Author Topic: Zee Needs Popcorn  (Read 19553 times)

Offline bruedney

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Re: Zee Needs Popcorn
« Reply #15 on: May 28, 2018, 06:49:56 AM »
Zee

Do you have access to the Model Engineering mag archive?

Issue 4424 has Stew's description of how he made his crosshead. No fancy boring at an angle. It is simply the end of the 20mm hole with a 20mm drill bit (not sure if 118 or 135 deg)

Bruce
ĎResults! Why man, I have gotten a lot of results. I know several thousand things that wonít work.í ó Thomas Alva Edison

Offline bent

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Re: Zee Needs Popcorn
« Reply #16 on: May 28, 2018, 06:52:54 AM »
I wouldn't think 12L14 or 303 would spring much, and if you have a reamer to finish the smaller bore (and clean it up again after milling the sides) you should be ok.  At most, I'd plan to tweak the follower (i.e. machine to fit and minus a couple thou) to make it run smooth.

Online Jasonb

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Re: Zee Needs Popcorn
« Reply #17 on: May 28, 2018, 07:09:20 AM »
O/A length is 110mm so your 4" does seem a bit short

C.Bored Hold means counterbore and Hold means the dimension is important and that needs to be a good fit to the cylinder end cover to keep things concentric.

Looking at the actual drawing as said a drill will do for the larger diameter hole as nothing touches it unlike the smaller one that guides the crosshead 3/4" OK

Offline sbwhart

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Re: Zee Needs Popcorn
« Reply #18 on: May 28, 2018, 07:39:42 AM »
Hi Zee pleased to see that you've decided to bite the bullet popcorn with this engine, you'll find that the guide looks nasty but it isn't really just turning, the critical features are as Jason has pointed out the short bore at the front and the smaller bore where the cross head works need to be concentric, from memory the transistion I machines with a big drill that I append to have, and you will find that things will move when you mill away the cross section so its a good idea to rough out those two critical features mill away the cross section let it stand for a few days to do its moving act then finish them off.

Good luck with the project I hope you have fun with it.

Her's a picture of my finished engine







And a Video



If any one wants a set of drawings just drop me a PM.

Stew
A little bit of clearance never got in the way

Offline Brian Rupnow

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Re: Zee Needs Popcorn
« Reply #19 on: May 28, 2018, 12:43:10 PM »
Zee--when I convert a metric drawing to inches, it's not an exact linear conversion. Sometimes things have to change a bit to fit inch tooling and inch size stock. I know my drawings work, because quite a few people have built from them with no problem. I see that others have answered your other questions correctly.---Brian

Offline zeeprogrammer

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Re: Zee Needs Popcorn
« Reply #20 on: May 28, 2018, 01:04:00 PM »
Thanks everyone!

Do you have access to the Model Engineering mag archive?
Issue 4424 has Stew's description of how he made his crosshead.

I got your PM Bruce. Thanks! Stew's article made many things clear. Well worth a read.
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
"To work. To work."
Zee-Another Thread Trasher.

Offline zeeprogrammer

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Re: Zee Needs Popcorn
« Reply #21 on: May 28, 2018, 02:11:43 PM »
Got the dimensions on the crosshead guide sorted out.

I saw in Stew's article and Brian's plans that a ball nosed end mill, along with an end mill is used to mill away the radii on the sides.
The guide was mounted that all milling was done in Z.

Is there any reason why just an end mill or boring head couldn't be used by mounting the guide on its side and working along the XY?

If the ball nosed end mills have to be a certain size...I don't have them and, if there's no need for them in the future then it seems a waste to buy them.
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
"To work. To work."
Zee-Another Thread Trasher.

Offline crueby

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Re: Zee Needs Popcorn
« Reply #22 on: May 28, 2018, 02:20:13 PM »
A couple small ball nose mills are handy to give inside corners that casting look rather than a hard corner. also can be used to do fluted columns, though an angled normal mill will do the same.
 :popcorn:

Offline Brian Rupnow

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Re: Zee Needs Popcorn
« Reply #23 on: May 28, 2018, 02:29:19 PM »
Zee--You might get away without using a thumpa thumpa thumpa ball nosed endmill, but that's what worked for me. I've made 3 of those popcorn engines and they turned out beautifully. That crosshead guide is the most eye-catching part of the build. ---Brian

Offline zeeprogrammer

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Re: Zee Needs Popcorn
« Reply #24 on: May 28, 2018, 02:44:31 PM »
Zee--You might get away without using a thumpa thumpa thumpa ball nosed endmill, but that's what worked for me. I've made 3 of those popcorn engines and they turned out beautifully. That crosshead guide is the most eye-catching part of the build. ---Brian

Wouldn't that mean the ball nose has to be rather large? The diameters I'm looking at are 5/8 and 3/4. (One other is 1.5 but it looks like Stew used a hacksaw and files.)
Or was it done 'freehand'.

On a different note...I've not used a steady rest before. Even with oil, is it normal for fairly heavy gouges to be made in the metal? Granted, this is on aluminum which is fairly soft compared to the steady. Not much pressure at the pinch points.

What I'm really asking...is there a procedure one goes through to 'prepare' a steady rest? That is, should the pinchers be dressed in some way?

At some point I'll have to flip the part to turn the bigger end and that means the steady will be on a finished diameter. Seems to me that finish will be ruined.

Thanks.
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
"To work. To work."
Zee-Another Thread Trasher.

Offline sbwhart

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Re: Zee Needs Popcorn
« Reply #25 on: May 28, 2018, 04:12:25 PM »
Blimey Zee:- You've really taxed my memory on this one  :noidea: I,ve just had a look through my photographs of the build to try and recall things.

