Mcnaughton Center saver users

[chrisdaniels]

Here I go again trying to pick your brains. I have tried a couple dozen cores now with my mcnaughton, I only have 1 lampshade thankfully but I'm not getting the angles right. my cores are coming out uneven and almost always thinner at the bottom 1/4 of the bowl with some getting so thin that I know they are going to crack during drying. I have the standard set, and the small set now and i'm trying to get proficient before I start jumping into the nicer wood and the burls that are piling up. I have mike mahoney's dvd which is fun to watch but didn't teach me much as far as the aiming and visualization process goes. He says you have to have some imagination to visualize where the cut will be but like Dale Bonnert says, you're new you don't have the imagination which is my issue.

I have watched dale bonnert's video a dozen or more times and I like his process but for the life of me I can't get it aimed right even then.
I have also watched robo hippy's video a handful of times for tips and have picked up on some good cues there.

Does anybody have any good tips on getting the cut laid out and setting up the angle of entry? I don't know that it could be explained any more than Dale Bonnert does but maybe someone has some tips or tricks that I can't find.

I don't want to spend another hundred dollars on the laser guide since i've allready dropped almost 700$ on this set up as it is so I want to exhaust every other option first.

I have a large supply of 22" diameter hard maple logs that I want to make a lot of bowls out of but when I try to core them I get a fight like i'm battling vikings everytime I try. Thanks in advance for the info!

Chris

 

[hockenbery]

Chris,
Always try to keep the big bowl

Start out coring them an extra inch thick for the wall thickness.
If you want a 1.5" thick wall for drying cut the walls 2.5" thick
You are planning to loose at least one bowl from the cores
Better than loosing all of them or the big one.
When you are getting an even 2.5" thickness when you wanted 1.5
Switch to the target thickness.

I put the coring bar on top of the bowl.
This first confirms I have the right bar for the bowl shape.
Then it shows where the gate needs to be set and the entry angle.
It has always been easy for me to see where the tool,needs to be to cut by laying it on top of the bowl to be cored.
I hope that works for you.

Al

 

[hockenbery]

Also rough turn 3 bowls to be cored and have them ready to go
Then you can just core and core and core and you have 9 bowls


My sequence for three bowls
My process is to cut most of the big core first.
Then cut the next core put a Tenno on the small core
The cut the middle bowl free and put a tenon on it

 

[robo hippy]

Well, if you want another video to watch, here is a link to mine:

https://www.youtube.com/watch?v=xk-Z-scS84w

Aiming is probably the most difficult part. Shortest version is before you start, I lay the blade up against the outside of the bowl (I take the biggest one first). How close the arc of the blade is to the arc of the outside of the bowls determines where to point the tool. If the blade is tighter/smaller arc than the bowl, you can aim pretty much down the side of the bowl as the blade will curve away from the outside. If the blade matches or is flatter than the arc of the bowl, then you aim in more towards the center. If both are pretty close to the same arc and you go parallel to the outside of the bowl, you will hit your chuck. Both Dale and I, after setting the tool post in position, like to hold the blade up above the support fingers and over the bowl in the path we want the tool to follow.

The laser pointer is actually a good idea. It really helps when learning to know where you are. If you have a hollowing system that has a laser pointer, most of the time, they can be adapted to fit. If you don't have one, and are planning on picking up hollowing, then it is a multi use tool.

If I lived closer, I would have you by for a hands on session. Where are the transporters when you need them.

robo hippy

 

[Clifton C]

Chris,
I follow Al's method of visualizing with the tool on top of the bowl but then pretend that the tool is in the groove (kerf) and slide it out along the imaginary groove. This shows how far to the right the handle has to be to start the cut. Usually father then I had thought. The other thing I started doing that calmed down the tool was to set the tip of the tool about 1/4 inch above center when the tool was fully extended from the gate. If I set the height of the cutter at center with the gate next to the bowl blank, the first 2/3rds cored great, the last third would fight all the way to the bottom as if the bowl was trying to climb over the tip of the tool, and it was, because by now, the cutter was below center by about 1/2".

