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cuemaker
03-06-2005, 01:16 AM
Is the top slide generally at 90 degrees to the cross slide for most of the basic turning?

I realize that its movable for a reason. But in general, if your turning OD is 90 degrees best.

This brings up the question of proper tool angle. I have a insert holder with that is a triangle shape. Is the proper angle straight in? or at some kind of angle.

Thank you

Rob

Jim Caudill
03-06-2005, 01:42 AM
I think if you were to walk into many shops you would find the compound set about 30degrees to the right (29-1/2 to be exact). This is very common for single point threading as the compound is used for altering the depth of cut and the cross-slide is used to rapidly withdraw the cutting tool and then returned to the same position for the next cut.

Another reason for offsetting the compound is to provide greater clearance for handwheel operation. If the compound and crosslide are set in alignment, the wheels often do not have enough clearance to prevent pinching your fingers.

A third reason for offsetting is to allow "fine positioning" of the depth of cut by using the compound feed. If you feed the compound in by .010" you will increase the depth of cut by only .005".

Generally, you will set the shank of the indexed toolholder perpendicular to the stock running thru the spindle. The insert will then be positioned according to the toolholders spec. This is not to imply that you can't skew the toolholder slightly to provide a different geometry, it just isn't the way that it is usually done.

May I suggest that you get a basic lathe operation book such as SouthBend's "How to Run a Lathe" or Sheldon's "The Care and Operation of a Lathe". Both should be available as reprints from Lindsay's website for a modest cost. Don't go buying on ebay - I've seen folks pay more for a ratty old copy than what they could've bought it new for. Also, check out your local library for machining texts with chapters on turning, tool grinding, etc. Carbide and High Speed Steel (HSS) cutters use different geometries in how they are ground and how they are fed into the work. Toolholders for lantern-style toolposts that are intended to hold HSS cutters will not work with carbide and vice versa. Now I have to cover my 6 o'clock and say that if you grind a cutter in a specific way, any cutting tool can be used in any holder - but that is not the way it is usually done.

tattoomike68
03-06-2005, 01:55 AM
I only use the compound set at 29.5 deg. to thread. <4 to 6 tpi.

also the gap was pulled out years ago and not needed so the 90 deg helps the tooling reach over the gap.

with a triangle insert tool I set the tip slighty towards the chuck so you can face or turn with it.

here is a face cut with a turning tool 5" aluminum at 1,300 rpm.
http://img.photobucket.com/albums/v488/miketattoo68/clipsfly.jpg

hammerhead74000
03-06-2005, 03:15 AM
OK, 2 basic answers -- http://bbs.homeshopmachinist.net//biggrin.gif

Well, what my machine shop instructor said, way back when a few years ago, was that "If it works, it's not wrong - but we will think you're a wacko, and there are better, more elegant, safer, etc, ways to do it". This was uttered after seeing someone trying to run a lathe with the compound facing away from the operator... http://bbs.homeshopmachinist.net//eek.gif

Jim Caudill's basically right... I have always seeen the compound (the top slide on an engine lathe) set at about 30 degrees, and the tool roughly perpindicullar to the bed, adjusted to provide the required relief angles.

Check out these sites, they've got online tutorials on them:

http://www.jjjtrain.com/vms/lessons_lathe.html

This one has a diffrent approach:
http://www.mini-lathe.com/Mini_lathe/Operation/operations.htm

John Stevenson
03-06-2005, 04:40 AM
In answer to the top slide question.
On many lathes if you have the top slide set at zero, ie. parallel to the bed there is often a conflict between the top slide and the tailstock.
You only have to look at older lathers to see the mising paint that proves this.
I normaly have the top slide at about 30 degrees just for clearance. Most of the time it's not used and the gib screws are tightened.

On my medium sized lathe that does most of the day to day work I don't have a top slide at all.

http://homepage.ntlworld.com/stevenson.engineers/lsteve/files/TOS2.jpg

This was removed when the lathe was new, greased and put in the cabinet with the 4 way tool post still attached.

This was replaced by a solid steel spacer block with a cut away on the rear to miss the tailstock. It's impossible for this block to hit the tailstock in any position.

In the four of five years I have had this lathe I have needed to replace the top slide 3 times for some taper work. I don't infeed at an angle for threading as I use sections of die blocks for threading tools which are correctly ground with the correct root and crest radii so I don't miss the angualr adjustment.

