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Mill cylinder head/seat work without pilot

General engine tech -- Drag Racing to Circle Track

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dannobee
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Re: Mill cylinder head/seat work without pilot

Post by dannobee » Wed Jan 01, 2020 12:53 pm

Factories drill the guide hole and seat recess in one operation, then press in the guides and seat. I remember seeing a video of the cylinder head robot machine but don't know if it was available outside of GM (Tonawanda factory)

Here's how Brodix does them. Starting about 8:53 in the video. With a pilot.


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Re: Mill cylinder head/seat work without pilot

Post by bentvalves » Wed Jan 01, 2020 1:14 pm

whats a set of those above BRODIX heads fetch brand new?

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Re: Mill cylinder head/seat work without pilot

Post by modok » Wed Jan 01, 2020 4:12 pm

Newen and Serdi uses a quick change 30 taper spindle.
Although they don't SAY that's what it is....that's what it is
so, you get a milling machine with that that size spindle, can make it fit, and use it with or without the pilot.
Heavy cuts, like the counterbore for the seat deeper, in many cases the pilot is not really doing anything, it's all in the spindle of the machine.

A decent general machinist should be able to make the entire holder(arbor?) to adapt newen/serdi tools to any spindle.
Boring the hole for the pilot is tricky, but you can do it, single point bore it with a little carbide boring bar, in YOUR own spindle so it will have virtually zero runout, then hone to final size. OR, just don't use a pilot at all, if you can align it, and then switch tools easily.

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Re: Mill cylinder head/seat work without pilot

Post by SchmidtMotorWorks » Wed Jan 01, 2020 4:25 pm

I should explain something about using a CNC to cut valve seats.
Multiple cutters are used, one for each angle, the typical diameter is about 1/2".
So the machine interpolates around in a circle.
The advantage of doing this is that chatter and deflection are a non-issue.
Spindle is run at the max speed that the machine is able; could be 6,000 for older machines and 30,000 for some new machines.
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Re: Mill cylinder head/seat work without pilot

Post by hoodeng » Wed Jan 01, 2020 6:21 pm

As a bit of an aside to the OP's post but still relevant is ,, as a machinist i have always had to work out how to hold jobs for different machining processes. A lot of guys think we just clamp a job in a machine and go for it, this is not the case, as inaccurate datum's, reference points or unstable clamping points/surfaces are sometimes used to clock up a job and machine to effect a result that looks good but is not right, full stop.
[i have seen guys machine themselves into a corner, with no way to back out of a looming failure, bit like paint]

Over the years i have had the good fortune to see production lines in process that have given me valuable input as to how to hold something to give the best result, some guys think this comes naturally to machinist, it doesn't, I have seen clamping and datum fixtures that don't seem obvious to the parts production make sense after seeing them in practice. As we work on a number of makes or models, having dedicated fixtures for each corrective operation we may be performing is impractical so we tend to go about it in a way that is a generalization of original production process.

In some parts manufacture processes there are extra casting protrusions that facilitate machining steps that are removed after machining, Its these parts that get tricky to hold for weld and machine repair processes and we have to see how it was held in the first place.
As i am not a production engineer the mystery of the perfect jig/fixture will always be just that.

The Brodix video gave me a couple of ideas, Thanks.

Cheers.

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Re: Mill cylinder head/seat work without pilot

Post by ProPower engines » Wed Jan 01, 2020 6:36 pm

modok wrote:
Wed Jan 01, 2020 4:12 pm
A decent general machinist should be able to make the entire holder(arbor?) to adapt newen/serdi tools to any spindle.
Boring the hole for the pilot is tricky, but you can do it, single point bore it with a little carbide boring bar, in YOUR own spindle so it will have virtually zero runout, then hone to final size. OR, just don't use a pilot at all, if you can align it, and then switch tools easily.
FWI
Newan sells the adapter arbor for most milling machines to adapt both Rottler+Serdi as well as all other ball drive tooling so most any cutter system can be used in any mill.
That would make it easy to use a mill to do head work it will just take longer to index each guide X and Y for center.
At the same time there is many members here that do it that way with no issue.

It comes down to time and preference as well as machine capabilities and time to do the job. :D
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Re: Mill cylinder head/seat work without pilot

Post by ClassAct » Wed Jan 01, 2020 8:05 pm

SchmidtMotorWorks wrote:
Wed Jan 01, 2020 4:25 pm
I should explain something about using a CNC to cut valve seats.
Multiple cutters are used, one for each angle, the typical diameter is about 1/2".
So the machine interpolates around in a circle.
The advantage of doing this is that chatter and deflection are a non-issue.
Spindle is run at the max speed that the machine is able; could be 6,000 for older machines and 30,000 for some new machines.

That's a bit surprising as I assumed it would all be done with a single point cutter.

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Re: Mill cylinder head/seat work without pilot

Post by mt-engines » Wed Jan 01, 2020 8:58 pm

SchmidtMotorWorks wrote:
Sun Dec 29, 2019 12:49 pm
You can produce more accurate seats on a machine without pilots.
The clearances and taper involved in pilots are multiples of the accuracy of a good machine even if it is interpolating.

The main advantage of CNC milling seats is that you can have designs where the non-sealing faces have shapes or angles that change around the the perimeter of the seat. The best shapes in the center of the cylinder are different than the best shapes along the chamber walls.