cc

 

[dbonertz]

Chris,
If you are making the bigger bowl to thin then you are exaggerating the tool handle to far left as you look down it for an aiming point. If the smaller bowl or core is getting to thin then you are not going far enough with the handle as you look down it for sighting. When sighting down the handle make sure your sight/aiming point is as close as you can get it. I find that if I try to sight the handle to something farther than 5 feet from the lathe then there is to much room for error. Closer than 5 feet is even better. I am sure Robo or anyone who responded would be willing to talk to you over the phone to coach you through it. If you need me then email me or private message me and I'll give you my number.

 

[SMawson]

I found that practice more than anything else helps a lot. The more you core the easier it gets.

 

[Paul Gilbert]

I don't have a coreing system, but do use a video system for hollowing. Do you have an old XP PC lying aroung? Hook it up to a camcorder camera, add some boat rail tubing and you have a video system that is superior IMHO to a laser. If you have the PC, it is cheaper than $100 and will give you the picture of the whole coreing bar.

 

[idahohay]

Chris, most bowl turners have circle templates out of 1/4" plywood. Find one that best matches the curve of the knife.

Hold the disc over your blank representing the arc you want to cut (looking down from top)

Hold the knife so the tip is plumb with the face of the blank and against the disk. It will know be at the proper entry angle.

 

[chrisdaniels]

I will need to figure out the diameter circle to cut out for each of my knives, I have the regular set and the small set, I like that idea that's a good one thank you. makes it easier to rotate the tool to the entry stage and more accurately aim for the entry angle like Mr. Bonnert says to do it. Thank you

 

[Mike Johnson]

I picked up a used McNaughton center post tool gate and need to acquire some coring tools to complete the system.
I might try and forge a couple of tools or I thought if someone has some coring tools missing the carbide tips I could
do the repairs and put the tools back to work. This is an older style center post tool gate with 3 pins. The description of the
tool I bought listed 7/8" diameter for the post, I can't find any information on the older tools to determine which knives go with this tool.
If anyone can direct me to an archive for the older tools or if they have any knives they want to unload let me know.

 

[Bill Boehme]

Here is a CAD layout that I made for my use. I used the right side to determine the radius of the blades that I have. On the left side the chart shows different diameter and depth templates for each cutter. I created it to determine the maximum diameter vs. depth for each blade assuming a one-inch tenon remaining. The templates aren't exactly self-explanatory because I made it for my own use. I might work on a better version that is more useful to others. I print it on 13" X 19" paper and then can lay the cutter on top of the template to see what the entry angle is for a desired diameter and depth.



Disclaimer: Although I have had my Center Saver for a couple months, I haven't been able to do any coring due to rotator cuff surgery a few months ago. For the past year it's been mostly just thinking about turning and no real turning. My total experience was working with another club member coring a large bowl over at his shop and he did most of the actual coring. It was basically a new experience for both of us, but things went very well and with some forethought, it seemed like a fairly intuitive process for a couple inquisitive engineers. We probably over-analyzed everything, but that's what we thrive on.

EDIT: If you want to print the file, it requires A3+ (13" X 19") paper. Set PPI to 101.

 

[Emiliano Achaval]

We had Andi Cole gave us a demo on the Mcnaughton. He gets up to 7 cores!!! Definitely the master along with Mike. The best and biggest single tip was to hold the handle UP all the time!!! I had given up on it, now I'm coring! aloha

 

[john lucas]

I made a replacement blade after breaking one using my really poor technique ( A Mike Mahoney I aint) I didn't do a serious search for the right size metal and this one is just a little too thin. Not far off but it makes a difference in how much it chatters. Since then I've also been reading up on making spring steel so I can (if I ever get time) make the steel stronger by heat treating it to the spring steel level. I also now have a larger metal bender so some day when I settle down from this move I'll fire up the forge and make myself a whole set and get serious about this coring stuff.

