Screwcutting Simplified

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Graham Meek	13/03/2011 12:09:01
851 forum posts 163 photos	Screwcutting Simplified, photo courtesy Graham Meek. Hi KWIL Following several enquires after commenting on this unit in another posting I have posted the picture here. I apologise for the image quality but is taken from the original 35mm negative. This attachment puts the Myford in the same League as the Hardinge HLV Toolroom lathe and at a fraction of the cost when it comes to easy screwcutting. There is no stopping and starting of the motor when cutting metric threads, nor is there any reversal of the motor. The clasp nuts remain engaged through out the entire process, no need to worry about engagement at the right moment, Combined with the Retracting Toolholder or Retracting Topslide this unit makes a chore into a dream. Graham Edited By David Clark 1 on 17/05/2011 16:42:44
KWIL	13/03/2011 12:21:27
1436 forum posts 41 photos	Graham, Looks a nice piece of workmanship. Please explain operation and any other details. PM me if you want to go into great detail. K
Tony Pratt 1	13/03/2011 12:47:27
238 forum posts	Hi Graham, indeed a nice piece of work, I too would appreciate a run down on this as I feel another project coming on! Best wishes, Tony
ady	13/03/2011 13:15:53
615 forum posts 50 photos	A lovely and clever bit of kit that. Is it the dropdown lug on the left that connects this unit to the Retracting Toolholder or Topslide?
Graham Meek	13/03/2011 14:04:01
851 forum posts 163 photos	Hi All I designed this attachment back in the 1980's, it sits where the Tumbler reverse sits on the S7 and trips the leadscrew drive from left to right via stops which the operator sets at the rear of the carriage, which equates to the length of thread required. Once the lead screw clasp nuts are engaged they are left closed until the thread is finished. There is no need to stop and start the motor, merely retract the tool at the end of each pass, the pass itself controlled by a ball handle lever where the tumbler selector used to be. To go left push the lever to the left, the carriage moves to the left, the LH stop trips the drive , it returns the lever to the neutral position one then retracts the tool, and a flick the lever to the right, this reverses leadscrew rotation and again the lever returns to neutral via the RH stop, you then just put on another cut on and away to go, metric threads a doddle. The operation of the unit does only require a flick of the finger to engage and dependent on the pitch of the thread you can cut most threads at or around 200 RPM. I have had several emails following a previous posting so I thought I might put one picture on the forum. The attachment was extensively used by Neil Hemingway and Ken Swan, combined with the retracting topslide of GHT's screwcutting is made simple, it is exactly the same principle as used on the Hardinge HLV Toolroom lathe, considered to be a Rolls-Royce of its class. The original seed was sown by an article in ME by Martin Cleeve but his attachment meant you could no longer have the Countershaft Bracket in position, plus you had to dis-engage the clasp nuts and return the carriage my hand a predetermined number of Pitches to the start of the thread, then re-engage clasp nuts after each pass. The only modifications required to the lathe are a 2BA or M5 tapped hole in the rear lower left-hand corner of the Head stock casting and a slot to clear the operating lever in the change wheel guard. I do not approve of hacking about machine tools and it grieved me to have to do the above two mods, many options were tried but I could not escape these two. Best regards Graham
Anthony Rhodes	16/03/2011 16:51:51
80 forum posts 27 photos	Graham, Details are everything! I understand the Hardinge reversing mechanism but I'm having difficulty with your design, based on the one photo you've posted. It appears in your photo as if the three gears on your attachment are all meshed together which would prevent any of them from rotating. Also, of course, preventing the spindle from rotating and any gears meshed below your attachment from rotating. Please clarify this matter as it seems likely that I'm missing something. Whatever is happening in the gears, I see your controls. Nicely arranged. Move the ball handle in the direction of desired motion. Drop link on the back of the spindle on which the ball lever operates to trip the gears at the desired point of traverse. Not certain if your trip gear is functional in both directions, although it could be made so. Any possibility of getting drawings, or even sketches, of your design? I don't have a Myford but the principal should be adaptable to many machines. This concept greatly simplifies screw cutting, especially for odd pitches which are not native to the leadscrew pitch system. Please contact me directly. Anthony
Tony Pratt 1	16/03/2011 17:04:48
238 forum posts	Hi Anthony, looking closely at the photo, it appears the top R/H gear is in fact not in mesh with the bottom gear. Tony
Anthony Rhodes	16/03/2011 17:32:08
80 forum posts 27 photos	Tony, Maybe you can clarify it for me. What is the gear train for forward and what is the gear train for reverse? How does the mechanism switch from one to the other? I would presume forward, spindle drives top-right drive silver. Reverse, spindle drives t0p-right drives back drives silver. I don't see ho these configurations can be realized. Additionally, for the Hardinge-style reversing mechanism the gear teeth must never be disengaged during the entire threading process. In the photo, if my suppositions are correct, I don't see how to shift between the two modes I described when changing from three gear axes (spindle - top-right - silver) to adding the fourth gear axis. Any help sorting this out? Anthony
Tony Pratt 1	16/03/2011 17:45:11
238 forum posts	Anthony, I am only a very interested bystander on this one and I cannot really help you[if only I could!] I was hoping for some sort of drawings from the OP like many others but we have to respect the decision not to elaborate further on his neat piece of work. Tony
KWIL	16/03/2011 18:53:19
1436 forum posts 41 photos	I think a little patience will be rewarded in due course.
