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Thread: Lathe/grinder dog name?
02-04-2009, 09:40 AM #1
Lathe/grinder dog name?
Is there a particular name to call the ones with the two ears other than one of the above names?
02-04-2009, 10:03 AM #2
B&S grinding dogs. Originally came in this cast iron holder with the various sizes of square female recess wrenches for the set screws.
02-04-2009, 10:10 AM #3
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.
02-06-2009, 12:21 AM #4
"Fido" ??? <ducking and running!>
I got one for ya. Send me a PM.
02-06-2009, 09:07 AM #5
Sent you a PM.
02-06-2009, 05:59 PM #6
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?
02-06-2009, 06:07 PM #7
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.
02-06-2009, 07:03 PM #8
They are also known as carriers.
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?
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.
02-06-2009, 07:38 PM #9Why does a "grinding" dog need the the two straight legs
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)
02-06-2009, 08:02 PM #10
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.
02-06-2009, 10:04 PM #11But that doesn't really explain why these dogs have a forked end does it?
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.
02-06-2009, 10:57 PM #12
So, there's no real profound technical reason......B & S just wanted to be different on their grinders. And sell more dogs! I understand now....
02-07-2009, 12:05 AM #13
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.