Re: [atlas_craftsman] Re: Single tooth dog clutch?
Ah, yes, you are right Anthony,
I was responding to Charlie Gallo's one liner
snip> Except with the dog clutch, the lathe never stops, the lead screw reverses while the lathe is running...... and then I went and muddied the water with the reference to Hardinge (my bad)
I never did see the finished published article by Gray Meek, only some of the info he released to the Myford group, when he was developing it. Don't have any literature to hand on picking up the thread and maintaining the registration ??
This is the second shirt sleeve day this year in the UK, hope it lasts.
Keep the revs up jb
--- On Wed, 10/4/13, anthrhodes@... <anthrhodes@...> wrote:
From: anthrhodes@... <anthrhodes@...>
Subject: [atlas_craftsman] Re: Single tooth dog clutch?
Date: Wednesday, 10 April, 2013, 17:50JB,Ah, but it isn't a copy of the Hendey unit. It reverses like the Hendey unit but, because it comes after all the gear changes, it won't pick up all threads as does the Hendey unit. Remember the Real Estate motto, Location, Location, Location! Read up on the application of single tooth dog clutches for picking up threads during screw cutting.AnthonyBerkeley, Calif.************************************************In a message dated Wed Apr 10, 2013 4:28 am (PDT), john baird writes:
Hi Charlie, Atlas had a dog clutch system of reversing the leadscrew, while under power, on early versions, it was a copy of the Hendey system from the 1800s, using three bevel gears or two bevels and a crown, some found it prone to failure, but I think that was caused by a lack of sympathy for the zamak gears. Certainly simpler and neater than the Hardinge system.
- Doc,You'll probably notice that I'm not Charles.I'm attaching a couple of photos of the Hendey reversing gear which is covered by US patent #519924 issued to Wendell P. Norton, the same guy who is particularly well known for his QC gearbox patent. The first photo appears to be looking up into the bottom of the headstock, you'll notice the V-way to align it with the lathe bed. Feed from the spindle comes down to the left hand gear with a 1:1 ratio, passes through the casting to the left bevel, then by way of the bottom bevel to the right bevel. There is a coaxial shaft running through all of this to which the sliding dog between the bevels is keyed. The left and right bevels have a single dog facing each other and the sliding selector has a single dog on each face. You will see these details in the second photo which shows the components disassembled.Selector in the middle no drive, selector to the left connects to left bevel so coaxial shaft turns same direction as the spur gear, selector to the right connects to right bevel so coaxial shaft turns opposite of spur gear. In operation, engage split nuts and LEAVE THEM CLOSED! With spindle turning select direction with whichever bevel is appropriate. When you get to the end of the cutting pass select neutral feed, the traverse will stop and the cutter will cut its own relief groove. Retract cutter, select other bevel, and the carriage will traverse back to wherever you wish to stop. Put on cut for next pass, select first bevel and repeat sequence until you've completed the thread or other machining sequence.Because the selector has a single dog to engage with the 1:1 gear it will always have the same relationship with the spindle as if you had never disconnected it. This is the same as leaving the gears and split nut engaged and reversing the motor for return to the next cut. You do have to be careful to select neutral at exactly the right time so that it completes the cutting pass but doesn't overshoot. Either one of those would find the cutter suddenly cutting deeper than you wanted it to do. It is common for lathes set up to operate in this way to have a disengagement device to kick the gear into neutral at the right time.While the details of the reversing mechanism are different for the Hardinge, the large Rivett, and a number of other lathes of which I know that use this principle, the principle is the same for all of them. Graham Meeks' design also uses this principle. The Atlas bevel reversing gear doesn't work this way because the intervening gears between the spindle amd reverser prevent assurance of picking up the same relationship with the spindle.AnthonyBerkeley, Calif.In a message dated Wed Apr 10, 2013 1:54 pm (PDT), email@example.com writes:
help me out charles
i am not familiar w/the hendy or any other dog clutchfeed ,but if i throw in the reverse tumbler on either my 6x18 or 12x36 crftsmn while running the spindle, there will be teeth spitting everywhere.. ...only way this cud be is if the reverse gearing is past the opened up dog clutch ????
- On 4/10/2013 Doc wrote:
> help me out charlesActually, the dog clutch generally goes in the same place as the tumbler, and really has TWO dog clutches - one with the extra idler (reverse) and one without (forward) (or visaversa). Throw the dog clutch one way, and the carriage moves towards the headstock, the other away. The fun comes in, you set it up so it gets to the end of the thread, it stops, throw the lever, it moves away, throw the lever, it moves back, always in sync. SOME have a neutral setting in the middle (most), although I've heard of ones that don't, then you can (almost) totally automate the thread, particularly if you have a quick retract cross slide, set your first cut amount, start the thread, when it gets to the end, retract the quick retract, and dial in the next cut amount while the carriage moves away, and when it is about to feed again, set the quick retract back. All nice, simple, and you can even do metric threads
> i am not familiar w/the hendy or any other dog clutchfeed ,but
> if i throw in the reverse tumbler on either my 6x18 or 12x36
> crftsmn while running the spindle, there will be teeth spitting
> everywhere.....only way this cud be is if the reverse gearing is
> past the opened up dog clutch ????
> best wishes