# Square vs dovetail ways?



## wrmiller

So which is better, and why? Or do each serve a purpose in a specific application? 

I'm considering making a more robust compound and would like a tapered gib. Gib for square way seems doable. Not sure I can get my ears wrapped around making one for dovetail ways. As for the dovetails I just assume you cut one side on a small angle. TIA. 

Bill


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## Bill C.

wrmiller19 said:


> So which is better, and why? Or do each serve a purpose in a specific application?
> 
> I'm considering making a more robust compound and would like a tapered gib. Gib for square way seems doable. Not sure I can get my ears wrapped around making one for dovetail ways. As for the dovetails I just assume you cut one side on a small angle. TIA.
> 
> Bill



I guess you could tilt the parts to make a dovetail.  Most would use a pre-ground dovetail cutter and leave the parts flat. Either way would work.  Good luck


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## David Kirtley

Neither is "better." Just different trade-offs.  Boxed ways need more parts for full constraint.  Dovetailed ways have fewer parts. You have to remove material for the dovetails so to make them equally strong, they have to be larger than boxed ways. Dovetails have fixed alignment. Boxed ways can be more adjustable. Boxed ways can be an advantage to home building as you can make square edges with relative ease with simple tools. Can be especially important for long pieces that might be too long to fit for machining. Boxed ways can have more friction due to more contact area. More contact area means better distribution of forces.

I believe the fixed alignment has been the main reason for using dovetails in machinery to be preferred. Time spent tinkering on machine adjustments is not making anyone any money. 

The tapers for adjustable gibs and such for either boxed ways or dovetailed ways is about the same. It is not that critical as the angles are complementary. machine the taper on one piece and the other piece ends up a square cut.  I made tapered gibs for my lathe and I milled the angle in the gib holder. When I put the mating piece on that angle, I machined the other side flat.


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## wrmiller

How do  you machine the taper on a dovetail? Just cut its mating surface on an angle that will also be cut on the gib? (did I ask that right?)

How would you machine the gib?

Bill


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## David Kirtley

wrmiller19 said:


> How do  you machine the taper on a dovetail? Just cut its mating surface on an angle that will also be cut on the gib? (did I ask that right?)
> 
> How would you machine the gib?
> 
> Bill



You cut the first dovetail, then rotate the part to cut the tapered dovetail. 

Cut the first side of the gib to fit the tapered dovetail in straight stock. 

Position the gib at the taper angle. Cut the second side of the gib.

You can use a fixture to hold the gib or the actual part. Last one I made, I stuck the gib onto the part with superglue to cut the second side.


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## Richard King

If you look at the high dollar machines they use a dovetail.  The cheap ones use box ways.  As Senna said the taper gib not only takes out the side to side wear it pulls down to remove the lift or up and down movement.  David is also correct on the number of parts needed.  You should have asked this question in the Machine restoration forum as we have several machine rebuilder in there to help and a lot of photo's too.  A friend of mine on another forum who unfortunatly just passed away has a great thread about making gibs.  I find usually gibs are tapered about .008" per inch.  The key to a taper gib is the top and bottom clearance is angled too on the gib.  If my memory serves me right Rich in the UK shows how he made a tapered gib in his thread on the machine scraping forum.   I would think if you bought the book "Machine Tool Reconditioning"  Look it up on Amizon where you can find new and used copies.  It was written by Edward Connelly.  You would find a lot of info on making a tapered gib.     Because of the rules on here we can't share a link to the post on the other forum. If you PM me with your email address and I will try to send you  a link to that thread.   Rich


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## wrmiller

PM sent, thanks. Also, if this thread is in the wrong forum, my apologies and feel free to move it.

Bill


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## Richard King

Thead moved by Richard King 10/21/13 1:55.  From General Machining questions to Machine restoration and Scraping forum.


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## george wilson

To make a tapered gib,I would also mill one side at an angle,then straighten it and super glue in a prepared gib and mill both sides straight. Mild heating will melt the glue,or you can soak it in acetone for hours if you don't want to heat the work. The acetone will take longer,but will melt the glue.