 

[Fred Belknap]

I have McNothing coring system and so far it has been mostly . I don't have much problem with alignment, my problem is getting it to cut on hard burl wood. I have bent one of the blades, it's pretty easy to bend it back to normal looking, which gives me an idea how good the metal is. As for using the micro blades so far it has been a bust. For now it is a considerable bit of money down the drain. My take on the system is that the blades aren't strong enough to work off tool rest the distance that is required for coring. I don't like being a wet blanket on this system but I have tried just about everything that has been suggested without and appreciable results. I'm thinking a system like the Oneway which supports the blade through the cut might be money better invested. My system was given to me as a Christmas present from the wife, which gives me moral obligation to get it to work.

 

[Clifton C]

The first turner I saw demo this tool bulldozed his way thru a few cores, but I still had to have one. Got it home and had the same results, it beat me up.

For the first year and a half it lived in the corner. Every once in a while I’d dig it out and have another go, but mostly with the same results. Read, reread, watched, rewatched everything I could find. From the results of others, I knew the tool worked, it just didn’t work for me. So, I kept at it. When coring, I noticed that the first 1/2 to 2/3rds of the process was relatively painless, it was the last half that got me in trouble. One day while trying again, I got the feeling that the blank I was coring was trying to climb up and over the knife blade, and the proverbial lightbulb went on…

At the end of the cut the blade was too low. I had been setting the cutter to center hight with the gate next to the bowl blank, when I rechecked the hight with the blade fully extended, the cutting edge was a good 1/2 inch below center. With the blade extended, the downward force of the cut probably dropped the cutting edge another 1/4 inch for an easy 3/4 inch below center by the time the cutter made the turn to the back half of the bowl, it was no wonder the bowl was trying to climb up and over. Now, I start with the blade 3/4’s of an inch high. The shavings flow, the blade almost self feeds, I just guide it. I’ve shown this to a few guys and the response is usually “where is this written” or “you could have told me this a year ago” or “dangit, I just sold mine last week”.
Some folks know this, some folks don’t, hopefully it will help somebody.
Ps. I'm usually coring 14" and up and > 4" deep.

 

[Bill Boehme]

What Clifton said ... plus watching the YouTube video by Dale Bonertz on using the Center Saver, paying the money for the Mike Mahoney DVD, and even reading the printed instructions are all valuable information. Two points that Dale stressed that I think are very important are setting the cutter height with the blade fully extended and you can't steer the blade ... you push it. Dale's video mentions the self feeding that Clifton described as the blade gets deep into the cut. There is clearly a lot to learn about using this tool.

 

[Fred Belknap]

What Clifton say sounds good. I did try setting the cutter above center but I only set it about 1/4" and I realize sometimes a small change can make a big difference. I'm setting on several large burls I would like to core so maybe I will try it again. The uneven on the outside of burls does present a challenge. I have managed to beat out a few cherry burl blanks which are relatively soft but most of what I have now are maple/birch and a couple unknowns.

 

[Bill Boehme]

I think that you should save the burls for later and practice on some less interesting plain vanilla free wood.

 

[Emiliano Achaval]

I have McNothing coring system and so far it has been mostly . I don't have much problem with alignment, my problem is getting it to cut on hard burl wood. I have bent one of the blades, it's pretty easy to bend it back to normal looking, which gives me an idea how good the metal is. As for using the micro blades so far it has been a bust. For now it is a considerable bit of money down the drain. My take on the system is that the blades aren't strong enough to work off tool rest the distance that is required for coring. I don't like being a wet blanket on this system but I have tried just about everything that has been suggested without and appreciable results. I'm thinking a system like the Oneway which supports the blade through the cut might be money better invested. My system was given to me as a Christmas present from the wife, which gives me moral obligation to get it to work.

I had given up on it. But a hands demo by a Pro was the eye opener... If Andi Cole can get 7 cores, I can get 1!! Koa wood is way harder than a lot of mainland woods, I'm happily coring Koa...

