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Phil McCrackin
12-21-2008, 09:49 PM
Hi all, I have been away for a while (and no, not prison..college... lol).

Anyhow, I have been working on a very important project (turning a big bar into a small one..lol) And I am having some problems.

I have a Chinese 9x20 lathe, that i just made a 4 bolt tool post clamp for. I have modified it with a variable speed motor, and just recently bought a live center for the tail stock, and I am using a 5/16 cobalt tool bit that I sharpened with an oil stone. I have tried all kinds of different speeds.

I am turning between centers, with no lube.

Its a Home Depot 1" x 12" bar, and from what I gather, that could be the problem, but...

How deep should I be able to cut before it starts to chatter.

Currently i can get to about .025 inch before it starts 'screeching'.

Is this about all I can expect? Or am I doing something wrong?

I thought I could cut .100 per pass with no problem, but.....

Is .100 only reserved for the 'big boys'?

Thanks, Phil

recoilless
12-21-2008, 09:57 PM
Phil:

What speed is the spindle turning at?

Also, steel bought at HD may be of some dubious origin.
Perhaps a pic of your tool bit may help...if you can get away w/ .020 per pass and finish the job, try that. .100 is probably pushing a 9x20 CL, I've never run that particular lathe maybe some owners may chime in.

torker
12-21-2008, 10:06 PM
A sharp and properly positioned tool bit should never screech. It may if your spindle speed is too high and it's burning the bit.
It should be too busy cutting to screech. JT will tell you how to sharpen that bit.
I use his methods for HSS now and it's pretty amazing how deep the cuts can be.
Think .125 doc (.250 total)with an underpowered SB9..in backgear

macona
12-21-2008, 10:13 PM
Crappy CRS steel can be a nightmare to turn. Cut deep and feed fast. Try not to take light cuts or it will tear and chatter.

Phil McCrackin
12-21-2008, 10:16 PM
recoilless,

I do not have an rpm meter (yet), so I can not give you the exact rpms, but trust me, I have tried all kinds of different speeds.

As far as finishing the job, I am just experimenting. I would just like to know what the capabilities of the machine/me are.

I have found occasionally, that if I start at .030 it will do o.k. for a while and then start chattering after a few inches.

Phil McCrackin
12-21-2008, 10:29 PM
"JT will tell you how to sharpen that bit."

I would like to talk to JT. Does sharpening the bit have that much to do with it?

I thought I did a decent job.

I know I am ignorant in these matters, but doesn't the bit basically get "dull" after just a few seconds anyway?

Hell, I cant sharpen my steak knives without my wife/kids using them for cutting open packages, Barbie packaging tie downs, screwdrivers, marble carvings, ice sculptures,.....etc.. and ruining the edge.

J Tiers
12-21-2008, 10:34 PM
The machine is a bit light and a bit more flexible than some, so that will limit depth.

Sharpen the bit to cut on the side, and not the end, with a 30 deg rake from left to right, you should get maximum depth of cut....

Minimize the radius on the end, and relieve the bit away from the work on the end.

Works for me.....

The major issue is how much edge is in the cut, and how much cutting force is needed. With a flat top, "neutral rake" you have a lot of force. With strong positive rake, that is drastically reduced.

Then also, radius on the end is all cutting edge, in the metal, but some of it is much longer than it needs to be per MM of cut depth.

So a straight cutting edge, at 90 deg or so to spindle axis, gets the max depth of cut per mm of edge in the cut. Minimal radius, and raking away from the work on the end, both help.

I can cut leaving an 0.090" "stem" when starting with a 0.312 diameter rod, in one pass, and let the stem stick out an inch.... With a radiused cutter, no way, you will push over the stem. (I use a 10" Logan, which admittedly is stouter than the 9 x 20).

Your 9 x 20 needs all the help you can provide, because the flexibility encourages chatter. So use lots of rake, etc, and you will do the best it can.

BillH
12-21-2008, 10:50 PM
Tonight I found a rod of HRS. Ground a 1/4" hss bit, and tried a cut with my new lathemaster 8x14. Depth of cut was around .050, made very nice BLUE chips, no screeching.
The 8x14 though IS a beefier machine than your 9x20, not a whole lot but enough for me to say that it is very close to my South Bend 9".

