Author Topic: Questions on the Elmer 33 Engine  (Read 10075 times)

Online Jo

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Re: Questions on the Elmer 33 Engine
« Reply #15 on: February 27, 2014, 03:37:59 PM »
4-40 is an american thread size. As you are in the UK it is probably better you look to make all your threads either BA or Metric (depending on what taps/dies you have).

I find that this is a useful chart for converting between thread sizes: http://www.metricmcc.com/catalog/ch10/10-1012.pdf

Jo
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Offline Heffalump

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Re: Questions on the Elmer 33 Engine
« Reply #16 on: February 27, 2014, 03:50:07 PM »
So on the drawing here It lists a thread size, but I should be drilling not tapping?

 :help:

Online Jo

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Re: Questions on the Elmer 33 Engine
« Reply #17 on: February 27, 2014, 04:00:02 PM »
Those are clearance, the holes they line up on the other part are tapping size. (Assuming you don't have DROs) I would start by drilling the tapping size then later use the base to drill through into the parts they attach to.

When you get that far ask how to accurately align the two parts, there is a simple trick to do with drilling and tapping for one mounting screw and then putting the screw in and using that to secure for drilling the second one. Only after then do you finally open up the base holes to clearance size  ;)

Jo
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Offline Heffalump

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Re: Questions on the Elmer 33 Engine
« Reply #18 on: February 27, 2014, 04:06:09 PM »
Ah OK, so it's telling me to drill a hole big enough to allow for the #4-40 screw that will be passing through. That makes more sense.

I'm lucky enough to have a nice big DRO on the bridgeport, so I'm being as accurate as I can and hoping everything lines up afterwards, or is that a bit too hopeful?

Offline arnoldb

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Re: Questions on the Elmer 33 Engine
« Reply #19 on: February 27, 2014, 04:08:10 PM »
Hi Jim

The two countersink screws should be drilled for clearance for #4-40, and the hole showing between them should be drilled and tapped for #6-32 thread.

Don't drill the hole between them through into the groove either - it should be a blind hole.  Basically, looking at the base, all the blind holes from the top must be threaded for #3-48, the three blind holes from the bottom must be threaded #6-32, and all the through-holes should be drilled at clearance size for #4-40.

M3 metric screws are a great replacement for the #4-40 American threads on most parts of Elmer's engines.  If you do use different fasteners than the American ones specified, make a note on your plans to that effect next to mating parts - so that you can keep track of which holes must be what sizes.

Kind regards, Arnold
Building an engine takes Patience, Planning, Preparation and Machining.
Procrastination is nearly the same, but it precludes machining.
Thus, an engine will only be built once the procrastination stops and the machining begins!

Offline Heffalump

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Re: Questions on the Elmer 33 Engine
« Reply #20 on: February 27, 2014, 04:12:15 PM »
Hi Jim

The two countersink screws should be drilled for clearance for #4-40, and the hole showing between them should be drilled and tapped for #6-32 thread.

Don't drill the hole between them through into the groove either - it should be a blind hole.  Basically, looking at the base, all the blind holes from the top must be threaded for #3-48, the three blind holes from the bottom must be threaded #6-32, and all the through-holes should be drilled at clearance size for #4-40.

M3 metric screws are a great replacement for the #4-40 American threads on most parts of Elmer's engines.  If you do use different fasteners than the American ones specified, make a note on your plans to that effect next to mating parts - so that you can keep track of which holes must be what sizes.

Kind regards, Arnold

That's grand, thank you.

I have replaced #4-40 with M3, and the #6-32 although they should be M3.5 I have the hardware for M3 and scaled them down, whether this comes back to bite me I do not know! Good point about annotating the drawing - I know too well the dangers of head knowledge ha! :)

Offline Heffalump

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Re: Questions on the Elmer 33 Engine
« Reply #21 on: March 05, 2014, 10:19:34 AM »
Hiya - I'm struggling a little with my visualisation. I'm going through my drawing and converting to metric sizes as I go, and I'm looking at the con-rod. I've rounded down the measurement indicated below to 4mm, but I can't work out what actually fits in that hole. I think this must be the crank pin? Just looking for confirmation really, as on my plans the very right hand side of the page has been clipped and some information is missing.

Online Jo

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Re: Questions on the Elmer 33 Engine
« Reply #22 on: March 05, 2014, 10:25:33 AM »
Yes it is the crank pin.

I would look to go up to 5mm rather than down to 4mm. If you are worried about the amount of metal left either side of the pin you could reduce the diameter of the curve on the top and bottom (hand file rather than turn).

Jo
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Offline Heffalump

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Re: Questions on the Elmer 33 Engine
« Reply #23 on: March 05, 2014, 10:46:27 AM »
Yes it is the crank pin.

I would look to go up to 5mm rather than down to 4mm. If you are worried about the amount of metal left either side of the pin you could reduce the diameter of the curve on the top and bottom (hand file rather than turn).

Jo

ED just realised I said 4mm but I meant 4.5mm
« Last Edit: March 05, 2014, 10:52:09 AM by Heffalump »

Offline sshire

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Re: Questions on the Elmer 33 Engine
« Reply #24 on: March 05, 2014, 12:52:02 PM »
Jim
Print this chart. Keep it handy. I use mine (Imperial) all the time.
https://littlemachineshop.com/Reference/TapDrillSizes.pdf
Best,
Stan

Offline Heffalump

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Re: Questions on the Elmer 33 Engine
« Reply #25 on: March 14, 2014, 12:10:17 PM »
What's the best way to cut out a chunk of aluminium from a larger billet? Our bandsaw is too weedy. Is it time for more hacksawing?

Offline sshire

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Re: Questions on the Elmer 33 Engine
« Reply #26 on: March 14, 2014, 04:52:58 PM »
Reciprocating saw (Sawzall)
Oxy cutting torch
Angle grinder
Chain drilling/hacksawing
Water jet  :Lol:
Plasma cutter :ROFL:
Best,
Stan

Offline Stuart

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Re: Questions on the Elmer 33 Engine
« Reply #27 on: March 14, 2014, 06:35:00 PM »
Bigger band saw would help  :mischief:

Or get some smaller stock


Sorry only joking

Stuart
My aim is for a accurate part with a good finish

Offline ian cable

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Re: Questions on the Elmer 33 Engine
« Reply #28 on: March 14, 2014, 08:16:29 PM »
use your weedy band saw cut part the way turn the material cut part the turn again and you can get through the worst if not all the way if you have no cutting fluid rub some ordinary hand soap (bar of)on the teeth also good when filling aluminium stops it clogging. ian c

Offline Heffalump

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Re: Questions on the Elmer 33 Engine
« Reply #29 on: March 25, 2014, 08:50:05 AM »
Thanks Chaps.

If I want to run this engine on steam, what is the best material for the cylinder? I know that Ali is a good choice for running on air, easy to machine, cheapish, but will it stand up to a battering from steam?

 

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