Author Topic: Bernay Build - MZT  (Read 27522 times)

Offline mzt

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Re: Bernay Build - MZT
« Reply #15 on: July 25, 2012, 01:21:31 PM »
Parting off one of the ?new? lower heads: had to get a bit creative into holding it into the chuck: no way to close the workpiece into the normal jaws, no way to part it if held into the lower step of the external jaws?




 

Here?s the heads, before drilling the holes. (They?re finished, now ? but for tapping the foot holes). 







Back on the waterpipe crosshead and al. steam chests.

Spent too much time turning, lately: needed a little milling for a change.

Took no pictures of the works, here?s the results, yet to be deburred.



 

As a side note, the opening into the first steam chest came out definitely tapered. ? ?Strange! Sounds like a milling bit flex problem. I might have been feeding too heavily while milling?.
(...)
The second came out as bad as the first: ?this al. is definitely a bad alloy!!?. 
(...)

When I started milling the slot into the steel, I realized there was again more than a fair share of play into the spindle: that recent session with the large flycutter (60mm, radius) more than 1mm deep cuts...

Bet I know what You will say.

Had to spend a little time into re-setting the spindle preload.

 







? and back to the bronze cylinders block.

?Gotta get that done, soon or later!? (In other words, I could find no excuses to postpone this operation a little more).
Here it is, the, still mounted on the faceplate, first side already made:





 

It barely swung on the lathe: about 1mm of clearance between the lower corner and the V on the lathe ways.
The tool is an insert holder, with a carbide insert made for cast-iron: had to mount it into the holder as back as I could to reach the external end of the workpiece.
Another option would have been a LH tool, turning the QCTP 90deg towards the operator.

Had to make a temporary chip shield extension, too.
 




Here?s how I mounted the block:

The 8mm rod fits nicely into the faceplate hole and into the (still undersized) crankshaft hole of the cylinder block: that should ensure alignment.






The two aluminium rods will go through the cylinders bores, and the aluminium disk on the faceplate will accept the already machined bearing taper


 
A couple of pictures of the finished block, with the crankcase bore already enlarged to 11.85mm (drilled to 10 and then bored to the final size) and the tool I had used to face it.









You have probably noticed there?s a counterweight, still mounted on the on the faceplate, if not its absence in the previous pictures:  definitely, a must I should have added before.
I could complete the first side without it, by turning the wp. at very low speeds, but it took soooOO long?
Much more than what I spent into drilling a couple of holes, and tapping the one I had put on the faceplate.

Reaming the crankshaft bore, to the (chosen) final size of 12mm.




Marcello


This is a fitting job,
not a production job that can be measured in.

Offline mzt

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Re: Bernay Build - MZT
« Reply #16 on: July 25, 2012, 01:22:05 PM »
Small progress

Had very little time left from work lately: the shop was freezing cold, and I figured that chopping woods, shoveling snow and occasionally giving heat to iced water pipes was much more fun than working at the lathe or mill. Sort of.

Anyway, I managed to make some bits and fittings:

The piston rod gland nuts, turned from the 12mm hex brass bar,  tapped M10x1, now being chamfered on the outer end.




The feet

made them in pairs from some al. offcuts.





A nice surprise.
Got a phone call from a friend, one evening: ?show Yourself at the pub, tomorrow. Got something You?ll appreciate?




They?re all finely grained cast iron!!  but for the flywheel (gear) blank which is steel.  Definitely appreciated.

I was a bit worried about scale, hard spots or blows (they were risers from castings) : turning and facing four or five of them revealed no flaws. 
But I don?t think the lathe will ever get clean again, however hard I will scrub it.

Used one of them to make the pistons (though the use of CI pistons into bronze/aluminium cylinders makes me wonder?).





A temporary mounting of what I?ve made so far.

 





 
The piston rods.

After drilling some holes into the steel block to remove the bulk of metal, I milled a pocket to (my) size and then slit the ?finished? part.

