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Mill cylinder head/seat work without pilot

General engine tech -- Drag Racing to Circle Track

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tt911er
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Re: Mill cylinder head/seat work without pilot

Post by tt911er » Tue Jan 07, 2020 7:11 am

Thank you all the replies and comments!
For me it looks that it's doable but the time it takes makes it far from practical.

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Re: Mill cylinder head/seat work without pilot

Post by HDBD » Tue Jan 07, 2020 12:29 pm

SchmidtMotorWorks wrote:
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.
100% right
A single point cnc seat and guide machine works in concentric circles around the datum, guide axis. It does not interpolate and allow for shapes except in z axis

BigBlocksOnTop2
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Re: Mill cylinder head/seat work without pilot

Post by BigBlocksOnTop2 » Tue Jan 07, 2020 6:04 pm

You're a damned great machinist with a rock solid machine....

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Re: Mill cylinder head/seat work without pilot

Post by modok » Wed Jan 08, 2020 1:47 am

tt911er wrote:
Tue Jan 07, 2020 7:11 am
Thank you all the replies and comments!
For me it looks that it's doable but the time it takes makes it far from practical.
Finding ways to make it faster is the trick. could be done very rapidly if you make a way to do it, perhaps even optically.

Now we have low cost lasers and cameras and sensors and computers, WIRELESS digital dial indicators and so forth.

Belgian1979
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Re: Mill cylinder head/seat work without pilot

Post by Belgian1979 » Wed Jan 08, 2020 5:19 am

A general question to this : with some good tools (and I don't mean machining benches) is the replacement of valve guides and seats a job that one can do themselves are is this something that always needs to be done in a machine shop ?

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modok
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Re: Mill cylinder head/seat work without pilot

Post by modok » Wed Jan 08, 2020 8:01 pm

Many tools for replacing guides, sizing guides, and re-FACING valve seats can be considered "portable", meaning they would fit in a small toolbox, a "kit". so....you could do it anywhere. If you have the right tools for the specific job and know how.
Collecting enough tools for every kind of engine, and to get out of any jam, and/or turn a good profit, then the amount of tools escalates into the category of tonnage.
Installing seat inserts...that's more of a "maybe". Maybe sometimes.

Valve seat 1
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Re: Mill cylinder head/seat work without pilot

Post by Valve seat 1 » Fri Jan 17, 2020 8:56 pm

The best way and simplest way to machine seats on a vertical mill or Bridgeport is bolt/ weld some square bar stock together a rectangle box shape 2” will do.
And bolt them to your rotary table standing the table straight up on one end of the table and then bolt a piece of round bar to the other side. Which will go in a pillar block radial bearing . A good sized one. 1-1/4 dia So you got two bars running parallel to the x axis. Skim cut the bars to the machine. Now you have a flat surface to put the head on. You can locate on the deck or valve cover surfaces or bolt a plate to it with slots and bolt it on the intake or exhaust surfaces . The sky’s the limit here.
You can Spin the rotary table to get the guides straight up
In one direction. The other direction is usually straight to up and on plane to table . If not . A simple machinist jack will do to tweak the head. To locate the guide straight to the spindle use bar stock/ pins / ground rod or drill blanks
Or just turn your own to various guide sizes. Could be Aluminum.Now take a block of metal drill and team various holes of different guide bores . Lay the block on the table of machine find a tight fitting rod. push it thru the guide with the head loose and when it goes in the reamed block lock the head down. Your straight up. Now you can indicate the the pin or the guide. Ready for rigid machining. No pilot to flex or two piece tool that’s a weak link.
And cost a 1000 dollars. I buy the cutter tip holders only and inserts
And machine the slots to hold it in 1-1/4 round stock with a hard end-mill holder a few set screws to lock it.
No need to spend thousands to make a mill into a valve seat machine. This is the job shop machinist approach. And it can be done without the bar fixture if you don’t do
A lot of heads.just a different set up. Same principle.

Valve seat 1
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Re: Mill cylinder head/seat work without pilot

Post by Valve seat 1 » Sun Jan 19, 2020 3:03 pm

The only reason every Head machine seems to use a pilot is to take advantage of the floating table or Spindle head. It’s not magic or Rocket science. It’s saves time. However on a Bridgeport mill if the guide bore is straight up to the spindle by pinning a Rod threw it to a block square on the table with a hole in it slightly larger then the Rod then indicate. You will be able to cut with no pilot perfectly concentric. I do this everyday in the Aerospace shop where I work on parts with the same features, a hole and a angle. The difference is it’s not called a cylinder head. The Machine doesn’t know!
As far as I’m concerned seat roundness to itself is more important then concentricity. They are different symbols on a Blueprint. The reason being, The distance the valve
Sticks out of the guide where it contacts the seat allows for a lot of wiggle room. You can wiggle the valve back and forth quite a bit more then the clearance between the guide bore and valve steam.The valve face will find its seat angle to angle . Unless your way off! From there the seat being round to itself comes into play because a round valve on a round seat equals a good seal.

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