# Need Help With Carriage Gib Installation Problem



## Nogoingback (Mar 11, 2017)

When I removed the carriage  on my Logan 200 a while ago, I noticed an uneven wear pattern on the front
gib where it contacts the bottom of the way.  When I got around to looking at it
more carefully, I measured the spacers that are bolted between the gib and the carriage and discovered
they weren't the same length, with a difference of about .016".  I checked my Logan parts list, which
showed they were the same p/n.  A follow up email with Scott Logan confirmed that they should be the
same.  So, I assumed that the difference in length was the problem, and shortened the longer spacer to
match the shorter part, which, because of the size of the notch milled in it's edge, appeared to be the
correct part.  They are now the same length to less than .001".

I  bolted the assembly back together, and found that spacer on the right (unworn) side is loose,
when the spacer on the worn side is snugged up.  I was also able to slide a .006 feeler gauge into a
gap between the bed and the gib on the right hand side.

Here's a pic looking up, under the carriage at the gib as it's installed.





This pic shows  the parts on the bench.  The wear pattern can be seen on the left side of the gib.  The right
side shows no wear at all.  The amount of wear on the gib seems pretty small, though I
didn't have a good way to measure it.  The gib has three points of contact: at the way, and under the spacers.  All
three points were machined when the part was manufactured.





I decided to measure the gap between the two small contact points on the gib, and the carriage.   The
pic below shows the gib clamped to the bed with spring clamps.  The only tool I had to measure the gaps was
a spring caliper, which I carefully slid between the parts on each side, and then measured with a micrometer.
Not the best method, but I think I was consistent about how I did it.  The gaps measured .514" on the left
side, and .523" on the right.  (The spacers are .516" long.)  So, it seems that the gib itself is the problem
and, I assume, was machined that way at the factory.  It may be that someone put the longer spacer in
at some point without really solving the problem.  So, what do I do?  The only option I can think of is
to have the gib ground correctly, and then figure out what length spacers I would need.  I think I'll
run this past Scott Logan next week, but I'm interested in what you guys think of this.


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## RandyM (Mar 14, 2017)

WOW! I am surprised that no one else has any comments on this. Unfortunately I am not familiar with your machine. It could be that you mentioned contacting Scott directly and we are all waiting to see what he suggests.

Now! Come on Logan 200 lathe owners what say you?


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## wa5cab (Mar 14, 2017)

I have always been surprised that, unlike with several other lathe makes, the hold-down plates weren't designed with shims for the final fit and to take up for future wear.


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## Nogoingback (Mar 14, 2017)

Thanks Randy!  I called Logan, but Scott was out of the office for a few days, so I'm waiting for him to come back.



wa5cab said:


> I have always been surprised that, unlike with several other lathe makes, the hold-down plates weren't designed with shims for the final fit and to take up for future wear.



I'm glad you mentioned that Robert.  The design is interesting: the contact points only support a portion the spacer and they're offset, so I assume snugging the screws a little put some upward pressure
on the gib, allowing them to be adjusted.
In order to properly grind the part, I need to know the height difference between the two small contact points and the part of the gib that contacts the bed.  Then I can use the original spacers.  If I can't get
that information from Scott, or can't get a replacement part, then one possible solution would be to grind the top flat, make new spacers and use shims to make up the difference. 





This end view is a little blurry, but the difference in height between the machined surfaces can be seen.


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## Mister Ed (Mar 14, 2017)

Just thinking off the top of my head, but I think this is how I would approach the issue at hand:

use the shaper (or grinder) to even out the gib
add shims as suggested (although for our purposes we'd probably never need to remove any)
trim the top side of the spacers a tad if needed


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## Nogoingback (Mar 14, 2017)

I think you're pretty much correct Ed, but the exact approach I take depends on what information I can get from Logan.  If I can get the gib dimensions
and the spacer length, then I could either regrind all the surfaces on the gib with their correct heights, and then use the stock spacers or,  if I grind one
point of contact down to match the other, I'd have to lengthen the spacers by that amount, (unless I add shims).  Because this design is adjustable and 
never used shims, I'll only shim it if I can't get the dimensions I need. 

My preference is to correct the problem, but assemble it the way the factory designed it.


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## Mister Ed (Mar 14, 2017)

I missed something earlier. I missed the difference in the measurements on the two outward contact points (where the spacers go). I was referring to machining the sliding surface, in order to remove the wear on the one side.

So I will amend my earlier thoughts. I would probably machine the long surface flat and then machine the other two points so they are even and on a parallel plane with the long surface. Then you'd probably have to take a tad off from the spacers. It will be interesting to hear what Scott can tell you.

I have never really understood that design, but I have never had the apron completely out of the way to study it. To me you either have the screws for the gib tite or at some various degree of loose. I have always wondered why the raised (machined) portion on the outboard side of the gib and why the recess in the spacers. In the later models those spacers were a rectangular block, but the gib remained the same part number. Not sure if they had the notch or not.


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## whitmore (Mar 15, 2017)

Nogoingback said:


> When I removed the carriage  on my Logan 200 a while ago, I noticed an uneven wear pattern on the front
> gib where it contacts the bottom of the way.