Where I do score is in the increase in rigidity affored by this large solid block against the slides and screw of a hardly used top slide.

John S.

aboard_epsilon
03-06-2005, 06:10 AM
JOHN SAID

I use sections of die blocks for threading tools which are correctly ground with the correct root and crest radii so I don't miss the angualr adjustment.


Show us a picture John of how you use these die-blocks.
have you made a special tool to hold them.
whats it look like.
all the best..mark
......

Allan Waterfall
03-06-2005, 06:29 AM
Like John, I have only used my topslide for turning tapers since I made a solid toolpost bolted to the cross slide about a year ago,it's a more rigid set up and the compound isn't fouling the tailstock or the hand wheel in the cross slide.

Mark...
I think by die blocks what John means are Coventry die chasers and one is mounted in a holder.I seem to remember a pic in the tips thread of one being used to cut the grooves in a pulley for a Poly "V" belt.
The chasers are always coming up on ebay,usually go for about 4 quid a snatch.

Allan

[This message has been edited by Allan Waterfall (edited 03-06-2005).]

aboard_epsilon
03-06-2005, 06:36 AM
YES ALLAN
I HAVE LOADS OF COVENTRY DIE CHASERS
AND NO COVENTRY DIE HEAD.
as the coventry die heads sell for too much on ebay..still looking.
and will be for sometime I think.
so in order ,so I dont have to do any hard thinking.
was just going to copy Johns die-chaser holder...when he shows it
all the best..mark

Your Old Dog
03-06-2005, 07:12 AM
Cuemaker, if you are new enough to all this lathe stuff to ask the question you did, you should also be made aware of the angle of the bit versus the direction of feed. Maybe some of the vets (I'm new too) can explain it better but if not, here goes.

If the angle of the bit to the work is not perpendicular on the horizontal, and IF something goes wrong it will cause the bit to dig in if moving in one direction and simply move out of the way going in the other direction. Having said that let me say that my bit is rarely perbendicular but I always cut in the direction that will not cause the bit to dig in if something goes wrong. I do that because I think I get a nicer cut. The word bias comes to mind.

Sorry if I'm telling you something you already knew.

Like others here I also recommend the Southbend Lathe book noted above, it's good throne room reading! It has great information but not so much that what you need to know is buried in a multitude of pages!

Ray.......

cuemaker
03-06-2005, 11:15 AM
All the information is great. I have already done lots of expermintation have come up with the same basic results. I was just kinda checking to make sure I was in the ballpark.

The real reason for the questions was that I was installing my QC tool post (my first "serious" use of the lathe where a mistake would have cost in machining the t-nut) and I notice that the handle to disengage/engage the holder was at what I thought was a funny angle. It was moving over the ways.

I havent played with it enough to see if the handle can be repositioned to make it work. But it made me wonder if I had the correct basic angles correct.

Keep it coming.

Rob

Lew Hartswick
03-06-2005, 11:19 AM
Jim Caudill
A third reason for offsetting is to allow "fine positioning" of the depth of cut by using the compound feed. If you feed the compound in by .010" you will increase the depth of cut by only .005".

Jim, If the compound is set for threading,(ie. 29 1/2 or in the other convention, 60 1/2 deg)
the infeed will be sq rt 3 times the compound.
Not one half.
...lew...

Jim Caudill
03-06-2005, 01:07 PM
You're close Lew. Sin 30 = .5 Cosin is SqRt of 3 divided by 2. When I need to, I can figure it out, but this was late and I was just trying to illustrate why some turn their compound. I still remember my elderly trig teacher drumming the different functions into our heads. I use Sin & Tan but rarely use Sec & Cosec. The good 'ol 30-60-90 triangle and its 1,2,SqRt3 sides.

Allan Waterfall
03-06-2005, 01:28 PM
<font face="Verdana, Arial" size="2">Originally posted by aboard_epsilon:

so I dont have to do any hard thinking.
was just going to copy Johns die-chaser holder...when he shows it
all the best..mark</font>

Mark...

If you've got any back issues of MEW. Page 39 issue 56 there's a sketch of one among several other things from Harold Hall.
All you basically need is a to make a toolholder with the chaser clamped on the end.

Allan

John Stevenson
03-06-2005, 01:38 PM
Mark,
Pic of the holder it's that simple no drawings are needed.

http://homepage.ntlworld.com/stevenson.engineers/lsteve/files/screwcut10.jpg

Holder for doing internal threads.

http://homepage.ntlworld.com/stevenson.engineers/lsteve/files/screwcut4.jpg

Pic of the loose pieces from a die head to be used as a screwcutting tool.

http://homepage.ntlworld.com/stevenson.engineers/lsteve/files/screwcut5.jpg


John S.

