Author Topic: A Beginner's First Engine (Single-acting Oscillator)  (Read 11533 times)

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Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #60 on: February 22, 2019, 10:21:11 AM »
Gary, and others

Consider the good book!     Machinery's Handbook.

https://www.amazon.com/s/?ie=UTF8&keywords=machinery%27s+handbook&tag=googhydr-20&index=aps&hvadid=213926653103&hvpos=1t1&hvnetw=g&hvrand=15141559827872613349&hvpone=&hvptwo=&hvqmt=e&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9001782&hvtargid=kwd-324143135994&ref=pd_sl_9bh0gjicgc_e

Many of the answers you seek....such as press fit tolerances....can be found there.   Good Stuff    the 23rd edition has been next to me since 88'  8)

Dave
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Offline Gas_mantle

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Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #61 on: February 22, 2019, 10:21:45 AM »
Gary, I've found that for making crankshafts etc where accurate running is necessary it is better just to buy silver steel of the required diameter, it's hardly worth the effort of turning down the diameter. I bought a metric set of budget reamers from Tracy Tools, they didn't cost the earth and cover exact mm sizes from 3mm to 12mm, for the price I paid they have been a great buy.

Offline gary.a.ayres

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Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #62 on: February 22, 2019, 10:49:22 AM »
@ Dave - yes, Machinery's handbook looks like a great resource, though it could be almost a bit too comprehensive for a rookie like me. I might try to find something similar but a bit less expensive in the first instance, if such a thing exists. I notice that one of the editions of Machinery's has an 'expanded metric section'. Metric would be a criterion for me, though info on imperial would also be useful.  :ThumbsUp:

@ Peter - I was hoping someone would say that. I feel relieved! It would be great to have a small bespoke rack holding lengths of silver steel of various diameters, just to pick out what you need  :)

That said, having drilled and reamed a 6mm hole, might I not find that when the 6mm silver steel arrives it makes a press fit in it (which as Tony notes above is of course no good for a bearing)? Maybe will  just have to suck it and see...

I got my reamers from Tracy Tools too - not the set, but all the metric sizes I need for this engine. No doubt will be acquiring more in the future...

Another question - do you harden your silver steel shafts or do you just use it as it comes?

Cheers,

gary

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Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #63 on: February 22, 2019, 10:57:56 AM »
umm   OK.    If I come up with something less comprehensive I'll let you know..    by the way, google is your friend.   Hunt around and I'm sure you can find old copies in PDF  format for free.

Dave
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Damned ijjit!

Offline gary.a.ayres

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Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #64 on: February 22, 2019, 11:00:25 AM »
Thanks Dave. Good point - I'll have a browse for it later online. Free pdf sounds good to me    :)

Online Jasonb

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Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #65 on: February 22, 2019, 11:04:54 AM »
Most reamers you buy in the UK will be H7 or H8 tolerance, with H8 being slightly looser and they will give a fit that is fine for a shaft run rotate in with minimal play. This will vary a tiny amount depending on meterial being cut, pilot drill size and condition of reamer. This is why I don't like to ream flywheels as the slight clearance can cause a wobble.

If you want a press fit then if you have hand reamers you can take advantage of the long tapered lead in and not go all the way through, machine reamers won't do this. On little engines like this Loctite is your friend.

I tend to use PGMS - Precision ground Mild Steel which is easier to work than silver steel particularly if you need to thread it. If I did use Silver steel I would not harden it.

Offline Gas_mantle

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Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #66 on: February 22, 2019, 11:06:08 AM »
Not really Machinerys Handbook but you may find some interesting reading here :

http://campkahler.com/files/How_to_Run_a_Lathe_SB_1of2.pdf

http://campkahler.com/files/How_to_Run_a_Lathe_SB_2of2.pdf

Offline Ramon

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Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #67 on: February 22, 2019, 11:08:14 AM »
Gary - you'll probably find your silver steel will be a tight fit as stock as said by Tony but that's not a real problem to overcome.

