Making carbide valve guide pilots

[Michael Moore]

Are valve guide pilots (for seat work) a lot more difficult to make from carbide than HSS?

For small diameter valve stems (4-5.5mm) carbide offers significantly more stiffness to help get more concentric seats. These pilots have a 3.5" long .375" OD cylindrical top section and a slightly tapered section of about the same length. HSS pilots are in the $22 range, but carbide pilots are $190. HSS vs carbide end mills in the same size/length tend to have a 2-4X price differential, not 9X.

I'd think that the carbide pilots would be less bother to grind as they'd deflect less, so that the big difference in the price would be the material.

Is the price differential due to actual machining costs, or just the "oooh carbide" blingyness factor?

cheers,
Michael

 

[JRIowa]

Probably more to the fact that there's a lot more competition in the end mill business than the valve guide pilot business. If you'd buy 10K, I'm sure the price would go down
JR

 

[adama]

Would have thought they would have been centreless ground, hence diameter to length is nothing like as much of a issue.

 

[tomwalz]

Much of the price difference is an issue of materials. Tungsten carbide is primarily tungsten with a few percent cobalt. Any steel has a really high percentage of iron. Iron is much, much cheaper than tungsten or cobalt.

Steel, even high speed and tool steel, is made in huge quantities. By comparison tungsten carbide is made in relatively small quantities. As an example, a ton of steel is very little steel whereas a ton of tungsten carbide is a huge amount of tungsten carbide.

You can machine tungsten carbide once it's been sintered and fully hardened but it takes a long time and requires the use of diamond tooling.

When tungsten carbide is formed, and before it is fully sintered and hardened, it is softer than sidewalk chalk and you can whittle it into shape. However tungsten carbide shrinks during the final sintering so you have to whittle the pre-sintered part into something oversize. You want to leave yourself a little fudge room which means it will require some machining after it is sintered and fully hardened.

So tungsten carbide is much more expensive than steel because the materials are much more expensive, because it is not made in anywhere near the volume steel is and because it is much harder to make.

However tungten carbide can give up to 100 times the life of any steel. It depends very heavily on the grade, the application and the procedures.

"Wear parts" are big part of the tungsten carbide industry. When downtime is measured in thousands of dollars per minute using a couple thousand dollars of carbide to prevent wear can be a very smart investment.

 

[Tank]

I work for a company that makes aircraft parts that require a lot of custom ground cutting tools, on top of the standard off the shelf cutting tools. (we spend in the 7 figures a year on cutting tools) Although we have manual tool grinders we looked into the feasability of getting a 5th axis tool grinder. In order to keep the machine running enough to justify it it would have required us to make some standard "off the shelf" end mills.

When looking into the cost savings of doing this we found we could not buy quality carbide, (blanks or rods) for less than we could buy complete endmills from companys like Fullerton.

These endmill companys buy carbide in such volume that they can sell their endmills for less than we could by the raw material. That came as quite a surprise and killed the 5th axis tool grinder in it's tracks.

It may be possible to buy some odds and ends or low quality carbibe cheaper than the end mills but you won't do it consistantly. Every time I post something like this someone finds carbide at Harbor Frieght or some place like that and has to show how cheap it is just to prove me wrong. I think you guy's here have the right idea of why low volume carbide parts are expensive.

 

[stephen thomas]

I'd think that the carbide pilots would be less bother to grind as they'd deflect less,

Michael,

If you try grinding your own, do support both ends. It sounds like you are looking for a piece of 3/8" x 7" long ground carbide (C2?) that you want to grind one end to a pilot with a slight taper? Even if you support the rod in a collet in, say a spindex with "only" the 3-1/2" length sticking out unsupported, I doubt you will have success grinding it. At some point when the right (wrong?) frequency is struck, suddenly the part will just disappear. You may find the end in one piece where it broke off, or maybe just some pieces scattered about.

It's not that hard to grind (with diamond) but it does require good support.

Apologies if I didn't understand your description. I still have an old set (bought new early 70's) of Triumph twin cutters somewhere. And have made radius seat cutters and blending tools. But not up on the late stuff. Your dimensions sound thin and long, to me.

Oh, and your probably know that carbide and cobalt binder dust is awfully hard on the lungs.

smt

 

[Michael Moore]

Thanks for the interesting information.

Here's what a pilot looks like:

I have no intention (or ability/equipment) to make my own pilots, I was just trying to figure out why HSS vs carbide pilots would have a bigger price differential than what I'm used to seeing in HSS vs carbide end mills.

Either it is harder to make, volumes are too low for economies of scale, someone is benefiting from a very large profit margin, or some combination of the above.

I bought the 5 and 5.5mm pilots in HSS as I can afford that, and I'll have to hope that I can be careful enough to not run into flex issues. I'd liked to have carbide pilots, but even one was a budget breaker when I'm trying to get a basic set of seat tools together.

