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Jeff J
PostPosted: Mon Dec 24, 2018 8:26 am 
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I noticed I have quite a bit of play between the jack screw and the nut. The assembly the builder used does not match the drawings. I have the tools to fabricate the nut and could use some practice using them so I figure I will give fabrication a shot. The drawing calls out aluminum plate for the nut but mine appears to be made from brass. What is the most popular metal being used to make the nut?

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bfinney
PostPosted: Mon Dec 24, 2018 1:43 pm 
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Mine is made from aluminium bar stock as called out on the plans. How do I know this you ask? I recently made a new one cause I had what I thought was excessive play in my trim system.

Merry Christmas to all and to all good night. ;D

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James Grahn
PostPosted: Mon Dec 24, 2018 9:27 pm 
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Per Plans...in stock.
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fytrplt
PostPosted: Tue Dec 25, 2018 7:45 am 
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An old newsletter talks about putting a thrust washer in the bearing block to take out the end play in the jackscrew.

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Jeff J
PostPosted: Tue Dec 25, 2018 11:07 am 
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My first thought was to call Cubes but when I saw how the assembly differed from the drawings I decided to look at making my own. I already have a couple of extra parts I ordered that don’t fit because of deviations from the drawings. I may still call Cubes if the dimensions match up or I decide I can’t make the part. I have other things I am considering and need to call him anyway. I have aluminum I bought to practice welding and machining on hand although I am not fond of using it for this application because aluminum is abrasive. I don’t use aluminum rods to clean my guns for the same reason.

There is a little slop throughout the system but the bulk of the movement is between the nut and the jackscrew. There is more slop in the pins holding the assembly than end play in the screw.


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"The joke in aviation is, 'If you want to make a million, you'd better start with £10m.' " -Bruce Dickinson
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jrevens
PostPosted: Tue Dec 25, 2018 11:47 pm 
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Jeff,

As I believe John Thorp himself pointed out, aluminum and steel actually make a pretty good bearing pair, with proper lubrication of course. I don't remember what alloy is called out on the print for that "nut", but I believe it is 2024-T3. That's what you should use, IMHO. You also should have the proper thread type. Like you said though, your assembly is obviously not built to plans, based on the picture.

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Jeff J
PostPosted: Wed Dec 26, 2018 6:44 am 
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I don’t have the drawings handy but I remember thinking the thread called out was a standard bolt thread. If it isn’t, then I cannot fabricate as I don’t have what I need to turn an internal thread. All I have for cutting threads is a standard tap and die set.

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jrevens
PostPosted: Wed Dec 26, 2018 12:06 pm 
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It’s been so many years since I built my T-18... I was building in the 70’s and 80’s, and I no longer have the prints to check, but a jack screw like that is frequently an acme thread. Anyway, Cubes has the right part I’m sure. I didn’t mean to muddy the waters, Jeff. That thread may indeed be a “standard” thread, but I believe I may have borrowed an acme tap to make mine. I could be wrong.

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bfinney
PostPosted: Wed Dec 26, 2018 3:35 pm 
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Per plans, drill 5/16" tap 3/8-16 NC, this is how mine is made works fine, so far. 8)

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James Grahn
PostPosted: Thu Dec 27, 2018 3:44 am 
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Look at the 694 drawing. It is 2024t3. It’s made from .500 bar.
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