If the spacers were uneven at the factory, and held the gib at a slant, that explains uneven wear.   Because of the wear, the
contact footprint is no longer flat (though the spacers are now even).   One really wants to re-flatten the
contact area, if only to make the whole surface hold way oil, and check with the factory on the
correct spacer length (make or buy new spacers if the short one was the out-of-spec unit, because
cutting down the long one... means both are now the wrong depth).
I'm guessing that the bearing surface, and the (fulcrum) surface pressing on the two  spacers, have to be parallel,
and that the spacer optimum depth depends on the distance between those two planes.   Wrong
spacer height, and the uneven wear goes from front-versus-back to right-versus-left.

What ought one to allow for an oil film?  Two mils?


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## Nogoingback (Mar 15, 2017)

Ed, notice that the contact points for the spacers are higher than the bed contact surface.  If I machined all those surfaces flat, I'd have to make the spacers longer, not shorter.  If I did that, I'd have
to use shims to adjust since the designed in "adjustment" would be gone.

Look at the location of the spacer contact points: outboard of the bolts.  When the bolt is tightened it has a tendency to tilt the gib, which tightens the gib on the bed.  The notches in the spacers
are  there to clear a step in the bottom of the carriage.


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## Nogoingback (Mar 15, 2017)

whitmore said:


> If the spacers were uneven at the factory, and held the gib at a slant, that explains uneven wear.   Because of the wear, the
> contact footprint is no longer flat (though the spacers are now even).   One really wants to re-flatten the
> contact area, if only to make the whole surface hold way oil, and check with the factory on the
> correct spacer length (make or buy new spacers if the short one was the out-of-spec unit, because
> ...




When I first took it apart, I thought the uneven spacers were causing the  wear.  What I discovered was that they weren't.  I think that someone noticed the difference and added a longer
spacer thinking that that would solve the problem, but it didn't.  The problem is that the contact surfaces for the spacers aren't the same "height" relative to the surface that contacts
the bed.  The uneven wear has probably made the situation worse, since it has a tendency to "tilt" the gib.  What I would like to do is regrind all three surfaces to the original factory
dimensions.  Then I could use factory spacers.  You're right, the spacer contact points have to be ground to a plane parallel to the bed contact surface and the spacer length depends
on the difference between those two planes.  That's the info I want to get from Logan.


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## Mister Ed (Mar 15, 2017)

Nogoingback said:


> Ed, notice that the contact points for the spacers are higher than the bed contact surface.  If I machined all those surfaces flat, I'd have to make the spacers longer, not shorter.  If I did that, I'd have
> to use shims to adjust since the designed in "adjustment" would be gone.
> 
> Look at the location of the spacer contact points: outboard of the bolts.  When the bolt is tightened it has a tendency to tilt the gib, which tightens the gib on the bed.  The notches in the spacers
> are  there to clear a step in the bottom of the carriage.


See I was thinking the notches were down. I can remember having  a heck of a time with them ... but that was way too many years ago to remember clearly!! Thinking about the notches being up, now I understand the adjustment.

What I was trying to say before was, I would not remove the spacer contact points completely, just remove enough so that they are even ... *but after* all wear is machine from the bed contact surface. You will want the spacer contact points machined parallel with the bed contact surface. And the spacers the same size ... or you will end up in the same boat with wear on one end.

A different twist on my thoughts above: The two spacer contact surfaces really should not have any wear (and it looks like original machining marks on both sides). Use those surfaces as a reference to machine out the wear on the bed contact surface. That will make all 3 surfaces parallel. Then you would have to determine how much to shorten the spacers. Because you did not take any material off the spacer contact points, you would still have the same level of adjustability (I think).

If you hold the gib (by hand) so that the unworn right side is flat to the bed (or surface plate), how much clearance is on the worn side? Maybe I missed that above.

Maybe Scott will have a new one laying around, LOL.


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## Nogoingback (Mar 15, 2017)

You're right Ed, the bed contact surface should be machined, and the spacer contact points machined to match.  The problem is I need the design specs to know how to do it correctly.  It's true that there
is no wear to the spacer contact surfaces, but I can't reliably use them since I don't know if either one was machined correctly in the beginning.  I can ASSUME that the left hand one is correct,
but at this point I'd rather talk with Scott first.  He's supposed to be available tomorrow.  What I hope for is that he has access to the original design drawings, and is willing to dig it out for me, or that he knows how much clearance between gib and bed there should be.  If I get that
number, I can work out the machining.

If I clamp the gib flat to the bed, I can slide a .004" feeler gauge between the bed and the (worn) end of the gib.

I did have them check stock for a new one.  They don't have it and I believe that they don't
keep castings like this in stock.  I know when I spoke with Scott previously about the spacers,
he told me that they don't stock them.


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## Mister Ed (Mar 15, 2017)

Nogoingback said:


> ... no wear to the spacer contact surfaces, but I can't reliably use them since I don't know if either one was machined correctly in the beginning.  I can ASSUME that the left hand one is correct...


That is a good point.


Nogoingback said:


> how much clearance between gib and bed there should be.



That would be something I would like to know as well.


