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Del Gets Burnt!

08/08/2018 10:47 AM

I bought a second hand micro mill off Ebay. (Clarke CMD10, no room for anything bigger in my workshop, and it will only me used on wood and ali', honest guv' ).
As I stripped it down I found the column moved, but thought it was 'cos the bolts weren't tight... oh no... it was cracked at the bottom... .
Could have been damaged in transit, or I could have been stitched up, however I suspect the bloke maybe just didn't know, as it looked like it had never been stripped and adjusted correctly. I'll just take the hit like a cat)

Fortunately I have ordered a replacement for £58 including postage, so it's no too big a hit.
My real question is the adjustment procedure for the leadscrew nuts. They have a long split and two allen screws which I imagine take out the backlash as they are tightened.


I couldn't feel any backlash anyway, and the screw weren't actually making contact. I tightened them lightly but couldn't really feel any difference.
I didn't go mad 'cos I didn't want to crack the casting.
So, any ideas on procedure guys?
Del

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#1

Re: Del Gets Burnt!

08/08/2018 11:06 AM
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#2
In reply to #1

Re: Del Gets Burnt!

08/08/2018 12:24 PM

What ya makin' Del? Arrow tips?

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#3
In reply to #2

Re: Del Gets Burnt!

08/08/2018 12:49 PM

Nope, I make them on my lathe (only tiny ones for flight arrows... I buy the regular type)
I'll be machining a crossbow prod mounting bracket .
Del

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#4
In reply to #3

Re: Del Gets Burnt!

08/08/2018 1:39 PM
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#5
In reply to #4

Re: Del Gets Burnt!

08/08/2018 3:15 PM

Hrrruump I say ol' chap...how's that old euro thing working out?

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#6
In reply to #4

Re: Del Gets Burnt!

08/08/2018 4:34 PM

Yes...
Del

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#7
In reply to #3

Re: Del Gets Burnt!

08/09/2018 12:17 AM

" flight arrows..."

Pardon my ignorance; I thought all arrows were intended to fly! What other kinds of arrows are there besides flight arrows?

Oh yeah, the ones that come back and hit the archer...

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#8
In reply to #1

Re: Del Gets Burnt!

08/09/2018 12:47 AM

"Check page 7...."

Page 7 is the electrical diagram. Did I miss something? What a strange page arrangement!

I also found it strange that they call left-to-right the Y axis and front-to-back the X axis.

Yes, Del, those two screws are indeed for setting backlash. The main hole is drilled and tapped before the slit is cut, so the leadscrew should fit easily when there is no tension on the screws. As long as the threads in the split section have not been damaged or badly worn, you should easily feel the (cleaned and lubricated) leadscrew tighten up when the allen screws are tightened sufficiently. Once you feel the tightening, back off just a tiny bit so the leadscrew turns easily.

If the leadscrew is worn, you may find that you have little backlash nears the ends of travel, but more backlash near the center, or that the leadscrew tightens up near the ends of travel. The only real solution in that case is a new leadscrew.

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#9
In reply to #8

Re: Del Gets Burnt!

08/09/2018 2:47 AM

Thanks, that's what I figured...I just didn't want to over tighten and do some damage.
Flight arrows are V skinny, V light with tiny flights designed for maximum distance rather than penetrating armour
Here's a pic for comparison... the flight arrow is painted bright yellow so you can find it when it's gone 320yards !

Del

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#10

Re: Del Gets Burnt!

08/10/2018 7:23 AM

seems like a fillet weld should be a good fix for your crack?

also, if the threaded rod is in the nut, you cannot apply too much stress on it, the threads stop any damaging strain.

too tight and the motion will be very tight and will cause undo wear. these things all have some slop in them. the way i have gotten around that is to add a DRO. these can be purchased for cheap on-line and are very accurate. the linear bar can be cut to size and mounted onto any table. i have used mine for years without any issues.

once you have one of these in place, it doesn't matter the amount of slop as you can easily get back to where you need to be in seconds.

https://www.ebay.com/itm/Shars-6-Digital-DRO-Large-LCD-Readout-Scale-IP54-For-Bridgeport-Mill-Lathe-New/351424698587?hash=item51d28b58db%3Ag%3AbpcAAOSwEgVWS4-T&_sacat=0&_nkw=x-y+lathe+readout&_from=R40&rt=nc&_trksid=m570.l1313&LH_TitleDesc=0

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#11
In reply to #10

Re: Del Gets Burnt!

08/10/2018 10:11 AM

I did consider welding, but as it's cast iron it is a bit tricky, also it would be hard to keep the alignment. Got a new one installed now so I'm good.
I've been trying it out. Fine with Ali' and I took a light cut on some EN8 steel with 10mm end mill which was fine too
Del

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#12

Re: Del Gets Burnt!

08/10/2018 8:56 PM

Del, post any questions on mills, lathes, etc on this web site. They have many experts on machine tools of all kinds. http://www.chaski.org/homemachinist/

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#13
In reply to #12

Re: Del Gets Burnt!

08/11/2018 5:00 AM

Cheers
I'll have a look.
Del

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