PDA

View Full Version : compound slide position



jack3140
01-08-2011, 03:25 PM
is there a preferred angle for the compound slide for day to day use? i have mine set at 30 degs on my lathe

vpt
01-08-2011, 03:30 PM
Mine is always left at 29-30 as well.

rohart
01-08-2011, 03:41 PM
I can see why you two do that, but - and bear in mind I'm new to proper leadscrew lathes - my first priority is to know that tools I put in my toolpost will be cutting at 90 degrees, so I leave my compound at 90 degrees.

Today, I did need 30 degrees. But I needed thirty degrees the other way - to make a 30 degree point, not a socket.

With my plain lathe, I now have two crossslide units - one I keep at 90 degrees, because I have to have one that's as dead nuts straight as a bed would be, and the other is the go to for angles. This one has never been put on without my having to alter the angle, as far as I can remember.

jack3140
01-08-2011, 03:43 PM
Mine is always left at 29-30 as well.
i am trying to learn as much as i can being a newbie so much i dont know

jack3140
01-08-2011, 03:46 PM
I can see why you two do that, but - and bear in mind I'm new to proper leadscrew lathes - my first priority is to know that tools I put in my toolpost will be cutting at 90 degrees, so I leave my compound at 90 degrees.

Today, I did need 30 degrees. But I needed thirty degrees the other way - to make a 30 degree point, not a socket.

With my plain lathe, I now have two crossslide units - one I keep at 90 degrees, because I have to have one that's as dead nuts straight as a bed would be, and the other is the go to for angles. This one has never been put on without my having to alter the angle, as far as I can remember.
i do that thinking it gives me extra reach to stay away from the chuck guess how i learned that lol

krutch
01-08-2011, 04:22 PM
I was taught in metal 101 to set at 25 degrees toward spindle for turning. Don't remember any real reason why. I usually have it at that for the same reason(?) today. But it does depend on whether I'm doing a lot of chamfers or some other repeat angles on the work. I do index for 29.5 for threading and will leave it there if the work has threads to do. Mostly depends on what the jobs are and what works for you.

SGW
01-08-2011, 04:26 PM
I leave mine at 30 degrees (allegedly 29.5, but the graduations are pretty small!) most of the time. It seems like a convenient place to have it.

John Stevenson
01-08-2011, 05:27 PM
Mines always set / sat ? on the top shelf in the lathe cupboard.

Compound slides are ugly things and need to be kept out of sight.

http://www.stevenson-engineers.co.uk/files/toolblock.jpg

loose nut
01-08-2011, 05:36 PM
Setting it to 30 Degs, according to my trig program, with a .001" feed on the compound will give you .0009" (effectively .001") feed towards the headstock and .0005" deep cut or .001' off the diam. Some people like to leave it in line with the bed axis so that they can make a direct reading fine cut againdst the face of the workpiece.

Apples and oranges.

brian Rupnow
01-08-2011, 06:01 PM
In days of old, (when I was about 15 years old) in "metal shop" at school, we were taught to have the top slide set at about 30 degrees swing to the right of the bottom slide. I have no particular idea why.---And you are absolutely correct----When set that way, the tool is not even close to being in the correct rotational aspect to the workpeice, so to compensate for that fact, one must then rotate the toolholder. About the only thing I can say in favour of having it set that way, is that it gains you a great deal more clearance from the tailstock, if the bed of your lathe is not a long one.

vpt
01-08-2011, 06:04 PM
30 degrees for reference.

http://img21.imageshack.us/img21/706/toolpost005.jpg

http://img444.imageshack.us/img444/5374/toolpost004.jpg

MuellerNick
01-08-2011, 06:11 PM
Must be a cultural difference!
I have never heard of someone telling to let it at 30°. I'm more with Sir John.


Nick

oldtiffie
01-08-2011, 06:17 PM
Setting it to 30 Degs, according to my trig program, with a .001" feed on the compound will give you .0009" (effectively .001") feed towards the headstock and .0005" deep cut or .001' off the diam. Some people like to leave it in line with the bed axis so that they can make a direct reading fine cut againdst the face of the workpiece.

Apples and oranges.

Perhaps not.

For each 0.001" feed along the top/compound slide (hypotenuse):

1). the cross feed will be (0.001 Sin30) = 0.0005" or 0.001'" off the diameter (as you say); and

2). the longitudinal feed (along the lathe bed axis) will be (0.001 Cos 30) = 0.000866" or 0.866 "thousandths" aka "thou".

I leave my top-slide parallel to the lathe bed axis.

