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View Full Version : putting a carrage (feed) stop on my PM 1027 lathe. Anyone ever do anything like this?



Stern
04-04-2013, 01:39 PM
Kind of a weird question, but Im looking for a way to "disengage" the carriage from the feed screw on my lathe. Currently I can just use the lever, but want to put an adjustable stop on it, mostly for safety. Sometimes I need to get really close to the chuck and it gets a bit nerve racking watching and playing "beat the buzzer". So far I have had no issues, but find it really draining and would love a way to make it stop feeding at a selected point. The lathe I have is a PM1027 and think it uses a half nut type idea on the feed ON/OFF handle, but not sure. I figured I would check here and see if anyone had ever done something similar. Would be nice to be able to run up to a collar and have the feed stop at the same spot every time.

theGallery
04-04-2013, 05:50 PM
Kind of a weird question, but Im looking for a way to "disengage" the carriage from the feed screw on my lathe. Currently I can just use the lever, but want to put an adjustable stop on it, mostly for safety. Sometimes I need to get really close to the chuck and it gets a bit nerve racking watching and playing "beat the buzzer". So far I have had no issues, but find it really draining and would love a way to make it stop feeding at a selected point. The lathe I have is a PM1027 and think it uses a half nut type idea on the feed ON/OFF handle, but not sure. I figured I would check here and see if anyone had ever done something similar. Would be nice to be able to run up to a collar and have the feed stop at the same spot every time.

I built a carriage stop for my Frejoth 12" x 36" lathe several years ago, I use it all the time. It stops the carriage about .015" before hitting the stop. I also built an holder for an indicator to measure the last 1" of travel before the stop.

Pherdie
04-04-2013, 05:55 PM
Search this forum with the term "dog clutch". You'll find quite a bit of info on the subject

Stern
04-04-2013, 06:46 PM
Thanks very much for the info, going to take some time to go through it all.

Hopefuldave
04-04-2013, 08:30 PM
Looking at a pic of the 1027 on line, it doesnt have a separate feedshaft, so you're a bit limited in what you can do... I guess it feeds using the leadscrew and half-nuts, other than the already-suggested dog clutch the only way I can think of is using a stop to trip the half-nut lever, which would need a firm spring to disengage it and w latch that released it when hitting the stop? I'm not sure how repeatably it would stop, it would need to be very very rigid and tight tolerance!

Dave H. (the other one)

David Powell
04-04-2013, 08:33 PM
Thanks very much for the info, going to take some time to go through it all.

Beware, IF you put a fixed bed stop on a lathe which does not have a slip clutch somewhere in the driveline and you end up trying to move the stop one of two things will happen, 1, the stop will move, the tool will plough into the shoulder on the work/ or chuckjaws or 2, The carriage will stop moving and something in the driveline will break. Either way you will have a mess on your hands, maybe a very expensive one. It is good practice to use power feed almost up to the stop, disengage the feed and feed by hand to the stop. My Standard Modern lathe has an easily adjustable slip clutch, My Busy Bee lathe has a " Solid" drive with a shear pin and I use whichever is the most useful for the job in hand, so have learned to be careful.( IF things go south they do so remarkably quickly, last time I seriously missed disengaging the feed in time I tore the compound off a 16" TOS lathe, breaking two 1/2" bolts and hurling the slide and work across the shop.)Regards David Powell.

Hopefuldave
04-04-2013, 09:15 PM
Damn David, I'm glad my lathe has all the trimmings! Micrometer stops on both feeds, independent adjustable torque-sensitive feed trips... It's consistent to under a thou" in any direction as they're *dead* stops - it's nice to be able to set a long, slow finish cut going (1 thou"/rev at 22rpm gets dull...) and walk away for a coffee or a smoko or even to work on something else, knowing it'll shut the feed off if I forget about it! I just wish it had trips for threading, got left out on this model's, that would be the icing on the cake!

Dave H. (the other one)

Stern
04-04-2013, 09:47 PM
Thanks for the replies. I sure dont want to take any chances with damaging anything, as I planed on using it as a fail safe more than anything else. After going over a lot of data I dug up regarding the dog clutch I figure maybe I can tackle this a slightly different way. I like the snap trigger idea, and would use something like that to disengage a 1/2 nut .... either the existing one, or if thats two difficult, a second one. This way when a stop point was reached, it would stop motion. Since I have never, and will probably never thread on the lathe I don't need to worry about syncing.

Boucher
04-04-2013, 10:31 PM
This post is worth reading. It probably will not work for you unless you also have a similar magnetic brake.
http://bbs.homeshopmachinist.net/threads/42596-Threading-to-a-shoulder-worry-free!

My Nardini lathe came with a carriage stop from the factory. It is a very nice feature to have. A micrometer stop can be set to keep you from running into the chuck but you don't want to run into it on power feed.

David Powell
04-04-2013, 10:53 PM
This post is worth reading. It probably will not work for you unless you also have a similar magnetic brake.
http://bbs.homeshopmachinist.net/threads/42596-Threading-to-a-shoulder-worry-free!

My Nardini lathe came with a carriage stop from the factory. It is a very nice feature to have. A micrometer stop can be set to keep you from running into the chuck but you don't want to run into it on power feed.

