Author Topic: New compact, compound-lever, selectable MA press  (Read 10107 times)

Offline awakephd

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Re: New compact, compound-lever, selectable MA press
« Reply #15 on: April 07, 2015, 08:42:23 AM »
Yes, first acme thread, but not my first machined part. And the pictures don't give you enough close-up to see the chatter marks down in the root of the threads. :)

I did some testing last night to see if the actual MA matches the calculated MA. I'm pleased to say that the match is quite good -- a small deviation from the predicted values, but since the scale I am using is not overly accurate, I felt that it was within the expected range.

I also tried a bit of stress testing, putting a 25-lb. weight on the lever with it set to 24x MA, for a calculated press force of 600 lbs. I let the weight down slowly ... but there was no creaking or protesting. I thought about adding another 25 lbs for a total of 1200 lbs press force ... but I chickened out. :)
-- Andy

Offline Al Lewis

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Re: New compact, compound-lever, selectable MA press
« Reply #16 on: April 07, 2015, 10:00:05 AM »
Yeah Andy, I don't think you'll ever need any more unless you decide to press hams under it. LOL  BTW  CNC turning centers get those same chatter marks, usually on the trailing edge.  Your machine work looks excellent to me.  Did you gage the pitch diameter on the threads or just make them fit?
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Offline Kern

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Re: New compact, compound-lever, selectable MA press
« Reply #17 on: April 07, 2015, 10:31:26 AM »
And yes, as a home-shop/hobby machinist, ........
Then am I correct in assuming that you machined the acme threaded "swivel" bolt that really seems to be the critical part of your design?

Offline smolt1

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Re: New compact, compound-lever, selectable MA press
« Reply #18 on: April 07, 2015, 11:38:37 AM »
Andy, If you want to see all the forces in play, try "Autodesk forceeffect". It is a free android app that will work on the Chrome browser. If you have a PC, just enable the Chrome browser and click the APP icon in the top left corner to get started.

Offline awakephd

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Re: New compact, compound-lever, selectable MA press
« Reply #19 on: April 07, 2015, 01:59:29 PM »
Yeah Andy, I don't think you'll ever need any more unless you decide to press hams under it. LOL  BTW  CNC turning centers get those same chatter marks, usually on the trailing edge.  Your machine work looks excellent to me.  Did you gage the pitch diameter on the threads or just make them fit?

Coming from someone who works professionally in the field, that is high praise indeed! But as you know well, "looks good" does not mean that it actually is made correctly. As a case in point, I'm afraid I did not gage the PD -- I confess that I still need to acquire a set of thread gage wires; I've always "cheated" and just made my threads until they fit a desired reference (usually something highly sophisticated and accurate like a hardware store nut. :)) In this case, of course, I didn't have a 1-6 acme nut lying around to test against, so I made the screw just by advancing the distance that "should" be correct, and then made the nut to fit. I figured it would be adequate for this purpose. Interesting to hear, by the way, that you get chatter even on the CNC ... but if something is going to chatter, I'm not surprised that it is an acme thread form!

Then am I correct in assuming that you machined the acme threaded "swivel" bolt that really seems to be the critical part of your design?

Yes, I made the nut, and you are right -- that is the critical piece. Fortunately, there is plenty of "give" in the system, so it did not require super-high accuracy. Of course, accuracy in a machine shop is rather a different matter than it is in the woodworking shop -- in this case, I wasn't worried if the ears were, say, +/- .010" from being perfectly perpendicular to axis of the threads, which is a HUGE tolerance in the machine shop ... but pretty near exactly on the money in the woodworking shop! :)
-- Andy

Offline Al Lewis

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Re: New compact, compound-lever, selectable MA press
« Reply #20 on: April 07, 2015, 02:30:58 PM »
If I were you I wouldn't concern myself with acquiring thread wires for acme threads as they, like the inserts, only work for one pitch.  You would have to buy them for each pitch you wanted to measure.  There is however, a computer program that will allow you to change the wire size for any thread pitch as long as it is within a certain range.  If you need some numbers I would be happy to give them to you.  Wires for a 6 pitch acme are Ø .08608".  Usually you can pick up a cheap set of wires from McMaster Carr.  On those large sizes you'll want a disc mic to measure them though as they are spread too far for a standard mic.    http://www.mcmaster.com/#thread-measuring-wire/=wnh6j2
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Offline awakephd

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Re: New compact, compound-lever, selectable MA press
« Reply #21 on: April 07, 2015, 04:08:24 PM »
Andy, If you want to see all the forces in play, try "Autodesk forceeffect". It is a free android app that will work on the Chrome browser. If you have a PC, just enable the Chrome browser and click the APP icon in the top left corner to get started.

