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Lathe/grinder dog name?

B&S grinding dogs. Originally came in this cast iron holder with the various sizes of square female recess wrenches for the set screws.

DCP_0940.jpg


John Oder
 
John,

That is what I have with my B&S #13 Universal, except mine only has two wrenchs and less dogs since it only swings about 8 inches. I am missing some of the smaller dogs from the 1" range & down and wanted to know what to call them.

Roger
 
Okay, I'll be the dummy who has to ask: Why does a "grinding" dog need the the two straight legs, as opposed to the usual single bent leg on a "lathe" dog? What is used to drive it?
 
My guess would be that's so you can use a regular chuck rather than a faceplate to drive it. The two legs would straddle the jaw. You'd still use a dead center in the chuck.
 
They are also known as carriers.
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As to why they are double ended - I have wondered about this myself in the past. Possibly it is to balance the carrier/dog? They are commonly used when grinding between two dead (stationary) centres on a cylindrical grinder when absolute precision is required, it would remove any possible inbalance in this operation.

Another possibility I mentioned on the forum a while back didn't get much support - but I'll try again :)

Joseph Clement invented the double driver (the Clement driver) for turning between centres. Not sure when, but sometime around 1820-30.

"When turning work between centres, it is gripped by a carrier, the peg of which is driven by a pin on the catch plate screwed to the lathe mandrel. The effect of having a single point of contact was to bend the work at the point it met the tool tip, a result of the twisting action of the force applied. Clement overcame this by designing a double driver with two pins, which equalised the forces tending to make the lathe cut eccentrically".

Taken from Henry Maudslay & the Pioneers of the Machine Age (various authors). A diagram of Clement's driver is included in this book. What say ye?

:o edit: oops, must be day dreaming - answering an unasked question....ignore the above comments, thought we were looking at the forked but double-ended type commonly found around here for grinding. :o
 
Why does a "grinding" dog need the the two straight legs

Simple. Forget face plates with slots or formal dog driver plates you put on the spindle nose. If a plain cylindrical there is no taking off and putting on things, there is just the driver plate with a stud to fit in between the two legs of the dog. Usually the stud is positionable radially to accommodate differing size dogs.

If a Universal grinder, you would have a choice of spindle nose tooling for the workhead - a dog driver capable of revolving around a non rotating center, a grinding chuck capable of being rotated by a revolving work head spindle and possibly a face plate and/or rotary magnetic chuck, both revolving with the work head spindle.

If you are grinding between centers in the Universal, ordinarily the dog driver assembly is in place and the work head spindle is prevented from turning.

(at least on this 1947 B&S)

http://smg.photobucket.com/albums/v337/johnoder/BS 4 Grinder/

John Oder
 
John,

But that doesn't really explain why these dogs have a forked end does it? A single leg would still do the same thing on a grinder - however I have never seen one so equippped.

Sometimes when I have a part that needs grinding all in one operation, i.e. no place to put the dog/carrier, I tap the end face of the workpiece before hardening, then screw/lock nut in a piece of threaded rod and bend it into the shape required to pick up the driving pin. No fork required.
 
But that doesn't really explain why these dogs have a forked end does it?

In my mind an explanation would be that "places have been switched"

Instead of a single tail in a slot, we have a drive stud in a fork.

Yes, we know other ways work, but these were not part of the machine tool designer's intent for these details before us.

Single tails were intended to be captured in the dog plate's slot, even though they work fine, or seem to, resting on a chuck jaw.:)

Here is one of the fork tails in use. I could have also bent some sheet metal around, attached it to the drive stud, and let it drive the work by fitting between the bevel gear teeth, but I did not.

http://img.photobucket.com/albums/v.../Older One/Rework Double Bevel/Dcp_1147sm.jpg

John Oder
 
Roger:

While grinding dog is the more popular term for these two lug dogs, I have to agree
with Peter S., I have always called them carriers. I prefer this style of dog instead of
the straight or bent tail single lug dog. The double lug carrier has one major advantage
over the single lug type, the ability to remove all backlash between the driving pin and
the carrier. Even if the pin is smaller than the narrowest space between the lugs, a
snug fitting bushing fitted to the pin solves the problem. The pin can be nicely slid down
into the "V", making perfect contact. When properly adjusted, there is no stain on the
center or any backlash. I use this type of carrier for all of my gear cutting and grinding
work were any lost motion could cause problems. They are also very handy for turning
between centers in a lathe.

Hendeyman
 
cawysong, I don't know the original source, but the phrase "dog the hatch", where the dogs are lugs which engage with the hatch frame to lock it shut, clearly comes from the same source.
 
cawysong, I don't know the original source, but the phrase "dog the hatch", where the dogs are lugs which engage with the hatch frame to lock it shut, clearly comes from the same source.

OK, for me that adds intrigue...and confusion. Is the "hatch" being referred to a hatch on a ship?
 
I don’t know about the origin of the term but there is an explanation about some of the types and comparison of the action on the work piece by dogs with and without bent tails.
It goes on for a few pages starting here
International Library of Technology: A Series of Textbooks for Persons Engaged in the ... : International Textbook Company : Free Download, Borrow, and Streaming : Internet Archive
On my computer all the pages don’t display the same size but I can make it readable but it may be different on other more up to date devices.
There is another discussion here about the drivers used on grinders in another book of the same series in the chapter on grinding .
International Library of Technology : International Textbook Company : Free Download, Borrow, and Streaming : Internet Archive
Jim
 
Does the origin of the word 'dog' in machinery have to with teeth like a dog clutch on a lathe?
 
I am pretty sure that dogs on a clutch, dogs as in locking lugs, and dogs as in arbor drivers all stem from the same original usage. They all share the nature of being stout projections that engage with something else to provide (or prevent) motion.
 
I think Clement was a real perfectionist/stickler for detail. I've done enough work on centres,some of it slender. I have not detected bend(due to driver)when testing between dead centres.
 








 
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