 





As it goes, I drilled the first hole for the 6mm shaft using a 5.8mm bit: result, was a fit a bit too-tight.
When I enlarged the hole with a 5.9mm bit I got it exactly how I wanted it to be. Drilling the next three holes using the 5.9mm bit (without pre-drilling 5.8) it brought an almost sloppy fit.
Sure, not tight enough to hold the shaft in place. (GRRRR!!!)
A bit of light knurling on the ends of the piston rods should solve the problem, maybe some loctite, a cross pin? ?all the above options.

Marcello


 


This is a fitting job,
not a production job that can be measured in.

Offline mzt

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Re: Bernay Build - MZT
« Reply #17 on: July 25, 2012, 01:22:30 PM »
Connecting Rods

The two items were sawed and milled roughly to shape from a 4mm brass plate




 
Then, I drilled and tapped M5 four carefully spaced holes on a piece of scrap (that?s iron, not even steel), three of which were subsequently counterbored 9mm dia. for a depth of 7.




 
After a few minutes spent on the on the lathe, the simple fixture was ready to hold both the blanks in place. 








Then, I chucked a 15mm end-mill and brought them near to dimensions, cutting full depth: they still need rounding the ends and tapering.  That will probably be filing work, for a change.
 


As for the making the bearings, which are plainly missing at the moment, I still have no clear ideas: will have a look into the metals shelf next time I will go to the shop.

Marcello
This is a fitting job,
not a production job that can be measured in.

Offline mzt

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Re: Bernay Build - MZT
« Reply #18 on: July 25, 2012, 01:23:05 PM »
Connecting Rods (continued)

Here, I?m chain drilling and milling two pockets on the top of a 25mm brass square





Next, came the splitting of the item, milling to size, polishing, and then filing the lower edges of the connecting rods.
Here they are, together with the still unused filing buttons.





 
Tried to press fit the rods into the bearing area, using the bench vise, but they showed a tendency to bend: solution came through holding each of them upside down into the vise (aluminium jaws) and hammering the bearing area in place, having a piece of plywood interposed  among the bearing and hammer face.

Here?s a picture of them, the bearings already split, ready to be drilled (and reamed?) for the crank.





At this point I realized I had forgotten putting a bit of loctite into that hammer-fitted joint: I?m quite sure they would not move anyway, but decided to drive a few nails through them, just to make myself sure ...

Almost ruined the job when I broke a bit (1mm dia.) into one of the holes but with a lot of patience (and another sacrificial bit) I managed to get it done.
After driving them into the holes, I cut those (soft iron) nails a little longer then needed and punched them into the brass forming  some sort of head on each side. I suppose that will do for the entire five minutes working life this engine is gonna expect.





 
Crankshaft

However hard I tried to postpone this moment, time came: I definitely need one on this engine.
The blank is pure unknownium (hope that?s steel, not iron) not large enough (only 35mm) and, worse of all, already to size.






Milling the webs was easy: that Dormer 8mm roughing mill cuts steel like butter.
 




Working among the centers, for the first time on this lathe. I soon realize I have no lathe dog, nor driving plate.





The driving plate came from the ER32 backplate I had made some Years ago, the dog..  ..well, I had that couple of car safety belts locks hanging around the shop for Years, hating the idea of throwing them away.
Loda springs inside the plastic cases, too.





 
Had to content myself with turning the bearing areas, still oversize, for the day. I need to make myself a few more tools to get it done.




Marcello


This is a fitting job,
not a production job that can be measured in.

Offline mzt

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Re: Bernay Build - MZT
« Reply #19 on: July 25, 2012, 01:23:33 PM »
Crankshaft (continued)

Here?s the tool, shown into the temporary mounting I used while I?m waiting for a skilled hand to come and solder a dovetail to the shank.
It worked very well into cleaning one of the cheeks, not so into turning the throws. (The cutting edge being 8mm wide: a bit too much for my 7x10)
Some grinding work on the insert (a notch in the middle of it) should help when I will turn the main bearing, where traversing the cutter will be possible.