Michael Moore
03-06-2005, 02:03 PM
Hello Rob,

A lot of it appears to be a local practice thing. If you look at photos of lathes taken in Europe and Japan, you'll pretty much always see them with the top slide parallel to the ways, while in the US setting it at an angle for threading and leaving it there appears to be very common.

My guess is that if you leave the top slide parallel to the ways then you'd move the carriage up to a hard stop and then use the divisions on the top slide for moving in to the final position. It the top slide reads direct (.001" on the dial is .001" of movement (radius), not .001 off the diameter) then that would make a lot of sense to me. If it reads on the diameter you'd need to remember to double the top slide reading, but you'd still have more control than cranking the carriage along.

I'd suggest putting it in whatever position makes things work best for you and/or the particular job.

I forgot to mention that on my Mori Seiki the OEM indexable turret toolpost indexes with the sides parallel to the sides of the top slide, so it would seem to indicate the manufacturers intended the top slide to be run parallel to the ways.

cheers,
Michael

[This message has been edited by Michael Moore (edited 03-06-2005).]

snowman
03-06-2005, 02:29 PM
I find myself keeping the compound set at 45 degrees more common. Most everything I make ends up with a small chamfer to make easier insertion into another hole.

I will however soon be doing this by "feel", moving cross and saddle at the same time, as I am switching to John's method of just having a solid block. I need more rigidity.

-Jacob

John Stevenson
03-06-2005, 02:44 PM
I have a tool ground at 45 on the front face and 45 on the side face with bags of undercut on the side face.
Front face does external chamfers and de burrs, side face does internal ones hence the undercutting.
This is on the lathe with the block.

My other lathe, a CVA with top slide is unusual in that the sliding clutch lever and the surfacing clutch lever are not interlinked.
You can select both together and the gearing is in built to give you a perfect 45 chamfer regardless of what tool is fitted.

John S.

darryl
03-06-2005, 04:28 PM
From my perspective as a hobby guy with many years on the lathe and mill-
I orient the topslide to satisfy a few basic requirements. One is to keep the overhang of the cutter as short as practical, another is to enable it to reach the extremes of the workpiece, another is to angle a boring bar properly so it cuts well without interference with the workpiece, another is to lessen the possibility of the workpiece hitting the carriage- all this is in conjunction with rotating the toolpost to do the same things. It's better if you can adjust both topslide and toolpost to keep the cutter closer to being centered over the carriage. Mostly it's to the left of center, and if the job requires, it may be far to the left of the crosslide. This condition can lead to chatter and inaccuracies, but if that's what angles you need to have on both toolpost and topslide to make the cutter reach without interference or a large overhang, then that's what the right adjustments are.
I also remove the compound sometimes and just use a block bolted to the crosslide to hold a cutter. I have made several custom holders to do this, and each is more or less optimized to hold it's cutter to the proper angles. I kind of like this because I'm not that keen on playing with the gib screws all the time to remove play from an axis that isn't going to be needed. That's another thing- if you're going to be leaving the topslide free to move , even if it's motion is not being used, then the play in it's slide will add to errors in cutting. Depending on what kind of cut you're making, a facing cut or turning on a diameter, or an inside cut, you can minimize the error by orienting the topslide so it's play has the minimal effect.
When I am using the crosslide to hold the toolpost, I find more often than not that it is set around the 30 degree or so mark, that seems to be where it suits most often.
Conditions where the angle is critical- threadcutting, taper turning, precice concave or convex facing cuts, and when wanting to use the crosslide to make fine adjustments to tool bit position. This last use has to take into consideration all the various plays, or it becomes of limited usefulness.

aboard_epsilon
03-06-2005, 05:04 PM
THANKYOU JOHN
Not had chance to look until now, took a lot of time to download them machine shop practice manuals... 515mb's !!! and 41mb's for the advanced machinist
Thanks JC.
Yep the pics are easy to understand.....you got to find tiny ones to do the internal threads by the looks of it.
all the best.mark

John Stevenson
03-06-2005, 05:17 PM
<font face="Verdana, Arial" size="2">Originally posted by aboard_epsilon:

Yep the pics are easy to understand.....you got to find tiny ones to do the internal threads by the looks of it.
all the best.mark</font>

Not if you do big internal threads http://bbs.homeshopmachinist.net//biggrin.gif

John s.

