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I bought a Neway seat cutter set specific for Triumph heads on ebay-- -- thanks for all your info below guys-- that info and the Neway instructions and videos should get my work done nicely

Hi Bob,

A 46 degree seat and a 45 degree valve face is common production machine shop practice. It produces a fine line contact and it's purpose is to provide a good seal without lapping, which takes more time. For what we do, I prefer lapping which can be done on either a 45 or 46 degree seat.

Stuart

Neway cutters

I have a set of the UK made cutters for British bikes, next to useless. CBS's recommendation of Neway cutters is spot on, my Neway set spends more time being lent out than being in my workshop.

Neway cutters come in different size ranges (as well as a range of angles), and they sell several tools for turning them. I have Neway cutters for my Ariel's and Gold Stars' valve guides, and they are well worth having. However, the limitation of these cutters in producing seats that are accurately Concentric with the valve guides is the operator's ability to turn the cutter without exerting any sideways force, which will distort the seat geometry. This is more difficult than it might seem. Without having a valve seat runout gauge to measure the results I wouldn't have known that what I thought was negligible sideways force actually was producing seats distorted by a few thou. With the gauge I was able to train my hand to reduce the sideways force to an even "more-negligible" value.

Their crank-type tool is held with one hand while turning the cutter with the other, which would seem to be better for eliminating sideways force than their key-type tool. However, it has a longer lever arm than the T-type tool, which can offset that advantage to some extent, depending on the skill of the operator.

A final note is that while a head with 45° (or 46°) seats will be fine for many uses, and while additional cutters cost additional money, anyone who plans to cut their own seat should consider buying the two additional cutters needed for a 3-angle valve job.

Absolutely correct!
I was fifteen when I first used a Neway seat cutter working in a lawn mower repair shop. (My part time high school job.) The valves were tiny, no more than an inch in diameter with 1/4" stems (Flexy), and even at that size it was difficult to hand turn the tool evenly enough AND without side loading. The cutters would tend to dig in and leave a choppy surface UNLESS the rate of rotation and pressure were just right. Done by hand, we felt it was good enough but always lapped the valve in. Larger valves are more difficult and take greater consistency.

All that to say that yes, Neway cutters can do an acceptable, even excellent job but lots depends on the skill,or even the feel of the one doing the job. By hand in the workshop, a universal joint connection to the cutter head and a long tee handle to turn it helps and a tight fitting pilot helps too.

Having just come from the dentist with a referral to the endodontist, I'm acutely aware that people don't always want to hear the truth. But, Stuart speaks the truth.

Neway cutters are very easy to use, but it's also very easy to use them to cut bad valve seats. That's not to say there's a better solution in the same price range, because there isn't as far as I'm aware. Luckily, it's not incredibly difficult to use them to cut good valve seats, but the task has to be approached carefully, with awareness of the pitfalls so they can be avoided.

"By hand in the workshop, a universal joint connection to the cutter head and a long tee handle to turn it helps and a tight fitting pilot helps too."

Stuart--I get the" tight pilot" instruction but need you to better explain the "universal joint connection and long tee handle"
Magnetoman--- my late model Honda's have 3 angle seats-- Triumph manuals don't mention this as necessary -- what will it improve on my Triumph heads?
I have found that a Neway kit # KM 2339-- is made for Triumph valve seat work--- I have old heads I can practice on-- that and 40 years experience in a university prototype machine shop should be ok.

100% of the h.p. of an engine is generated in the head, and two things limit it:

1) the fact that most of the energy of combustion ends up as heat, not h.p., so the upper limit for the h.p. of a given air-cooled engine is restricted by the flow of cooling air over its fins, and;

2) how much air is sucked into the engine on the intake stroke, to be mixed 14:1 with gasoline. The more air, the more h.p. Superflow even gives a formula for this in their manual: h.p. = cfm/1.67.

To get into the cylinder the air has to get past the intake valve, and the less abrupt the angles are the easier it is for the air to flow. Three angles simply smooth the way for the air to flow into the cylinder better than one angle, and the result truly is additional h.p.

Here's another reason to use a 3 angle system because off center seats result in leaky valves..

Often, the seat cutter cuts more on one side of the seat due to head distortion, the guide not installed straight or non Concentric valve guide ID and OD. This leads to a wide cut on one side and a narrower cut on the other side and tends to result in a non Concentric seat. A three angle seat will have a top relief and a bottom relief that narrows the seat to a relatively even width so the final cut will be closer to Concentric to the guide bore.

The u joint can help reduce side loading and the long T handle helps with leverage and control. But having said that, if the seat isn't very true to the guide axis, side loading can be used to help correct the problem.