 

[john lucas]

I have limited experience with my McNaughton. I simply don't do many large bowls and rarely have wood good enough to bother with saving the core. I did find that my main problem was the cutter getting below center as I got deeper. Clifton's experience is dead on in my book. I did have one cutter replaced by Mike Hunter and that tool cuts much easier. However if i let it get down at or below center it's the same fight. I do have some Walnut I may core pretty soon. It depends on whether I decide to make platters from it or bowls.

 

[robo hippy]

The getting below center is always a problem. If you have ever tried to remove the nub that is left after the core has popped off, by using the McNaughton blade, when it contacts, the tip can drop an inch or so. This is a bigger problem with bigger bowls. There is a considerable amount of 'flex' in the whole set up, which is planned because a rigid system that is suspended out that far off the rest might snap. I can 'feel' this now, and use the long handles and drop the handle to raise the tip. This is Master Level skill. You can raise the tool rest a bit, and mine is set so the tip is about 1/4 inch above the center if I am really lifting hard against the top bar. You can't raise it too much because you have a square peg in a round kerf, and it can only go so high without rubbing top and bottom.

I have taken to putting my blades on a circle template and checking the curves. While they are considerably better than early versions, most of the time, the very last inch near the tip goes straight rather than following the curve. I have a couple of 5/8 inch bolts through hickory with about a 3/8 inch gap which I clamp down to the bench top, and put the blades in and tweak them to perfection. They no longer track to the outside of the cut.

robo hippy

 

[Bill Boehme]

I have taken to putting my blades on a circle template and checking the curves. While they are considerably better than early versions, most of the time, the very last inch near the tip goes straight rather than following the curve. I have a couple of 5/8 inch bolts through hickory with about a 3/8 inch gap which I clamp down to the bench top, and put the blades in and tweak them to perfection. They no longer track to the outside of the cut.

That is very good information to know. I recently bought a standard large replacement blade from CSUSA and the curve didn't look right when eyeballing it. I laid it on top of a template and I could clearly tell that there was a straight section about three inches long at about mid span in the curve.

Your suggestion of making a hickory bending form is an outstanding idea. And, I think that your observation about the last couple inches of the blade being straight is a dead on accurate explanation of why the cut tracks to the outside.

I guess that I shouldn't be surprised to hear about the amount of flex in the blades considering the overhang, but that is impressive.

 

[robo hippy]

I have argued that point with Kel for years, and he doesn't agree. My 'fixed' blades cut on a much truer arc. I did retip one of my blades with the tantung that I use on the Big Ugly tool, and think it cuts better than what ever Kel has on his blades. I did send him a piece and some silver solder to play with.

Ideally for making the blades, I think I need to find a laser cutter for tubing as it would be easier to bent the tang flat than bend the curve to a perfect arc. For bending straight stock to an arc, you bend it a couple of inches longer, and snip off the flat parts. Some of Kel's old blades were cast stainless. Not sure what he is using now.

robo hippy

 

[Bill Boehme]

I did a bit of playing around with a couple blades today to see how much flex I could see. With the largest blade from the large set (CSUSA calls it the Jumbo set) extended to its maximum out of the gate, I could only get the tip to deflect down about 1/16" below center when applying about fifty pounds of force downward at the tip and it appears that a good portion of that was due to free play in the tool post and the yoke/gate assembly. I repeated the test using the largest blade in the standard set and the deflection was a bit more, but still less than 1/8" judging by eye. I had the tip of the blade sitting about a half inch away from the center point of the tailstock live center. This led me to wondering about the source of the flexing. I have the new Mark 8 design and being new, everything is reasonably snug. Maybe if it had a lot of hours of use on it then there might be a lot more looseness allowing the blades to deflect downwards a lot more.

Funny that you should mention tantung because I have been wondering about it as a better alternative to what I assume is just a piece of HSS brazed to the blade. I figured that the blade is probably carbon tool steel that has been tempered so that it doesn't bend too easily.

The curvature of the bottom parts of my blades near the tip seem to be OK, but the top part that is flared out to make the wide kerf seems to be too straight. I'm thinking about using a stone to reshape that a bit on one of my blades, but I probably ought to use them for a while to get the feel for what they do before I go off redesigning it.