Firstly - just check the ends of the piece of silver steel - sometimes it is cut off with a grinding wheel and this can harden the very end by it's action. Just cut off the first 5-6mm off the end. Cut a piece long enough for your shaft plus a piece for chucking. Hold in the lathe and just reduce the diameter with emery - about 240 grit. Failing emery you can use wet and dry but this will not last as effective as emery to do this. Begin dry and then use light oil as a lube.  Make sure you have a small chamfer on the end of the shaft and keep trying the shaft - gently at first until it will slide nicely in it's bearing. This will give you the nice running fir required. If you can back the abrasive with something nice and flat that will give you better control. Make sure you clean the shaft each time otherwise any grit from the process will bind and give you a false impression

If you are canny you'll just do the area that fits the bearing leaving the stock size to Loctite into your crank disc  ;)

Good luck - you're doing fine

Tug
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(a very apt phrase - thanks to a well meaning MEM friend)

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Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #69 on: February 22, 2019, 11:17:59 AM »
Most reamers you buy in the UK will be H7 or H8 tolerance, with H8 being slightly looser and they will give a fit that is fine for a shaft run rotate in with minimal play. This will vary a tiny amount depending on meterial being cut, pilot drill size and condition of reamer. This is why I don't like to ream flywheels as the slight clearance can cause a wobble.

If you want a press fit then if you have hand reamers you can take advantage of the long tapered lead in and not go all the way through, machine reamers won't do this. On little engines like this Loctite is your friend.

I tend to use PGMS - Precision ground Mild Steel which is easier to work than silver steel particularly if you need to thread it. If I did use Silver steel I would not harden it.

Additionally, pay attention to which reamers you buy.   As Jason pointed out, they come standard undersize, Standard Size and Standard Oversize.   As denoted by the ISO tolerance letter number that Jason has listed.    And Yes   Agreed about the Loctite!!!    used sparingly.

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline gary.a.ayres

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Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #70 on: February 22, 2019, 11:26:55 AM »
Thanks all.

@ Jason -I don't know what tolerance my reamers are but I will investigate. They are machine reamers. Once the steel arrives I'll have a better idea, and I take on board your point about precision ground steel. Next time!

@ Tug - I was using an abrasive paper and a flat piece of wood last night - not sure what it is; may be wet and dry: cheap, black in colour and sold by the sheet in various grades. It was working but I think I was expecting it to remove too much metal and I'd have been there all night  :-). Great advice though - I can see how emery would reduce that diameter to a sliding fit without it being too much of an ordeal. Thank you!

@ Peter and Dave - thanks for the info.

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Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #71 on: February 22, 2019, 02:05:33 PM »
Just as an aside re: shafting....if you know of an injection molder or mold maker nearby, ask them about cut off bits from ejector pins used in mold making. Typically these some in standard lengths and must be cut off to the mold's requirements. The cutoffs can be long enough in many cases to be used for shafting up to about 3/8". Ejector pins are case hardened and usually a few tenths undersized for a nice slip fit in a standard reamed hole. Their hardness also helps in terms of grub screws not digging into them.


Bill

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Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #72 on: February 22, 2019, 02:17:17 PM »
It looks like they can even be had from Amazon. Something like this is what I am talking about:

https://www.amazon.com/TCI-Nitrated-Straight-Diameter-Annealed/dp/B06Y3N4X1G/ref=sr_1_145?ie=UTF8&qid=1550844560&sr=8-145&keywords=ejector+pins

Looks for precision ground ones and nitride is even better. The above example seems to be for a package of 12. Other sizes, lengths, and metric are listed too if you look around amazon.

Bill

Offline gary.a.ayres

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Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #73 on: February 22, 2019, 02:32:16 PM »
Thanks Bill.

The idea of that easy slip fit quite appeals. It's becoming clearer to me that the advantages of using a ready made bar of the correct diameter are widely recognised.

Will keep this in mind for the future.

gary

Offline gary.a.ayres

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Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #74 on: February 24, 2019, 10:35:59 AM »
Not a bad day yesterday.

I spent some time checking that the mill was in tram ( :ThumbsUp:), then aligned the lathe tailstock as precisely as I could. Found my new digital clock gauge to be very handy and user-friendly for these jobs.

Then, in keeping with the plans, I milled a flat on the cylinder to a depth of 2.5 mm:



The flat forms the port face but also creates an offset when held in a 3-jaw chuck which correctly positions the bore. I then drilled and reamed the bore to 12 mm (sorry no photos). The port face was cleaned up by some fine-grit sanding on the surface plate. The cap was then made via a simple turning operation. I'm quite pleased with the results. The outside of the cylinder ended up with a few marks but it should be easy enough to deal with them at a later stage:





Back out to the shop again shortly to continue...