Thanks for the pointer to the app -- I haven't had a chance to try it out yet, but look forward to seeing what it has to show!
-- Andy

Offline Spoons

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Re: New compact, compound-lever, selectable MA press
« Reply #22 on: April 07, 2015, 10:45:15 PM »
You've got some serious press building skills, Awakephd!!

AC4U!!!

Offline awakephd

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Re: New compact, compound-lever, selectable MA press
« Reply #23 on: April 08, 2015, 01:36:10 PM »
Thanks!
-- Andy

Offline awakephd

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Final details
« Reply #24 on: April 11, 2015, 10:41:16 AM »
Here are pictures of a couple of final details that I finished up last night.

The first two pictures show the press, including the final details, in its permanent home on top of my cheese "cave."

The next two pictures show a close up of the first of the final details, a "ship's wheel" adjuster, to make it easier to move the screw up or down as needed. I had debated whether to go with a socket in the top end of the screw, into which I could put a standard 1/2" drive socket extension, or whether to go with something like this. Originally I was thinking that the ship's wheel route would require cutting a keyway ... but then I decided that I don't necessarily want to use this while under weight; rather to adjust as needed between changing weights, or if needed to move the screw up and down when pulling the mold out for flipping. So it doesn't need a super-strong drive system (such as a keyway); instead, just a pressure pad will suffice. If you look at the peg in the lower right quadrant of the picture, you'll see that one picture shows it unscrewed part-way, and the other shows it screwed in to provide clamping force. (The screw does not bear directly on the acme screw -- I don't want to mess up my nice shiny finish! :) Instead it presses against a pad of hard maple, which then presses against the acme screw.)

The last three pictures show a close-up of a detail that I transferred from my previous press -- a flanged knob that will keep a weight from sliding off the end of the lever. (In actual use on my previous press, the weights never seemed to have an inclination to do this -- friction was sufficient to hold them in place -- but I am not comfortable not having some insurance to make sure I don't drop a 25 lb. weight onto the floor!) The last picture shows the brass threaded insert in the end of the lever, into which the knob threads -- I wound up making the insert, because a) I didn't have one of the right size on hand, and b) this is something that only takes a few minutes to make out of brass. Actually, I made two, one of which is used in the "ship's wheel."

It is possible I will decide the ship's wheel adjuster is not the way to go, after all -- I can see that I will have to move it up and down to get it out of the way, and I don't know how tedious that might get; I may still machine the 1/2" socket in the acme screw, so that I can choose between the systems. But for now, I think I'm done! So today I am planning to make some cheddar and put the press through its paces.
-- Andy

Offline Al Lewis

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Re: New compact, compound-lever, selectable MA press
« Reply #25 on: April 11, 2015, 10:55:41 AM »
Okay Andy, this is becoming an obsession! LOL  Beautiful work!!!
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Offline Spoons

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Re: New compact, compound-lever, selectable MA press
« Reply #26 on: April 11, 2015, 11:00:57 AM »
One thing comes to mind about your press... ;)

Offline awakephd

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Re: New compact, compound-lever, selectable MA press
« Reply #27 on: April 11, 2015, 11:33:17 AM »
Okay Andy, this is becoming an obsession! LOL  Beautiful work!!!

:) Thanks! As for the obsession ... I hate to end a project without finishing up all of the details that I had in mind from the start. And the ship's wheel was a lot of fun to make -- not too hard, just a bit of lathe work to make the hub, and a lot of lathe work to make the pegs (including a couple of extras that didn't quite work for one reason or another). And it just looks cool ... okay, maybe I am obsessed. :)

Spoons, I blush. I also can't imagine what something like this would have to cost to make it commercially feasible -- there are "just a few" hours of work invested in it ... at least that's what I try to convince my wife. :)
-- Andy

Offline Al Lewis

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Re: New compact, compound-lever, selectable MA press
« Reply #28 on: April 11, 2015, 01:53:34 PM »
Not sure what woodworking goes for but machine shop time is about $150.00 an hour.  Mind you if you built in bulk you could get the screws/nuts at a bulk discount.  You would want stainless steel of course, or CRES as it's known in the defense industry.  303 would do just fine.
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Offline qdog1955

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Re: New compact, compound-lever, selectable MA press
« Reply #29 on: April 11, 2015, 01:54:19 PM »
Andy----you really should get an award for aesthetics-----but out of curiosity---how many inches of thrust do you get in each position----and the rest of you guys, get your minds out of the gutter ;)  That really did sound a little Kama Sutra.
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