 
In the meanwhile, I experimented a bit with finishing cuts, on the still oversized throw bearings: my T-blades revealed to be too thin to be used with that overhang (they flex)
but a cutter purposely ground from a 8x4mm vanadium bar brought decent results.
 
Now I?ve gained some confidence into machining the throws, I?m willing to see what happens to the main bearing area.
A bit of chain drilling (3.9mm bit, holes spaced 4mm).


 
The munched area on the top left being an extra hole to let the hacksaw blade turn 90 deg. when cutting the vertical area.
A few minutes later, I realized the little hacksaw I planned using for that part has no means of setting the blade at any angle but vertical.

Had to do without the frame.


Sawn.


 
And a bit of filing, just for the fun of doing that.






Marcello
This is a fitting job,
not a production job that can be measured in.

Offline mzt

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Re: Bernay Build - MZT
« Reply #20 on: July 25, 2012, 01:24:06 PM »
Crankshaft (continued 2)


With the throws bearings still oversize, I decided to finish the main bearing area.
First of all, I cleaned the cheeks to ?finish? and then searched  the scraps box for a couple of  items to be used as temporary fillers for the gaps.

Two short portions of aluminium square wrapped into a strip of writing paper till they got a push-fit (finger force only) among the cheeks may solve the problem.




 

Then it will only a matter of bumping the workpiece against the cutting tool for a long while.  That cutter id definitely too wide for the job on my little lathe:
ended with cutting a thin groove with a parting tool on the HS. side, subsequently enlarging it using only half of the big cutter.
As You can see, the finish is ugly, and I?m slowly tapering the bearing. But the job is getting done in seconds.




Later, I cut a second grove almost to depth close to the TS. cheek and traversed the tool back and forth till it was almost to size,
switched the cutter to whatever material that bar is made of and finished the part to a close fitting with the bearing.




Had I been a little more confident into my skills of bringing it to the correct size, I?d have left this ?finishing? where it should be: the last operation.
 
Back to the throws, I filled the gap into the main bearing area with rod and screw, interposing a couple of strips of paper not to marr the surfaces.




Got curious about the eventual distortion into the workpiece after a good locking the screw: a few tenths of millimeter.  Bet it would be too much.
Filed a nut, turned the screw VERY LIGHTLY ad prevented unwanted motions by locking it in place through the nut.
In a few tries, I got a distortion of about 2 hundreds (of mm). I can live with that, but would not trust spinning the object without having taken some safety measure.



 
I realized I could make use of some gauge when bringing the throws to size. What about the connecting rods themselves?

One of them is shown into the vice, wrapped into paper so I can slid and screw the foot in place after finding the edge and centering the cutter among the vice jaws.
Drilled a pilot hole and enlarged it using a plunge mill to whatever size it came.
It came out a bit less than the 12.065mm reamer I had, so that will be the throws size.




Here?s the thing, I will break the sharp edges through filing.





More Heads

Some more shop time to spend, with no intention of working to close tolerances: just interested into filling a basket with coiled swarfs. 
Two head broke while tapping them, two are still missing?
The steel blanks I used had a thick crust, which had to be removed before they?d give a decent finish: as it goes, I got six of them undersize, while making the four shown below.

Left the hacksawing for another day, took the picture, cleaned the hands..




..and changed my mind.



Marcello



This is a fitting job,
not a production job that can be measured in.

Offline mzt

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Re: Bernay Build - MZT
« Reply #21 on: July 25, 2012, 01:24:53 PM »
Connecting Rods Bushings

Had a small chunk of bronze rod with dozens of blow holes in it: the right material to make short bushings (providing You?re positive into discarding two third of the semi-finished parts)





One of the bushings had a too light interference with the hole in the rod: at some point during the reaming it started turning. 
When the long line of self expressed comments finally ended, I went for a gentle  squeezing of the part into the bench vise:
the deformation I got (on second try) was enough to set it firmly. And that should do.

Then, the sixth of the bushing rings cracked partially while being driven in place: it took quite a while of fiddling with needle files and
sand paper to realize I had that already turned and bored to size rod still set in the lathe chuck, even the hacksaw blade parting tool still
in the post. One minute? Probably less.