My cross and top slide movements are very accurate and comply with what I set.

If I am very fussy, I will mount and use a good (0.01mm ~ 0.0004") dial indicator and use that instead.

My main use if my top-slide is to get the tool forward or back relative to the cross-slide.

terry_g
01-08-2011, 06:26 PM
I found this in "Popular Mechanics Lathe Handbook" from 1925.
Terry

http://farm6.static.flickr.com/5127/5337461622_0612926100_b.jpg

strokersix
01-08-2011, 06:33 PM
I suggest watching the compound slide angle relative to cutting forces to avoid unintended motion from cutting forces and compound backlash.

I generally keep my compound gibs fairly tight and swung out to 30-45 degrees because it seems to be out of the way in that position.

I don't like the compound all the way forward because of how far the tool overhangs the cross slide. I think this is one advantage of the old lantern posts, they don't overhang like a QC post.

The Artful Bodger
01-08-2011, 06:35 PM
The most obvious reason for NOT setting the compound to 90 degrees is that the handle clashes with the cross slide handle, on my lathe anyway!;)

dp
01-08-2011, 06:57 PM
I have mine offset so the handles are conveniently placed. I rarely have a need for the compound except it is what my QCTP is attached to. I try to keep the compound set so that the tool post is over the pivot as a means of reducing flex.

Carld
01-08-2011, 07:44 PM
This is one of those things that don't really matter but where ever you have it set you will have to move it at some time.

The advantage of setting it at 30 deg is so you can set up to thread after turning.

Having it at 45 deg is just having it at 45 deg.

Having the compound handle over the crossfeed handle is disrupting and blocks your vision of the crossfeed dial.

Having it set parallel to the bed many times interferes with the tailstock when turning small diameters and using a live center.

I used to keep it at 45 deg, then I started using 30 deg. For a few years lately I set it parallel to the bed because I was using a four way tool post. Now I have a QC tool post and have went back to the 30 deg setting.

Any where you set the compound at some time or other it will have to be moved. If you thread a lot as I do, use the 30 deg setting.

lane
01-08-2011, 07:57 PM
To each his own. But it does not matter. No right and wrong way. But if set and left at 30ºwhen turning something the need to thread drop in threading tool set quick change and thread .No monkey-en around.

darryl
01-08-2011, 08:10 PM
I change it regularly to suit the position requirement of the cutter. I don't like to have the crosslide cranked ahead to the point where the carriage dovetail ways show, but sometimes I can't avoid it. In general, my compound is oriented roughly at that angle- I don't make it exact.

I've always wondered about the angle, though. So with a 30 degree angle, one thou dialed in on the compound is 1/2 thou advancement towards the chuck- good to know.

Bill Pace
01-08-2011, 08:28 PM
Another 30 user deg here - totally aside from the advantage of having the compound pre-set for threading, if I never threaded I would still park it some where in the range of 30-45 deg simply because thats the range of where its best out of the way of the tail stock and the handles are the most convenient.

baldysm
01-08-2011, 08:59 PM
I keep mine at whatever it happens to be when I last needed it. I move it after I use it only when it interferes with either the tailstock or the cross slide.

I have set it at 30 deg so that it's easy to face off a specific amount. I don't often need to do that.

Don Young
01-08-2011, 09:51 PM
I generally keep the compound at about 30 degrees or so as it seems to not generally be in the way there. It is also handy for fine feeding when either turning or facing. It does, however, make it easy to catch the corner with the chuck jaws!

Carld
01-08-2011, 11:46 PM
Then move the tool post to the left.

jack3140
01-08-2011, 11:59 PM
thank you all for the great response i again have profited from your collective experience regards jack

J Tiers
01-09-2011, 12:19 AM
I keep mine at whatever it happens to be when I last needed it. I move it after I use it only when it interferes with either the tailstock or the cross slide.


yep...... me too.

I had mine set at the taper of an MT2 for a month or so recently...... It was the last thing I did, and I didn't need to change, it, plus I figured whatever I last did I might beed to do again, so why change?

There is some point to compounds being an invention of the evil one...... a lot of extra joints and slides in a compound, adding places for chatter.

form_change
01-09-2011, 02:00 AM
For a dissenting view, I keep mine at 0 degrees (that is, parallel with the bed). The tailstock on the lathe has been specifically designed with a cut away so that it does not interfere. I have it at 0 degrees for two reasons -

I thread that way (move the tool in with the cross slide and use the compound to tweak for fit), and
When I want to turn something to a specific length I can use the compound dials for a fine adjustment.


