Mini lathe gib strips question

[dervmonkey]

Hi guys, I'm new to the site so hope this is the right section to put this in - I've done a quick search and couldn't find this particular issue.

I've been dialling in my Amadeal mini lathe and have found a potential issue that will need sorting with the cross and compound slide gibs.

The 3 recesses for the adjustment screws to locate in seem to be at the wrong angle, which is effectively jacking the 'screw side' of the jibs up into the upper edge of the dovetails and then pushing the jibs into the opposite side of the dovetails.

While this does take up the play, I feel it isn't the best way to adjust out the play in the slides - it makes them a little tighter than I would hope for.

Would it be feasible to take a small milling flute and 'square' the bottom of the holes so the walls of the newly milled holes are parallel to the top and bottom of the jib strips (when looking at them as installed) and the flat bottom of the holes at 90 degrees to the top and bottom of the jib strips.

In my mind this should push the jib strips horizontally into the bottom of the dovetail and not at it's current odd angle.


Sorry if I have used some odd terminology in this post, I've only had the lathe since Saturday and have been doing lots of reading and swatting up after spotting a video by Bogstandard on youtube: "Darrens Lathe"  

[dervmonkey]

Well, that wasn't quite the response I had hoped for.....

After thinking about my suggested fix I figured I'd go for it, so I ordered a set of brass gibs from ArcEuro as backups and using a 4mm milling flute and the stock gibs mounted squarely in the adjustable tool post I milled out the adjustment screw locations on the gibs, taking off just enough to ensure the bottom of the indentations were flat.

I then lapped the gibs for good measure, cleaned, lubed and reinstalled, the slides feel better and easier to move so I'm happy with my mod.

[jihe]

I have the same problem with flipping gib strips. I've been thinking about either your solution or putting two more screws in at a slightly lower position. The problem with adding screws is that there would be very little metal left under them, and I'm afraid that the slide would have to be reground after threading the holes. So I'm glad to here you're happy with the solution, I'll probably do the same. I already have the replacement strips from Arc.

[Artie]

G'day mate, I think the lack of response was a result of folk not knowing the answer to your question. Admitedly I saw your post and had no answer for you. Glad it went well.

Rob T

[dervmonkey]

I have the same problem with flipping gib strips. I've been thinking about either your solution or putting two more screws in at a slightly lower position. The problem with adding screws is that there would be very little metal left under them, and I'm afraid that the slide would have to be reground after threading the holes. So I'm glad to here you're happy with the solution, I'll probably do the same. I already have the replacement strips from Arc.

I've seen some extra screws added on a website somewhere, but no mention to it as a mod - they must have been added for a reason though - I can't think why you'd need the slide reground if you added two holes and tapped them though, surely the face of the slide you drill and tap would be static in relation to the gib strip, unless I'm missing something due to the slight Vodka haze I'm enjoying

I forgot to mention that I've swapped out the stock adjustment screws for good quality stainless cap heads (with flat bottoms to compliment the modded jibs) and retained the stock lock nuts.

I'd like to think my mod sucess is part placebo, part fettling of the gib locations and partly down to the lapped gibs, what ever it is, it has made an improvement.

G'day mate, I think the lack of response was a result of folk not knowing the answer to your question. Admitedly I saw your post and had no answer for you. Glad it went well.

Rob T

Thanks Rob, I had the "First thread nerves" - you know how it is on a new forum!

[jihe]

I can't think why you'd need the slide reground if you added two holes and tapped them though, surely the face of the slide you drill and tap would be static in relation to the gib strip, unless I'm missing something due to the slight Vodka haze I'm enjoying

The original screws are 1.8 mm from the bearing surface. To get any tipping prevention effect out of the extra screws I figure I need to move them at least 1 mm closer to the edge. With only 0.8 mm of meat outside the thread I think there would be risk for fractures and deformation of the outside surface when tapping. With M3 instead of M4 there would be 1.3 mm material and a little less risk, but still a risk I guess.

[jihe]

Here is a picture of the distance I'm speaking about.

[dervmonkey]

That makes sense! - I'll blame last nights Vodka haze 

[simp]

I have been working on that to.  I got longer screws and chainged the screw seat,  works good!  going on to brass gibs now!            

[simp]

To explain a little more on what I did.  Some of this I`m sure you allready know.  Take the gib and sand it flat on a mirror with 320, Drill the gib screw seats wider and on a slight angle.  grind your screws to a point.   Also I lapped my compoud with comet cleanser and 30 weight oil,  mix tel it`s thick.  Take off your handle and adjusting rod and  put the mix on your dovetails.  Start with the middle screw and adust tell it has a drag on it.  Make sure you lock it,  set the other screws the same way ,  now lap it back and forth .  What you need to do is remove the high spots. keep doing this,  take apart wipe off the old and put more on and keep adjusting your screws ect. you will start to see shiny spots,  But don`t go to far some ruffness is good for holding oil.   This take`s about 30 to 45 min but it`s well worth it , Just make sure you clean it all off and relube it with good oil.   Hope this helps someone.                 

       Jim

[simp]

Well this is to the op if hes still around,  this is what my lathe cuts like.  By no means does this mean,  I think my lathe cuts good..  It is just not choppy like his cuts. 

[jim]

hi, i had to add extra screws for the compound (top) slide, no matter how i adjusted it, it went to slack or too tight, now its ok.

[madjackghengis]

dervmonkey, I made a couple of extra cross slides for my lathe years ago, and found set screws made with a nice sharp point available from various fastener manufacturers, and putting the gib strip in place, lightly tightening down the pointy screws to make a good mark, then center punching those marks, will eliminate the problem forever.  Such screws have their points ground in a screw machine, so they are on center, and in my experience, very accurate in placement.  I have found this solution superior to milling flats and machining the ends of gib screws flat, as they still want to wander, if there is any room at all to do so.  Hope this helps a bit, mad jack

[Dunc]

Dave Fenner's multi-issue The C3 Mini-Lathe, part 13 addressed saddle adjustment. See Model Engineers' Workshop, #145, Dec 2008.
This series on the C3 started in issue 133 (Christmas 2007). The first article is reprinted (with permission) at
http://arceurotrade.co.uk/reviews/C3_Articles.html

The usual disclaimers here: not affiliated etc...