# Making a tapered gib



## T. J. (Oct 25, 2021)

I need to make a tapered gib for the cross slide of an Enco lathe and I could use some advice from someone who’s done this. I’ve got the basic process and work holding problems figured out (I think). My question has to do with how much extra material to allow for fitting the gib. The length of the finished gib will be 12.25”. It is .355” on the thick end and 0.213” on the thin end (0.0116” taper per inch). The dovetail angle is 60 degrees. 

I’ve studied the chapter in the Connelly book where he discussed gib construction. In the example he gives, he suggests making the gib 3” longer than it’s finished length. I understand this - when scraping the gib, you’re going to be removing material and it will insert farther into the cross slide. When you’re done, you cut off the excess on each end.

This is what I don’t get. He goes on to suggest that you should add 1 - 2 times the taper per inch (0.020” in his example, 0.023” for mine) of thickness to the machined gib to allow for fitting. That’s a ton of material to remove by scraping!  Why this extra safety margin?  I’m inclined to make this margin much smaller (say 0.001-0.002”), but I want to make sure I’m now missing something. What do y’all think?


----------



## benmychree (Oct 25, 2021)

Ask Rich King. But I would allow the 3" extra length with the gib starting  to pass trough the small end or not quite there.  The gib will undoubtedly have some bend in it after machining, so likely there will be plenty to scrape before it fits correctly.


----------



## rabler (Oct 25, 2021)

First add three inches.  Does this three inches get added to the short end or the long end?  Because adding 1-2 times the taper/inch may not have to be scraped off if you just shift the gib 1-2 inches.  Could this be interpreted as shooting for the excess to be on fatter side? Just trying to think it through, I’m an interested neophyte.


----------



## T. J. (Oct 25, 2021)

rabler said:


> Does this three inches get added to the short end or the long end?


This would be added to the thicker end


----------



## matthewsx (Oct 25, 2021)

I needed one for the cross slide of my Samson lathe and just found one from a similar Grizzly machine. It works great, I suppose give time and tooling I could have made one myself but I was happy to shell out the $12 + shipping to have one sent to my door.

This is the one I got, I plan to scrape it at some point and may need to start with a new one but I know where to get it.









						Parts for 12" x 24" Gear-Head, Cam Lock Spindle, Lathe at Grizzly.com
					

Grizzly Industrial, Inc. is a national retail and internet company providing a wide variety of high-quality woodworking and metalworking machinery, power tools, hand tools and accessories.  By selling directly to end users we provide the best quality products at the best price to professionals...




					www.grizzly.com
				




John


----------



## woodchucker (Oct 25, 2021)

are you milling it or grinding it?
I would add the length like you say to the larger end since  you are always looking to tighten it, and you can always remove but can't add.
Next, when you say add it to the taper per inch... I think he meant to the overall thickness in general, not changing the angle..

if you don't have a surface grinder, you're going to be working hard to scrape it. Do you have a magnetic sine plate?


----------



## T. J. (Oct 26, 2021)

woodchucker said:


> are you milling it or grinding it?
> I would add the length like you say to the larger end since  you are always looking to tighten it, and you can always remove but can't add.
> Next, when you say add it to the taper per inch... I think he meant to the overall thickness in general, not changing the angle..
> 
> if you don't have a surface grinder, you're going to be working hard to scrape it. Do you have a magnetic sine plate?


I’ll be milling it - I don’t have a surface grinder. Yes, the thickness would be added over the entire length, keeping the taper angle the same. He was just using the amount of taper as a rule of thumb for how much thickness to add.


----------



## ErichKeane (Oct 26, 2021)

So as you've figured, there are 2 ways to make sure you don't make your gib too 'thin' initially to get it prepped.  The first is to make it 'thicker'.  The second is to make it longer on the thicker side.  

The former is 'cheaper', the latter is 'easier' to get it fine-tuned.  With the former, you have to keep taking material until it fits perfectly, and if you go even a little too far, you scrap the part.  Making it too long means you scrape/etc until it 'fits', then just cut off the excess.


----------



## Richard King 2 (Oct 27, 2021)

He and I spoke or wrote on my FB forum.  I suggested he check the taper with 2  feeler gage sets at the same time instead of telescope gages.  I also found a web-site that sell manuals.  They might sell parts too.  That's a great idea Matthew


----------



## Janderso (Oct 27, 2021)

It seems to me Kieth Rucker made one for someone.
An interesting job. Pretty complex.
I would think a compound, magnetic sine and a surface grinder would be in the tool list.


----------



## Larry$ (Oct 27, 2021)

Janderso said:


> compound, magnetic sine and a surface grinder would be in the tool list.


I'd like to make a replacement gib for my cold saw. Everyone recommends cast iron. As thin as a gib is, it seems like I'd break the cast iron very easily. Someday when I feel like punishing myself I'm just going to make one on the mill, in steel. Put some oil channels in it and call it good for a 50 year old cold saw. It currently has a plastic one that some previous owner made. It doesn't move as freely as I'd like.