I was doing this at Honda in the 90's with new CNC machines for that era, it wasn't fast but the work produced was excellent.
With modern CNC equipment the same work could be done in seconds to tolerances and finishes vastly superior to what a single edge cutter could do.
I agree with you on the angles above the seat and below the seat. A cnc can give you the best shape because you can indeed interpolate the bowl into the angles. But bottom line the seat angle has to be perfect.. Most factory heads use tooling that could be worn or tapered or offset ever do slightly from cylinder to cylinder, and a CNC doesn't know that unless you probe each guide and seat, intake bolts hole cylinder head dowel etc. And since stones produce the best and most concentric seats with straight pilot, it's a no brained for a basic automotive machinist to use what they can and not add 6 hours of unnecessary work for an oem rebuild. A stock engine doesn't care.. This isn't formula 1.

But for how quick a VGS can do a valve job within. 001"-.0015" it makes no sense for the average guy to try and use a mill without a pilot. It would take too long. Unless you wanted to see blueprint the heads.

I have fixed many epoc valve jobs with a VGS that were off. 008-.015". That's a CNC

On a production level the CNC has the biggest advantage. Over piloted tooling. But for me i want the calve seat to be as concentric as possible. I can't warranty a dropped valve from a non concentric valve job.

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Re: Mill cylinder head/seat work without pilot

Post by englertracing » Thu Jan 02, 2020 3:18 am

dannobee wrote:
Wed Jan 01, 2020 12:53 pm
Factories drill the guide hole and seat recess in one operation, then press in the guides and seat. I remember seeing a video of the cylinder head robot machine but don't know if it was available outside of GM (Tonawanda factory)

Here's how Brodix does them. Starting about 8:53 in the video. With a pilot.


At 9:22 they washed it.
At 9:30 they start grinding on it again #-o

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Re: Mill cylinder head/seat work without pilot

Post by sbcharlie » Thu Jan 02, 2020 7:56 am

I have set up both EPOC and BB Contour Newen machines to size or ream guide and cut new valve seat. the cycle time was 38 seconds per valve seat.tooling is expensive and need coolant for valve guide reaming. I have also cut offset seat angles below the contact angle with out using a pilot on a Newen BB interesting things to view in this post. Charlie

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Re: Mill cylinder head/seat work without pilot

Post by hoodeng » Thu Jan 02, 2020 5:37 pm

Charlie, is it that the Contour already has the head rigidity for guideless machining and only uses the pilot for datum? is there a feature in the machine that can be utilized to pick up true?

Cheers.

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Re: Mill cylinder head/seat work without pilot

Post by SchmidtMotorWorks » Thu Jan 02, 2020 7:17 pm

ClassAct wrote:
Wed Jan 01, 2020 8:05 pm
SchmidtMotorWorks wrote:
Wed Jan 01, 2020 4:25 pm
I should explain something about using a CNC to cut valve seats.
Multiple cutters are used, one for each angle, the typical diameter is about 1/2".
So the machine interpolates around in a circle.
The advantage of doing this is that chatter and deflection are a non-issue.
Spindle is run at the max speed that the machine is able; could be 6,000 for older machines and 30,000 for some new machines.

That's a bit surprising as I assumed it would all be done with a single point cutter.
A typical CNC spindle would not have the mechanism required to control a variable diameter tool.
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Re: Mill cylinder head/seat work without pilot

Post by sbcharlie » Fri Jan 03, 2020 7:32 am

on a newen machine you have auto center or you can push a tab and have no auto center. in this position the head stays ridged.i designed a fixture to hold the head in its place after you center the pilot to the guide. when we offset machine there is no pilot. I guess I do not understand why you would machine a valve seat profile without a pilot. I have learned a lot from this post on how you can machine a profile without a pilot.... I like to keep machining simple. Charlie

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Re: Mill cylinder head/seat work without pilot

Post by ClassAct » Fri Jan 03, 2020 12:09 pm

SchmidtMotorWorks wrote:
Thu Jan 02, 2020 7:17 pm
ClassAct wrote:
Wed Jan 01, 2020 8:05 pm
SchmidtMotorWorks wrote:
Wed Jan 01, 2020 4:25 pm
I should explain something about using a CNC to cut valve seats.
Multiple cutters are used, one for each angle, the typical diameter is about 1/2".
So the machine interpolates around in a circle.
The advantage of doing this is that chatter and deflection are a non-issue.
Spindle is run at the max speed that the machine is able; could be 6,000 for older machines and 30,000 for some new machines.

That's a bit surprising as I assumed it would all be done with a single point cutter.
A typical CNC spindle would not have the mechanism required to control a variable diameter tool.

Ok, that makes sense. Is that something that could be adapted to a CNC machine or is it even worth it?

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Re: Mill cylinder head/seat work without pilot

Post by SchmidtMotorWorks » Sat Jan 04, 2020 1:34 am

ClassAct wrote:
Fri Jan 03, 2020 12:09 pm
Ok, that makes sense. Is that something that could be adapted to a CNC machine or is it even worth it?
Too incompatible.

If you have a good CNC, you can make as good or better seats than a single point machine can make.

A single point machine is limited revolved shapes, a CNC can make any shape you want.
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