Auto Feed ML 3” 1/8”

[woody1Participant @woody1]

Evening all,

Im not sure where I read this but its not a good idea to use a manual machine to auto feed as it wears the lead screw? For finishing cuts I can't see a problem? Any how just wondering if any of you fine gents can help me in calculating a gear train for auto feed. I have the program from lathes.co.uk for calculating threading combinations but have know idea of how to calculate a combination for auto feed. Im not to worried about rough cutting manually but for finishing cuts I guess it will make a world of difference finish wise. I have around 15 or so change gears I'll have to check along with number of teeth.

Thanks,

David.

[woody1Participant @woody1]

[Neil WyattModerator @neilwyatt]

It depends on how you use the lathe. Most hobby lathes get a relatively easy life, so it isn't a huge issue. In industry or with bigger lathes where cuts are heavier, it make sense to have separate feedscrew & leadscrew.

You may also be influenced by the availability & relative cost of a new leadscrew…

Neil

[Ady1Participant @ady1]

Input a setup for about 150TPI thread on the calculator and experiment from there

Autofeed can give you a good finish

It's also great for roughing down if you have a leadscrew clutch, takes a lot of the drudgery out of the drudgery bits

[woody1Participant @woody1]

Hi,

That was my thinking it doesn't take a hammering so should ok. thanks for the info ill have to dig out my old laptop Nthreadsp doesn't seem to work for my apple mack.

[Swarf, Mostly!Participant @swarfmostly]

Hi there, David,

Regarding your lead-screw and auto feed, lubrication is your friend. Also, make sure your lead-screw is rust-free – rust is abrasive.

Regarding the auto feed, the precise value of the pitch is irrelevant, it just needs to be fine. Lay out all your change wheels on the bench in order of size, smallest on the left and largest on the right. Fit the largest on the lead-screw and fit the smallest on the intermediate stud. Fit the next largest on the intermediate stud keyed to the small one already there. Fit the next smallest on the tumbler, fit spacers where necessary and adjust stud and banjo until all the gears mesh. (feed a strip of paper between each pair of meshing gears while tightening the stud and then remove the paper.) If the combination you've chosen won't mesh, swap gears until you get a combination that does. For fine feed, you want small drivers and large drivens.

Check for free rotation, switch on and assess the feed-rate. If it's so slow you fear you'll die of boredom, swap gears to reduce the ratio of the meshing pairs and re-adjust the banjo and studs to restore correct mesh and test again.

It's quite easy to proceed by trial and error until you get a set-up that's OK for the job in hand but do be prepared to get your fingers greasy. (I lubricate my change wheels with spray-on chain oil.)

Best regards,

Swarf, Mostly!

[woody1Participant @woody1]

Thanks,

Pretty obvious when you think about it smallest driving progressively larger or a combination that like you mentioned doesn't take an hour to complete a one inch pass! thanks again for the detailed post i shall have mess around which I know will be tedious. Once set up with the combinations logged future use will require a simple glance at the logs.

David.

Edited By woody1 on 22/09/2015 16:44:12

[woody1Participant @woody1]

Well!

looking through the literature I have, to try and find the thread specs for my buggered cross slide lead screw

I found the below on the very last page (Fine Feeds) Hope it may help others.

Edited By woody1 on 22/09/2015 23:58:38

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