 
First assembly

Now that thing starts looking like an engine!
The two (long, You see) 6mm printer shafts were rather stiff into their bushings: after a while, I removed them one at a time and
hand reamed the bushings in line. Another bit of oil ..hey! It turns smoothly!
 


Having (in hindsight, regretfully) spent most of the remaining shop time (and there was still plenty) playing with the moving parts,
I found no points into wasting my dinner time into the same activity, so?


 
Connecting Rod Shafts (..of course)


They  were supposed to be made into two pieces only (to say nothing about the diameter reduction from ?? to 10mm) but I had
a 6mm threaded bar just a little bit too long to fit into the so labeled box. Now, I can close the lid.




 

I left them slightly over length, just in case I got a bit creative with the dimensions of the parts they will be fitting to.
As for the missing runout groove clearly not visible on those threads, I decided to postpone that work till I will grind a thin round
nosed grooving tool purposely made for the job, the parting tool being too wide and the hacksaw blade too thin.

As it usually happens on the (frequent) occasions I wander from the drawings, the single-piece ?crosshead pin and bolt? cannot
be set in place unless BOTH the connecting rods were disconnected from the crankshaft.
Not sure it can be seen as an improvement.

Marcello


This is a fitting job,
not a production job that can be measured in.

Offline mzt

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Re: Bernay Build - MZT
« Reply #22 on: July 25, 2012, 01:25:50 PM »
Eccentric Strap


Had no brass plate thick enough to make it, no better option than hacksawing a portion of a brass block.
Here it is, the first cut already made, scribed and ready for the second half.





Before cutting it, a second check on the metal shelf revealed a brass remnant large enough to make the lower part of the strap. Its thicker than needed, but not much.

Here?s the two of them, already milled on all faces and drilled for the joining screws.




 
The two parts fitted together and roughly scribed: I will probably use the DRO and ROT-table, but a visual check of what I will be doing...





Had I checked twice the drawings before drilling the screw holes, I might have put the clearance holes on the correct part.
Now, I will have to insert the mounting screws from the top, or drill again and make use of bigger screws.

Will face that the day it will come.
For today, I?ve really no interest into working with the rot-table, will use the remaining shop time to make some more small items.


 
Piston Rod Inserts

Material is 20mm brass square: I set it vertical in the vice, faced the top and drilled a 5.9mm hole through the center.

Next, I set it on a couple of stacked cheap man parallels and hogged a 12mm wide full depth (minus ?safety? allowance)  slot on the four sides,
taking care to have the workpiece re-aligned with the vise jaw side anytime I turned it 90deg.



The four pieces were then hacksawed and filed to a ?nice fit? into the matching area of the piston rods.


Machining the outer surfaces was no problem: I just fit them into the vice and face milled away all the unwanted material, maybe a little more, maybe a little less.
All I wanted was having the four of them as identical as I could.

Holding them inserts by the larger square to machine the roughly hacksawed  inner surface is a bit different: aint sure the vice would hold the wp. on that thin surface.
I could figure a few safe ways to do that, but had to sit for a while in that (comfortable, really) armchair with a cup of tea to think for the best one.


It took a while?

 
When I was awake again, I decided a mandrel in the lathe would do.

Made use of the already present hole in the items and screwed them to the mandrel, by interposing a paper washer not to marr the external surface should they slip. 
Then used a parting tool to remove the metal till it reached the screw head, and made the four of them in a row.




The little area that was under the screw head was then filed away.



 

Connecting Rod Shafts and Piston Rods


Took no pictures at all, sorry.

Now I had the inserts finally brought to size and polished, I could take a few measures and bring the connecting rod shafts I had left a bit too long to the correct length.
As simple as chucking them in the lathe and facing .55mm  from each of them.

Then, I mounted the engine, measured more than carefully, and cut the piston part of the piston rods to a fitting length.
It came 5.5mm shorter than the 3?.01 + ((0.90 - 0.504) / 2) shown on the drawings, but the piston travels the same amount of cylinder on both strokes*  and that should be ok.
Won?t know for sure for another while.

