Anyone done this with a QCTP ?

[nickel-city-fab]

Loosen top nut. Turn 90° Tighten top nut. Indicate it if you care.

TMB nails it in one. The position of the tool post means nothing, because the tool path is determined by the carriage, cross feed, and compound feed. I generally leave my compound feed at 30 deg. and the tool post "square" to the lathe... but the actual tool mounting surface can be spun around to the rear, or any angle in between to reach difficult spots, etc. None of that changes which way the lathe is going to move, though.

[Doozer]

Not having turned one, i dont know what is involved.., if it indexes.. not a problem.. if it doesnt it may need clocking ir alignment. .

Mind blown.

-Doozer

[Doozer]

Loosen top nut. Turn 90° Tighten top nut. Indicate it if you care.

LIKE!

--Doozer

[luthor]

This post from a few years ago explains the process that I use with the double tool holder.
https://bbs.homeshopmachinist.net/fo...iscussed/page4

[Doc Nickel]

Local college machine shop had a setup for exactly that same reason. Big U-shaped burnout made from 1" plate, with some extra bits welded on for both the mounting and the tool bit holding.

Tool bits were typical cheap 1/2" shank triangular-insert lathe bits, like you use to see in the sets from Enco and the like.

It was ugly, but it worked, and every time I took a semester of class, it was used at least once, usually two or three times.

And yes, it was built to plunk right onto the CXA posts fitted to each of the big Colchesters.

Doc.

[The Metal Butcher]

Loosen top nut. Turn 90° Tighten top nut. Indicate it if you care.

[754]

Not having turned one, i dont know what is involved.., if it indexes.. not a problem.. if it doesnt it may need clocking ir alignment. .

[The Metal Butcher]

I posted it with that title for a reason... due to recent QCTP discussion. Although they are easy to use, and generally quick to use.. there are a few situations that they may not work as well.., this appears to be one of them.

What? It's literally no different. You just turn the toolpost 90°.

Explain. Please explain how it functions any different.

[754]

Its a video from Instagram... the rotor has a lot of runout on the side it is cutting, like 20 thou or more, very visible. It seems to be cutting it fine.
turning a disc around, easy to end up with runout, and 3 thou, you will feel it at least on a bike, and longterm it will wear a tire unevenly.

I posted it with that title for a reason... due to recent QCTP discussion. Although they are easy to use, and generally quick to use.. there are a few situations that they may not work as well.., this appears to be one of them.
Why turn your rotors.. a few reasons.. you dont want to spend the money or dont have it. Because you can.. and for me at times, you are working on a vehicle, you have the brakes off, you realize the rotor needs turning..... then you realize too late in the day to get it done, or you have no way to get them back and forth... and now you have a vehicle sitting apart.
I could not count the number of times, I just make something or just deal with it, so you can continue and get finished.
If you are going to invest 10 or 20 K in machining stuff.... imo... you better be able to produce things..

[sarge41]

OK my simple mind has a question here. Why not just flip the rotor 180* and cut the other side from the front? I'm probably missing something? I too have seen the older style brake lathe machines that cut both sides at the same time and have dial adjusters to set the DOC for the rotor. From what I've read before you do not get the cut real smooth or you get the pulsing like a warped rotor which is something to watch out for.
I have a classic car that uses solid rotors from another make of car, I have to cut the diameter down to fit my car, but I have never done the sides so far.

Good post to learn from.

TX
Mr fixit for the family
Chris

By cutting each side while on the one setup, you are assured that both sides are parallel. It could be done by flipping the rotor, but this way is easier and more likely to be parallel, not .002 or .003" out of parallel. If out by that much, it will be felt. Just need to be careful about minimum thickness when done.

Sarge41

[Mr Fixit]

OK my simple mind has a question here. Why not just flip the rotor 180* and cut the other side from the front? I'm probably missing something? I too have seen the older style brake lathe machines that cut both sides at the same time and have dial adjusters to set the DOC for the rotor. From what I've read before you do not get the cut real smooth or you get the pulsing like a warped rotor which is something to watch out for.
I have a classic car that uses solid rotors from another make of car, I have to cut the diameter down to fit my car, but I have never done the sides so far.

Good post to learn from.

TX
Mr fixit for the family
Chris

[junkaddict]

The standard thing now for any later model seems to be to just change out the rotors. The ones for my two vehicles at present are about $70.

They are pretty cheap these days for many cars, but if the OP's' are one piece. They don't look all that cheat. But I will keep this setup in mind should the opportunity to use it arise.

[BCRider]

Mechanic at my old job was showing me how they don't even have to take the rotors off to turn them any more. The brake lathe uses the vehicle's own wheel bearings fro a spindle bearing, spins it with the lug studs and feeds the tool after you bolt the brake lathe onto the vehicle. Entire operation only takes minutes, but the machine ain't cheap.

The standard thing now for any later model seems to be to just change out the rotors. The ones for my two vehicles at present are about $70.

[nickel-city-fab]

Mechanic at my old job was showing me how they don't even have to take the rotors off to turn them any more. The brake lathe uses the vehicle's own wheel bearings fro a spindle bearing, spins it with the lug studs and feeds the tool after you bolt the brake lathe onto the vehicle. Entire operation only takes minutes, but the machine ain't cheap.

[JoeLee]

Doesn't that inside cutter chatter ?? That's a lot hanging out there plus going around the rotor. Looks like one big torsion bar setup to me.

Are you turning both sides at the same time ? if so how are you adjusting it ? Or are you doing one side at a time ?



JL................