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## Nogoingback (Mar 16, 2017)

Spoke with Scott Logan this morning.  He said that the parts are not available and the drawings no longer exist.  His
suggestion was to machine  with the goal of minimum clearance.  I asked if .001" would be good to shoot for and
he said yes, though I'll need to take bed wear into account as well.  So, I'll have to take some very careful measurements to see where I'm really at and do the math.  I'll
plan on doing it so that I can use the spacers that I have.  And I have to find someone with a grinder.


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## TomKro (Mar 16, 2017)

I'm coming to this party a little late and my brain is a bit fried from a rough day, but I think I'm reading that the height difference between the two outer contact points and the bed grip surface is what's required. 

I went thru the Logan pile-o-parts, placed the casting face down on a plate and stacked 3 razor blades and a shim to try to get the height delta.  When using an 0.022 shim while holding down the bolt points, pushing the shim sideways caused the shim to rotate along one edge of the bed contact surface, while using a 0.024 shim and pushing the shim sideways caused the upper shim to rotate off the other edge, so I'll call it 0.023 + 3 stacked razor blades (0.075 inch for three), for a ballpark height of 0.098 inch.  There was a very slight ridge on the tapped side of the bed contact surface, but just barely detectable with my index finger.  

Also, both of my spacers measured about 0.516 inch height.

I believe the part I'm measuring came off a model 210 carriage, which appears to be the same part.  If you don't have a way to square up your casting, I can send this one your way.  Send a PM with your address if you want to give it a try.


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## Nogoingback (Mar 17, 2017)

Thanks for checking Tom.  Right now I'm out of town for work and can't compare your numbers with my part, though
the fact that your spacers are the same length as mine is helpful information.  I haven't had a chance to talk with anyone 
about getting the part ground yet, though I know of at least one local machine shop that might be able to do it. I would 
be interested in borrowing your part to compare with mine, and very much appreciate the offer.  I'll PM you.


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## expressline99 (Mar 25, 2017)

I can probably measure mine if it would help?

Paul


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## Tozguy (Mar 25, 2017)

I am not familiar with Logans but a few observations make me wonder why the fit of this part has to be better than it is now. That might not be wear showing on the part but rather some grinding marks from when the part was initially fitted at the factory. 
The design does not provide for adjustment like other style gibs have. Normal forces during operation are against the top of V ways and there should be no pressure on the 'gib' in question. There is no obvious need for this part to maintain an accurate sliding contact with the underside of the front way. The rear of the carriage is different because it is much lighter and forces may tend to lift it. Hence an adjustable gib is provided back there (on my lathe). I apologize if I am missing something and should mind my own business.


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## Nogoingback (Mar 25, 2017)

expressline99 said:


> I can probably measure mine if it would help?
> 
> Paul



Thank you for the offer Paul.  TomKro has shipped a spare part to me which I'm waiting for.  I'm also going
to take some accurate measurements on my lathe, so with all of that I probably will work it out.  If I still have any doubts, I'll let you know.


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## Nogoingback (Mar 25, 2017)

Tozguy said:


> I am not familiar with Logans but a few observations make me wonder why the fit of this part has to be better than it is now. That might not be wear showing on the part but rather some grinding marks from when the part was initially fitted at the factory.
> The design does not provide for adjustment like other style gibs have. Normal forces during operation are against the top of V ways and there should be no pressure on the 'gib' in question. There is no obvious need for this part to maintain an accurate sliding contact with the underside of the front way. The rear of the carriage is different because it is much lighter and forces may tend to lift it. Hence an adjustable gib is provided back there (on my lathe). I apologize if I am missing something and should mind my own business.



You have no reason to apologize at all.  I did consider just putting it back together the way it is since as you said, 
the pressure on this part is minimal.  But, if I did it would be a thorn in my side: I just wouldn't be happy leaving it that way.  So, I plan on fixing it.

The pattern on the part is actually wear: the photo isn't that great but if you had the part in front of you I think you would agree.  The design of the front gib actually does provide for a small amount of adjustment by tightening or loosening the screws that are accessed at the top of the carriage.  If you look again at the part, you can see that 
tightening  the mounting screws "pivots" the gib slightly off the contact points under the spacers.


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## Tozguy (Mar 25, 2017)

Thanks for the explanation. Certainly makes sense to put it right the way you want it. Weird how it got 'out of spec' like that to begin with. Good luck, am looking forward to seeing how it goes for you.


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## Nogoingback (Mar 27, 2017)

FIXED:

I owe TomKr0 a big Thank You for sending a good used gib to me.  Installed it this afternoon and it fits perfectly, so that's another item to check off the list.  Both front and back gibs
are installed and adjusted up fine.


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## Nogoingback (Mar 28, 2017)

wa5cab said:


> I have always been surprised that, unlike with several other lathe makes, the hold-down plates weren't designed with shims for the final fit and to take up for future wear.



As it turns out, the rear gib also is adjustable in the same manner as the front, so snugging up the bolts a touch compensates for wear.  No shims needed.


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## TomKro (Mar 28, 2017)

Looks like it's coming together nicely. 
Good to hear the front gib worked out.


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