Park it where it most suits you, but don't feel you must park it (or use it) in a particular way because others do.

Michael

doctor demo
01-09-2011, 02:41 AM
It has not been mentioned yet so For the new guy or the old guy with a new to him lathe.
Not all cross slides and compounds are graduated the same , some are direct read and some are not. So I would suggest to look before you leap.
My Asian import and the old Axleson take off the dia. what ever the dial is turned, providing the compound is set parallel with the cross slide. My Le blond's cross slide is the same as above but the compound is direct read, so if you turn the compound .050 it moves .050 and if it was set parallel to the cross slide it would reduce the dia. by .100. My new (to Me) Polish lathe is direct read on the cross slide and the compound, so if you turn either of them .050 the dia is reduced by .100.
If I have bored you to tears please excuse Me.:)


Steve

The Artful Bodger
01-09-2011, 03:09 AM
I have two lathes, both imports.

The most modern one (from 2002 or so) has metric graduation for diameter on the cross slide and metric graduations on the compound for compound travel.

The other lathe, an import from about 1908, has no cross slide but there is a compound on the saddle but no graduations to be seen.

jugs
01-09-2011, 03:52 AM
Not wishing to agree with sir john :p - but -

Compound slides are a taper turning attachment that have traditionally been left mounted on the lathe, but why would you ?? you wouldn't normally mount a small milling vice in a big milling vice because it leads to instability, inaccuracy & chatter, so why do a similar thing on a lathe ??

Most work on a lathe is shoulder/shaft/face, if you want a ball on a shaft you mount a ball/radius attachment, & when you've done you put it back on the shelf. If you need a taper, mount the taper attachment/compound slide, & when you've done you should put that back on the shelf too.

A lot of people have troubles with chatter & parting off -the solution is -
Remove the compound, use a BIG solid tool-post ( as in post 8 ) mounted directly to the crosslide - problem solved. :D

Edit.... note sir johns tail-stock measuring device


john
:)

Black Forest
01-09-2011, 03:59 AM
John you just need to lay your compound on the floor. It will be out of sight. Lost in everything laying around!

rock_breaker
01-09-2011, 04:19 AM
is there a preferred angle for the compound slide for day to day use? i have mine set at 30 degs on my lathe
Could the 29 - 30 degrees be a holdover from thread cutting ? At tech school one of the early projects was to cut 1/2" thru 1" threads on a piece of 1-1/4 stock. The compound was not moved afterwards as I recall. Mine is usually at 29, but I move it if I can get better support for the cutttig tool.

Rock_breaker

Ian B
01-09-2011, 04:21 AM
I've found that it depends on the make & size of lathe that you're working with.

When I had a Myford ML10, the topslide was always fouling the tailstock, so it was often at 30 - 45 degrees to the axis.

Now, on my bigger (Harrison M400) lathe, as Form_Change said, there's a cutout in the tailstock and the topslide is pretty much always dead parallel to the axis.

The quick change toolpost (mine's an S3 Dickson) is usually pinned to the topslide, so also square to the lathe. It neer rotates under cutting load. Makes drilling from the toolpost easy, and I always know how the tools are set.

On fouling on live centres, I have more troubles with the actual tipped toolholders than with the topslide / toolpost, but that's what the long diamond-shaped carbide tips are for I guess...

Ian

Jaakko Fagerlund
01-09-2011, 05:08 AM
Parallel to the bed unless angle is needed. This is because the toolpost is pinned and thus keping it parallel provides more rigid setup when drilling and provides a nice way of getting the last hundreds from the workpiece length if needed.

Usually if I need a thread (up to like 4-5 mm pitch), I just feed in with the cross slide and half of that figure with the compound. That won't cut only on one side of the threading tool but eases the cutting force to the other side quite much.

I think I have never angled the compound for threading.

.RC.
01-09-2011, 05:27 AM
It must be a cultural thing.... I have mine set to 0 degrees..

MCS
01-09-2011, 05:28 AM
I'm with the Europeans.

No angles. Usefull for stepped surfaces (length), without losing diameter position. Threading with the 2:1(or less) trick.

Only angles for uhm angles.

Iraiam
01-09-2011, 06:10 AM
Mine stays at 30 degrees mostly, it is a convenient position for turning and facing with my turret tool post as well as the required position for threading. I have to move it occasionally for other operations but I put it back to 30 when finished.

MuellerNick
01-09-2011, 08:05 AM
Only angles for uhm angles.


Not even for the most common 45° chamfers. I drop in a tool for that.