Another dismounting and remounting (how many more???) of the whole engine to fit the heads gave the pleasant result of having the parts positively checked for smooth moving.



Marcello

---

*) On drawing B1-D, I could not find a way to calculate the distance from the top centre hole to the bearing centre.
Bet I made some error when I took it from the graphics scale.




This is a fitting job,
not a production job that can be measured in.

Offline mzt

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Re: Bernay Build - MZT
« Reply #23 on: July 25, 2012, 01:26:25 PM »
Back to the Eccentric Strap ?

My previous scribing was no good: rather wipe off and start over.





Now I have a visual check I can feel comfortable with, time to align the RT





Setup the WP spaced from the holding plate by 4 washers not to ruin it and milled away all the unwanted material plus the uncareful machinist?s share.







 
4 cheap, ready made, commercial filing buttons





And a lot of polishing.




 
..then the Eccentric

Decided to turn the bearing area first, then offset the bore.
Here it is, being hugged off in the 3jaws, then grooved



 
..a bit too deep.




 
Another foundry scrap came out to a better fitting





Took a break from the eccentric: now, the 10.5 to 13mm step .5 drill bits will fit 10mm keyless chucks I have on both the mil and lathe TS!




 
Here?s the eccentric in the mill: centered under the spindle then offset 4.76mm. Centre drilled and drilled in a few steps to 11.5mm. Next, it?s been reamed to 12.





Back on the lathe, held on the mandrel by the two grub screws, to complete the machining.





 
Finishing the Piston Rods ?

Them clips on the knurl wheels arbors had ever been a pain to remove, to say nothing about finding them again among the swarfs on the shop floor.
Here?s the result of 10? work on a 11.5mm rod and two nuts.



Switched the wheels to a medium coarse couple, and ruined the end of one of the top rods enough for press fitting purposes into a hole a bit too large.


..and the Top Support Bracket
where the bushing were still missing. Material is 21mm bronze, held in a collet mounted chuck to be faced and reduced to 20mm for a length of about 200.
Then, I reversed the WP holding it into a 20mm collet, and machined the two bushes to be press fitted into the top bracket.




 
Some more parts going to place. A bit stiff at the start.




Dremel polishing compound mixed with oil made wonders, after a while.


Marcello


This is a fitting job,
not a production job that can be measured in.

Offline mzt

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Re: Bernay Build - MZT
« Reply #24 on: July 25, 2012, 01:27:00 PM »
Rocker arms support brackets

One of the blanks as it came from the scraps bin, and two already skinned and scribed.
 



Parted to lenght




 
Replacement heads

I had left them uncompleted ages ago,  I took the occasion of having the lathe in a mess of cast iron powder to bring them too to finish.
Here, I?ve centered the jig and I?m drilling the bolt holes at coordinates.





The jig. With a total of ten heads, having made it paid well.
 





 

Rocker arms support brackets

Back to the C.I. risers, some facing to bring them to the required sizes. The blue clamp on the side of the vice will be used later as a wp. stop,
so I won?t have to find the edges more than once for all the faces.




Carving the shape with a 10mm four fluted mill, depth of cut being 1 / 1.5mm



 
Centre drilling, drilling and reaming the required holes.






 

 
Working on the sides, now with a 6mm end mill. The wp. is laying on parallels (HSS blanks) and held into the vice jaws through
a short portion of steel rod. Not much of contact surfaces, but it did not move. I carefully avoided climb milling.




Here they are, all but finished. A lot of rounding, filing and polishing is still in order.
Gotta think something about the missing portion on one of the flanges, too: it came there on the last op.
?too simple to be worth bluing and scribing? ? Then, I turned the wrong wheel to the expected reading on the display.



Marcello

This is a fitting job,
not a production job that can be measured in.

Offline mzt

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Re: Bernay Build - MZT
« Reply #25 on: July 25, 2012, 01:27:28 PM »
Rocker arms support brackets(continued)

Made this simple jig with the intentions of using it to bring the brackets to a higher finish.