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## Bill Gruby

I believe you would have to recut one side of the existing dovetail, but yes it could be done

 "Billy G"


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## wrmiller

bill said:


> I can see the advantage of tapered gibs. My inexpensive Asian tool has  dovetails with flat gibs held in place with screws. The adjustment of  the pressure on the gibs
> greatly affects backlash. Is it possible to convert to a tapered gib? and how might this be accomplished?
> 
> Thanks



I've been thinking along this line as well. I 'assume' I would just have to take one of the two pieces comprising the dovetail (like my lathe compound) and re-cut one side to a taper. Gross oversimplification, but you get the idea. 

Bill


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## DMS

If you re-cut the dovetails to take a tapered gib, just make sure you cut the right half. Also, if you are doing it in a really small machine (like a 7x mini lathe) be aware that you don't have a lot of material to work with, so be careful about depth of cut. You will also need 2 adjusting screws on the front and back of the gib to adjust it. If you have access to a machine with tapered gibs, it is instructive to pull the gib out, examine it, replace, and re-adjust. I didn't really "get" how they worked until I did this with my mill, but afterwards it was like "duh".

I have been under the impression that box ways were the "better" deal, and were only used on higher end machines. Course, I have never seen a machine with box ways in real life.


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## wrmiller

DMS said:


> If you re-cut the dovetails to take a tapered gib, just make sure you cut the right half. Also, if you are doing it in a really small machine (like a 7x mini lathe) be aware that you don't have a lot of material to work with, so be careful about depth of cut. You will also need 2 adjusting screws on the front and back of the gib to adjust it. If you have access to a machine with tapered gibs, it is instructive to pull the gib out, examine it, replace, and re-adjust. I didn't really "get" how they worked until I did this with my mill, but afterwards it was like "duh".
> 
> I have been under the impression that box ways were the "better" deal, and were only used on higher end machines. Course, I have never seen a machine with box ways in real life.



I have a bit more material on my SB, but thanks, point taken with respect to depth of cut.

I also was of the same impression as you about square ways, as I've only seen them on the bigger BP clones like the 10x50. Maybe they're primary purpose is to support the extra weight these machines might see?


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## Richard King

bill said:


> I can see the advantage of tapered gibs. My inexpensive Asian tool has  dovetails with flat gibs held in place with screws. The adjustment of  the pressure on the gibs
> greatly affects backlash. Is it possible to convert to a tapered gib? and how might this be accomplished?
> 
> Thanks



A number of years ago I was rebuilding a Goss & Deleeuw Machine it was a cam fed special machine that had a turret and 3 boxed way slides with spindle heads.  Anyway the customer asked to convert it to tapered gibs to make it faster to adjust them when they wore.  These machines were in a company that made water facets out of bronze and they were constantly filthy with coolant and chips.  So the gibs needed to be adjusted a lot more then and these square gibs were a pain to get at from the sides where with a tapered gib usually has one adjustment screw on the back side and the screw fits in a notch or has a L shaped end with a hole throw it and a jam nut on each side of the L to keep it from moving.  Other's have a screw on each end, but if the machine has lots of swarf adjusting the front gib screw can be a pain.   
We had to widen the opening in the head stock slide way that rode on the base box way that was flame hardened (grinding the base was a pain and another story sometime).  I bought some Dura-Bar and Then made an insert with one side tapered and the other straight to rest against the widened original surface.  We epoxied it and bolted in place usuing the original holes that had been the adjustment screws.  We made the taper in our Bridgeport with 3 Kurt vises mounted on the table and adjusted the taper using a dial indicator and made it .008" per inch taper.  I picked that number as I believe that's what Cinc. Centerless grinders use and it is another Heavy Duty casting machine that wears a lot.  We machined the insert in the same way.  We scraped the tapered insert face and the back (positive) of the gib to 5 PPI but flat to .0002" per foot as sit is what we call a static fit and  the riding surface of the gib to 20 PPI and flat .0002" per 12".  We also relieved the center of the riding side of the gib middle 40% .001" and cut oil grooves in it. 

