Drum Resurfaced Finish

[wildwilly]

I just had some drums turned on a 96 K1500. I honestly cannot say I have ever done this before ... primarily replacing rotors these days ... but for only 30 bucks on this being my backup truck figured I would save a little. I do remember as a kid my Dad had this done often ... but was more common back then that replacing these days.

They were not bad by any means and had never been turned before. The front shoe was getting close and needed replaced for sure with lots of miles on these rear brake ... mostly doing front brakes over time as you know. I did sort of expect them to have a "smooth" finish, but honestly do not know. It seems maybe they just went over it with some sandpaper or something after the machining and possibly this is intentional to get a little more random finish or something.

Does this finish look normal after getting drums turned?

 

[Caman96]

Almost looks like it was hand sanded.

 

[Knuckle Dragger]

Yes, that's fine. The guy turning them broke up the "record grooving" with sandpaper or the like after he turned them.

 

[HotWheelsBurban]

From what I remember when I used to turn drums and rotors, back in the 80s( yes kids we had lathes then, just not fully automatic) the first cuts to remove material ( to get rid of grooves and out of round conditions) were faster speed. My lathe only had 2 speeds for rotors, and the slow one was for the finish cut, which should be smoother as the cutting but isn't moving across the surface as fast.
Think in terms of fine threads versus coarse threads.... The machinist probably felt it was still too coarse a surface, so they used emery cloth on it, maybe while hand spinning the drum on the shaft? That's how I did back in the day, if I didn't like how the surface came out. The drum function had several speeds, but you'd use the faster ones for the removal or truing cuts, then slow it down to make the finish cut.( Sorry if this sounds confusing, I sold the lathe several years ago and wasn't remembering it right to start with. Need another cup of coffee I guess!)
Point to all this is, the machinist did a good job, didn't take too much out of the drum either. So you should be good to go....

 

[sewlow]

Long-winded answer to a 'Q ' that could of been answered with a simple 'yes' or 'no'.
Got on a roll. A couple or 3, maybe 4(?), espresso's will do that. Bzzzt.

I've turned hundreds of drums. Yea. Hundreds. Rotors, too.
One of my duties working in a machine shop right outa school. 18 months. Some weeks, that would be ALL that I did! All day!
The Corporate rear end brake drums under 3/4 & 1 ton trucks were a PitA. Pretty heavy.
The drums from 2-5 ton trucks took two of us to mount on the machines. Stupid heavy!
The last part of the process was to scuff the machined surface, both drums & rotors, with some 100 grit before removing the drum from the lathe. The random cross-hatching helps to seat pads & shoes against the D&R's.
There was hell to pay if I short-cutted and skipped that step.

D&R's don't get machined as much any more. Easier to toss & replace because of those off-shore producer's cheap-cheap prices.
That also means that they're made cheap! Recycled steel with lots of foreign matter, plus a lower nickel content than those of 30-40 years ago.
It's the nickel content that gives the steel it's strength, durability & resistance to repeated heat cycles. Without that content, the Chinesium parts don't last. Too soft. The pads & shoes eat 'em up, especially with high friction pads/shoes.
They are also prone to warping. Can't take the heat. They really don't like extended periods of towing or canyon carving antics.
Even the OEM GM-labelled D&R's are off-shore-made now-a-days.
Junk.
I'm hard on brakes. A set of the jobber rotors lasts me about 8 months. So warped, hard braking would shake the S/wheel almost out of my hands. $60.00/pair.
After 20 years of owning 400's, I've gotten pretty good at doing brake jobs on em. It was getting expensive, though.
So...I bought some aftermarket U.S. Made rotors/pads, drums/shoes. The rotors/pads were close to (!) $400.
But they lasted for 9 years. 2 sets of pads & 2 turnings.
That's less than $50.00/year.
The jobbers were costing $90.00/year + pads.

Even still, no matter how much the parts cost, I always, ALWAYS, get new D&R's machined right outa the box. They go from the parts counter up front to the machine shop out back so there's absolutely no doubt.
I've had some that were so warped straight from the parts store that they could not be turned. So outa whack that by the time the surface was cut down to be nice & even all the way around, they were beyond the max cut spec.
I've returned as many as 3 sets drums & 2 sets of rotors in a row right back to the front counter before I even left the building.
When the machine shop guys brought the U.S. Made stuff back, they told me that they were damn near perfect right out of the box. They were surprised.
I also test fit the brake shoes against the newly turned drums. A check to determine if the shoes need to be arced. A process that matches the brake shoe's curvature to the drum's for best contact.

Anyways...the coffee cup's empty. 1 more? Hmmm...
Better check the B/P first.

 

[HotWheelsBurban]

Long-winded answer to a 'Q ' that could of been answered with a simple 'yes' or 'no'.
Got on a roll. A couple or 3, maybe 4(?), espresso's will do that. Bzzzt.

I've turned hundreds of drums. Yea. Hundreds. Rotors, too.
One of my duties working in a machine shop right outa school. 18 months. Some weeks, that would be ALL that I did! All day!
The Corporate rear end brake drums under 3/4 & 1 ton trucks were a PitA. Pretty heavy.
The drums from 2-5 ton trucks took two of us to mount on the machines. Stupid heavy!
The last part of the process was to scuff the machined surface, both drums & rotors, with some 100 grit before removing the drum from the lathe. The random cross-hatching helps to seat pads & shoes against the D&R's.
There was hell to pay if I short-cutted and skipped that step.