Paul Alciatore
03-06-2005, 05:19 PM
A little bit more on the "30 degree / 1/2 / half the sq root of 3" thing.

The 30-60-90 triangle does have sides of 1, 2, (sq rt3)/2. If the cdompound is set at the standard 29.5 degrees for threading, them the infeed will equal (sq rt3)/2 times the dial reading but the axial feed will be 1/2 the dial reading. If it is set to 60 degrees, then those two are reversed. The 60 degree/1/2 dial reading will provide a direct diameter reduction reading. This can be handy.

Another angle I have written down is 5.74 degrees or the supplemental angle of 84.26 degrees. This setting, 84.26 degrees, from the angle of the cross feed, will provide a radius reading of 1/10 of the dial or the dial will now read tenths (1/1000" per division). This can also be very handy. Since things are getting very linear at these small angles, half of the 5.74 degrees or 2.87 degrees will get you down to half tenths or 0.00005 per dial division. So one division on the dial will reduce the diameter by one tenth.

Paul A.

wierdscience
03-06-2005, 07:34 PM
<font face="Verdana, Arial" size="2">Originally posted by aboard_epsilon:

Yep the pics are easy to understand.....you got to find tiny ones to do the internal threads by the looks of it.
all the best.mark</font>

Mark,I pop a thread tap of the needed pitch in the boring bar holder and thread away.Makes life easier on the 1-1/4-20tpi threads I do a lot of.

kap pullen
03-06-2005, 07:37 PM
John,

What's the advantage using a chaser to thread with?

The following teeth will drag on the job and push it away? Seems that way to me.

I do a lot of stainless and dragging is not a good thing there.

Stainless and titanium taps have the following threads removed so they don't drag and "pick up".

If you set it to clear in the back, the thread angle will be off.

I have to thread on center often. That tool
would foul the center.

When you have to do a "pull out" thread job, or end in a one pitch wide groove, or against a shoulder, the couple threads cutting will not give a clear end of the thread.

Every one does things differently, just curious what the advantage of a solid block is too.

The engine lathe has been evolving for two hundred years. Is this the next step?
Make it a more versital machine?

Darryl is right,

The compound can vibrate into, or out of a cut when roughing, depending on tool pressure, backlash, and compound angle.

That is why I run with the compound all the way in, bottomed out.

I have scrapped more than one job because that compound handle cought on my shirt, or badge.

Kap Pullen

wierdscience
03-06-2005, 07:40 PM
As to the cross slide question I leave mine set at 29-1/2 on the small lathe and 0 on the big one.Reason is I use the small lathe most often for threading and the big one for cutoff and roughing.

John,what make QC post is that? Thats the first I have seen with the dovetail reversed.

wierdscience
03-06-2005, 07:45 PM
Kap,what John has is very similar to a TRW "Uni-chaser".It used a wide chaser and cut finished threads in two passes.

I haven't tried it,but I would wager that a projection style chaser would thred to a shoulder or single pitch relief groove.

I too keep the top slide bottomed out and the gibs tight,don't use it unless I am threading or turning a steep taper.

Timewarp
03-06-2005, 08:25 PM
For the guys who have no top slide:
This looks like a much more rigid setup. How do you approach facing cuts? I usually move in close, lock the apron, advance the cutter with the top slide and feed with the cross slide. Take away my topslide and how do I do this?
I get a feeling the answer is going to make me feel a bit ignorant, but hope to learn the right way to do it.

cuemaker
03-06-2005, 09:34 PM
I just love how my 2 basic questions evolve into stuff I dont even begin to understand!

Someday I will.........

Dave Opincarne
03-06-2005, 09:52 PM
<font face="Verdana, Arial" size="2">Originally posted by cuemaker:
I just love how my 2 basic questions evolve into stuff I dont even begin to understand!