I thought that for grinding slender parts like this they'd have something like a Swiss lathe, where the part being worked on was right at the face of the collet and the stock was extended as grinding progressed. But then I know next to nothing about fancy grinding equipment so that was just a WAG on my part.

cheers,
Michael

 

[gas pumper]

If you are not doing production volumes on heads, and are doing once in a while repairs and head work I think the Neway seat cutters are the way to go. I've been using this system for about 20 years now and am always impressed on the nice cuts I can make. No matter if the head has seat inserts or not, I get a great result.

I do my valves in a collet on the lathe and do a final lap to check the seat contact.

Neway Manufacturing Inc.

I just have pilots for the sizes I commonly use and a few cutters to cover the valve seat sizes I work with. I normally do 3 angles on the seats and sometimes 4 if there is room. I cut manually. And can correct off center factory seats very easily.

Making chips is so much nicer than grinding.

 

[Michael Moore]

I got a set of Neway cutters, pilots, and some bronze-guide reamers delivered about a week ago. I'm waiting for another set of pilots to arrive on Monday to match the guides in a head I can use for practice. I figure doing the first seats on 7.5mm pilots will let me get a feel for things before I try any of the more flexible 5 and 5.5mm valve seats.

I do have an old Kwikway grinder, but none of the guides were of a suitable size and it looked like it was going to be awkward to use on the small-stem valve seats.

Some people claim the Neways are junk, but there seem to be plenty of people who are satisfied with them. They are also what the Japanese OEMs specify in the manuals.

Pretty much all I have is competition bikes, and rather than cutting new seats in worn valves it makes more sense to me to just install a fresh $20-30 valve for that should give years of intermittent use. That saves me having to spend money on valve refacing equipment.

cheers,
Michael

 

[Grind]

Don't worry about getting carbide pilots for bobbing stones by hand, they first came out for use on Serdi and Newen seat and guide machines with the floating heads.
Regular pilots will work fine for a hand grinder, just be careful not to put side pressure on the grinder, just let it float. FWIW most of my metric pilots were made on the lathe with the customer wanting there head by the end of the day and new pilots 2-3 days delivery. Just check them by spinning them in the guide with a dial indicator at the top and again as close to the seat as possible. Check your new pilots as well both to qualify them as well as to get an idea what new tolerances are. If you can get your shop made pilots to .0005 your good to go.

 

[gas pumper]

You need to check new valves for concentricity. Stems to the heads. I had recently repaired heads on a Ford 5.0 that had aftermarket AL heads and had leaky valves. The "top of the line" valves were not concentric. I took a cleanup cut on the seat area of the valves. Some were OK, some were .010 off. You can't trust new stuff unless you check.

I'm glad you got the Neway stuff. I'm real happy with their method.

Frank

 

[pistonskirt]

Michael

The 5.00mm carbide pilots may well be more rigid but they are most commonly used on Serdi type machines where there is substantial support for the cutter above the pilot, the Neway system has no upper support & you would find that the pilot will break the moment you get any chatter or uneven loading, if cutting manualy I would be surprised if you managed a couple of seats before snapping the carbide pilot.

I use Neways for a lot of my work but would not want to use them manualy, I did that many years ago & can still remember the blistered palm & shoulder muscle spasm that will certainly ensue
The Neway power drive works well enough but doubtless expensive, it is however nothing fancy at all & I am sure you could knock something up quite economicaly, if you want some pics & dimensions just let me know.

regards

Brian

 

[Michael Moore]

Frank, I've heard other people mention that even the nicer race valves do need to be inspected before use. I've got some Ferrea SS valves for a project and I'll make a point of checking them out.

Hi Brian,

I hadn't thought there'd be a problem with breakage, but I can see how that could happen since carbide inserts and endmills certainly seem to chip easily. In any event I'm starting off with the HSS pilots as I was able to buy a full set of those in three different major stem sizes (and -, on size and + within those) for the price of a single carbide pilot.

Since I won't be doing seats on a daily (or probably even monthly) basis I may be able to survive the "armstrong" method. I did have the thought that perhaps my 3/8" drive air ratchet would turn slow enough to use and would also be fairly controllable for not putting side loads on the pilots. I think I've seen about 40RPM mentioned for the Neway power head. What do you think of that idea?

cheers,
Michael

 

[gas pumper]

I actually wondered why they offered a power drive. But I am not production either.
I do make an effort to put no side load on the pilot. I try to carefully turn with only down pressure on the cutter head. It does not take much force.

The cutters are especially nice when you are refreshing a head you previously did. Just a quick twirl and a fresh seat. Minimum material taken off.

Add: Maybe just a variable speed battery drill would power the cutter?

 

[pistonskirt]

I did have the thought that perhaps my 3/8" drive air ratchet would turn slow enough to use and would also be fairly controllable for not putting side loads on the pilots. I think I've seen about 40RPM mentioned for the Neway power head. What do you think of that idea?

Maybe just a variable speed battery drill would power the cutter?

Not sure exactly what RPM mine gives, probably around 40 as you say, I will be cutting some seats later this week so I will check with a rev counter.
Not sure about the air ratchet or gas pumpers suggestion of the battery drill, both could obviously provide enough torque but I would not fancy having to hold any weight concentric with the pilot, perhaps some sort of flexible coupling would work but I am not sure that you would retain the necessary feel for the cutter.
All of this is of much less concern when cutting on 7 or 8mm pilots & 5 blade 200 series cutters of course, but I can be certain that you will soon recognise the importance of feel when you need to work with 5mm & smaller pilots using 3 blade cutters.