 

[Mike Johnson]

Can anyone identify this McNaughton tool gate, the post is .80" in diameter.
I am assuming this is an older model/version.
There are only 3-pins on top and (2) of them have a short riser base.

 

[robo hippy]

That gate is probably the original, and my favorite to use. No idea about the narrow post though, I thought they were only 1 inch or a metric one to fit the Vickmark lathes. It will fit the standard and jumbo or large set of blades. On the newer Mark 8 blades, the jumbo set are a thinner gauge, and will wiggle a bit more.

As for the blade and tool rest flexing, I have no idea how much downward pressure is on the blade when coring. I figure that there is a lot of torque on a 1 1/2 inch nub if you are trying to remove it with the coring blade. Exceeding 50 pounds, I would guess would be easy. I have lifted up the handle and applied at least that much pressure to see how far the tip would move down, and yes there is flex in the tool rest. Try to take the nub out and see what happens...

robo hippy

 

[Mike Johnson]

Thank You Robo,

The odd sized post was kind of throwing me off, I might get a 1x3/4" sleeve and drill it out or make a banjo with that
size of opening fot the .80" post.

If anyone has any knives for the McNaughton system that they are not using I would be interested in what you have.
I will either forge some knives or purchase several new ones, but thought I would check here first.

 

[hockenbery]

Also some lathe beds and banjos flex too

 

[Bill Boehme]

That gate is probably the original, and my favorite to use. No idea about the narrow post though, I thought they were only 1 inch or a metric one to fit the Vicmarc lathes. It will fit the standard and jumbo or large set of blades. On the newer Mark 8 blades, the jumbo set are a thinner gauge, and will wiggle a bit more.

As for the blade and tool rest flexing, I have no idea how much downward pressure is on the blade when coring. I figure that there is a lot of torque on a 1 1/2 inch nub if you are trying to remove it with the coring blade. Exceeding 50 pounds, I would guess would be easy. I have lifted up the handle and applied at least that much pressure to see how far the tip would move down, and yes there is flex in the tool rest. Try to take the nub out and see what happens...

robo hippy

I agree that the gate looks like the original design that I have seen in several videos and that particular one is probably for the standard and small blade sets just guessing because of the smaller size tool post. According to the Kelton Industries website they have a number of tool post sizes available. The tool post on this one can be replaced with a inch diameter post, but you need to make certain that you get the one for the original gate and not the one for the newer M8. I believe that they are different.

I watched Mahoney's DVD again today. I didn't see any noticeable flexing of the blades. However, he did mention in the tool tips section that he has bent a few blades in the past and the reason was because of overheating them due to rubbing.against the wood. That's one reason that he stressed frequent clearing of chips and shavings. He also suggested using a spray bottle to spritz water in the kerf to cool the blade and to keep the kerf clear of chips and shavings. I wouldn't be surprised if repeated overheating of a blade made it flex more than a new blade.

The full load stall torque at the spindle of a 3 HP Robust AB in the low speed range (assuming it has three speed ranges like my model) is approximately 12 to 13 foot-pounds (I don't remember off the top of my head the exact pulley ratio). If we measure the force at different diameters just before stalling the motor, it would increase as the diameter gets smaller -- 13 lbs @ 1 ft diameter 2 foot diameter, 26 lbs @ 6 in diameter 12 inch diameter, 52 lbs @ 3 in diameter 6 inch diameter, 104 lbs @ 1½ in 3 inch diameter, etc.

