understanding screwcutting

[michael shaw 1Participant @michaelshaw1]

[michael shaw 1Participant @michaelshaw1]

As a complete newcomer I know nothing about engineering. My interest is in stationary engines (full size). In the past people have made parts for me but was told to get a lathe and i would be taught to use it. A few months ago I purchased a Warco GH1236, the reason for a big machine was the need to skim 12,and 14inch flywheels. Having learnt how to skim these and also do basic turning I now need to cut somelarge threads but do not understand the lever that locks onto the lead screw, it has three positions why? also what is the indicator table. At the moment cannot work out how to put photos on here any help would be muh appreciated. Mike..

[JasonBModerator @jasonb]

Are you talking about the lever with the red knob? if so this is not the one to engage the feed. You need the alloy one to the right of the apron front to engage the half nuts with the lead screw.

The indicator table is likely to be one of the engraved plates on the front of the machine, it gives the number on the thread dial indicator that you need to engage the feed as the number comes round on the dial.

Take a look at this PDF for the manual of a similar lathe sold in te US, they are generally written better than the warco ones.

 

J

Edited By JasonB on 24/02/2015 20:55:11

[Harry WilkesParticipant @harrywilkes58467]

Hi Michael at the weekend I cut my first internal thread 1.125" x12 so after you have looked at the manual Jason suggested maybe you may want to do what I did and watched a load of youtube videos on screw cutting start with 'doubleboost' and try this one for starters https://www.youtube.com/watch?v=8SV7lDiSXto

H

[HopperParticipant @hopper]

Sounds like you could use a good basic textbook on how to use a lathe. South Bend's "How to Run a Lathe" is a good one, as is LH Sparey's "The Amateur's Lathe". There are plenty of more modern ones too, but principals are the same.

The Workshop Practice series of books have an excellent beginner's lathe book by Harold Hall and another specifically on screwcutting, whose author I don't recall.

All are available cheap from Amazon, Book Depository etc.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Hopper on 25/02/2015 03:06:03:

…. and another specifically on screwcutting, whose author I don't recall.

.

That would be "Martin Cleeve" as referenced on this recent, but almost lost, thread.

MichaelG.

[chris stephensParticipant @chrisstephens63393]

One of the best threading primers on Youtube is "Toms Techniques" (youtube.com/user/Figbash3) "thread cutting on the lathe" in his playlist. Some of the others on YT are, at best, awful and a waste of time to watch but I doubt you will go far wrong if you follow Tom's advice, even if some say he is doing it all wrong because that is not how they were taught. His way is logical and it works and that is all that matters.

[Bob Brown 1Participant @bobbrown1]

Not so sure he'd get any points for safety, hand under the chuck with the machine running, and wiping swarf off with his finger. Also not so sure it is that representative of the lathes most of us use.

[michael shaw 1Participant @michaelshaw1]

Many thanks Jason for a copy of that manual it is now easier to understand. However my thread dial has three positions on it and three gear wheels inside, this must somehow effect the gearing onto the lead screw. Has anybody any idea what it changes. I do have the book on screwcutting but did not find that very helpful. Will also look on Youtube as suggested by others many thanks, Mike..

[Nigel McBurney 1Participant @nigelmcburney1]

Thread dial indicators on imperial machines only have one gear, on fully metric machines the thread indicator usually has a number gears ,each gear only covers a certain number of pitches,so there is usually a plate attached to the indicator stating which gear to use for the pitch required. My metric Colchester has a stack of gears held within the indicator,and the machine has been around for 40 years. Prior to 1970 most uk lathes were imperial, or in some cases had metric top and cross slides with imperial leadscrews , so although 40 years seems to be a long time I have yet to see a book on lathe work describing metric screwcutting in detail.

My metric Colchester Master has dual dials on top and cross slide ,imperial leadscrew,imperial tailstock dial, and a metric rack, The metric rack is useful as one turn of he saddle handwheel moves the saddle exactly 25 mm, An option on metric colchesters was a dial for the saddle handwheel,I managed to aquire one of these dials and have fitted it to the master so though it is essentially an imperial machine I can now get a very accurate indication of saddle travel albeit in metric. I just live with it. A lot simpler than the complicated dials required for imperial dp racks.

[Bob Brown 1Participant @bobbrown1]

I've added Boxford's words of wisdom in my photo's which covers both imperial and metric options.

Bob

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