01-04-2014, 08:38 PM
Hi,
Thanks for asking Colin; yes the marks you refer to are "indents" these being very accurately spaced; indexing plates are available with lots of rows of such indents giving many permutations of spacing's.
Thanks Alan D; there is a reason for all the various indent spacing's usually associated with gear cutting but this is only part of what can be achieved with a lathe; gears; cogs and splines can all be cut by adding a motorized tool drive to the cross slide greatly increases operations which can be carried out on a lathe; in the old days these drives used to be called "overheads" and were very elaborate indeed; it's amazing what can be accomplished using a lathe with imagination? The indent numbers on this Lorch are marked on the gear but I was too busy to take notice of them this morning. Lathes are available for home workshop use with milling heads already attached but at a price.
Good luck with your Drummond Big Al; I hope you made sketches and took notes if as you say you've already removed the mandrel? It's so easy to forget immediately the most obvious things? The back-gear unit on this Lorch is very easy to remove and replace; I can remove it in a minute now its all cleaned up and replace it just as quickly; I wanted it off the bench before it got messed up again?
I don't have the indexing pointer on the spring steel strip Alan B but I can make one; the trunnion is in position though on the head-stock to accept it.
Thanks Refugee; the indents are not intended for use with screw cutting; screw cutting is an entirely different function being controlled by a gear train at the head-stock end and the lead-screw or through a gearbox if a gearbox is fitted. For screw cutting the chuck revolves. These indents (markings) are very precisely spaced and as Big Al rightly states there should be a spring with a sharp point attached the point engaging the indents allowing the mandrel to be rotated in degrees and locked in position preventing it rotating; the 180 row of indents will actually relate to two degrees for each indent position; given the correct row of indents just about any gear could be cut to the capacity of the lathe. If the lathe is large enough then a "dividing head" can be used for indexing but these dividing heads are very expensive bits of kit whereas an indexing (dividing) plate is relatively cheap by comparison. Here are both indexing plates and a dividing head.
http://en.wikipedia.org/wiki/Indexing_head
Indexing plates are used directly on the mandrel locking the mandrel in any desired position of rotation and the work is secured by any convenient method such as in a chuck or on a face-plate; the revolving tool is applied to the stationary work. Just the opposite applies whilst using a dividing head; the work is attached to the dividing head and the tool is made to revolve by the mandrel. I'm only discussing lathes here because I'm well aware dividing heads are used a great deal on other machines such as milling machines. Not the easiest subject to put across in text but screw cutting (threading) is not carried out using an indexing plate.
https://www.google.co.uk/search?q=overhead+drive+lathe&espv=210&es_sm=122&tbm=isch&tbo=u&source=univ&sa=X&ei=IBI7U4a1FcyYhQezmIGwCw&ved=0CC0QsAQ&biw=1920&bih=955
For want of a better term the indexing trunnion on this Lorch can clearly be seen in the picture it being bottom left. A long flat spring with a sharp pointer is attached here the free end of the spring is usually turned to form a neat finger pull. The picture below shows how the indexing pin works and how the spring is attached on a different lathe.
Whilst faced with wanting 45 cast iron gears for my AVO Wave Winder restoration I came up with my own method of gear cutting which I had never previously seen and for it's intended purpose was certainly accurate enough; I used paper templates secured to the gear blanks and attached the blanks one by one onto a home made vertical slide; the single point cutter was secured in a robust bar set between chuck and tail-stock; the lathe put in motion revolved the cutter and the gear blank was simply wound up on the slide the cutter imparting one slot at a time; after a slot was cut the next slot was aligned by eye and I could cut a slot in a minute; as the slots were cut gear teeth remained the cutter was HSS ground to suit the tooth profile.
I never tire of lathes as they are the daddy of all machine tools and as I say a bit of imagination goes a long way but play safely.
Sunshine stopped play today; sunshine together with a dry calm day are rare so I took Bron to a garden center this afternoon; work will resume on the Lorch tomorrow morning.
Kind regards, Col.
