# Making a new Y gib for a Grizzly G0704



## mhackney (Aug 4, 2014)

I don't know how this journey is going to end but I do want to capture the process!

Basically, my G0704 is 3-1/2 years old. I converted it to CNC 3 years ago (Hoss Phase 2 for those that know). Earlier this year I decided to do a Y axis extension to bump the travel up to about 9". Once it was back together I had a serious backlash problem - .005" on Y. I had a new ball screw (Roton) and packed the nut with oversized bearings and it was nice and smooth but with no slop. I measured everything and its brother. No axial screw movement, not play detectible anywhere. A couple of guys on the 'zone suggested it might be wind up friction. Then, last week I took the Y gib out and noticed that it was twisted. About 1mm twist from corner to opposite corner. One corner is actually worn! That set me off on this journey. It is possible that the friction from the twisted Y was contributing to (or the cause) of my backlash. I need to keep backlash down to about .001-.002" to make my fly fishing reel parts.

As I posted here over the weekend, I ordered replacement gibs (I ordered a spare X too just in case) from Grizzly. They arrived as 13" long rough cut/ground blanks. This makes sense in retrospect since the gibs must be fit to the individual machine. But, my blanks were much thicker than the thin end of the stock. I have a support call into Grizzly but I don't expect any help s this is what they have. So I need to thin down the blanks before I can get started.

With 2 blanks, I realized I could sandwich them thin end to thick end and get parallel surfaces that I can mill. Simply clamping the blanks to my mill table and milling between the clamps should get me in the ballpark. I decided to use my X2 since it is very nicely trammed and my G0704 is a mess right now. The gibs are cast so easy to mill. I have a very nice 1/2" solid carbide 4 flute end mill that leaves a great finish so I used that. I clamped the two blanks directly to the mill table (making sure it was nice and clean with no burs). Here's the setup on the mill.





I milled in .005" increments to remove a total of .035" of stock - with flood coolant. I wanted to go slow and steady so as not to overheat the blank. The last few passes were .002" to get a nice finish.

Here is the finished milling before cutting the ends off. The stock gib measured .1770" at the end. The milled gib is .1610" - I deliberately milled it a little thinner so I can position the blank more in the middle of its length. You can see the pretty nice finish on the blank.





I then cut the ends off with a hacksaw and filed them nice and smooth. I marked where .1770" thick is on the blank so you can see how it lines up. Pretty good calculat'n to arrive right in the middle of the blank! I also relieved the now-sharp edge of the blank.





With the blank in hand, I disassembled the table and saddle then did a quick test fit. It is "thick" at the narrow end (towards the column). But that's what the hand work is supposed to fix, right? 



I have to pick up some Dychem tomorrow as I don't have any around (I think I leant it to a friend and that's the last I saw of it!). I also need to remove the Y axis screw so I have free access to the saddle, so I'll finish off the disassembly tonight.

By the way, if you look at the stock Y gib - on the lower right corner - you can see where it is polished from rubbing on the dovetail. That is the high corner of the twist. It must have been this way for a while to wear that much.

Cheers,
Michael


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## Fairbanks (Aug 4, 2014)

Thanks for your post Michael.  I have a G0759 coming in September (hopefully?) and expect some growing pains.  I appreciate your input.

By the way, I hope to be turning out a fly reel or two as time goes on.

Steve


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## mhackney (Aug 4, 2014)

Steve, thanks for the thanks! If you are interested in making reels, check out the forum I run on reelsmithing: www.reelsmithing.com/forum.

cheers,
Michael


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## astjp2 (Aug 4, 2014)

Now you just need to get it scraped in.  A good scraping will make a world of difference on that machine.  Tim


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## mhackney (Aug 5, 2014)

I do know that the gib blank I machined has an incorrect taper - it seems to be a little too thick at the thin end. Do I correct this with scraping or should I lap or file to get in the ballpark? I suppose that will depend on how far off it is, which I won't know until I get the Dykem today.


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## mhackney (Aug 5, 2014)

Well, I think I have it! First I lapped the milled face of the taper on a diamond stone to get it flat. Then I ground a scraper edge on a Nicholson file I had laying around. It is about 3/4" wide by 5/32" thick at the tip and 12" long plus a wooden handle. I ground a 4" arc and then a 5° relief as I saw on youtube. I did hone it lightly with a very fine diamond hone. 

I then coated the dovetail on the base with Dykem, positioned the saddle and inserted the gib. Once seated I pulled it out and sure enough, the thin end was coated with indicator as I suspected. I could tell that the thick end was not seating and could wiggle when the thin end was in all the way. I clamp to my bench with 3 screws for stops for the far end and "had at it". It is a surprisingly light touch to scrape. I scraped the high area, cleaned, stoned and cleaned again and then reinserted. It took 5 scrapes to start getting the taper to seat further and further in the dovetail. But I was finally able to get the taper pretty good. I was surprised. Even though it looks like crap due to the scraper (it still had remnants of the file teeth) but it did a good enough bob to scrape the taper in. I then did a "finsih" pass over the entire surface and reindicated in the dovetail. I had a few high spots. I had to do this process at least 8 times before I started getting a reasonably uniform pattern of indicator. But I could immediately tell how much smoother the gib inserted, it just felt "right". This was about a 3 hour process. I'm beat so I cleaned up for the evening. Glad I wore gloves, that indicator gets on everything.

Tomorrow I'll cut the gib to length, mill the notch and fit it up on the mill. Should be an interesting time!

cheers,
Michael


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## astjp2 (Aug 5, 2014)

Scrape your ways also before you cut the gib, you may find some high spots that can really make that axis smooth compared to the others.  Tim


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## mhackney (Aug 6, 2014)

Thanks Tim, I checked them and they should be good to go.

cheers,
Michael


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## mhackney (Aug 12, 2014)

I got everything back together one axis at a time. Starting with the problematic Y. I cut my gib to length, milled the notch for the screw head and the hole for my oiling system and then fit it in the way. I then carefully adjusted the saddle slide to be smooth with no slop. It took a bit of tweaking but I'm down to about .003" backlash. Most certainly the issue is "sticktion". The gib is very sensitive to the adjustment screws. If I tweak even a 32nd of a turn tighter my backlash jumps up to .007". I also noticed that when this happens, if I push the table in the direction of the "stick" it will move and recover about .005" of that slop. I did measure the end of the ballscrew for axial movement and there is none. There is also no movement of the ballnut mount. And, I can see the ballscrew turn 1 click at a time when I jog .001". I think this is about as good as I'm going to get and it should be fine to get me through this batch of reels I have to make.

The X axis was easier to adjust, again very light tension from the adjustment screws did the trick.

Both ball nuts were packed with oversized bearings and are smooth but tight. Probably the best ballnut-ballscrew fit I've experienced on all my machines.

And Grizzly did call back "that's the way they are - provided thicker and longer so you have to thin them down by grinding and then fit to your machine"

regards,
Michael


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