Lathe Carriage/Saddle Stop

Please excuse my ignorance but I was completely unaware of carriage or saddle stops until I saw them mentioned in places like MEW.

I can see that they enable the saddle to stop in the same place each time, but how are they operated? Does the power feed automatically disengage when the saddle comes up to the stop? Without damaging anything? Can they be fitted to any lathe? I have a Weiler 280 lathe, a German machine from the 1960's which has power feed.

regards, ChrisH

There's various threads, just search for "stop"

Wolfie did the last big one

http://www.model-engineer.co.uk/forums/postings.asp?th=65651

Speaking of which, we haven't heard from wolfie for a while, I hope he's okay...

The saddle stop can be a simple block that you clamp to the lathe bed, or a more complex arrangement with a turret that allows several independantly adjusted stops to be rotated into position. This would allow several positions to be repeatably attained rather than just one.

Some lathes have a slipping clutch built in to the feed drive - others don't. We had a large-ish Colchester at work (Mastiff, I think) that could be left to run up to the stop un-attended. When the saddle contacted the stop the clutch slipped. The Harrison VS330, though, does not have a clutch - when one of my collegues who was used to the Colchester used it, he broke a roll pin on one of the apron drive gears by letting the machine run to the stop under power feed.

I am not familiar with manual Weilers (I retrofitted a CNC one many years ago - quality machines), so I suggest it would be prudent to try and ascertain whether or not the saddle feed drive has a clutch fitted not before trying running up to a stop under power.

HTH

Nigel B.

With some possible exceptions the stop is not intended to stop the saddle and damage may result if you attempt it so using it as a marker intending to stop before is risky. Even lathes with a friction clutch rather than dog clutch eg Boxford are not intended to be used this way. The mass of the saddle hitting the stop would hammer it off setting. (see later)

With a plain stop, after roughing, the saddle is moved up to line up the tool with a shoulder for the final inward cut. lock saddle and topslide if available and take the cut forming the reference point. Then say you want a 1/4 shoulder release the saddle and put a suitable sized block in front of the stop to reset the saddle exactly. Take cut and move again as required. A multiposition stop allows the steps to be preset and repeated easily on repeat items. Some people make little trays to hold blocks in position. This is intended to be simpler and more repeatable than using the top slide.

With a micrometer stop which can be adjusted on a dial the blocks/spacers are not needed but are still better for repeat work. This method of working allows the topslide to be left set over for screwcutting.

'Later' Off topic but to save asking the way to use the friction clutch is to hold the saddle handle gently as it cuts to take up the slack and as it reaches the target hold firm and stop it. If you think the clutch has to be so firm the force is too great to hold it like that then ask yourself what is going to break when it whacks into the stop. Then set a smaller cut.

Have a look here Chris. This gives some basic info regarding the purpose for, and method of, using a lathe's saddle stop.

Harold

Neil

To my mind, ChrisH, there are two sorts of saddle stop.

The first is only useful if you are traversing the saddle by hand, and consists of something like the one Neil (Stubmandrel) has shown. On repeated cuts, the saddle bumps up against it, stpping the saddle in the same place each time. For obvious reasons, you can't use it when the saddle is being traversed under power.

The second sort can be used under power, because it either:

(a) cuts off power to the motor when the saddle reaches a predetermined point; this is tricky, because inertia in the motor and spindle may cause problems with repeatability, and trailing wires to switches are needed.

(b) disconnects the power feed by triggering a dog clutch on the leadscrew (as on a Cowells lathe) or by opening the half nuts. I made one which opens the half nuts, which is shown here:

< http://andysmachines.weebly.com/semi-automatic-saddle-stop.html >.

I got the idea from John "GadgetBuilder", though the geography of my lathe meant I could work more in two dimensions than three. His is here:

< http://www.gadgetbuilder.com/ThreadingTools.html#AutoStop >

Andy

Nigel B has mentioned an accident when a machine without a clutch/disengegement mechanism hit the stop and broke a roll pin. On my lathe (Warco 918) the only protection against such an accident is the "roll pin" in the end of the leadscrew, but what should this roll pin be made of to ensure that it breaks before any serious damage is done?

Mick

Thanks to all for your very useful replies, esp to Nigel B for saying the Weiler is a quality machine (I think so too!), to Harold for his guide to using it, and also Andy who's semi-automatic saddle stop has given me food for thought.

I was concerned that using a saddle stop would cause damaged to the saddle when used under power feed. I had thought of trying it using a bit of light wood so damage would be to the wood not the saddle but I don't think I'll bother. I may try a version of the semi-automatic stop in time - I am following Wolfie's learning curve on the miller at the moment - and until then will limit a saddle stop to when using 'handomatic' manual feed on the saddle!

Chris

Mine is much like the one posted by Stub Mandrel but instead of a bolt it has a micrometer head fitted so i can face off to fine limits [ I don't run with a top slide fitted, rigidity is worth more to me ]

To this end I persuaded Ketan at ARC to stock just the micrometer heads so anyone can make the same sort of attachment.

http://www.arceurotrade.co.uk/Catalogue/Measurement/Micrometers/Micrometer-Heads

John S.

[Edited because this damn keybaord kan't spel. ]

Edited By John Stevenson on 06/04/2012 11:10:40

Hello Mick H!

In my Emco Compact 8 i use a 3mm PVC rod and it has saved my day various times.

Best regards

Dias Costa

Both the above links are excellent developments. It is interesting (disapointing) that none of the plethora of hobby lathes now available have incorproated either clutch or trip. Not even a brass shear pin on most. Even the larger ones with the non-essential complication of a system for power switch lever on the saddle have not built into that an overrun trip which could be done for barely a £ of parts.

There is one albeit a bit small for most people. The Cowells lathe has a dog clutch which is tripped out by a lever attached to the saddle.

I you have the space you can retro-fit a clutch, I do not know an Englisch supplier but this German one is fine http://www.maedler.nl/Product/1643/1622/1650/2155/502.aspx?result=61200600. For little extra money they altered the boring and made a keyway on part nr 612 010 00 to fit the input shaft on my Myford gearbox. I fitted it on the wide 72 teeth input gear and it works fine. When you want to cut thread you change it for the normal one without clutch.

On the Emco Maximat 11 that I used the pin was soft Aluminium, it was a plain pin but had a knurled portion at one end to keep it in place by friction.

I only ever snapped one in 10 years use!

Clive

Edited By Clive Hartland on 06/04/2012 14:14:52

Dias,,,,,plastic sounds good.....the previous owner of my lathe did a tremendous amount of damage which I did not recognise when I bought it and which subsequently cost me dearly. I am therefore a bit sensitive on this issue.

Clive....does soft aluminium snap cleanly and immediately if the worst were to happen?

Mick