Thanks for asking Colin; yes the marks you refer to are "indents" these being very accurately spaced; indexing plates are available with lots of rows of such indents giving many permutations of spacing's.
Thanks Alan D; there is a reason for all the various indent spacing's usually associated with gear cutting but this is only part of what can be achieved with a lathe; gears; cogs and splines can all be cut by adding a motorized tool drive to the cross slide greatly increases operations which can be carried out on a lathe; in the old days these drives used to be called "overheads" and were very elaborate indeed; it's amazing what can be accomplished using a lathe with imagination? The indent numbers on this Lorch are marked on the gear but I was too busy to take notice of them this morning. Lathes are available for home workshop use with milling heads already attached but at a price.
Good luck with your Drummond Big Al; I hope you made sketches and took notes if as you say you've already removed the mandrel? It's so easy to forget immediately the most obvious things? The back-gear unit on this Lorch is very easy to remove and replace; I can remove it in a minute now its all cleaned up and replace it just as quickly; I wanted it off the bench before it got messed up again?
I don't have the indexing pointer on the spring steel strip Alan B but I can make one; the trunnion is in position though on the head-stock to accept it.
Thanks Refugee; the indents are not intended for use with screw cutting; screw cutting is an entirely different function being controlled by a gear train at the head-stock end and the lead-screw or through a gearbox if a gearbox is fitted. For screw cutting the chuck revolves. These indents (markings) are very precisely spaced and as Big Al rightly states there should be a spring with a sharp point attached the point engaging the indents allowing the mandrel to be rotated in degrees and locked in position preventing it rotating; the 180 row of indents will actually relate to two degrees for each indent position; given the correct row of indents just about any gear could be cut to the capacity of the lathe. If the lathe is large enough then a "dividing head" can be used for indexing but these dividing heads are very expensive bits of kit whereas an indexing (dividing) plate is relatively cheap by comparison. Here are both indexing plates and a dividing head.
http://en.wikipedia.org/wiki/Indexing_head
Indexing plates are used directly on the mandrel locking the mandrel in any desired position of rotation and the work is secured by any convenient method such as in a chuck or on a face-plate; the revolving tool is applied to the stationary work. Just the opposite applies whilst using a dividing head; the work is attached to the dividing head and the tool is made to revolve by the mandrel. I'm only discussing lathes here because I'm well aware dividing heads are used a great deal on other machines such as milling machines. Not the easiest subject to put across in text but screw cutting (threading) is not carried out using an indexing plate.
https://www.google.co.uk/search?q=overhead+drive+lathe&espv=210&es_sm=122&tbm=isch&tbo=u&source=univ&sa=X&ei=IBI7U4a1FcyYhQezmIGwCw&ved=0CC0QsAQ&biw=1920&bih=955
For want of a better term the indexing trunnion on this Lorch can clearly be seen in the picture it being bottom left. A long flat spring with a sharp pointer is attached here the free end of the spring is usually turned to form a neat finger pull. The picture below shows how the indexing pin works and how the spring is attached on a different lathe.
Whilst faced with wanting 45 cast iron gears for my AVO Wave Winder restoration I came up with my own method of gear cutting which I had never previously seen and for it's intended purpose was certainly accurate enough; I used paper templates secured to the gear blanks and attached the blanks one by one onto a home made vertical slide; the single point cutter was secured in a robust bar set between chuck and tail-stock; the lathe put in motion revolved the cutter and the gear blank was simply wound up on the slide the cutter imparting one slot at a time; after a slot was cut the next slot was aligned by eye and I could cut a slot in a minute; as the slots were cut gear teeth remained the cutter was HSS ground to suit the tooth profile.
I never tire of lathes as they are the daddy of all machine tools and as I say a bit of imagination goes a long way but play safely.
Sunshine stopped play today; sunshine together with a dry calm day are rare so I took Bron to a garden center this afternoon; work will resume on the Lorch tomorrow morning.
Kind regards, Col.
Happiness is a wreck of a cabinet to restore.
