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Morning Patrick, now off for a day in the garden for a change but before I go ........ The mandrel wants to fit the rear bearing housing as a plug gauge would - the front portion of the gauge is the part that does the gripping - a 2 BA/4mm cap head would be fine for the expanding screw. The...

Well it's not as bad as you might think Patrick and yes you can learn from it - not only the mistake but how to rectify it. Fit the front bearing and try the shaft and rear bearing - if theres any form of misalignment don't force it just remove the bearings. Turn a ring of ally say .5mm bigger...

Good progress Patrick but if you get the front and rear bearing in line concentrically and parallel with each other on a four jaw set up you will be a lucky. I'm not saying it can't be done but there is no way of knowing exactly where the rear housing is in a four jaw set up. For the tolerances...

Andrew A link to the book (disc) designs for free down load are actually on here courtesy of Ken Croft, one of the engine boys. A quick google found this Go to RCLibrary : Motor Boys International Model Engine Plan Book title : download free vintage model aircraft title That should help...

Agreed - if you are making your own the expanding area needs only to be sufficient to provide the grip. The rest of the mandrel should be as close a tolerance as you can get and particularly so when doing the front bearing housings either on a case or a separate crankcase front - the plain part...

Hello Peterha I always cut the slits with a standard hacksaw (or a junior one if very small - I have made them as small as 1/8 diameter but just the one slot in that case) On a couple of larger diameter ones made I cut three slots but most at two at 90 degrees by eye. I was shown this tip many...

Hello Patrick, In answer ..... 1, Yes best if done with a 45* cutter having gashed the slot with an endmill to relieve the bottom. Do the groove and clamp first. Turn a piece of steel to a parallel dimension (no taper) and clamp the part to it then face the bolting face with very light cuts...

Hi Pat, I'm not keen on using a block to hold in the four jaw for a couple of reasons. Even with careful set up there is no 'absolute guarantee' that the shaft is co axial so the pin could, might, be off to the shaft. However slight that is not a good thing to have. Obviously it would have far...

Hi Patrick, Yes good to see you back on this again. Re the mandrel. You will get a far better grip if you put four cuts in rather than two. Secondly it's best if the cuts do not go past the work piece. I always turn the mandrel over size then tap and deeply centre before cutting - the actual...

Hello Mark - I remember it well - work that is, and how it could get in the way of more 'important' things ;) If you made your cutter from silver steel did you quench it in water ? (as you are normally supposed to) I ask as I find it's much better to do it in oil and not to temper it - very...

Mark - I have made the McOnie but didn't spotface the cylinder bolt holes - used studs instead. Here's a reverse spotfacer made recently - The drive is the pin held inplace with the blob of blue tack! I have a sometime made a reverse countersink for something just loctited to an 8BA bolt...

A good start Patrick 👍 Given that you are making two a drill jig that could fit both case bore and front and back housings would be a well considered way to ensure compatability. Second option would be to wait until after the bores are done then do them on the mill using co-ordinates - much...

Well I did say I was a dynasaw :) I'm speaking from a home workshop point of view based on working experience with non CNC machines. With the advent of CNC which after all from a production point of view is a relatively recent but incredible advance in machining techniques and particularly so...

Hi again, I had this problem on here several years back. It was suggested the PDF was saved as a Jpeg and inserted as a picture. I recall it worked at the time. Regards - Tug

Will, The forces at play are just as you describe. Although it may seem unlikely it is a fact that slot drills do cut a more accurate slot (and very close to the cutter's diameter). If a four flute endmill is used to 'size' a slot to the cutter's diameter, even if roughed out beforehand, it...

Valery, as a fellow diesel engine maker, congratulations on some fine machining and a really super result. To see them run, once all is complete, is a never ending reward so I can imagine your satisfaction😊 Though my efforts are much larger - I prefer 5cc - I can well apreciate the skill and...

Well we are all entitled to an opinion but I can't say I share yours Goldstar Someone without the knowledge came on here to ask a basic question. As did some others I replied specifically to that question based on personal experience of being shown the technique some 40 years ago and in order...

Well I'm pleased to hear you know your 'bottom' from your 'bottom' K2 Keep smiling :) Tug

Engtech ,K2 Here is a link to Tracy Tools in the UK please note they list in the left hand menu 'Slot Drills' and 'EndMills' as two separate items. Tracy Tools A visit to either will confirm the visual difference. If you refer to my post #58 - I do say this terminology is correct for the UK...

Alex, this is a phemomena of the material - most definitely not the drill. Whilst I agree that a dull or poorly ground drill will not be ideal to say the least and really lead to difficulties anyone familiar with this material would always sharpen the drill before using - such is it's...