Graham Meek	16/03/2011 20:17:28
851 forum posts 163 photos	Hi all, Once again my apologies for not responding earlier,working for the NHS demands an early 5 am start, and as some of you know I cannot comment during the day, I finished tonight at 6.00 and this is the first opportunity to answer your queries. Tony, Thanks for stepping in and doing what you can to explain things to Anthony. Anthony, Sorry for the delay, what you cannot see from this photo is a fourth gear exactly the same as the "Grey" one but it is obstructed by the Selector Fork. This photo was taken around 1985, this was one of a pair that I made for two people who supplied the Model Engineering fraternity parts for locomotives and parts for workshop equipment. In between these two gears is the selection medium or clutch, the peg you see in the lower gear is the single dog which takes its drive from the rear most bronze gear. the innermost gear being identical takes its drive from the uppermost bronze gear. These gears are in constant mesh, drive to the standard Myford gear comes out at the normal point via a sleeve which the "Grey" gear rotates on. If anyone purchased the worms for his VDH along with the castings then 10 to 1 they were made using this attachment. I am currently writing this up as an article, a more pressing article has delayed this as well as I need to perfect a new twist on an old way of gear cutting. Two units are again under construction in order to provide photo's for the article. I also have designed but not yet made although Emco very generously sent me their drawings of the Headstock, a version for my Maximat Super 11, not having another lathe I do not want to strip my own down only to find I have to put it back together to modify a part. Further my health over the past 5 years has left a lot to be desired, but fortunately I had good news on that front on Monday. Keith, Thanks for the last posting, you know my position a little better than most, Gray
Tony Pratt 1	16/03/2011 21:03:27
238 forum posts	Hi Graham, glad to hear you have received some positive news on your health! I am very interested to see how you cracked this problem in a practical way and will be a most avid reader of your article when it appears. Best wishes, Tony
Anthony Rhodes	17/03/2011 02:48:44
80 forum posts 27 photos	Graham, I've sent you a personal message which I hope adequately expresses my interest in this design. Sorry to hear of your health problems and glad for your possible good news regarding the same. Your health definitely comes first. Anthony
Anthony Rhodes	17/03/2011 06:10:11
80 forum posts 27 photos	Graham et al, Okay, I think I may have most of it. Double width gear meshed with spindle gear. Below and hidden, same axis as the gray gear, single width gear meshed with the above gear, used for feed towards headstock. Behind first gear, double width gear half-meshed with first gear. Below first gear, single width gear, same axis as hidden gear, meshed with rear double width gear but not with first gear, used for feed away from headstock. Hidden, selector mechanism keyed to shaft on which coaxial gears run. Hidden and front gears free to spin on shaft except when selected by dogs. Throw ball lever left moves dogs right for feed towards headstock. Throw ball lever right moves dogs left for feed away from headstock. Outer end of shaft on which dogs are mounted has key to serve as stud on which to mount first change gear. All gears same tooth count until you get to first change gear. Any thoughts? Anthony
KWIL	17/03/2011 09:12:35
1436 forum posts 41 photos	Anthony, Surely the double width gear is the rear most bronze gear, driven by the spindle gear via the upper most gear?
Anthony Rhodes	17/03/2011 09:39:40
80 forum posts 27 photos	KWIL, My error, I was over complicating the train. What I missed is there is a gear directly below the first gear which, in the photo supplied, doesn't show. My first impression was that the forward gear was hidden somewhere in the block. First gear drives directly down to hidden "forward" gear. First gear drives back to double width gear which drives down to "reverse" gear. Forward and reverse gears run freely on stud shaft with a dog assembly keyed to the stud shaft between them. Dog assembly controlled by steel plate between the forward and reverse gears, plate controlled by the ball lever and the hanging lever at the rear. Stud shaft must run in some kind of bearings in the block behind the gears. I'm going to be very interested in seeing the details of the components. Anthony
Graham Meek	17/03/2011 13:16:20
851 forum posts 163 photos	Hi all The rear most bronze gear is 25 teeth all the rest are 30 teeth. There is a definite dwell when the trips are triggered, motion can only be engaged by the use of the ball handle. This dwell is necessary to retract the tool, (micro seconds with RT device), and also to put the cut on , but dependent on thread length this can be done an the return stroke if you are using the RT device. In order to complete this device I could do with access to a S7 locally and preferably someone who is keen on making the unit, as I do not want to impose myself on anyone who is not. If they had AutoCAD it would be helpful but I can send drawings as pdf,s Gray.
John Stevenson	17/03/2011 13:59:39
Moderator 1780 forum posts 2 photos	Graham, Where is locally ? Can't help with a S7 but got a ML7 that's only used for experiments and don't mind hacking about. Also got gear cutting facilities. john [at] stevenson-engineers.co.uk John S.
Graham Meek	17/03/2011 16:22:48
851 forum posts 163 photos	Hi John, I hail from the Forest of Dean, Gloucestershire. Whilst I designed this unit for the Super7 it may well fit the ML7, but my preference would be for S7, there is no hacking about required, just one tapped hole and a slot in the change wheel guard. How do you cut your gears, form cutters or Hobbing facilities? I am currently working on a revised method of that which was used by J A Radford to cut another set of gears, as I like to make all the items I write about to prove that it can be done that way. However you may be able to help those who cannot cut their own gears. I currently have enough gears from the batch that were made for the first two units by Neil Hemingway on his Mikron hobbing machine, they are 14.5 degree pressure angle. Please do not think I am trying to shun the offer, I would like to keep my options open at the moment. Gray
Tony Pratt 1	17/03/2011 17:20:13
238 forum posts	Hi Graham, I have a super 7 but live in Bedfordshire so not local. I am prepared to make any bits if you need them, I believe my cad program will read autocad drawings Best wishes, Tony