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Drilling crankshaft hole

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Former Member19/01/2021 13:58:23
1085 forum posts

[This posting has been removed]

John Haine19/01/2021 14:18:52
4632 forum posts
273 photos
  • Machine base flat
  • Mount base to vertical surface (angle plate so valve port face is uppermost and as level as you can get it (probably by eye) - machine port face flat.
  • Also machine upper end of crankshaft bearing boss flat.
  • As accurately as possible, by eye and whatever measurement equipment you have - or by reference to drawing - set drill over centre of crankshaft bearing boss
  • Centre drill, drill through and ream for shaft.

But it does depend on what equipment you have available.

Martin of Wick19/01/2021 14:38:15
249 forum posts
5 photos

I have a similar issue, but not quite such a fugly casting as that one - I assume it is quite small, so my choice would be:

set up as best you can in a vice with the shaft as parallel and normal to the cutting plane as you can judge by eye (by any means possible with whatever packing you need).

mill base as reference plane, mill long edge of base likewise

prepare piece of scrap to parallel on all surfaces large enough to overhang base of casting by 20mm or so, bolt said casting to your prepared plate with at least two fixings of appropriate size - If you are really keen you could mill out a slot in the mounting plate to fit the milled base to ensure stability for subsequent operations.

set up plate with mounted casting in vice square and parallel, mill port face and shaft bearing boss face flat, turn over mill rear of port block flat (and rear of shaft boss).

Without removing, find centre of crank boss, punch, spot drill, then drill drill through crank shaft bearing boss with correct size of drill prepared for brass/bronze etc in one go.

With luck this should result in the main surfaces parallel and normal to each other.

nb The author accepts no responsibility in any way for broken drills, mis- aligned or oversize holes or any other unsatisfactory outcomes, how so ever caused cheeky



Edited By Martin of Wick on 19/01/2021 14:48:45

Steviegtr19/01/2021 20:14:45
2422 forum posts
336 photos

You may like to have a peak at Joe Pesinski on youtube & Quin on Blondiehacks. They have both just built small engines from casting kits. They both went into a bit of detail to get everything square.


Peter Jones 2019/01/2021 20:44:22
61 forum posts
9 photos

I've watched a few of the 'Blondihacks' video's and can't believe she has so many subscribers or Patreon's. She talks to camera as if she has been machining for decades which may fool absolute beginners but anyone who has been a machinist wonders what's going on.

She may have a basic understanding but anyone with internet connection can find much better tutorials. The 'novelty' of a woman machinist doesn't make up for the lack of safe operation or 'this is how you do it'.

If it was 'this is how I do it because I don't know what I'm doing' (which she has said a few times) it wouldn't maker her appear to be an 'expert'

Just because you have money for half decent equipment and a great line in BS it doesn't make you an expert or fit to 'teach' beginners

(I taught total beginners motorcycle technology for almost 12 years so do have an idea what I'm talking about, bad advice is much worse than no advice)

Joe 'Pie' is a very experienced machinist.

Even after 45+ years of working with lathes and mills I often find something new or novel in his video's. (and often confirmation may way is the same as his for some processes)

First thing to do is take a file to it and get rid of the worst of the flash and bumps (particularly what looks like a taper on base?)

Set uo as accurately as you can to machine base flat, use that as datum for bore location. It may be easier to remove tool-post, measure height to centre of lathe spindle and drill using lathe chuck after setting suitable packing height. That way you don't need angle block

Edited By Peter Jones 20 on 19/01/2021 20:51:14

Edited By Peter Jones 20 on 19/01/2021 21:00:43

Edited By Peter Jones 20 on 19/01/2021 21:01:27

Tim Hammond19/01/2021 21:09:44
74 forum posts

+1 for Joe Pie. videos on YouTube. Every one very high quality and always well worth watching.