 
Then, I changed my mind (that?s a habit!) and decided to go for a bit of hand work with files and sandpaper,
maybe a coupla small grinding wheels on a Dremel..

Managed to STOP that right before the poor thing got mangled beyond recovery: the picture below shows it being set up on the lathe.

The second picture was taken while the lathe was spinning the second bracket, the chuck side already finished.

The pictures do not show the carriage stop I set on the lathe bed to prevent cutting too deep.
The small parting tool I used  is ?? square with a huge overhang: took that into due account and never fed the cross slide more than .25mm.







 
 
It worked.



 
They are far better than what can be seen in this picture (others I?ve taken are worse, btw),
especially the one on the right which I?ve polished using a wire wheel on the Dremel till I got it shiny.
I?m definitely satisfied with the job I?ve done.

Next two will be made differently.

Marcello
This is a fitting job,
not a production job that can be measured in.

Offline mzt

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Re: Bernay Build - MZT
« Reply #26 on: July 25, 2012, 01:28:18 PM »
Two more rocker arms support brackets

Here?s the starting piece: being already to the same length as the sum of the brackets heights, I?ve gotta pay special attention into avoiding wandering cuts.
 




Managed to do a decent job with that hacksaw.



 

 
Flycutting the rough cuts, and squaring the faces. Love that finish!



 

Scribed





Drilled.  I?m now milling all what I can using a 10mm 2fluted mill.
Just hogging most of the unwanted metal, will have to finish the work later with a smaller mill.





Forgot about a couple of holes (per bracket). Not a precision work, here: I could use an old drill chuck in held into a collet to speed-up the tool changes.




 
Into the vice, to mill the brackets sides. Had to use a piece of al. square between the workpiece and the fixed jaw, to put holding pressure on a convenient point.
 




The opposite face of each bracket was milled holding them into the vice through the flange only: was a little concerned about deflections
and eventual breakages, so I clamped the top area to the big blue mill clamp I?m using as vice stop. It worked.
 



 
Here they are: ugly as the picture can improve improve their look. I?ve never found a way to get a decent finish when milling aluminium, except flycutting.
 




Jig turned on the lathe. Too early: now, I?ve gotta put many more attentions into polishing them flat areas.






 
Constructed crankshaft

Being lazy, looking for troubles. (Will get them).
Didn?t want to waste time switching the lathe from collets to 3jaws to machine a short portion of the two blanks so I could hold them into a collet.

Decided  for an attempt with my collet held 3jaws for small works, no TS center: You guess what it's gonna happen.





Here?s the workpiece after recollecting it from the floor, the insert cutting edge being completely destroyed.
But the lathe missed the throw: so, I learnt it cheap in the end.




 
Put the chronometer at work: switching to lathe setup to the 4? 3jaws took 3?15?, and I had to hunt for the 14mm wrench.
Getting back to collets took 3?10?. Shop gremlins had hidden the 14mm wrench again.





After a short session on the mill, to drill 2 carefully spaced 11.5mm dia. holes on the face, back on the lathe to part off.




 
Facing. Scary setup again, though more reliable than the previous. Someday I will get some soft jaws for these types of works.





Here?s the crankshaft cheeks. What I will choose among the thousand options for a built up crankshaft from now on, I still don?t know.




Marcello
This is a fitting job,
not a production job that can be measured in.

Offline mzt

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Re: Bernay Build - MZT
« Reply #27 on: July 25, 2012, 01:29:02 PM »
Al. Conn. Rods


Here?s the blank, not quality aluminium, but the plate should do for the job. 




Chain drilled
 



Using the vice as it were an angle plate




Overtightening a toolmaker?s clamp: cracks among the marker lines.




Bearing areas completed.




On the holding plate I had made before. A strip of paper (half circle) between the bearing feet
and the rod secured a firm hold without affecting the distance among the centers.