If you are getting screeching, I would first look at your tool bit geometry, make absolutely sure nothing is rubbing and that the cutting edge is the only part of the tool touching the workpiece. A finishing bit has a large radius so more of the bit is contacting the workpiece, you must use a small doc or it will chatter.

torker
12-21-2008, 10:53 PM
See..I told you :D
You got pics of your cutter?

dp
12-21-2008, 11:01 PM
There's a guy on Ebay that sells electronic optical RPM counters and also has an online store. I bought one long ago and it's excellent, and I received it within days of ordering it.

http://www.meter-depot.com/

Phil McCrackin
12-21-2008, 11:11 PM
I assume JT is short for J Tiers. Thanks for replying.

When you say "30 degrees from left to right", does this mean that that the bottom of the bit should be 30 degrees behind the top(a 30 degree slant from top to bottom)?

What does "relieving the bit from the work" mean?

The only example I can give, is in the book I bought. For Aluminum, it tells me to grind a very, very steep angle on the bit. Is this what you are talking about? However, for steel it says only 10 degrees or so.(almost flat-slightly tilted back).

I bought pre-made bits from my local supplier and the 'rake' is not very steep, and from the book I have, the 'rake' for steel is also very shallow. However I don't think they had my machine in mind when the went to print.

Is this the price I pay for a small machine?

Phil McCrackin
12-21-2008, 11:21 PM
"you must use a small doc or it will chatter."

What is a doc?

OMG, I am learning so much, it's like am back in class.


DP, no money for rpm counters right now, but trust me, it's on the list.


Torker, yea you were right.


BillH, My 9x20 could beat up your 8x14...LOL

KiloBravo
12-21-2008, 11:26 PM
DOC = Depth of Cut

How about this picture

http://upload.wikimedia.org/wikipedia/commons/0/0e/Tool_Bit_Geometry.JPG

This is a good read too... http://en.wikipedia.org/wiki/Tool_bit

BillH
12-21-2008, 11:26 PM
"you must use a small doc or it will chatter."

What is a doc?

OMG, I am learning so much, it's like am back in class.


DP, no money for rpm counters right now, but trust me, it's on the list.


Torker, yea you were right.


BillH, My 9x20 could beat up your 8x14...LOL
Well size does matter, measure the bed width of your lathe, also measure the width between the dovetails of your crosslide. Now compare that to the 8x14 lathe. Hey, you just learned something new :)

Seriously, post some pictures so we can help you better.

dan s
12-21-2008, 11:27 PM
Phil,

This will help with the angles.

http://littlemachineshop.com/Reference/RakeRelief.php

J are you saying 30 degrees of side rake?

Fasttrack
12-21-2008, 11:32 PM
Well if you bought a real lathe, you could be taking .25 DOC no problem :)

http://i108.photobucket.com/albums/n22/fasttrack237/Pacemaker/100_0589.jpg

That is a .20 DOC at 400 rpm and .035 ipr, IIRC. It was on a piece of an old motor shaft that was too hard even for 8% cobalt bits. The carbide left a beautiful shiny finish behind. (For reference, that chuck is a 10" chuck)

I couldn't resist, sorry :o

I think we'd all like to see some pics of the setup, it sounds like you've got a problem with the toolbit. I've got a small 3-in-1 machine (the Smithy Midas) and I can take .1 DOC with out any major issues. There is enough flex that it actually only takes about .09 DOC, but no chatter or anything. And I know all about the HD mystery bars! That was a main source of metal for a while. Then I wised up :D

Phil McCrackin
12-21-2008, 11:52 PM
Well size does matter, measure the bed width of your lathe, also measure the width between the dovetails of your crosslide. Now compare that to the 8x14 lathe. Hey, you just learned something new :)

Seriously, post some pictures so we can help you better.

O.K., but what pictures do you need? Close ups of the bit itself, or my set up or both? ....And BTW the ladies know that length is where it's at...and stop calling me 'Seriously' (Airplane 1977)

Fasttrack, My shaft is much larger than that, so unfortunately, your mini-shaft comparison will not work....LOL

Dan S, thanks for the link, I am looking it over now.

kben77, thanks for the pic, that clears a lot of things up for me.

BillH
12-21-2008, 11:54 PM
give us a picture of the setup in the lathe, the workpiece, the tool, and the tool touching the workpiece.

torker
12-22-2008, 12:00 AM
Yup...sharpen that bit just like in the diagram shown. Back rake and side rake.
I grind/sharpen mine a little different but the idea is the same. I seldom grind the bit after that...a good hone...nice and shiny. The tool is very sharp...it actually CUTS the metal... unlike an insert that has to displace the metal first.

