to be no closer than 63.5 mm (2.5 in.) from the top or bottom flanges and no closer than 89 mm (3.5 in.) from any suspension attachments. For frame holes drilled rearward of the rear spring hanger bracket, hole centers are to be no closer than 51 mm (2.0 in.) from the top or bottom flange and no closer than 89 mm (3.5 in.) from suspension attachments. Required large holes such as 20 mm (75 in.) diameter or larger, should be kept to a minimum required opening. Tubes should be welded in place if holes in excess of 25 mm (1.0 in.) diameter are required.
Anyone know what these are?

- radius tangent
- raw edge

Vertical side web

g1g 11-27-2007 02:00 PM

I believe the flange is the top and bottom of the frame (not the side) and the radius tangent my guess is where the flange is bent or any other bend. I have drilled holes in several frames and although I didn't engineer anything I believe if it is just a small hole it doesn't matter much. I think quarter inch bolts would hold up a battert box. Also if it can be mounted in a place where there is not much stress. I think there would be more stress around the suspension points. When I mounted my fuel pump for the generator I drilled quarter inch holes for that.

markopolo 11-27-2007 03:29 PM

Thanks - that's what I was thinking re: the flange. Guess I'll have to crawl under for some "quiet time" and contemplate :wink:

One nice thing about a cutaway chassis is that it's more open under the vehicle than a van body.

RS 38-40 11-27-2007 05:41 PM

How about U bolts or U brackets around the frame ? Not sure if there is a space between the frame and the body . Might be worth a look .

markopolo 11-27-2007 09:00 PM

I like that idea.

I'll know better when the part arrives. Right now I suspect that the frame is actually higher than the area with the bolt holes on the battery tray.

There is a gap between the frame and the body.

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