Kerzel hit&miss by Mike

Finished up the bearing block bores. Wasn't a 100% victory but close, I had a little more flex than I would of liked during the cut. I didn't have anymore holdowns that would work so I just went.005 infeed till I got to .9995. Was happy till the before final cut, it ended up about .002 which is .001 cut , that chattered on one block. I knew I should of taken it out the previous pass being a carbide tip. may finish with a lap to clean up a little ,although as you can't see it and being so close to being oversize I may pass. The first pic is the chattered one and 2nd is the nicer one.


One question though, on boring bars the flex needs taken out with non-feed multi passes at the end, are line boring bars the same? If so how do you get back to the start with out the cutter gouging the work on the return?

After a disappointing week of designing the crank webs (is it webs or cheeks) to fit the metal on hand, I felt they were to wimpy looking on the engine. Even though I only took out .120 of they just feel too skinny for this brutish looking engine
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While I am waiting on the bearing bronze to arrive I decided to tackle one of the chores. I would prefer not to have modern fasteners showing for an older engine, so am now making 10 1/4-20 studs.
I sized to thread limits plus a little for stainless. Around .245 gave nice threads. Chucked up in the lathe and power tapped with the tail stock pressed up against the backside of the tap holder and the arm resting on the compound. Was surprisingly easy as me and stainless have our issues when hand tapping.
Then flipped around and made a split collet (kinda)to grip the middle section and kept having issues with it spinning in the collet. So in a stroke of genius moment I took some 240 lapping compound and dabbed a little on the shank, After this I was able to power tap the other side. So now that the process is down, nine more to go

Finally able to return to the Kerzel. I spent a good while building Harold halls grinding rest, and a qctp, so as I've been busy not so much for for fun.

So first up was the crank, this peice really needs made from bar stock vs. a built up one. The problem I've found is the bearing guides on the webs, they overlap the main shaft. And with this setup I've seen no way yet to assemble and have the webs in place. Here I used a tight press fit on the top and a very close fit on the main shaft, to ease the pressing requirements.
Tommorow I will try to mill out the center, leaving enough to file and shape the rest.
I used a step drill and 15/64 to drill the hole, and made 303 stainless pins at .003 oversize for a press fit. Used a vice to press pins and some creative positioning to have them proud. Milled excess away very close then finished with a file. I did notice that I spent the afternoon working and it looks just the same as when I started. Lol.

First up was making sure the webs ran true to the shaft and square with the bearings.

I then milled out the center leaving enough to finish filing out the bearing diameters. Earlier I had turned a alum spacer to the same diameter as the bearing blocks. I used this to gauge the press fit,and later ,use it for a filing guide .

The plans call for a bearing flange on the main shaft, again this causes issues with a built up crank. I don't really have a good way to measure runout yet and with minimal runtime expected , I may just go with it, or try to make flange by pinning and grinding to size, haven't decided yet.

Tonites work was getting the main bearing to fit. I had purposely left oversize flanges not knowing the exact measurements. Don't know if I messed up or the plans were incorrect. But this is a custom build sooo,,,, moving on!!

The plans call for a .030 flange and I felt this may be a little thin. So went ahead and turned a recess to use the flanges .24 thickness with .030 proud to provide the clearance for the crank. Or at x2 size .60 clearance.


This was really my first time using a faceplate. After spending a good while trying to get it mounted and centered, the job went pretty well. Now I need a new set of clamps that are more user friendly, both size and safety wise. Balanced the wheel with strip magnets along the outer face and an extra pin . Without these, the job would of danced right onto the floor



Fitting to the caps was next . Astonishingly they mate with just enough interference so that when the caps are tightend they are held in place firmly. And I could take any out of roundness out with the reamer later. Thentried out an adj. reamer. For the record the Internet directions I found were obviously vague. They say to just tighten them up to size by turning both nuts torwards each other. Well tried that and was getting nowhere near my target. After almost giving up and calling it junk from eBay for 10$. Somehow the seas parted and I found out that, the farther up the shaft you put the blades gives the large dimension changes and when tight use the nuts for fine adjustment.