----------



## benmychree (Oct 27, 2021)

Janderso said:


> It seems to me Kieth Rucker made one for someone.
> An interesting job. Pretty complex.
> I would think a compound, magnetic sine and a surface grinder would be in the tool list.


One can also just shim up the magnetic chuck on the surface grinder on one end.  I made a gib for a Bridgeport type mill once for a customer, and did it with my G&E universal shaper, I was able to use the old gib to back up the new one while doing the taper on the top and bottom.


----------



## benmychree (Oct 27, 2021)

benmychree said:


> One can also just shim up the magnetic chuck on the surface grinder on one end.  I made a gib for a Bridgeport type mill once for a customer, and did it with my G&E universal shaper, I was able to use the old gib to back up the new one while doing the taper on the top and bottom.


I have seen steel used for thin gibs, particularly on parts that don't see a lot of motion.


----------



## Janderso (Oct 27, 2021)

benmychree said:


> One can also just shim up the magnetic chuck on the surface grinder on one end.  I made a gib for a Bridgeport type mill once for a customer, and did it with my G&E universal shaper, I was able to use the old gib to back up the new one while doing the taper on the top and bottom.


A shaper would be perfect for this application.
Then to the surface plate and scraper table.


----------



## Richard King 2 (Oct 29, 2021)

I told him that and I just didn't want to repeat it here and type it again.   He maybe smart to have John York make it for him as John is a master machinist and engineer.


----------



## Richard King 2 (Nov 1, 2021)

You told me you were going to start making it last weekend?  How is it going.   Once you mill it, you will need to scrape both sides flat to at least 5 PPI before fitting it.


----------



## T. J. (Nov 1, 2021)

Welll, I got started and then got called away for a work emergency (that’s about normal for me). But here are some pics the progress so far.

To catch everyone here up, Richard has been giving me some advise over on his FB group. He suggested I use the technique illustrated in this thread on PM: https://www.practicalmachinist.com/...ag-12-restoration-progress-237940/index3.html

The author formed the mating sides (the ‘flat’ side and the ‘tapered’ side) by side milling. The reason Richard suggested this method is that the tables on old mills tend to sag at the ends of their travel. (My mill definitely fits into the “old, worn out” category!)
With a long gib such as mine, this would be a problem if I was to form the mating sides by end milling.

The material I am using is a bar of extruded gray iron about 1-1/4” thick and 3-1/4” wide. I cut it to 15” long, which is how long I decided to make the gib. I then clamped it to the table and cleaned up one wide face with a fly cutter. 
	

		
			
		

		
	



Out of curiosity, after milling I put the bar on my surface plate. It hinges exactly in the middle and I’m able to insert a 0.002” feeler gage under both ends. That would definitely be a problem if I was forming the taper by end milling!

Next, I turned it over and clamped it to some 123 blocks to clean up one narrow side.



That’s when I had to quit. My shop time is going to be hit or miss for the next week, but I’ll post updates on my progress when I can.


----------



## Janderso (Nov 1, 2021)

Richard King 2 said:


> He maybe smart to have John York make it for him as John is a master machinist and engineer.


Challenge.....


----------



## Richard King 2 (Nov 1, 2021)

TJ, it looks good and .002 is acceptable  on and old mill.   You can scrape that off.  I can't wait for some more progress.  Thanks for sharing.  
Rich


----------



## Janderso (Nov 2, 2021)

Richard King 2 said:


> TJ, it looks good and .002 is acceptable  on and old mill.   You can scrape that off.  I can't wait for some more progress.  Thanks for sharing.
> Rich


.002" to scrape reminded me of an aha moment at Richard's class.
I was scraping a large angle plate, chasing my tail. It finally occurred to me, you have to scrape to the point where the lows become the highs.
In Richard's handout, (I don't have it with me) there is terminology for this.
If you just scrape the high points, deburr, clean, blue, hinge then rub to find you get to do it all over again and never get any closer to completion.
I learned that lesson!
Did I get it right Rich? I haven't scraped since the class. I need to change this.


----------



## Richard King 2 (Nov 2, 2021)

Yes.....You Got Mad at it and yourself wasting so much time.  It's a learning curve.   I call it step scraping and Blind scraping.  Paint on the yellow highlighter and figure out how many times you need to step it down. Most scrape of a minimum of .0002" per scrape and if it were off .002" You could divide the gib into  5 steps -  the ,002 end would need to be blind scraped 10 times and the thinnest end No times.


----------



## T. J. (Nov 21, 2021)

Well, it’s been a hectic couple weeks for me, but I finally got some shop time to work on the gib. This was my setup on the mill. I made two stops from some drill rod and indicated them to be in line with the long axis of the table. Then clamped the finished edge of my stick to them with a stack of feeler gauges in one end to produce the correct angle (kinda like a sine bar).
	

		
			
		

		
	




After clamping it down to the table, I removed the Kant twist clamps and milled a groove to an adequate depth.
	

		
			
		

		
	





I then brought the gib to final thickness by side milling and freed it with a slitting saw.
	

		
			
		

		
	




I’m pretty happy with it so far. It did acquire a slight bow (0.003”) as measured with feeler gauges on the surface plate.
	