Former Member19/01/2021 21:17:43
1085 forum posts

[This posting has been removed]

Jon Lawes19/01/2021 21:19:15
889 forum posts

Where Blondihacks excels is in being approachable and "human". A lot of youtube channels (and forums) are full of people who alienate others by coming across as superhuman machinists who left the womb fully trammed.

Her videos were a good jumping off point for me, one of the few that explained the basic principles of milling in a way that sunk in for me without too much jargon.

not done it yet20/01/2021 08:33:17
6736 forum posts
20 photos

She talks to camera as if she has been machining for decades which may fool absolute beginners but anyone who has been a machinist wonders what's going on.

Comparing Joe with Quinn is like comparing chalk with cheese - just not sensible.

Joe is a machinist engineer with many years experience and very good at it, while Quinn is a hobbyist who makes you-tube videos for income. She has no pretension of being the ultimate expert - clearly demonstrated by the mistakes and ‘work-arounds’ she shows, to achieve results when things go awry.

I would quite often carry out a machining operation much different (and better) to the way chosen by Quinn. I might do it different to Joe - but my method would not be better than his, for sure.

I watch both. Joe is technical and may not be fully understood by a lot of beginners whereas Quinn is practical like most hobbyists, making decisions to be able to get the job done.

Confidence in front of the camera is a good trait to be a successful you tuber. Her videos are far better than the majority of the non-professional cohort.

anyone who has been a machinist wonders what's going on.

Anyone in that position should not be wondering. It should fairly evident at first glance. Surely you were not befuddled - or were you? Many beginners could find far worse videos to watch - gloves, loose sleeves, rings, no eye protection, keys left in chucks, are obvious ones...

Just because you have money for half decent equipment and a great line in BS it doesn't make you an expert or fit to 'teach' beginners

Are you commenting on the kit you were supplied with? If referring to Quinn’s kit, it is not that special - but more like the equipment of many beginners. She does not have all the ‘bells and whistle’ tools like Joe has to hand.

I’ve taught a lot of students in a lot of different situations. They don't all respond to the same methods. But I still would not class myself as perfect, by any means.

Horses for courses, as they say. Live and let live. More than one way to skin a cat. And lots more.

Perhaps absolute beginners are not watching the right videos by going to youtube. Everybody has to start somewhere. Beginners may not be too sharp at risk assessment - there is no guarantee they will even start at the beginning...

Howi20/01/2021 09:20:36
354 forum posts
19 photos

That looks like a wobbler casting set. the trouble with kits like this is determining where to start.

Usually the base is the best place, you can then reference all the rest from that.

That is what I did when I machined mine, took ages to determine where to start. Once I started everything else seemed to drop into place.

Casting sets are not the ideal for a beginner to tackle as the importance of a reference face is not obvious.

It does make a nice engine though, mine runs realy well.

Ramon Wilson20/01/2021 10:16:35
1283 forum posts
367 photos

Hi br

I would concur with John Haine's recommendations but as he says it does depend on your resources. If you have a mill you should have no problems using an angle plate or even a piece of flat steel held in the vise to act as one. To do it accurately on a lathe would require an angle plate on the face plate set up.

Whatever the base needs to be machined or filed as flat and square to the standard first.

Some time back I renovated a very poorly built Blackgates V twin oscillator which I described here - some of the images may be of help to you

Good luck with your build yes


Howard Lewis20/01/2021 20:42:16
6024 forum posts
14 photos

Even if you do not have a mill, all is not lost.

With a lot of care, and some filing it ought to be possible to set up the casting in a 4 jaw, and machine a datum face. (As already said ) the base would be my choice. That dtum can then be used for many subsequent machining operations.

With a sutably sized packing piece, the casting can be faced (flycut? )and set up forto be centre drilled and drilled/reamed for the crankshaft . By using the reamer and the reamed hole to align the casting again, the other end of the crankshaft bore can then be flycut to face it.

Every machined face/ bore can be used to aid alignment for other machining operations.

Bonne Chance


Edited By Howard Lewis on 20/01/2021 21:28:48

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