However, the thing that we're interested in would be the load torque and that can be divided into two components -- load torque created at the cutting edge and load torque due to friction of the blade rubbing in the kerf. Both of those components are somewhat dependent upon speed. The load torque at the cutting edge ought to be somewhat comparable to the torque load created when using a scraper the same width and taking the same size "bite" into the wood. Normally, the force feedback that you feel gets less as you work closer to the center. That is mostly because of the lower cutting rate near the center. The other component of load torque caused by rubbing friction in the kerf is highly variable. Kerf width, sharpness, the amount of force applied, chip and shavings clearing, wet or dry wood, species of wood, skill level, and "goodness" of blade curvature all make this an impossible number to quantify. However, we can try to minimize the friction load. I am still a few light years from the coring skill of Mike Mahoney or Dale Bonertz, but I think that identifying problem areas will help accelerate my progress ... that's the plan anyway

EDIT:
Corrections in math shown in red.
updated 8-22-17

 

[Mike Johnson]

I have a metal lathe so I can turn a new 1" post to fit the banjos on my wood lathes.
Just need to get a few knives to start working with.
How thick and tall are the standard knives vs the large knives.
I might pick up some tool steel if I can find the right sized pieces to make the knives with.

 

[Bill Boehme]

I have a metal lathe so I can turn a new 1" post to fit the banjos on my wood lathes.
Just need to get a few knives to start working with.
How thick and tall are the standard knives vs the large knives.
I might pick up some tool steel if I can find the right sized pieces to make the knives with.

I'll make some CAD drawings. The basic blade material on the M8 system is ¼" thick for both the large and standard sizes.You should check to see what the pin spacing is for your older gate. It seems like I read somewhere that the large blades were thicker on the older system. You basically want the blades to glide easily through the guide pins neither binding nor rattling around. As a guess the clearance on mine is around 0.005". The height of the large blades is 1¼" and the standard blades are 1" tall. Unless you have a big lathe with a swing of 20" or more, you won't need the large blades.

The radius of curvature of the two large blades are 9.5" and 6.5". On the three standard blades, the radius of curvature of the large blade is ~9.5" and 3.5" for the small blade. I don't have the medium standard blade yet ... it's been on back order for several weeks and isn't expected to be available until mid November at CSUSA. I would guess that it has a radius of around 6".

Measure the height of the pins on your gate and that will tell you the correct blade height. The cutting end of the blade is the most difficult part to make because of the complex profile. It might be worth buying at lest one blade to study how they are made. Basically, the nose end looks a bit like the bow of a ship. I think that they use a welder to build up the profile and then use a grinder to shape it. The actual cutter is a thin piece of HSS welded to the nose of the blade, but you could create your own design ... maybe even using carbide cutters.

The top and bottom and sides need to be smooth so that they won't drag or bind. When they are under load, it wouldn't take much to cause a rough spot on a blade to make it get stuck. In order to get a nice smooth core you need to be able to make nice smooth flowing cuts. Chamfering the edges also would be a good idea. I did a little file and stone work on my blades to make them slide as smoothly as possible. I also put a little Johnson's paste wax on everything ... it makes everything nice and slick.

I'm not positive, but I think that the small (they use the word mini) blades are ¾" tall and probably 3/16" thick.

 

[Mike Johnson]

Thanks Bill,

When I have the time to make bowls watching the floor fill up with shavings always seems like a waste
of time and resources. I do enjoy the time practicing with different tools on the billets, but I have some
body parts that get inflamed when I spend too much time with a roughing gouge or encounter tool catches.
Has anyone done a time study to determine time wise which is quicker on a typical bowl roughing?
With a sharp set of tools which method would be quicker to rough out the bowl if you did not care about the core?
I run the risk of a tool catch using the McNaughton method the same as loosing focus on multiple cuts coring out
a bowl with conventional tools. I would imagine the turners who make bowls every day can most likely core a bowl
quicker with conventional tools then taking time to set up the jig and measure the bowl and determine the entry point.
I have several lathes which allows me to dedicate each machine to do different tasks which speeds up the process and
reduces the clutter around each machine. I plan on using this system on the billets that are highly figured and segmented
billets mainly.

 

[robo hippy]

Following this on 2 forums....