 
Constructed crankshaft (continued)


Chamfering the holes, using a wood board as support: the tool would surely grab the hard material (it did),
sharp edges, ? : rather keep fingers far from that area. 




A quick test into hand reaming the 11.5mm holes to 12H7 convinced me to chuck an old 12.06 machine reamer
from the ?purchased by weight? bag.
Back on the holding plate, I screwed in a rod end I had turned to 11.5mm (added a clamp) and reamed one
hole in each of the four throws. Then, replaced the rod end with a 12mm one, and reamed the remaining holes.
 



12.06 holes and 11.98 silver steel shafts in need for a press fit joint: solution came throgh knurlink.
Had ideas that straight knurlling would have been the way to go, but the wheels could not stand the work
on silver steel long enough. Had to revert to diamond knurling to complete the job.




A bit of loctite (permanent thread locker - what I had) may do. Or may not, who knows.




Testing for alignment: no point! I had reduced the ends in one of the two shafts (the ones I will cut!) to
whatever diameter they came,  after having used them as test workpieces to try the knurls. Now it rocks,
but that?s obvious.




A visual test spinning on the lathe showed no visible wobbles, and that?s the point I put it aside waiting for curing.





 
Al. Conn. Rods(continued)


On the rotary table, to round the ends of the bearing areas.
The single-screw hold worked better than expected: I had only one slip, when milling to full depth the arcs
around the bearing area.




Rounding completed on both sides, end of workshop time. Will get back to them for finishing.






Marcello
This is a fitting job,
not a production job that can be measured in.

Offline mzt

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Re: Bernay Build - MZT
« Reply #28 on: July 25, 2012, 01:29:45 PM »

Constructed crankshaft (finishing)

Decided to drill eight holes for some screws going from the webs to the bearing sections: not sure they?re gonna add any strength to the assembly,
but they should prevent the parts from chasing the spectators, should it fall into pieces during the five minutes working life this engine is
going to expect (providing it will run).

 I?d have rather used some 1/8? tapered pins, but in all the years I?ve had them in the box I?ve never got around making the appropriate D-bit:
I?ve ever postponed the job ?to the moment I will need to use them? and tonite..
Well, I?m definitely not interested into grinding tapers.



Some hacksaw work (and a lot of file work) later, I could spin the thingy into the lathe, for a visual check of eventual runouts: nothing I
could notice or ?feel? by applying a wood bar to the far end. Had ideas about bringing the DI into play. It was late (reads: didn?t want to
spoil the satisfaction), maybe tomorrow.
 
Put a dab of permanent thread locker into each hole, instead, and here it is with the screws I will later cut and file flush with the cheeks.



Marcello

This is a fitting job,
not a production job that can be measured in.

Offline mzt

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Re: Bernay Build - MZT
« Reply #29 on: July 25, 2012, 01:30:46 PM »
Piston-rods

The printer bar material was a little too tight into the packing nuts, decided to try to get some clearance by interposing
a strip of paper between the reamer and the bore. It worked.



 
Chain drilling a block of scrap to remove the bulk of metal before milling the rectangular pocket for the inserts and then
a big 10mm hole in the middle of the area.



 
Took a file, then. And it wasn?t a quick job.
The rectangular hole came out all but rectangular, centered and with parallel faces.



 
Put it back into the mill, the: faced the roughly cut surface as it can be seen into the previous picture, painted with
blue and scribed a few lines.
Back to vice & files, till I got this. It was fun.




 
Piston rod inserts

They should be square, but I cannot see why they should not work if made round.



 

Connecting rods

Tried enlarging a coupla bearing holes to the 6mm bearing size I needed (they were made 5mm dia. for mounting on the plate)
by hand drilling, but the idea was not good.
Rather make use of the plate again, to bring them to straightness and squareness again.
Took the occasion to remove some unwanted metal I had left on the body when I rounded the bearing areas on the rot-table.



 
The connecting rods will have brass bearings. 



 
The knurling gave a push fit only, so I put a dab of loctite and set them aside for curing.
 



Marcello


This is a fitting job,
not a production job that can be measured in.