In my experience,those lathes where the carriage feed is done by the half nuts often gave me an additional scare. IF the load on the tool accidentally increased, eg by running into a shoulder SO DID THE EFFORT TO RELEASE THE HALF NUTS.On more than one occasion I have been unable to release the half nuts, but managed to stop the spindle before ultimate disaster occurred.Turning the spindle backwards by hand usually will let the operator release the half nuts In one case the whole drive train jammed so solidly that the only remedy was to release the banjo holding the change gears and lever the gears out of mesh. I only ever run one lathe on which the feed is engaged the old fashioned way by tightening a nut on the saddle, that really has a high scare factor. Regards David Powell.

J. R. Williams
04-04-2013, 11:21 PM
My 30 year old Colchester/Clausing has a mechanical clutch on the carriage that disengages the feed system when the carriage hits the stop that is clamped to the ways. It will stop in a repeatable manner. It is very handy. The clutch is for the feed system only, not for threading. They did offer an automatic system for threading at the time.

firbikrhd1
04-04-2013, 11:27 PM
I just looked at a picture of a PM 1027 lathe and it appears that the lead screw comes equipped with a feed handle. How about using a variable speed DC motor with a belt to turn the screw via a pulley attached to that handle to feed during turning operations? Using that method it would be easy to hook up a micro switch on the ways that stopped the feed motor. Perhaps the micro switch could be attached to a movable clamp similar to a stop so the carriage could be stopped anywhere the clamp was placed.
Something like this seems like it would be far easier to set up than a mechanical means of stopping the feed.

Stern
04-05-2013, 08:57 AM
Yea, had thought about that, but adding a motor and PWM can get a bit expensive. I WILL be doing that on the mill to drive the X feed (just to save my arm from cranking forever) and see if its worth adding to the lathe. If I did do that I would probably add another feed screw, as I really dont want to start cutting up my lathe until I get mare skilled, plus the original feed screw works good as a carriage lock for facing (1/2 nut engaged, feed disabled).

JCHannum
04-05-2013, 09:26 AM
I have seen a few articles or threads describing shop made feedstops. Most of them were contrived of several linkages and gadgets or micro switches and solenoids. They all looked like a disaster waiting to happen and I would not rely on any of them to repeatably or safely stop the carriage.

It is all part of the learning curve of operating the lathe to manually stop the feed and finish the cut against a hard stop when needed. As the tool approaches the end of the cut, hold the handwheel and release the feed lever. You will get a sense of the feed rate from holding the handwheel and follow through to the carriage stop.

There have been quite a few threads here and articles in the magazines on making carriage stops, fixed, micrometer adjustable or equipped with a dial indicator. If you do not have one of these, fabricate one and practice its use. It is not that difficult.

GadgetBuilder
04-05-2013, 10:15 AM
I added a simple auto-stop to my 7x12, see: http://www.gadgetbuilder.com/ThreadingTools.html#AutoStop

As others noted, this type of stop isn't 100% reliable under all cutting conditions. Mainly, with heavy cuts it can take more force to release the half nuts than the little springs I used can provide. It does release reliably on light finishing cuts - these often take a long time because of the slow feed rate so I start doing other things and should I forget to come back in time this gadget prevents a crash.

However, if I provide upward force on the half nut handle and let the auto-stop trigger then it works every time on heavy cuts and repeats within a couple thou. This sounds like what you're interested in so perhaps you can adapt the concept to your lathe - it was quick and easy to add to my machine.

Stern
04-05-2013, 01:32 PM
That looks like exactly what im looking for, thanks for posting the link. Once I finish with the mill project I will work on this :)

Spin Doctor
04-05-2013, 05:15 PM
The PM 1027 is one of the BV/B 25 series of lathes. The Craftex 10 x 18 is the same lathe mechanically. There is currently a series of articles appearing in Model Engineers Workshop by James Aldridge about the modifications he is doing to his. The PM 1027 has its weak points (frankly all small lathes do even the esteemed Hardinge). The first is the Spindle face which harks back to the Emco Compact 8 http://www.lathes.co.uk/emco/page2.html which has of course morphed into the much loved/hated 9x18/20. The second is the half nut is just that. Only the bottom half of the nut. Plus the fit on the nut seems a little loose which seems to cause binding in its guide slot. Plus the Apron is not an enclosed design. None of these are deal breakers as long as you take into account what you are getting. The plus 1' spindle bore is handy. Old Tiffie and myself both have this model lathe. We both seem to be satisfied with them but I know in my case I when I purchased mine from Matt is that I viewed the lathe as a blank slate that allowed for modifications. One modification these lathes (or any small lathe that uses the leadscrew to power the feeds) needs is a variable speed DC powered feed unit. Think something like a Servo type feed unit mounted on the Apron where the hand wheel is. This would save wear and tear on the lead screw and nut. Plus a bed stop could incorporate a microswitch that would shut the feed off. For more info concerning PM1027's and similar lathes http://groups.yahoo.com/group/pm1027lathe/

Stern
04-05-2013, 08:23 PM
Thanks very much for the info, going to check it out now :)