Square vs dovetail ways?

wrmiller

wrmiller

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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
 
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
Click to expand...

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
 
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.
 
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
 
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
Click to expand...

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

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