Final was fitting of the crank. They are still a pretty tight fit right now , I can spin it but not freely yet.
Feels like a milestone reached though

I've spent the last week off and on working out the fitting of the crank, and slowly progress is being achieved.
I didn't have a good way to measure runout after machining , so tried to use the engine itself. And while I could get to .003 runout revolutionary, it was terrible axially. On one side it was .003 and .011 on the other, with .oo3 between planes.
Luckily I had bought two12 inch 3/4 ground stress proof rods , and when I cut off the crank journal I had enough left over to finish the main shaft from one 12 inch peice. After going off and building other side projects , I had forgot this bar was ready for install. Well, somehow I installed the second bar , and didn't realize until I needed a known straight bar that I had this one centerdrilled and chamfered. Note to self , Write Stuff Down
Well in between 2-3 days of fitting, I had ordered a set of matched v blocks I completely forgot about. I kinda wish they came a day earlier since I spent all day prepping a new crank from solid at 1.5x3x9. So a good chunk of metal.
Then my v blocks show up. So just for giggles I wanted to check the old crank, and at first I was getting the same reading as when using the motor. So used the vise and gave her a little squeeze on the bottom of the webs , pushing together, and threw it back in the v blocks. And to my amazement I am dead nuts on at zero axially and less the .001 on the other.


I mean I was so amazed that I kept asking myself , did I really get it perfect, maybe I am not measuring correctly , and of course, just stare at it for minutes trying to find what I did wrong to get a perfect measurement. So maybe by the end of the day it maybe it will sink in that my starrett guage IS correct and I did the job right for once.

Today's work involved grinding to od of piston to size. I bought a toolpost grinder for the 7x10 HF lathe, and decided to use it on my south bend also.
The centerlines are different between the two so I needed to make a adapter plate, and a rise of 3/4 inch. When mounted In the toolpost it is way above center. Also with the mounting between the SB and tp grinder it was less than friendly, to say the least.
After making a first plate with a squeeze fit I could never get it tight enough to stop moving. Without knowing the locating pin in the compound slide was spinning barely I made another one. So after slaving all afternoon I was able to finally get it mounted tight. Luckily I I had enough room to get one stud bolt that mounts in the crossslide channel. I spent in total about three afternoons on this mounting after becoming flustered each time with different issues. Soon as I got the mount down all was easy as pie.
After setting up a diamond dresser c clamped to the chuck, i faced the grinding wheel. Put lathe in slowest back gear about 50 rpm I think. Took four passes at .001 to reach 1.5. Test fit to the cylinder and if my measurements are correct, it is at -.001 or .0005 between cylinder wall and piston . I couldn't find any other info besides lapping to fit the bore, so I hope this will hold compression. I've never made a ic piston so wee will see.
As for the grinder it does feel a little underpowered and I was expecting a little better finish. Granted this is one of my best finishes to date, so I'm pleased but, as you can see in the pics it is a very light finish issue. May be flex somewhere,?
If any one had pointers please post them.

I may have missed it somewhere, but why did you need to grind the piston rather than just turn it to size? I don't think I've seen a piston made this way before. It should work I guess but it's unusual so I'm curious.

I have never seen anybody grind a piston as you have done. I have always thought it would be nice to have a set-up for grinding the face of valves, but grinding a piston seems very strange to me.---Brian

The instructions call on a od lapp to size the piston. Kerzel states to lap until piston will enter bore with slight resistance.
At double size my piston is 2.5 inches long and 1.5 round. That is a huge lap I don't care to buy or make.
But you guys are correct, I believe it was probably unneeded , since in theory it should not touch the walls throughout the stroke. I was working with some small two cycles lately and noticed theirs were super smooth also. I know they are cast but essentially smooth so I adopted the thought.
With this model I am really trying to ramp up my craftmanship . And I am getting whooped in the backfield sometimes, but when I'm done with this I can move up the scale to my ultimate goal of a v8. Most of the operations are the same just a larger scale.

Brian Rupnow said:

I have never seen anybody grind a piston as you have done. I have always thought it would be nice to have a set-up for grinding the face of valves, but grinding a piston seems very strange to me.---Brian

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(johwen here) Before CNC when reconditioning engines for the auto industry pistons were ground as they were not round but ground with extra clearance across the gudgeon pin axis to prevent seizure. Special grinders were made for the job and a variety of master profiles was supplied to vary these clearance dependent on piston design. Yes grinding pistons even aluminum pistons was common however in the case of models you're correct. Cheers John