Someday I will.........</font>

Welcome to happyland!

rbjscott
03-06-2005, 10:05 PM
The compound turned parallel to the work axis is less ridged than a 30 or 45 degrees. Also 90 degrees is less ridged than a 30 or 45 degree angle because the gib clearance of the cross slide and the compound add together. A way that a lot of machinists add stability when not using the compound, is to clamp a piece of Al. plate between the compound base and the slide-underneath.These plates are real handy when making an interruped cut.

precisionworks
03-06-2005, 10:17 PM
Rob,

It depends. 75% of the time it's set at 90 degrees. Allows you to bring the carriage up close for a facing cut and advance the cutter in rough increments. For finer stock removal (like boring for a Class V bearing fit) the top slide is set to 9 degrees so that 0.001 dial movement gives 0.0001 cutter movement. (For really close work you can use .9 degrees but you end up moving the cutter so far forward & so little inward that you can run out of travel).

Threading at 29 degrees + a hair.

Approach angle of cutter to work ("tool angle")...whatever it takes to make the cut. As long as point of cutter is on centerline (for OD turning) it seems not to matter how the point approaches the cut. Position the cutter for the most effective use of that particular profile, nose radius, chipbreaker, etc. For boring (ID turning, grooving) set the point 0.010" above centerline.

John Stevenson
03-07-2005, 04:07 AM
Kap asked:-

"What's the advantage using a chaser to thread with? The following teeth will drag on the job and push it away? Seems that way to me. I do a lot of stainless and dragging is not a good thing there. If you set it to clear in the back, the thread angle will be off."

The advantage is the thread is fully formed, it a poor mans way of having expensive lay down full form inserts.
If you can afford laydown inserts fine but for the people using home ground single point tools this saves the last finish operation with a die or chaser to get the correct root and crest radii.


I have to thread on center often. That tool
would foul the center. When you have to do a "pull out" thread job, or end in a one pitch wide groove, or against a shoulder, the couple threads cutting will not give a clear end of the thread.

That's true about the centre, there are ways round it like grind some teeth off or use an extended centre but there are always limitations with tools otherwise we would only ever need one lathe tool. http://bbs.homeshopmachinist.net//biggrin.gif

Pull out is no problem. When you pull the first tooth out all the rest follow http://bbs.homeshopmachinist.net//biggrin.gif


Every one does things differently, just curious what the advantage of a solid block is too. The engine lathe has been evolving for two hundred years. Is this the next step?
Make it a more versital machine?

Could be, CNC lathes that don't have turrets also don't have top slides.
Your remarks below seem to answer your own question.

Darryl is right,
The compound can vibrate into, or out of a cut when roughing, depending on tool pressure, backlash, and compound angle.
That is why I run with the compound all the way in, bottomed out.
I have scrapped more than one job because that compound handle cought on my shirt, or badge.

Kap Pullen

John S.

John Stevenson
03-07-2005, 04:24 AM
<font face="Verdana, Arial" size="2">Originally posted by wierdscience:
John,what make QC post is that? Thats the first I have seen with the dovetail reversed.</font>

Weird,
It's one of my own design, I did this ages ago before all the cheap imports came into the country.
At that time the only small QC post here was the Dickerson one, same as Myfords use but they were very expensive and only came with 4 holders, two realy as one was a parting off holder and one was a boring holder.

I sat down and worked out the simplist way to make one. I reckoned that you only have to make one block but many holders so the holders need to be the easiest to make.
It doesn't really matter how much work goes into the block if the holder is simple.

I chose this method as the holder with it's external dovetail can be done in long lengths on a horizonatl mill with a 60 degree cutter and then cut off as needed from the block.
An 18" long length of steel could be dovetailed in two passes, one either side in under an hour, then cut off and finished to suit the type of tool. Specials can be made from spare unfinished blocks.

http://homepage.ntlworld.com/stevenson.engineers/lsteve/files/toolpost.jpg

Since then I have made three more blocks so that all the tooling can be shared between three lathes with not alteration. The blocks vary on the stop height so the tip remains on centre.
One advantage I have found that I didn't work into the design is that with the block having an internal dovetail you can get closer to the work that the Aloris type with external dovetails.

This design was submitted and published in Model Engineer in about 1989 so it's getting on a bit.
It's also on the web on the Metalwebnews site:-

http://www.metalwebnews.com/howto/toolpost/toolpost.html

Would I go thru this exercise today in light of the import holders and their respective low price? Probably not but at the time I didn't have a choice.

John S.

precisionworks
03-07-2005, 08:36 AM
Nice work. Now I have MTBE (Multiple Tool Block Envy) &lt;LOL&gt;

Timewarp
03-08-2005, 02:34 PM
Hey guys, any answer to my previous question?

Pablo

John Stevenson
03-08-2005, 02:36 PM
Pablo,
I just move the carriage along then face off.

John S.