 It was an interesting fix.  I hope that makes sense.  I am sorry no pictures anymore.  Just memories.  I would think one could use the same method to convert a lathe compound.  You might not need the tapered insert and only machine the slide tapered and have a wide gib.  If you did that then I would think you would either have to use a front and back adjustment screw or have a .032" sheet metal support under the front side of the gib to keep it from tipping down.   Remember what your dad said thought measure twice and cut once.  I would also draw up some plans before hand.  No guessing or in your mind blue print on this one I hope this helps.  Rich 

PS:  It's 2:45 AM over here and Im having a real pain sleeping.  I can't understand how some people can work swing  rotating shifts.  It would kill me.  :whacky:  LOL


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## David Kirtley

bill said:


> I can see the advantage of tapered gibs. My inexpensive Asian tool has  dovetails with flat gibs held in place with screws. The adjustment of  the pressure on the gibs
> greatly affects backlash. Is it possible to convert to a tapered gib? and how might this be accomplished?
> 
> Thanks



Depends on if there is enough material on the piece. I can't say that it would perform much better. The gib strips with screw adjusters on the dovetails do a pretty good job. I converted my saddle to tapered gibs just because the stock adjusters are awful and it is miserable to get to them to adjust. I have thought about putting some of the aftermarket brass gib strips on my cross slide and compound but I have somewhat sworn off modifying the lathe in order to actually spend some time making things -- for a while.


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## wrmiller

All good information folks. Thanks!


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## Richard King

bill said:


> I have some brass or bronze scrap, will gibs made of this perform better than the steel ones that came with the machine?. I scraped those flat and it seemed to make a difference but they didn't have any oil grooves. Will adding oil grooves make a difference? Would it be better to make the gibs of brass/bronze AND add add oil grooves?
> 
> Thanks




Sure....how else will the oil move down the gib?  be sure to slot the back of the gib so when you move it the oil will flow.  You should know this my friend as you are a sharp cookie     Use a diagonal oil grove where the end where the oil flow through the gib it drains down.  Some manufactures also bevel like a funnel the top of the gib and the oil runs down off the flats and into the oil gove.  be sure the groove does not open at the bottom edge as the oil will just drain out.   You can also 1/2 moon flake the gib or square cut it.   Rich


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## wrmiller

I bought some bearing bronze for just that. 

I think the plan is to model my new compound in aluminum to get a feel for cutting dovetails and tapers therein. The only dovetail cuts I've made previously was to mount a Bo-Mar rear sight on a 1911.

Bill


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## markknx

I have Box ways on my Jet 15 with a wedge gib. It seems to work nice and is easy enough to ajust, but at some point the wear for up and down would seem to have to be addressed. I am guessing that the only way to do this is by removing metal from the clamping plate where it meets the bottom of the way, or the bottom of the way itself. But as a begginer I am just guessing and hopping someone will tell me/us if this is right or if there is a different method.

Thanks,
Mark


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## 4GSR

Mark,

I'm not familiar with the Jet 15 mill.  But with what you are saying, most of the wear is in the upper mid range of the slide.  

Traditionally, this is common wear for most any slide arrangement rather it being dovetail or box ways. To remove this worn area is not a simple task of removing material from the clamping plate.  This just adds to the "slop" in the slide, which will show up in the machining process to some degree.

This is where scraping and re-fitting needs to happen.  I'm sure the slides on the Jet mill were originally ground and the slide portion was scraped and fitted to  the box member.  I won't go into detail here its rather a lengthy detailed subject on scraping and fitting here. There are many threads dealing with this subject that may be of interests if you want to lean in that direction.

If you feel comfortable removing or maybe shimming up the clamping plate with brass shim stock, this maybe your best bet for the time being until more is learned about machine restoration.


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## markknx

Ken,

Thanks for the imfo. Yes I just had mine apart and there is next to no wear in it right now, but when I had it apart the thought of how came to mine (as it dose with machanics) I was not talking of taking material away from the slide area as much as the clamping surface. But I see your point about also scraping the slide surface to true them back up. It would seem shims would either have to have tabs or be glued on.
Thanks again,
Mark


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