Author Topic: Coles C-611  (Read 16533 times)

Offline iRon

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Re: Coles C-611
« Reply #15 on: April 24, 2021, 09:51:49 AM »
It is great to see you back posting. I enjoy and learn a lot from seeing how you do things. Thank you for putting in the time and effort.

Ron

Offline Admiral_dk

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Re: Coles C-611
« Reply #16 on: April 24, 2021, 11:29:33 AM »
Like the rest I'm really glad to see you back in the shop and posting Jo :pinkelephant:
and I also really apreciate that this one is a "Castings for Dummies - How to ensure your build is a Succes" :praise2:

I'm sure there will be a few that thinks it could be done differently, but this should not distract from the big help your contribution will be to a lot of Newbies  :cheers:

Best wishes

Per

Offline Jo

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Re: Coles C-611
« Reply #17 on: April 24, 2021, 03:00:36 PM »
Thanks Guys,  :embarassed:

Lets start on the covers, the temptation is to try to hold the cover by the boss in the middle on a three jaw chuck :ShakeHead:




Bad idea, if there was a lot more of it then maybe but the rough casting surface means the cover will not be held well and  is likely to slip if the tool digs in  :paranoia:. (I know the chuck key is in the chuck I needed to hold the cover and the camera...)

What we are going to do is hold it the other way round and machine that boss first. For this we are going to put a packer behind. An old bearing makes a good packer but I am using some aluminium discs as packers here and the casting has been held in the chuck and tapped down using a copper mallet so that the packer is held tightly:



We have all three of the surfaces on the top face of the cover available to machine and we are going to start in the centre and face it with a shallow (0.4mm) cut:



As you can see there is still a casting mark in the surface so another 0.2mm was removed, to leave a clean surface, which is our datum. Now for the horizontal surface it needs to be 31.75mm diameter so first take it to 32mm diameter but only to the existing depth and you can see by the yellow outlined arrow there is a mark on the cover I need to keep an eye on...:



Now to turn from the outside into the 32mm diameter and check if we have a clean surface. I took off 0.4mm as a cut which left a step back of 2.5mm. There is a slight mark still on the larger diameter but this could be hidden under a nut or I may choose to remove it later.



This face is the new zero for the saddle and now to take the 32mm diameter down to the required 31.75mm  :)


The other cover has been started the same way but it has a 4.75mm step back and the central boss is 25.4mm diameter.



Now we are in a position to hold the cover the other way round  ;) If you have a good three jaw chuck then it should have no problem gripping a boss 4.75mm deep but the 2.5mm is going to stress the jaws a bit and tightening the jaws may mark the piece  :facepalm2: So instead we are going to use a collet that is designed to hold thin pieces (like a 5C) or if you don't have one of those you can make yourself a collet like the little pot chuck shown in the picture below which can be held in a three jaw chuck and will hold your piece:



The next side will be much easier and now that my friend has finished his Snicker Ice cream I may be allowed to return to the garden/workshop  ::)

Jo



« Last Edit: July 28, 2021, 02:51:50 PM by Jo »
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Online crueby

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Re: Coles C-611
« Reply #18 on: April 24, 2021, 03:44:37 PM »
 :popcorn: :popcorn: :popcorn:

Offline scc

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Re: Coles C-611
« Reply #19 on: April 24, 2021, 09:08:12 PM »
Wonderful  to see your return Jo, you have been missed.  This build will address the inbalance between basic and advanced stuff referred to in the recent " lack of posting"  thread.  Besides that it's a masterclass for me to learn and hopefully improve.    Thank you.          Terry

Offline Dave Otto

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Re: Coles C-611
« Reply #20 on: April 25, 2021, 12:59:53 AM »
Good to see you back at it Jo!

Dave

Offline Flyboy Jim

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Re: Coles C-611
« Reply #21 on: April 25, 2021, 02:56:57 PM »
Thanks Jo.

Great idea on making a pot chuck for the 3 jaw. Looks like you've made numerous ones over the years.

Jim
Sherline 4400 Lathe
Sherline 5400 Mill
"You can do small things on big machines, but you can do small things on small machines".

Offline Jo

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Re: Coles C-611
« Reply #22 on: April 25, 2021, 03:01:51 PM »
Thanks Guys, we are off making swarf again  :)

The rear cover has been mounted in my collet and faced.



I am guessing that the cover should be 2 1/4" diameter what actually is going to be depends on what can come out of the casting, without leaving any marks. What I got was 57mm.

So now we need to cut the boss that will go into the cylinder. I have chosen to use a flange thickness of 4mm and this edge is 5.6mm thick so that will mean the cover will stick into the cylinder by  1.6mm. First mark the depth of the boss by taking a cut 1.6mm from the front surface and if you have it set your stop.



Now we turn the material away by turning in to just over the required diameter, so 32mm. I am taking 0.4mm cuts as the cover is only held by that small depth in the collet.



We now turn the centre so that it fits the cylinder. This is too tight as the fit holds the cylinder in place:



So another gnats whisker1 is turned off and it slides on nicely and has to be held to check the fit:



The front cover starts the same and 57mm diameter was achieved on the second cover. Once faced the piece is 8.4mm thick. The boss needs to stick out 1.6mm to go into the cylinder so it seems that we have lots spare. What we are going to do with this is keep this spare and add it to the boss on the other side.

