Brake Lining Countersink

[flyguy]

On the Shinn wheels, how thin can I leave the material under the rivet head when I do the countersink on the rivet holes? I've taken it down about as far as I am comfortable and the rivets are still just below the surface. Maybe .025 in. down. How thin is too thin? I know I will pick up a few thou. when I mash the rivets, but it sure doesn't allow much room for wear as is.
Darryl

[Guest]

Re: Brake Lining Countersink

Hi Darryl,

.025 doesn't sound like much.

A few thoughts;
Is the countersink shaped and angled proper to fit/seat the rivet?

I remember concluding that I didn't like the rivets that came with the lining then going to buy brake rivets at the auto supply that fit better.

Are you seating the rivet fully?

Check with a brake shop to see how much material they leave under the rivet head. I keep meaning to do that I pass one each week and forget to stop.

Dave.

[N74DV]

Re: Brake Lining Countersink

I read this thread then did some searching. I found a few threads that mention the use of an epoxy based adhesive to glue the loining to the drum.

That sound completely reasonable to me. I do the same thing on my linings for the centrifugal clutch on my gas powered RC helicopters. They get beat up pretty hard and have never slipped a lining yet. I use T-88 epoxy for that. Is T-88 a good adhesive to use for Shinn linings??

[flyguy]

Re: Brake Lining Countersink

Thanks Dave,
I think the problem is that the linings are just plain THIN. Regular brake methods probably wouldn't be applicable as those linings are much thicker. The rivets I received with the linings are about as good as could be expected (the heads are thin enough.) It is a problem getting the bottoms of the bore really flat but I have a pretty good tool for that. It just seems to be a lose/lose situation because of the design. The remaining material at the bottom of the counterbore is only about .030 in. now.

WOW- instant inspiration early in the AM. Install a thin piece of sheet metal with rivets first and epoxy the lining to the sheetmetal counterboring the lining on the outside surface to clear the rivet heads. No holes in the friction surface and minimum loss of wear thickness. Requires thinner lining? Have to do a mock up. Might work.
DC
DJ, must have been telepathy--I was geting my inspiration about the same time you were typing in your epoxy idea. To give credit where due I have to say that I must have had in my mind Rob Lees epoxy method. Always worried about chipping the linings out at replacement time if they are epoxied directly to the wheel; the metal band should take care of that problem.

[mhorowit]

Re: Brake Lining Countersink

This from Rob around Oct '03:
"... from the top of the rivet head to the surface is 1/2 the total thickness. . . May not be the way everyone else is doing it but it has worked for me on several different occasions."

Also, it's counter bored, not counter sunk 'cause the bottom has to be flat.
There is a dremel bit that does an excellent job; looks like a miniature milling machine bit. - Mike

[flyguy]

Re: Brake Lining Countersink

Thanks Mike, misuse of terms on my part. (definately not a machinist, LOL) The hole bottoms are flat. I may be a deeper than half, would have to measure. I am going to try out my idea with the thin metal backing, and I just figured a way to keep the epoxy from bonding to the wheel at the bottom. I have modified 2 drill bits to do the regular method by hand. Only used a power tool for the thru holes. Material cuts a little too easy for me to be comfortable using power.
DC

[M Jones]

Re: Brake Lining Countersink

Personally, I don't care for the epoxy route, but that's just my opinion. I used a Dremmel 5/16" flat bit in a drill press to counter bore the linings. This lets you go in at least 1/2 the lining thickness (deeper than recommended, take your time) Everything worked out just fine...

[mulwyk]

Re: Brake Lining Countersink

I used both epoxy and rivets. I figured the epoxy would hold the linings just fine...the rivets are for the inspector. Counterbored by hand with a brad point drill bit. About 1/16 deep. Photos here...click on brake rivets link.

Bob Gustafson

[flyguy]

Re: Brake Lining Countersink

Bob thanks for info,
Checked your link. Pretty much the way I am doing it. And the Brad point drill; ah yes the Brad point drill. What the heck is a Brad point drill?

OOPs, Nevermind. Just looked it up on the net. One of the drill bits I have is exactly that. Didn't know what it was.
I have an extra wheel so I am still considering experimenting with an aluminum backing plate to get more wear and avoid epoxying to the wheel. Don't know about other peoples experience, but when I epoxy something to aluminum the only way it is going to come off is with a grinder or a chisel.
Darryl

[mulwyk]

Re: Brake Lining Countersink

Sorry, Darryl, there's no reason you should recognize the term "brad point", it may be a regional term I picked up. The Photo below shows a "brad point" on the left and a ordinary drill bit on the right. The brad point (or whatever it's called) is designed for use on wood...the little point in the center serves to locate and guide the drill for an exceptionally straight and accurate hole. It's used for dowl joints or anywhere you want an exact size hole in soft material. If you try to use one on metals or fiberglass it gets dull in a hurry!

The advantage of the brad point drill bit for our Shinn brake applications is that the center point will follow a pilot hole...like the rivet-shank-size hole that you'll first drill when installing your brake linings. AND the outer part of the drill bit makes a beautiful, flat bottomed hole...just right for the rivet head. AND the flukes of the drill bit are sharp enough and at just the right angle so it'll easily shave away the soft brake lining material with only finger power (I wrap the shank of the drill bit with masking tape to save my delicate fingers). It's like a poor mans counter bore machine.

Bob Gustafson

[flyguy]

Re: Brake Lining Countersink

Thanks Bob,
The one that I have is actually a bit different and that is part of my problem. It has small triangular points on either side about in the middle of the cutting edge, so it leaves a small tapered edge on the hole. I modified a regular bit by grinding it off but it doesn't have good cutting edges at the correct angle. Since I am not in a hurry I'll probably look around for the real thing. I notice the brad point bits I saw on the net had little cutting teeth out at the edge. Don't think that kind would do as it would weaken the remaining material.
Darryl