# Lathing question.....



## Firstgear (Feb 16, 2019)

If I have a 7/8” diameter, 36” long bar and I need to turn down about 10” or so to 3/4”, is the best thing to do is face one end and put a center drill into it and then use my live center to support it and machine it down?  Or do I also need to line up the spider on the bar prior to facing off the one end?  Operation steps?


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## mmcmdl (Feb 16, 2019)

Face , center drill and turn . If you need to , turn it in 2 set-ups if you get chatter . ( turning 5" at at each set-up )

Edit . Not knowing what size lathe you have , you may need that spider for rear support . Watch your rpms and check out the " Bar whip thread " .


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## Firstgear (Feb 16, 2019)

mmcmdl said:


> Face , center drill and turn . If you need to , turn it in 2 set-ups if you get chatter . ( turning 5" at at each set-up )


When do I cut it off the 36” length?


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## mmcmdl (Feb 16, 2019)

Ah ..............you could cut it to length first and face and c drill both ends , then use a center in your 3 jaw and live center in the tailstock . Use a drive dog . Flip it and repeat . 

Or turn the 10 inches to diameter and cut it off the bar .


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## Firstgear (Feb 16, 2019)

26” overhanging the back side seems like a lot......


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## Firstgear (Feb 16, 2019)

mmcmdl said:


> Ah ..............you could cut it to length first and face and c drill both ends , then use a center in your 3 jaw and live center in the tailstock . Use a drive dog .
> 
> Or turn the 10 inches to diameter and cut it off the bar .


Drive dog?


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## mmcmdl (Feb 16, 2019)

Firstgear said:


> 6” overhanging the back side seems like a lot......



Look up at #2 post !

A lathe dog . Drive dog . Clamp it on your shaft and drive it with the chuck .


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## Firstgear (Feb 16, 2019)

Ok....I have a PM1440GS......


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## mmcmdl (Feb 16, 2019)

I don't know PM machines , 14 x 40 ?

Why can't you just cut the bar first to maybe 11"s , chuck it and turn it ? Then saw it or part it off to 10" .


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## Firstgear (Feb 16, 2019)

Bar whip.....after watching the video in that posting, not be something I soon forget!  I need to get that band saw sooner than later!


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## Firstgear (Feb 16, 2019)

mmcmdl said:


> I don't know PM machines , 14 x 40 ?
> 
> Why can't you just cut the bar first to maybe 11"s , chuck it and turn it ? Then saw it or part it off to 10" .


Don’t have a band saw...but it looks like I should get one!  Sooner than later!


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## mmcmdl (Feb 16, 2019)

Got an angle grinder and cutoff wheel ? Use that .


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## Firstgear (Feb 16, 2019)

I have my die grinder and can be hell on wheels with that.....I will come up with something.  Worse come to worse I can drive over to a friends shop and use his band saw.....


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## mmcmdl (Feb 16, 2019)

You could just part it off in the lathe to length , but be wary of your rpms . You don't  want that PM to walk on over to your neighbors house !


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## Firstgear (Feb 16, 2019)

mmcmdl said:


> You could just part it off in the lathe to length , but be wary of your rpms . You don't  want that PM to walk on over to your neighbors house !


My wife who has been very supportive might change her tune if that happened!


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## mmcmdl (Feb 16, 2019)

LMAO , I'm sure of it . Those whipping bars will destroy anything in their paths !


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## Tozguy (Feb 16, 2019)

Firstgear said:


> Don’t have a band saw...but it looks like I should get one!  Sooner than later!



What about a good old fashioned hacksaw? With a good blade the job would be done in two shakes of a lamb's tail.

Seems to me that I would cut to 11'' with a hacksaw, face and drill a centre divot in each end.
Zero the work in a 4 jaw independant chuck for cutting the centre divots.
Mount a centre in the 4 jaw and zero it. You will have 1'' of stock to mount a drive dog.
Turn it between centres using a follow rest. Cut towards the headstock.
Avoid skim cuts, use the right tool and grind, d.o.c. and feed rate.
After reaching final diameter, remove the work from the centres, chuck in a 4 jaw and part to final length.



Firstgear said:


> do I also need to line up the spider on the bar prior to facing off the one end?


Please explain this, what spider?


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## mmcmdl (Feb 16, 2019)

Hacksaw ? They still make them?  

32 years ago I walked into my production managers office with a tooling req loaded with Valenite insert drills and cutters . He looked at it and nearly fainted ! He asked what in the heii do we need these for ? I explained to him that he had a brand new , very large Makino VMC running production with HSS tooling at a snails pace . He didn't understand what I was saying , and stated the tools are cutting . I simply told him a file also cuts , and when those HSS tools give out , I'll send my men up on the platem with files to cut his parts out .  I got my tools . Correct tools for the job .


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## Mrlathe (Feb 16, 2019)

As said above give yourself an inch or two extra,say cut at 12",face it ,center drill chuck it up and off you go.


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## Firstgear (Feb 16, 2019)

Tozguy said:


> What about a good old fashioned hacksaw? With a good blade the job would be done in two shakes of a lamb's tail.
> 
> Seems to me that I would cut to 11'' with a hacksaw, face and drill a centre divot in each end.
> Zero the work in a 4 jaw independant chuck for cutting the centre divots.
> ...


Spindle spider, out the other end of the spindle, 4 bolts that contact the shaft to help give support to the work piece so the chuck bearings aren’t “loaded” in a cantilevered fashion.....


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## wrmiller (Feb 16, 2019)

If it were me, I'd hack saw off about 11-12" of it stick it in the chuck, center drill and support the other end on a live center and turn it.