I disagree. If the seat and guide are offset from each other your only choice is to keep cutting deeper until there is sufficient width all the way around, even though the width itself will vary. Under no circumstances will side load on the cutter make things better rather than worse.

If the seat and guide aren't coaxial, the cutter will remove more material on one side than the other. While loading toward the side whose cut isn't as wide will increase the width of that side, the seat will be oval, have a shallower angle on the "tilted" side, and no longer in a single plane, as shown in this famous automotive manual:



An imperfect set of three Photoshop drawings showing the effect of side-loading to compensate for offset between the guide and seat follow:

I think we do agree but are looking at the discussion from differing angles and I apologise for not making my underlying assumptions clear.

My point is that one could use side loading to encourage cutting toward the "wide" side during the "roughing in" phase because the wider surface will tend to deflect the cutter toward the thinner seat surface. Once that is done and a top and bottom relief are cut, the seat will be closer to the same width all round. Then a final cut without any side pressure can be made to finish the seat.

Your point stands as a valuable warning to RESIST THE TEMPTATION to push the cutter toward the narrow side of the seat to give the appearance of an even seat width. No disagreement there.

But this circles us back to an earlier point. Neway cutters are capable tools but much depends on the skill of the user.

SO anyway Bob, Get those cutters and attack one of those old heads for practice, first making sure the guides are as true as possible.

Maybe I missed it, but no one has mentioned the fact that new valves are often not Concentric to their stems.
..even with looser guides (.002-.003") a seat from a 46deg cutter will reveal a poorly made valve. Try it..use a strong flashlight in the chamber and spin your new valve on your new seat...watch the oscillation.
Standard practice here is to dress all the valves in a valve grinding machine after dialing in the stem in the chuck. The tiniest bit of grinding will do.
3 of the 4 black coated valves I have here for an A65 head are all off center as new....trust no new parts and you'll be much happier with your bikes performance when done.

I have no opinion on Neway cutters, but saw this related article by
Mike Nixon and it seemed relevant to this thread. Comments?

Valve Seat Tools

Hi Ray-- interested to read it but my computer says "Access Denied".

He doesn’t have anything nice to say about using valve seat grinders either. He should have a word with the folks in the aircraft industry about that.
I’ve used Neway cutters in the past and still have a few Kowa live pilot cutters. I don’t particularly like Neway, but they do have their place. It could well be the skill of the operator, but on some seats it seemed virtually impossible to avoid some chatter on hard seats. I may be urinating into the wind, but I still think stones have their place. A small air driven valve seat grinder does come in handy for touchups. The Black and Decker style grinders are a little unwieldy for most motorcycle heads, but I still use one on rare occasion.
If I was going to do any more than a few seats, I’d probably sell all of the valve seat tools (except for the air driven one and the truing stand) and buy some of the new carbide cutters that cut all 3 angles in one pass…. although that requires a way to drive them and we’re talking about cutting seats without a machine shop.
Another opinion…. I spent my entire career working with people that have a similar resume to his. Doesn’t mean they are always right. He actually sounds like a bit of a blowhard. I’m assuming that I don’t generally sound that way based on the fact that Hugh hasn’t pointed it out. but feel free to speak up if you think otherwise.

PS.. I suspect that 1/2 the time at least some of it goes out the window when you torque the head down.

Well, that's strange, Tridentman. I can open both links on my phone, tablet, or desktop.

Both links worked for me… maybe your anti virus software saved you and now I’m infested with something?

More likely his wife blocked the link so he wouldn't be tempted to buy that $100,000 Newen System mentioned in the article. But, she does "let" him buy all those motorcycles.

I haven't used my Neway cutter set yet-- I will report here when I do-- lot's of good input here--
1. regarding out of true valves, I put about 20 , good looking, used Triumph valves on the lathe, to indicate them, and most all were within .002" of true- I picked the very best 4 (.001" ) out of the bunch for one of my heads.
2. regarding new guides installed " out of true" to the seats-- I don't understand how a new guide can do anything but, exactly follow, the bore in the head. If the interference fit is correct (.001" to .0015") . I believe in freezing the guide and heating the head and it will tap into place. I know there are "pulling tools" available but I haven't been convinced of their superiority to using a drift.

If you have the extra $$$

Pick up some Serdi straight carbide pilots and get rid of the Neway collet pilot set-up

This way is much more accurate

Using a drift to remove the guide is fine, but if you can draw the guide in is "safer"

If the guide is not in line with the bore, you run the risk of pushing the alloy out of the guide hole (broaching)

Recently converted to the Goodson 3-D fast cut