The reason why I still have the compound installed, is that the dial at the saddle is way too crude and slobby (Chinese, you know) and I have no DRO.


Nick

Jaakko Fagerlund
01-09-2011, 10:01 AM
Not even for the most common 45° chamfers. I drop in a tool for that.

The reason why I still have the compound installed, is that the dial at the saddle is way too crude and slobby (Chinese, you know) and I have no DRO.


Nick
Yep, square inserts are good for chamfering, although I just usually use whatever tool is in the post to make a chamfer by using a precision two axis hand coordination :)

And yeah, the usual length indicator on lathes is prone to slip or give "just about right" lengths, so that is the reason I feed with the compound for last digits of the length.

J Tiers
01-09-2011, 10:45 AM
A lot of people have troubles with chatter & parting off -the solution is -
Remove the compound, use a BIG solid tool-post ( as in post 8 ) mounted directly to the crosslide - problem solved. :D


Not all machines make it easy or sensible to remove the compound.... depends what is left when you do.

if the machine has a milling table..... some chinese and Myford, you can.

if you have a stud sticking up without the compound, you have to make a toolpost to fit the stud.

In my case, I would have an 80mm diameter circular "track" for t-nuts, and a stud, so it is less convenient. I'd have to make a specialty toolpost. or I can take off the crosslide and put on the one that just has t-slots..... so I can mount any sort of massive block.

I don't have trouble with parting off even with the compound, so I leave that slide assembly on.

Carld
01-09-2011, 11:58 AM
I'm with J Tiers because having done repairs on many lathes removing the compound on many lathes leaves a boss or recess that has to be dealt with. Yes, you can make a mount to go on the boss/recess but why when the compound works so well.

If your cutting so hard that it turns the tool post during the cut maybe you should rethink your speed and feed.

It boils down to personal preference but the compound is so handy I see no reason to remove it unless the lathe is dedicated to a special job.

Jaakko Fagerlund
01-09-2011, 12:10 PM
If your cutting so hard that it turns the tool post during the cut maybe you should rethink your speed and feed.
It's not always because of rotation, but rigidity.

gnm109
01-09-2011, 12:24 PM
I learned that it's best to set the compound at 29 degrees for threading. I learned this from my machinist friend and also from my copy of "How to Run a Lathe", the South Bend book. Other sources say 30 degrees but the theory is the same.

"In manufacturing plants where maximum production is desired, it is customary to place the compound rest of the lathe at and angle of 29 degrees for cutting screw threads". (South Bend Book, page 77.)

They go on to say that "the compound rest is used for adjusting the depth of cut and most of the metal is removed by the left side of the threading tool......This permits the chip to curl out of the way better than if the tool is fed straight in."....

Another source I found shows a diagram with 30 degrees used. I guess there's really no reason to leave it at 29 or 30 degrees when not threading. In my case, it's convenient and it keeps the carriage a bit farther back from the chuck. It looks cool, too. :D

That's my story and I'm stickin' to it.


http://www-personal.umich.edu/~panchula/ToolTravel2.jpg

I found the diagram on the link above in an older HSM discussion from 2008....

http://bbs.homeshopmachinist.net/archive/index.php/t-27297.html

Alistair Hosie
01-09-2011, 02:17 PM
It is new and a surprise to me to think of removing the compound or top slide.But when you think about it I can see the reasoning behind it at times .Alistair

rohart
01-09-2011, 08:15 PM
I posted at the top of the thread that I keep my compound at 90 degrees. By this I meant at 90 degrees to the cross slide, and hence parallel with the bed. I had no idea anyone would interpret that as parallel to the cross slide. That didn't even stike me as possible, given the probable clash of handwheels.

My experience with the plain lathe means that I don't count the bed as something you move along.

And my lathe has plenty room for the compound without interfering with the tailstock.

My toolpost will be pinned soon, and pinned to a compound parallel with the bed. I should also soon have a second cross slide that I'm going to semi-permanently bolt a T-slot bed to. Maybe I'll even set up some new mounts and pins for my toolpost on that cross slide.

If I ever stop making new tooling for this da**ed lathe, I'll be lucky.

John Stevenson
01-09-2011, 08:27 PM
When I had the little Myford ML7 I was forever making MT2 tooling for it.
After one time of setting the top slide up for this angle, and checking it, I drilled thru the flange on the top slide, into the cross slide and reamed it with a small 1/8" taper reamer.

For subsequent jobs all i had to do was spin the top slide to the rough angle, tap a taper pin in and tighten the top slide.

Instant MT2 taper.