I wont say what it's like to cut seats with 4mm pilots....mainly because I dont like to see excessive foul language on this forum

regards

Brian

 

[Michael Moore]

I got the 7.5mm pilots in this morning and roughed in the seats on a NOS Motobi cylinder head. The factory did a pretty poor job of getting the intake guide and bronze seat aligned, and getting it to cut all the way around did take a number of cycles. The exhaust came in pretty quickly though.

I'd do about 4 or 5 half-turns (trying to lighten the pressure right before I stopped turning) and cleaned all the swarf away from the cutter and seat. I used a toothbrush dipped in the cutting fluid for that rather than trying to spray fluid on the seat.

This is reasonably fun.

Brian, I purchased the 1.25" OD 5 blade cutters for top and 45 but they only had the bottom cutter in a 3 blade head.

I put the seat dial indicator on and the exhaust (which started off pretty centered) looks to be .001" TIR and the intake is more in the .0015-.002" TIR. I did do the intake first and it may be that between trying to get a clue and the very offset seat the extra runout occurred. But I haven't done more than eyeballing with calipers on the diameters so there's probably room for a little more trimming in that will hopefully straighten things up some more.

How firmly should I be pushing the tapered pilots in, and should I oil them first (bronze guides) or leave them dry?

cheers,
Michael

 

[gas pumper]

Michael, I have expansion pilots, so I can't help there. All my jobs are 5/16 3/8. And I oil everything just to get oil between the pilot and the cutter head.

I always had a lot of anxiety grinding the seats. The Neway just seems so much more relaxing and "right". It's a pleasure to use.

I'd think that even the .002 would be fine. I don't live in Perfect. There is stem clearance to help with a little offset. And a final lapping will insure a good seal at startup. Possible to just set up and take another skim at that one and try to get it better.

Half turns is what I do, too. very light pressure, just enough to feel a cut.

So this is motorcyle stuff? really small? Not much material on the heads to lighten them up?
Pictures? Or is it secret?

I always thought that the exhaust sounded better and crisper with a nice valve job.
Frank

 

[Michael Moore]

Frank, this particular head is from a Motobi, and the same basic engine came in 125, 175, 200 and 250cc, all of which used 7.5mm stem valves. The 250 keeps the 200cc combustion chamber but bumps the bore about 8mm.

Index of /graphics/Benelli

That folder on my website has some photos of bikes and parts and period road tests. Look at the photos that start "Motobi250stockhead" to see the NOS head I messed with today.

As you can see these heads could almost be made from solid with a band saw and drill press.

There's a "250 cylinder head.pdf" which can be rotated/zoomed once you click on the image, and that shows how far I've gotten with modeling a head. I've got 5.0mm valves/springs/guides/retainers for a Suzuki Hayabusa which I'd like to use in a DIY head. One of the guys was given valves from an RM450 Suzuki MX bike and he put those into a stock head, but I'd like to make use of the longer valve stems to raise and straighten the ports.

Now I've got stuff so I can do valve seats, so that's one step closer. Plus I help a friend who vintage roadraces 160/175 Honda twins (including my old race bike) so I'll probably end up doing some valve jobs for him and maybe try some porting too.

The thing with these 1950s/60s heads is they generally seem so bad that it makes me feel like even I could improve them.

So I get to buy more tools, practice with CAD doing models of the parts, and hopefully eventually make some parts too.

cheers,
Michael

 

[pistonskirt]

How firmly should I be pushing the tapered pilots in, and should I oil them first (bronze guides) or leave them dry?

And I oil everything just to get oil between the pilot and the cutter head.

My established routine is to run a brush through the guide wetted with a blast of contact cleaner then blow dry, as Frank suggests providing a little lubricant between the cutter sleeve & the pilot will help reduce wear & keep things smooth running. Clean & check the pilot carefully then put one small drop of 3 in 1 oil wiped along the taper of the pilot, push the pilot into the guide with a twisting motion seating it sort of "finger & thumb" firmly (using the tommy bar of couse).....hard to explain but removal of the pilot should just require a lightish tug & twist with index & middle finger hooked around the tommy bar. One small drop of 3 in 1 oil on the running portion of the pilot is more than adequate such that I have very rarely had to replace a pilot or cutter, with your anticipated usage you probably never will.

.001" run out is fine for most jobs & very good indeed for your first attempt, getting below that figure is very difficult (nigh impossible consistently) with Neway's & is where the time factor ramps up enormously.
To check the surface finish of the seat face up a scrap valve & gently lap the seat with the finest grinding paste you can find (thinned with a drop of 3 in 1 helps) bearing in mind that the Neways are + 1 degree you will still get a decent highlight of the surface....it's then up to you to decide if you like it

regards

Brian

PS/ A Motobi head !.....pretty sure thats the first one I have seen.

 

[pistonskirt]

Just stumbled across the specs for the Neway power drive as follows

230v AC / 50 cycles / 50rpm

regards

Brian