C-Frame Bench Dimpling Tool
- A combination of the best features of several tools.
- Set holder in base features .401" shank and can also be used in rivet gun
- Base accepts all .401" shank rivet sets.
- Bronze bushings reamed to fit ram for more accurate alignment.
- Arm, Base and Front plate are powder coated separately to allow for adjustment (see adjustment below)
- Needed for both dimpling and setting rivets.
- Assures perpendicular placement of dimple dies and rivet sets to skin surface.
When to use the C-FRAME TOOL:
- For dimpling of all control surfaces and internal areas of aluminum sheets.
- For riveting stiffeners and hinge fittings to the wing and empennage spars, as well as other sub-assemblies.
- 22" Throat depth.
- Arm is 1" x 2" x .120" powder coated steel tubing.
- Base is 1.5" x 4" x 5/16" aluminum channel.
- Bushings are 1/2" ID sintered bronze.
- Base set holder accepts .401" rivet shank (same as rivet gun).
- Ram is stainless and heat treated.
- Ram accepts .187" shanks of dimple dies or squeezer sets.
- Ram has 3/16" hole in end to accept dies or sets; comes with flat set for flush riveting.
- Low tension return spring holds ram off skin for positioning.
- C-frame table: Prints for building a carpet covered wooden table top are included to provide a perpendicular work surface.
For using this tool with a rivet gun and extended back rivet set watch the EAA Video
featuring our tool!
If it seems that your c-frame may not be lined up perfectly. Below are a few notes on how to use it and what to look for.
1. Always keep down pressure on the ram with one hand before you strike the ram with the other. This pre-engages the male die with the female. 2-3 light taps are what you are aiming for to complete the dimple. Inherent in the process you will likely get some side load from the skin on the male pilot of the die. Manually pushing down the ram aligns these halves without stressing the pilot. This assumes the c-frame is aligned correctly, see bullet 3.
2. As mentioned above, make sure you don't have a side load on the dimple die. This is easily induced by the skin weight, or even by pushing the skin as you reach for the ram. It's best to push and pull the skin after it falls over the male die in order to feel if the bottom post is in a neutral position. It seems like a lengthy process, but as you know what to look for, it's actually quite fast.
3. Is your c-frame ram axis is inline with the bottom post axis? There are two adjustments for fixing this if needed. The front plate is adjustable by several thousands of an inch by loosening the two front screws until there is an air gap under the lock washer, but the lock washer is still compressed. Once loose the front plate can be tapped into position. If the limit of adjustment is reached here, the four back bolts can be loosened to accomplish the same thing (this is less desirable but may need done if frame has been dropped). The test to see if the ram and bottom post are collinear is simple. Remove all dies or sets from the ram and bottom post. Flip the ram upside down such that the 1/2" diameter O.D. of the ram is sitting on the 1/2" O.D. of the bottom post. Drop the ram without touching it, ensuring that there is no load on the ram or post. Aligning your eye at the elevation where the two parts come together, look for a wedge of light to make sure faces are parallel, if they are move 90deg. around the ram and look again. If there is no twist, make sure there is no parallel offset by ever so gently running your thumb and index finger up and down between the ram and bottom post. If one feels like it is protruding and the other is recessed, adjust the front plate as above. If they are in line, position your fingers 90deg. around and test again. These tests should show you if there is any misalignment in the c-frame. Generally misalignment causes the male die pilot to shear off when struck with a hammer because what was being forced into alignment now adjusts to it's natural state.
Mike talks about C-Frame usage on our YouTube, about 5 mins in.
Check out our YouTube channel for more how-to videos.