		
			
		

		
	





I won’t be surprised if I get some more warpage when I mill the 60 degree edges. My plan is to use a dovetail cutter like Kieth Rucker did in one of his recent videos on his Monarch restoration. I’m waiting on some tooling to arrive, so no more progress for now.


----------



## benmychree (Nov 21, 2021)

It





T. J. said:


> Well, it’s been a hectic couple weeks for me, but I finally got some shop time to work on the gib. This was my setup on the mill. I made two stops from some drill rod and indicated them to be in line with the long axis of the table. Then clamped the finished edge of my stick to them with a stack of feeler gauges in one end to produce the correct angle (kinda like a sine bar).
> 
> 
> 
> ...


 It is possible to straighten that gib as taught by Rich King, by carefully hammering on it with a soft hammer while resting on a couple of blocks on the ends, or just scrape it out, and likely as you scrape it, it will likely move around and need straightening.  Scraping can induce some bending by sort of a peening effect, sometimes it can be stress relieved by "ringing" the part while suspended loosely by a cord or whatever, I have done it, and it definitely works.


----------



## woodchucker (Nov 21, 2021)

benmychree said:


> It It is possible to straighten that gib as taught by Rich King, by carefully hammering on it with a soft hammer while resting on a couple of blocks on the ends, or just scrape it out, and likely as you scrape it, it will likely move around and need straightening.  Scraping can induce some bending by sort of a peening effect, sometimes it can be stress relieved by "ringing" the part while suspended loosely by a cord or whatever, I have done it, and it definitely works.


But.. is it necessary to straighten the bow? it should flatten out when it's in the slide. .003 is just a spring, not an out of flat or rise (excess material) at this point, right?


----------



## benmychree (Nov 21, 2021)

Leaving the bow in is not a good idea, and you could not rely on a perfect fit on the taper without scraping; a few thousandths do matter in fitting a tapered gib.


----------



## Richard King 2 (Nov 21, 2021)

benmychree said:


> It It is possible to straighten that gib as taught by Rich King, by carefully hammering on it with a soft hammer while resting on a couple of blocks on the ends, or just scrape it out, and likely as you scrape it, it will likely move around and need straightening.  Scraping can induce some bending by sort of a peening effect, sometimes it can be stress relieved by "ringing" the part while suspended loosely by a cord or whatever, I have done it, and it definitely works.


John, I never hit a gib with a soft blow hammer  You must be thinking of someone else.   Scroll to 5:30 on this You Tube show and it  shows how I do it.


----------



## benmychree (Nov 21, 2021)

Richard King 2 said:


> John, I never hit a gib with a soft blow hammer  You must be thinking of someone else.   Scroll to 5:30 on this You Tube show and it  shows how I do it.


Gotcha, Rich; now I know the RIGHT way to straighten a gib, thanks for the correction!
John


----------



## T. J. (Dec 11, 2021)

More progress - finally!  As I mentioned in my last post, I wanted to use a dovetail cutter to mill the angles on the short sides of the gib. I’ve had a pretty nice dovetail cutter in my toolbox for a while, but never used it since it has a 1” arbor. We’ll I figured this was the job for it, so I ordered a 1” R8 end mill holder from Shars the week before Thanksgiving. After 10 days of waiting on USPS to deliver it, I contacted Shars about it and the post office told them it was lost. They then sent me a replacement via FedEx. As luck would have it, both items showed up on the same day this week. 

So, back to work. Here are some pics of my setup.
The fixture:


Milling the first side:


Cutting a dovetail in the jig:


Milling the second side:


The finished product:


Here is the video Keith Rucker made on this process. He does a much better job of explaining it than I could do in writing.





After milling, I checked the straightness. The bow had actually improved to .001”. I successfully straightened it to within less than .0005” using Richard’s method. I am exceptionally pleased with the fit of the gib as milled. With the gib in place, I can detect no side-to-side play in the cross slide with an indicator. Now, on to scraping!

PS: My apologies for the poorly framed photos. I’ve managed to smear the main camera lens on my phone with something that won’t come off. These photos were taken with the forward facing “selfie” camera


----------



## Winegrower (Dec 11, 2021)

I just finished tearing the Takisawa apron apart to fix the oil pump, and examined the cross slide gib.   I wonder if it really needs to be extremely flat, since there are a bunch of gib screws for adjustment that could easily take some slight bow out.


----------



## Richard King 2 (Dec 12, 2021)

Winegrower, Most machines use a taper gib with two  retaining screws on each end to keep it from sliding in and out.  I suspect your gib is flat and it has several dog point set-screws holding it in from the side casting.  If the gib is not worn on the ends as all gibs are because the dirt slides under the ends first you can leave the middle side set screws looser then the ends.  But if you have a tapered gib, you have to scrape it and I would scrape the center 40% lower then the ends about .001"  -  why?  where does the dirt get in and wear the gib first?  You also need to leave the gib loose at least .0005"  when your done so you get a .00025 film of way oil on it to lube it.  If T J's machine ways where the gib rides against the section is worn and when he moves the slide to the ends it will bind up if he sets the gib in the worn middle.  So he has to set the clearance on the ends of the way.


----------