D&R's don't get machined as much any more. Easier to toss & replace because of those off-shore producer's cheap-cheap prices.
That also means that they're made cheap! Recycled steel with lots of foreign matter, plus a lower nickel content than those of 30-40 years ago.
It's the nickel content that gives the steel it's strength, durability & resistance to repeated heat cycles. Without that content, the Chinesium parts don't last. Too soft. The pads & shoes eat 'em up, especially with high friction pads/shoes.
They are also prone to warping. Can't take the heat. They really don't like extended periods of towing or canyon carving antics.
Even the OEM GM-labelled D&R's are off-shore-made now-a-days.
Junk.
I'm hard on brakes. A set of the jobber rotors lasts me about 8 months. So warped, hard braking would shake the S/wheel almost out of my hands. $60.00/pair.
After 20 years of owning 400's, I've gotten pretty good at doing brake jobs on em. It was getting expensive, though.
So...I bought some aftermarket U.S. Made rotors/pads, drums/shoes. The rotors/pads were close to (!) $400.
But they lasted for 9 years. 2 sets of pads & 2 turnings.
That's less than $50.00/year.
The jobbers were costing $90.00/year + pads.

Even still, no matter how much the parts cost, I always, ALWAYS, get new D&R's machined right outa the box. They go from the parts counter up front to the machine shop out back so there's absolutely no doubt.
I've had some that were so warped straight from the parts store that they could not be turned. So outa whack that by the time the surface was cut down to be nice & even all the way around, they were beyond the max cut spec.
I've returned as many as 3 sets drums & 2 sets of rotors in a row right back to the front counter before I even left the building.
When the machine shop guys brought the U.S. Made stuff back, they told me that they were damn near perfect right out of the box. They were surprised.
I also test fit the brake shoes against the newly turned drums. A check to determine if the shoes need to be arced. A process that matches the brake shoe's curvature to the drum's for best contact.

Anyways...the coffee cup's empty. 1 more? Hmmm...
Better check the B/P first.

Thanks as usual for your expertise! Yes sometimes I do get on a roll. We all do... sometimes

 

[TechNova]

in an effort to save weight for CAFE standards, there is no meat on OEM rotors to allow turning them. This is a good reason to use proper torque spec and sequence on lug nuts, you can warp the rotors.

 

[someotherguy]

(checks price on brand new OEM rotors) $700/ea .. good lerd I'm glad I'm not daily-driving this thing since I did the Hellcat / Brembo 6 piston swap on it.

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Richard

 

[thx1138v2]

My rule of thumb has always been, "if you can run your finger nail or thumb nail across the surface and it doesn't hang up on anything, you are good to go". So that looks OK to me.

 

[RichLo]

Long-winded answer to a 'Q ' that could of been answered with a simple 'yes' or 'no'.
Got on a roll. A couple or 3, maybe 4(?), espresso's will do that. Bzzzt.

I've turned hundreds of drums. Yea. Hundreds. Rotors, too.
One of my duties working in a machine shop right outa school. 18 months. Some weeks, that would be ALL that I did! All day!
The Corporate rear end brake drums under 3/4 & 1 ton trucks were a PitA. Pretty heavy.
The drums from 2-5 ton trucks took two of us to mount on the machines. Stupid heavy!
The last part of the process was to scuff the machined surface, both drums & rotors, with some 100 grit before removing the drum from the lathe. The random cross-hatching helps to seat pads & shoes against the D&R's.
There was hell to pay if I short-cutted and skipped that step.

D&R's don't get machined as much any more. Easier to toss & replace because of those off-shore producer's cheap-cheap prices.
That also means that they're made cheap! Recycled steel with lots of foreign matter, plus a lower nickel content than those of 30-40 years ago.
It's the nickel content that gives the steel it's strength, durability & resistance to repeated heat cycles. Without that content, the Chinesium parts don't last. Too soft. The pads & shoes eat 'em up, especially with high friction pads/shoes.
They are also prone to warping. Can't take the heat. They really don't like extended periods of towing or canyon carving antics.
Even the OEM GM-labelled D&R's are off-shore-made now-a-days.
Junk.
I'm hard on brakes. A set of the jobber rotors lasts me about 8 months. So warped, hard braking would shake the S/wheel almost out of my hands. $60.00/pair.
After 20 years of owning 400's, I've gotten pretty good at doing brake jobs on em. It was getting expensive, though.
So...I bought some aftermarket U.S. Made rotors/pads, drums/shoes. The rotors/pads were close to (!) $400.
But they lasted for 9 years. 2 sets of pads & 2 turnings.
That's less than $50.00/year.
The jobbers were costing $90.00/year + pads.

Even still, no matter how much the parts cost, I always, ALWAYS, get new D&R's machined right outa the box. They go from the parts counter up front to the machine shop out back so there's absolutely no doubt.
I've had some that were so warped straight from the parts store that they could not be turned. So outa whack that by the time the surface was cut down to be nice & even all the way around, they were beyond the max cut spec.
I've returned as many as 3 sets drums & 2 sets of rotors in a row right back to the front counter before I even left the building.
When the machine shop guys brought the U.S. Made stuff back, they told me that they were damn near perfect right out of the box. They were surprised.
I also test fit the brake shoes against the newly turned drums. A check to determine if the shoes need to be arced. A process that matches the brake shoe's curvature to the drum's for best contact.

Anyways...the coffee cup's empty. 1 more? Hmmm...
Better check the B/P first.

Sooo, thats a yes?

lol, JK, that was some great info that I never knew. I bet that pad arching process would improve a lot of GMT400 owners squishy brake pedal problem whenever that question comes up. Is that something a machine shop does when turning drums or do you just set the adjuster tight and let it wear in faster?