When finished turning to diameter, flip the part and either part or hack saw off the unturned part. Done.


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## benmychree (Feb 16, 2019)

Best to cut the stock off first an inch or two long, center drill one end, and chuck the piece so you can turn it down in one length; I would not turn it between centers, as there is much greater tendency to chatter doing it that way.  Only turn between centers to ensure concentricity when a part must be turned around for work on the other end.


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## jbolt (Feb 16, 2019)

You don't say what the material is. Unless it is thin wall plastic tubing you won't get bar whip with a 7/8" bar with only 2 feet through the spindle. I would face, center drill and turn with a live center as you said. Part off and face the parted end to length. No reason to waste a few inches of material.


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## Tozguy (Feb 16, 2019)

Firstgear said:


> Spindle spider, out the other end of the spindle, 4 bolts that contact the shaft to help give support to the work piece so the chuck bearings aren’t “loaded” in a cantilevered fashion.....


OK then, you don't have to worry about whip in a 36'' bar held concentric in the outboard end using a spider. So now I'm with the fellas above who would hold in a 4 jaw to face and cut a centre divot, extend the bar out 11'' and support the tail end with a live centre. Not sure how straight the jaws are on your 4 jaw so check that everything lines up. After turning to final o.d.  part to length.


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## Larry42 (Feb 16, 2019)

You will probably want a spider, sooner or later. I made one but made a dumb mistake. I should have made a test part that matched the threads on the end of the spindle first. That way I could test the fit W/O removing the work and loosing my thread position.


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## kb58 (Feb 16, 2019)

Or just buy 12" of 0.750" drill rod. Just depends upon your priorities.


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## Firstgear (Feb 16, 2019)

jbolt said:


> You don't say what the material is. Unless it is thin wall plastic tubing you won't get bar whip with a 7/8" bar with only 2 feet through the spindle. I would face, center drill and turn with a live center as you said. Part off and face the parted end to length. No reason to waste a few inches of material.


12L14......


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## Firstgear (Feb 16, 2019)

Larry42 said:


> You will probably want a spider, sooner or later. I made one but made a dumb mistake. I should have made a test part that matched the threads on the end of the spindle first. That way I could test the fit W/O removing the work and loosing my thread position.


My lathe came with a spider.....


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## Cobra (Feb 16, 2019)

mmcmdl said:


> Hacksaw ? They still make them?
> 
> 32 years ago I walked into my production managers office with a tooling req loaded with Valenite insert drills and cutters . He looked at it and nearly fainted ! He asked what in the heii do we need these for ? I explained to him that he had a brand new , very large Makino VMC running production with HSS tooling at a snails pace . He didn't understand what I was saying , and stated the tools are cutting . I simply told him a file also cuts , and when those HSS tools give out , I'll send my men up on the platem with files to cut his parts out .  I got my tools . Correct tools for the job .



For a guy getting started, yes hacksaws still exist.  Not every shop is a commercial enterprise.


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## kvt (Feb 16, 2019)

I agree with those above.   Spider, face it,  center drill, at a slow speed,  then extend out and use a live center to hold the tail so you can turn it at normal speed.   Not sure how big your headstock its but once you move it out 10 to 11 inches,  THen the thickness of your chuck and Headstock,  you will not have that much sticking out if  supported by the spider on the back side of the head stock.  Still watch your speed, but I would think it should still be good.    Then you could saw off, with a hack saw and face the other end.    I have done that on some stuff smaller that what you are doing it on.  I just had to watch my speed.  Also did one where I made a support for the outboard end where it kept it in supported and lined up good enough that it did not flop around   But that was on a much longer piece than you are talking about.


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## whitmore (Feb 16, 2019)

Tozguy said:


> What about a good old fashioned hacksaw? With a good blade the job would be done in two shakes of a lamb's tail.



And with a dull one, unless you want to start a new kerf, you just take longer.    A less-than-sharp woodsaw
occupied my right arm for an hour and a half when bisecting a burl last month...


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## mmcmdl (Feb 17, 2019)

Firstgear said:


> I have my die grinder and can be hell on wheels with that.....I will come up with something. Worse come to worse I can drive over to a friends shop and use his band saw.....



Only thing better than owning your own shop is having a good friend with one , or having one at work !   How did you make out with that shaft ?


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## Firstgear (Feb 19, 2019)

mmcmdl said:


> Only thing better than owning your own shop is having a good friend with one , or having one at work !   How did you make out with that shaft ?


I ordered the shaft and haven’t gotten it yet.  Also, we are in Guam for the week just doing nothing!  So I need to get home and sort through everything!  These vacations are costly when I have access to the internet....my credit card tends to melt down!


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## Janderso (Feb 19, 2019)

My wife took me to Mexico last year. I hung around the pool, drank beer, ate and spent money on the internet.
When I got back to work it was like Christmas.


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## mmcmdl (Feb 19, 2019)

Janderso said:


> My wife took me to Mexico last year. I hung around the pool, drank beer, ate and spent money on the internet.
> When I got back to work it was like Christmas.




Sounds like you left heaven !


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## ThinWoodsman (Feb 19, 2019)

heh, I just spent three weeks away for work, with low expenses and lots of time for browsing tooling sites. all of the packages arrive today. any minute now. come on, post office guy...


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## Firstgear (Feb 19, 2019)

I always feel bad for our postal carrier...we have the mail held and then they deliver everything when we get home.  They drive their own car and have to bring the items to the front door.  One time I had to make 4 trips!


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