So inner faces and edge turned but before we take it down we drill and ream for the piston rod. This guarantees that the piston rod hole is right in the middle of the cover. The hole is first drilled using a centre drill which, unlike a longer standard drill, will while cutting pull itself into the centre:



Now a drill will go in true but that is no guarantee it will continue through the piece true (drills get bored and go for a wander if the work is too deep
 :facepalm2: ). For this I started with a 4mm drill, then stepped up to a 6mm diameter before finally reaming 6.35mm (1/4"):



And now we can remount the cover the other way round and increase the length of the boss and counter drill and tap for the gland. As this now has a hole in the centre I can support the cover using a rotating centre while I take the cuts:



Not forgetting to rub a file over any sharp corners:



We now need to drill and tap for the gland. Yes it is a horrible threaded gland. I do not like them but we are going for authentication rather than prettiness. I have chosen a 1/2" 32 tpi thread for the gland: This is a special model engineering thread you can use anything you fancy but they look better (if that is possible) with finer threads. To tap the thread the hole must be taken out to the correct tapping diameter for the thread, the great thing about the 1/2 3s thread is it has a nice 12mm tapping size which is a common size.
So how can we do the hole?  You could bore this or drill it: I am drilling it so its worth using a centre again on this side to make sure the drill goes where I want it:



The cover is 13mm thick so I made the counterbore 9mm deep. Remember if you use a drill the point of the drill will go in further than the full diameter of the drill and the bit of the cover doing the guiding will be thinner. To avoid this I have used an end mill to cut the bottom of the hole:



We are going to use a tap to cut the thread and the thread must go in true to the bore. I do this by holding the tap in a tap wrench that is supported by a spring loaded point in the tailstock:



I am not going to drill the holes in the covers just yet - that will wait until I am set up on the mill. So a quick pic of the two covers and the cylinder (and yes I also made one of the glands I will cover those in another post)



I wonder if its Ice Cream time  ::)

Jo

1. Technical engineering term for a very small amount
« Last Edit: July 28, 2021, 02:52:32 PM by Jo »
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Online crueby

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Re: Coles C-611
« Reply #23 on: April 25, 2021, 03:26:24 PM »
Very good sequence and tips!

As for the gnats whisker, is that standardized on the European or Asian gnat?  .... flashbacks to the airspeed of an unladen swallow bit from Holy Grail movie.... 


 :popcorn: :popcorn: :popcorn:

Offline Jo

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Re: Coles C-611
« Reply #24 on: April 25, 2021, 04:53:55 PM »
 :thinking: Good point I had to look it up to check and found a better definition:

Quote
A gnat’s whisker a measure of distance used by engineers, being rather less than you can see with the naked eye and definitely less than a smidgeon

Jo
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Offline Jo

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Re: Coles C-611
« Reply #25 on: April 25, 2021, 04:55:24 PM »
 :facepalm: Forgot to define smidgeon

Quote
A smidgeon is the size of small adjustment made with the benefit of much experience, generally rather more than a gnat’s whisker and definitely less than a tad.

 :censored: and Tad

Quote
A tad is a measure of the carefully calibrated adjustment required to make something just spot-on. Most authorities consider it to be a little more than a smidgeon.

That's better

Jo
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Offline Jasonb

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Re: Coles C-611
« Reply #26 on: April 25, 2021, 05:32:25 PM »
Bound to be the Euro Gnat as that's Metric rather than the inferior quality Asian Gnat ;)

Online crueby

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Re: Coles C-611
« Reply #27 on: April 25, 2021, 07:40:15 PM »
An image extracted from the International Association Of Whisker Standards, from their early work on mouse-kers as a prelude to gnat standardization...
 :ROFL:

Offline Jo

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Re: Coles C-611
« Reply #28 on: April 27, 2021, 04:15:27 PM »
Surprisingly this engine's Soleplate has lots of parallel surfaces by which it could be held but I am not going to fall for that and have it move: No! It is going on a jig to be safe. We need to start by preparing the casting by flattening the bottom surface:



I have chosen to mill 0.2mm off but this can be done by hand filing - it does not need to be pretty, just not rock when on a surface.

On of the things you will find is some engines is they do not tell you where the holes for mounting to a base should go or often the size  :facepalm: I'm trying some 2BA allen screws to see if they would work and how big the heads are relative to the bosses. One of the bosses is showing someone in the foundry was heavy handed with an angle grinder  >:(



That will have to be repaired later.

The front engine mounting locations look much better:



Now we need to drill four clearance holes for the hold down bolts. Taking note of where the holes are relative to each other. To decide on the exact location for each hole I started by using a pointer to point at where I thought the hole should go, went round each hole writing down the measurements, then decided on a set of measurements to use (went round with my pointer again to check  ::) ) before drilling the holes in the Solepate 4.8mm for a tight 2BA fit.



A piece of square scrap-bin-ium (this case nice Aluminium) was then drilled 4.1mm and tapped for 2BA threads. and the Soleplate mounted up:



I have mounted it so that the rear overhangs the jig:



All will become apparent shortly..

Jo







« Last Edit: July 28, 2021, 02:53:22 PM by Jo »
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Offline rklopp

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Re: Coles C-611
« Reply #29 on: April 27, 2021, 06:53:19 PM »
Jo
Did you spot-face the holes?
Regards,
RKlopp

 

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