Neway cutters and seat concentricity

[AC sports]

Changed guides on a refresh head and wanted to use Neway 30*45*70* cutters to re do the seats.
The pilot / mandrel is of the type in the pic. Seats & associated angles are shiny all round. Valves lap evenly to the outside edge. Putting engineers blue on the seats however tells another story. Valve definitely contacting all round but only making contact with half the seat.
All seats are the same.
Am I missing something? It's been a while since I used the neways. I know they are not a pro tool but was hoping to finish this head before the weekend since the machine shops serdi is out of action

[mag2555]

Try this.
Load the cutters in the head the other way around then re-blue the seat.
Spin the cutter as lightly as you can, now does the cutting pattern change?

[Truckedup]

Some bike engine builders claim the Neway cutters cannot maintain concentric dimensions needed for tight valve guide clearances without stem galling or seizure..They claim only a Serdi or Newen can do the job properly...

[BillK]

I have the Neway system and have no problem getting almost perfect concentricity but it is time consuming. You have to have sharp inserts and use a light touch.

That being said I don't think you can do it with the expanding type pilots. I have a few of them but rarely use them. I probably have 80 or so different size solid pilots that I normally use. Also, I don't know that you can get that good of a job without the overhead track and drive motor setup. It is very hard to push evenly on the handheld driver.

[6.50camaro]

How wide is the seat on the head and how wide is the seat contact on the valve ? Dan

[pcnsd]

Do you have a concentricity gauge to check the seats? How do you know the error is with the seats and not with the valve? I am using a seat grinder, but have considered adding the Neway system especially for the copper/bronze seats that do not grind well. Seat run out error seems to be associated with worn guides. With new guides properly sized, the seat concentricity always comes in under .0006" of runout.

+1 on expanding pilots, don't use them.

[V Remian]

I'm wondering if your talking about seeing the 1 degree off set of the cutters?

[BillK]

I'm wondering if your talking about seeing the 1 degree off set of the cutters?

They are not all like that. Most of mine are 45 / 30 You can buy them both ways.

[Momus]

Some bike engine builders claim the Neway cutters cannot maintain concentric dimensions needed for tight valve guide clearances without stem galling or seizure..They claim only a Serdi or Newen can do the job properly...

I do a few small 2 valve Hondas and have never been able to get the Neway cutters to work more than barely OK with results as AC sports reports. I have graduated tool steel pilots for the nominal guide sizes- mainly 4.5 and 5.5 mm.

I changed to pink stones that I diamond dress on a true pilot in the lathe and now get very consistent results, especially on the superhard exhaust seats.

[rebelrouser]

So I am still old fashioned, I still grind all my seats with stones, using the Sioux tapered pilots. I have looked at the cutter systems, but really did not want to spend the money for the amount of work I do now. Is there any big advantages to the cutters except speed of doing the work? I read some guys are cutting with the seats and then touching up with a stone to make sure they seal.

[SupStk]

So I am still old fashioned, I still grind all my seats with stones, using the Sioux tapered pilots. I have looked at the cutter systems, but really did not want to spend the money for the amount of work I do now. Is there any big advantages to the cutters except speed of doing the work? I read some guys are cutting with the seats and then touching up with a stone to make sure they seal.

Another vote against expanding pilots. They will work but never give as concentric seats a soild pilot will.
Another shop in my town uses Neway cutters. From what I can tell they are no faster than stones and probably not as accurate.
After buying my Serdi I used to touch the seat angle with stones thinking it would be the correct way. Now its been years since the seat grinder has been used.

[cgarb]

I have used the Neway cutter bodies with the new3acut 3 angle inserts...I used the neway power head with some carbide pilots and I'm getting good seats. Every now and then I get one that's out, just remove the pilot and recut and it back in again. Maybe dirt? I used the hand cutter one time with the old style serrated blades just to try it out, seats were not very good. I think its hard to not influence where the cutter bites into the iron doing the work by hand. End up with seats that are not round or flat...a wavy surface.

[modok]

If I have read correctly the problem is not concentricity, it is the valve angle does not match the seat angle.
Grind the valve 1 degree steeper and try it again, perhaps that will solve it, and/or let you figure out what is happening.
I'd recommend you use a junk valve for lapping seats,
I think lapping might do some good for a seat but... it just puts a groove in the valve face which isn't good we now know.

[cjperformance]

Are you sure the neway cutter is a 45* ?, the neway seat cutters i used to use were 46*, outcome on a well cut seat was like you described.
If lapping was done the contact appeared full only due to the small v larger lapping particles settling in the seat v valve face angle differential. A light lap with fine paste proves this , showing the small angle differences. Lapping is not really needed if the seat is properly cut. Concentricity can be checked with a gauge or with a valve and blue. If using a valve it of course must have no run out, to be sure blue the seat 2 or 3 times lightly with the valve in 2 or 3 orientations and compare the witness mark.
Edit-typos!

[Keith Morganstein]

Changed guides on a refresh head and wanted to use Neway 30*45*70* cutters to re do the seats.
The pilot / mandrel is of the type in the pic. Seats & associated angles are shiny all round. Valves lap evenly to the outside edge. Putting engineers blue on the seats however tells another story. Valve definitely contacting all round but only making contact with half the seat.
All seats are the same.
Am I missing something? It's been a while since I used the neways. I know they are not a pro tool but was hoping to finish this head before the weekend since the machine shops serdi is out of action

That expanding collet is damaged from tightening when not fully insterted. Look at how it’s flared out/bent at the top. It also looks as it was too small for a guide and stretched. Those collets should return to straight or just about straight when relaxed.
I have a few of those, bought for oddball jobs. You have to handle them carefully.

The difference in angle of the valve and the seat is likely giving you the contact you see (as others have stated) but I wouldn’t expect good results with that collet.