I need to find a method/equipment (preferably something small enough I could take with me in a case), that will measure the sharpness of teeth we are broaching into a flat aluminum piece. The teeth will only be about .060" tall and .060" spaced apart.

Anyone know of equipment I could look for to do this?
How would you measure sharpness?

I need to find a method/equipment (preferably something small enough I could take with me in a case), that will measure the sharpness of teeth we are broaching into a flat aluminum piece. The teeth will only be about .060" tall and .060" spaced apart.

Anyone know of equipment I could look for to do this?
How would you measure sharpness?

How is the sharpness specified?

I would imagine teeth (like saw blades and knurls) might be measured by angles. If the blade is chisel shape - just the chamfer. Use a hand held optical comparator/magnifier to check for burrs and have a reticle with the desired angle etched in to check for the proper angle of the cutting edge or points of the teeth.


Edmund is a good beginning search for such optics
http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productID=1428&search=1

There is no sharpness specified on the drawing, yet. I don't believe engineering knows exactly how they want to specify it just yet. They are looking to me to provide a variable measurement, and they know they want the teeth as sharp as possible at this point.

These straps are up a against a rotating, painted, alum-diecast housing. Once the housing is rotated to the proper angle, bolts tighten the straps against the housing. They want the teeth to dig into the paint and provide holding force to keep the housing at its desired angle.

Saw teeth, looking at the strap from the side is a good way to describe what the teeth look like. I don't have a comparitor with enough magnification to get a large enough view of the teeth. I have a microscope on order but it has a long lead time, and I'm trying to see if there is an alternate method.

My initial thoughts to measure sharpness would be to intersect the two lines off of each side of the tooth to find a theoretical peak. Then measure from the theoretical peck down to the top of the tooth. The shorter the distance, the sharper the tooth.

There is no sharpness specified on the drawing, yet. I don't believe engineering knows exactly how they want to specify it just yet. They are looking to me to provide a variable measurement, and they know they want the teeth as sharp as possible at this point.

These straps are up a against a rotating, painted, alum-diecast housing. Once the housing is rotated to the proper angle, bolts tighten the straps against the housing. They want the teeth to dig into the paint and provide holding force to keep the housing at its desired angle.

Saw teeth, looking at the strap from the side is a good way to describe what the teeth look like. I don't have a comparitor with enough magnification to get a large enough view of the teeth. I have a microscope on order but it has a long lead time, and I'm trying to see if there is an alternate method.

My initial thoughts to measure sharpness would be to intersect the two lines off of each side of the tooth to find a theoretical peak. Then measure from the theoretical peck down to the top of the tooth. The shorter the distance, the sharper the tooth.

I have no feel for the size of the thing you're talking about, but it seems like a loupe/reticle such as Wes described might be useful. There might be a problem measuring angles though, because of the difficulty in establishing the reference plane.

Here's just a few stray thoughts....

Make a set of set of "chisels" that have varying angles on the tip. The points that are either too sharp or too blunt will be loose in the teeth, but the best fit should be fairly snug. Granted the teeth are only 1/16" deep, but you should be able to tell by feel which fits best.

Since you are interested in how well the teeth dig in, you could measure that directly. Make a little jig where you can press the part with the teeth down onto a blank chunk of aluminum. Measure, for example, the force (or torque on a bolt) required to press the teeth 0.020 into the blank.


Tim F

These straps are up a against a rotating, painted, alum-diecast housing. Once the housing is rotated to the proper angle, bolts tighten the straps against the housing. They want the teeth to dig into the paint and provide holding force to keep the housing at its desired angle.

I'd be more than a little worried that teeth biting into paint on a housing was being used to secure something:mg: It would be better from a purely engineering standpoint to bear into the unfinished casting and then paint over (if needed for protection).;)

Andy, I'd be going back to the engineers who dreamed this one up and getting them to change the spec., not trying to find an elegant solution to measuring teeth sharpness;)

Andy

I'd be more than a little worried that teeth biting into paint on a housing was being used to secure something:mg: It would be better from a purely engineering standpoint to bear into the unfinished casting and then paint over (if needed for protection).;)

Andy, I'd be going back to the engineers who dreamed this one up and getting them to change the spec., not trying to find an elegant solution to measuring teeth sharpness;)

Andy

The paint is needed for protection. But it would be an interesting study to measure the holding force on a part that had the strap area masked off.
Thanks,