Cutting valve seats.

[762SPR]

What is involved? I work in a machine shop and have access to a CNC and CAD/CAM.

How does a setup look like? What kind of tools are used? Anyone here do it themselves? What kind of tolerances are involved in a good seat cutting job?

I'm just wondering if it would be feasible for an experienced machinist to do, or if it's some ancient Chinese secret sort of deal.

Thanks!

[William1]

No, you need specialized equipment like a Serdi machine.

[Pr1malR8gw]

you can also do it by hand with the proper stones that cut the seats...

http://www.cylinderheadsupply.com/neway-valve-seat-cutters.html

[762SPR]

Well that's too bad. I'm curious though, I'm looking at a youtube video, and it just looks like a fancy cutter plunge cutting the seat. Looks like the cutter has some sort of guide rod that goes into the valve guide?

What does a serdi machine DO? Is it the fixture for holding it, or is there some sort of unseen movement going on? It looks just like a plunge cutting machine, lick a real fancy drill press...

Edit, if you can do it by hand, (probably like chambering a rifle by hand, in other words "=\") Then why couldn't you do it with a milling machine?

[Jeekinz]

There's cutters out that do all 3 angles at once which saves alot of time. There's alot more to just cutting valve seats, you have to check the guide and lap the new valves, etc.

[mxdj2003]

if your a machinest it should be no problem to do you can get the Neway cutter heads fairly cheap and you could make your own pilots to hold the cutters square in the valve guide i say go for it

[mikie]

There's cutters out that do all 3 angles at once which saves alot of time. There's alot more to just cutting valve seats, you have to check the guide and lap the new valves, etc.

I dont think you want to lap in the Ti valves. I believe you let them brinell themselves in.* And I think the cuts are 30,45,60 degrees. 30 first, then 60, then 45 degree cut.**

*,**: I could be way off though. But it sounds right.. ?

[Pr1malR8gw]

you do not lap the valves in dirtbikes.. Even the SS valves have coatings on them.

[762SPR]

Interesting, thanks guys! I asked my father, who has been working on race car engines since before I was born, and a machinist and he said he couldn't see why it wouldn't work. The main problem I see now is getting the cutter and knowing how much is enough when cutting. I'd imagine for the latter that you would cut until it is just kissing off metal all around that way you know you have a good square flat seat. Are there any good books I should pick up?

At this point, I'm only looking at it because I think it would be neat to be able to do... I don't need new valves put in and at only $100 to get it done I probably won't be saving any money. I just like doing stuff like this and doing it myself.

I turned and chambered my first center fire rifle barrel a little while ago. It ended up costing a little more than just buying one, not to mention the time that went into it. But in the end it turned out real nice and was a blast to do! Hopefully I'll be able to start doing some more intricate engine work myself!

[Jeekinz]

you do not lap the valves in dirtbikes.. Even the SS valves have coatings on them.

I ride smokers. Last valves I did was a big block Chrysler. Lol

[Montana-Snipe]

you do not lap the valves in dirtbikes.. Even the SS valves have coatings on them.

Based on what, out of what manual? Titanium, o.k. due to the oxide coating. In my Honda manual, I can lap my exhaust valves per the book to extend the service life. Strictly calls for the replacement of the intakes:thumbsup:

[Pr1malR8gw]

Based on what, out of what manual? Titanium, o.k. due to the oxide coating. In my Honda manual, I can lap my exhaust valves per the book to extend the service life. Strictly calls for the replacement of the intakes:thumbsup:

You can do what you want.. but kibble white, and pretty much all other manufactures of valves SS or TI alike coat their valves.

Now you can keep your hoonduh and its mixed valves. ?

[racerx_217]

I ride smokers. Last valves I did was a big block Chrysler. Lol

Thank you for your 2 cents, it helped to answer the question at hand. Why dont you go hang out here http://twostrokemotocross.com/forum/index.php ?

[Jeekinz]

Thank you for your 2 cents, it helped to answer the question at hand. Why dont you go hang out here http://twostrokemotocross.com/forum/index.php

Well I was 1/2 right. ?

If you think TT is 100% 4 strokes you better look around.

[Codeman00]

Try this article..

http://www.crfsonly.com/forum/viewtopic.php?t=16867&highlight=cut+seats

[762SPR]

Try this article..

http://www.crfsonly.com/forum/viewtopic.php?t=16867&highlight=cut+seats

Thanks for the link! This is beginning to look less and less like rocket surgery.

I'm pretty sure I want to opt for doing it on a machine rather than by hand. If I do it by hand I'll never get spot on... Although, if the guy is doing his with a pair of calipers that are only precise to the hundredth, I might be fine! (I thought he was measuring mm at first...)

Back to machine cutting I would need a cutter. I really like the Serdi cutters that cut all the angles at once. It even looks like you can get the inserts and holders!

So in theory: The seat needs to be cut to within the width specification, as round and flat as possible. The other two angles are just there for relief, and as long as they are the correct angle they just run out into space. The seat should be cut so it is just removing an even amount of material all the way around and ideally the same depth as the others (intake and intake, exhaust and exhaust).

What sort of RPM do the Serdi machines generally spin at? I can't imagine it would be too high with that offset cutter.

This seems really doable now, too bad my engine doesn't need valves done!?

[Erik Marquez]

Seat angle, Seat width and cut width for each of the non seat angles. Concentric cut, smooth finish (no chatter from the tool or stone), Installed valve height, installed spring height, valve guide hole concentric and properly sized.

It's not surgery, but it is more then being able to afford the right valve guide pilot and set of Neway cutters.