Those radia on the Cross Head Guide I just roughed them out in steps and finished them off with a 1/2 round file.

As for the cross head I forgot i'd used a steady but I know people have built it in two parts, all you have to do is make the 68.64 length 70 on the front end and the 68 length 65 on the back end and put a 20mm dia by 5mm on the back bit so that they fit together and secure with high strength loctite after you've milled the section away:- hope that makes sence.  :thinking:



I'm going to read the build article now that was published in ME to try and jog things a bit more

Cheers
Stew

A little bit of clearance never got in the way

Offline sbwhart

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Re: Zee Needs Popcorn
« Reply #26 on: May 28, 2018, 04:23:31 PM »
I lied  :mischief: :mischief: about not using the bull nosed cutter, from my notes I did but and 1/2 round file would do the job:- these are my notes

Cross Head Guide Part 15, was made from a piece of 32mm diameter free cutting mild steel, it would have been easier to make it from aluminium but I didnít have any of a suitable size, so steel it was to be. I think it would be possible and easier for people with some of the smaller lathes to make it in two parts, with a glued spigot joint at the 68mm point, I wanted to make it in one go, but as the spindle up the lathe was too small for the bar I would have to use a fixed steady to support the job.

Fist supporting the bar with the fixed steady face and centre the end of the bar, then using a running centre turn the 24 mm diameter down to length. J peg 0638 Flip the job round and again supported with the fix steady face and centre drill the other end, and with a running centre turn the 28mm diameter. Supported with the fixed steady, rough drill out the 15mm diameter with a series of ever increasing drills, you donít need to go all the way through just past the 70mm point. Then drill out the 20mm diameter to depth, here I have a confession, for some reason I didnít go deep enough with this drill, I probably got my sums wrong, and didnít notice my mistake until later, but it is of no detriment to the engine and no one knows but us. This 20mm bore is relatively short so if you donít have a drill it could quite easily be bored. We now need to machine the short 24mm * 7mm deep counter bore diameter, and the long 16mm diameter, its important that these two feature are concentric with each other as they ensure that the cross head is aligned with the bore, which aids free running. For the 16mm dia I was lucky and had a 5/8Ē which is near enough, as the cross head will be made to fit. If you donít have a suitable reamer you could always bore it out but its quite a depth and I think this would be quite difficult, I would suggest splashing out and investing in a 5/8 or 16mm drill this would be cheaper than buying a reamer, and if you rough the bore out to within 0.5 mm and you just break the corner of the drill and feed it through slowly with plenty of tapping fluid you should get a reasonable result. The short 24mm counter bore diameter can quite easily be bored to size, use the front cover as a gauge to ensure you get a tight fit. J peg 0645 and J peg 0648 Thatís that end done so turn it round and again using the fixed steady drill through to meet up, getting the two ends concentric is not important, just close is good enough, open up to 20 mm and to the correct depth, that the turning done on this part.

From now on its all milling work, as the part ends up as such an odd shape I though it best to roughly mark it out, the easiest way for me to do this was to chuck it up in the indexer, I know the centre height of the indexer is 70mm, so using my height gauge and the rotation of the indexer and with the part blued it was marked out and the lines lightly centre popped just to make then a little clearer, and prevent them being lost. J peg 0656

No great precision is required to mill it out to shape, working to the lines will be good enough. With the job sitting on a parallel first mill the long flat part along the front of the guide, finishing off the corner with a bull nosed cutter, but a round file would finish the corner off just as well. You now have a nice flat face to sit on a parallels and finish off the other side, to cut the 10mm wide section just feed the cutter in from each side until you come to the line, I used a trusty old hack saw to remove the last of the waist material J, peg 0673 and 0676, a good tidy up with a range of files and the jobs a good un.

Well not quite a good un, one final thing to say about this part, youíve removed a lot of material, this releases internal stresses in the bar, so things will move, particularly if your using bright drawn bar, this means that the 16mm bore will not be parallel, with mine it was small by about 0,1 mm towards the front, donít do anything with this at the moment weíll sort that out later.

Stew
A little bit of clearance never got in the way

Offline zeeprogrammer

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Re: Zee Needs Popcorn
« Reply #27 on: May 28, 2018, 04:32:46 PM »
 :Lol: Sorry if I gave you a headache Stew.

I'm going to think on the two-part possibility. I have a lot of time for thinking as I'm waiting on some supplies and tools.

Thanks.
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
"To work. To work."
Zee-Another Thread Trasher.

Offline zeeprogrammer

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Re: Zee Needs Popcorn
« Reply #28 on: May 31, 2018, 10:50:42 PM »
While I wait for supplies and tools...I thought I'd make some tools.

One being a lathe carriage stop which means cutting a 'V' so it rides on the (front) way.

Here's my question...

I was expecting the 'V' on the way to be 90 degrees. But I'm measuring more like 87-ish degrees.

 :help: Does that make sense? Would I cut the stop's 'V' to 90 or to match the way?

BTW I haven't measured the rear way. The follower and tailstock ride on the rear way while the carriage rides on both the rear and front ways.

The stop will include two holes. One for a rod that can be adjusted along Z and another for mounting a dial indicator in Z.

Eventually a vise stop will be made. I should also make some soft jaws for the vise.

[EDIT] That little step on the bottom is the pivot for the clamping bit.
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
"To work. To work."
Zee-Another Thread Trasher.

Offline crueby

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Re: Zee Needs Popcorn
« Reply #29 on: June 01, 2018, 12:22:01 AM »
If the V notch is just to clear the ways, a couple degrees off should not matter.