As for Mike saying that some blades have bent from heating due to friction, I have to scratch my head about that one.... Not sure how hot they have to get to bend due to heat/softening, but wouldn't think they could do that, though I have had some burn marks on the core and bowl, and I have burned my fingers more than once. For sure, with repeated use, and a catch or three, being curved and extending out a ways off the tool rest, the blades will twist, which is use and abuse, and will happen with or without heat. This is why we have the bent hollowing tools made so the straight part of the blade is on the tool rest, and the beginning and end of the arc are in line with each other so there is no torque with the cutting action. I put the blades in a vice and use a big adjustable or monkey wrench to twist them back up. The binding and friction is caused by the blades drifting, where you end up with two different arcs, the blade, and the actual kerf. This is why many open up or widen the kerf. Keeping the chips flowing is also a compounded problem because every stop/start you do leaves a ridge, which traps shavings. With a perfectly bent blade, the chips flow out a lot easier. With properly bent blades, I can remove an 5 or 6 inch radius core in one pass with out needing to remove the shavings.

Now, out to the shop to measure the arcs, some thing I have needed to do for a long time.....

robo hippy

 

[robo hippy]

Well, curiouser and curiouser...... I have several sets of large, standard, and small blades. I had always assumed that they were all bent to the same curves, but given the variance in the measured arcs, even considering the amount of use and abuse I have heaped on them, it appears that they differ from set to set. As near as I can tell:

Shallow curve on large set about 11 1/2 to 12 inch radius, on standard set, about 9, on small set about 9.

Standard/medium curve, about 9 on large set, 7 on standard set, and the small set, about 6

Small curve, no available on large set, about 4 to 4 1/2 on standard and small set.

robo hippy

 

[Bill Boehme]

Well, curiouser and curiouser...... I have several sets of large, standard, and small blades. I had always assumed that they were all bent to the same curves, but given the variance in the measured arcs, even considering the amount of use and abuse I have heaped on them, it appears that they differ from set to set. As near as I can tell:

Shallow curve on large set about 11 1/2 to 12 inch radius, on standard set, about 9, on small set about 9.

Standard/medium curve, about 9 on large set, 7 on standard set, and the small set, about 6

Small curve, no available on large set, about 4 to 4 1/2 on standard and small set.

robo hippy

Your large blades have a larger radius of curvature than mine. I was expecting the radius to be more like the radius of your blades on the large set. I made a PDF template (se attachment below) that you can printout on regular 8½ X 11 paper that makes it easy to check the radius of blades that have a radius of 5 inches and larger. I plan to make another template for smaller radius blades.

 

[Bill Boehme]

Here is another PDF template to check the radius of smaller blades.

 

[robo hippy]

Bill, I use one of those plastic templates with the different arcs drawn out on them. I was surprised at the variance, and will need to shape some of them, eventually. The variance could be from heavy use and abuse....

Also, on the Mark 8 system, Kel switched on the large set of blades. As near as I can tell, thickness is metric. On old blades, the standard set appears to be 6mm, and the large set 7mm. On the newer ones, Mark 8, they appear to both be 6mm. I have heard a couple of people say the large sets of blades were bending with normal use, but I haven't tried them out.

robo hippy

 

[Bill Boehme]

Using a carpenter's tape ruler, my calibrated measurement showed 1/4" thick. I suppose that I could whip out my fancy Harbor Freight digital caliper to see what it says.

 

[Mike Johnson]

I can only assume with a cold rolled steel tool the more you use the tool the quicker it will loose it's form
from the heat and pressures/forces applied by the user and exerted by the piece being cut. I would consider
using a harder steel and temper and anneal the tool so the tool will hold its curve without being too hard to
where it would break on a hard catch. A knife maker using a forge can usually temper and anneal the steel
and make the cutting edge hard and the other portion of tool somewhat softer to prevent breakage. The technique
takes time to learn and understand how the different metals perform. This would certainly add to the expense of
the tools being made which is the other part of the equation. By bringing the entire steel piece to the proper temperature
and plunging just the cutting end of the tool into oil you can make one end of the tool hard and the remainder somewhat
softer to allow flexibility in the tool. The tool is then reheated several times to a lower temperature to "temper" the steel
and increase the flexibility of the tool. A Rockwell hardness tester can be used to determine the hardness along the entire
length of the tool assuring you have a well "termpered" tool.