BadDog
12-22-2008, 12:01 AM
Well if you bought a real lathe, you could be taking .25 DOC no problem :)

Aint it though! I recently made some steel hubs where I had to drop for 3" to 1.300 over a 3" length. 3 passes at 0.023 feed took about 4 seconds each and had me 1.500, and with a nice finish!. I knew it was going to be nice to have real roughing capability, but that's not why I bought this lathe. Still, it's great fun to see that thing spraying a rooster tail of hot chips clanking when they hit... without even grunting...

BadDog
12-22-2008, 12:10 AM
On the original topic, I started out with a 9x20 and from what I recall, about 0.050 (0.100 diameter) was about all it wanted in steel. But get some decent steel, not hardware garbage, which is among the worst options you could pick. HSS bits sharpened similar to that pic should get you there, but keep the nose radius small and set with about 5-15* lead angle where possible (seems I had better luck around 5-10*???). Too much causes push away that that lathe can't handle it.

If you haven't already, look into replacing the compound mount. The stock item is pure garbage, and that upgrade is the single best you'll ever make. If you don't know what I'm talking about, join the 9x20 Yahoo group and do some reading. Lots of folks on there go to amazing lengths fixing the shortcomings of that lathe, almost becoming a hobby in itself. I wasn't that interested in making it another hobby, which led to my first upgrade to a Rockwell 11x37...

macona
12-22-2008, 12:21 AM
Fasttrack, you'll like this lathe. The monarch I got for TechShop, Sorry for the size of the pic! 15HP, 24" Swing:

http://i398.photobucket.com/albums/pp69/TechShop/Machine%20Shop/DSC04015.jpg

Phil, go to someplace like OnlineMetals and pick up one of their assortments of either 12L14 or 1144 "Stressprooof" rod. You get a good assortment to play with and the stuff machines great.

Even on my 10EE I have a hard time getting a good finish on crappy CRS.

J Tiers
12-22-2008, 12:32 AM
Phil,

This will help with the angles.

http://littlemachineshop.com/Reference/RakeRelief.php

J are you saying 30 degrees of side rake?

Yep. bag the back rake AND the "side cutting angle", just go with the side rake. And minimize the radius. With a fine feed it will still give a good finish with a very small radius.

The radius, and side cutting angle just resolve into forces that push the bit away from the work, and vice-versa. They have their place, but it isn't on my machine for large D.O.C. They add to the length of "cutting edge" without letting that edge all be depth of cut.

The forces they produce that push "out", all contribute to chatter, without necessarily helping with the cut. When you have a light machine, you don't want any extra forces, you want to cut with the least possible total force on the tool, regardless of direction.

Forces "out" also react on the work, leading to "spring", diameter errors, etc. For small diameters that cannot be effectively centered, that is deadly.

I learned this while making guide nosepieces for counterbores..... You may have a 0.3" diameter nose, that has a 1" + stem to fit in a 0.090 hole down the body of the counterbore. I can't center a 0.090 part decently, there is hardly any meat on it, even with my smallest center drill, which is pretty small. And I have no female centers (something I should fix).

Oldbrock
12-22-2008, 12:35 AM
No, No Bill. you should never get blue chips when machining with hss. that's carbide territory. You should be around 300 rpm, your lathe probably won't go that slow, or will it. I'm not familiar with china lathes except a new piece of junk my buddy bought. Took us two weeks to get it sorted and then the tailstock lock won't lock it to the bed no matter what setting we use. Even when the cam won't quite go over center you can't push a drill without the tailstock sliding back. Compound angular graduations are a joke. Bit of plastic stuck on the base and nowhere near correct. Give me US or European iron any day. Peter

macona
12-22-2008, 01:08 AM
Nothing wrong with blue chips with HSS. Though they shouldnt be turning blue till they pop off.

torker
12-22-2008, 01:11 AM
Here's some (crappy) pics of an old cutter I use for almost anything. It gets reground from right to left etc. It's kinda hard to tell what I'm doing with it...but it's got plenty enough side rake to cut well...plus I grind a little chipbreaker into it...it actually gives it back rake but it's very nice to have curls instead of ribbons of swarf.
And believe me...this thing will cut. It needs to be totally reground now...too many changes for certain work etc.. BTW..I have this ground for facing right now.
http://img.photobucket.com/albums/v210/torker/IMG_0046.jpg
http://img.photobucket.com/albums/v210/torker/IMG_0047.jpg
http://img.photobucket.com/albums/v210/torker/IMG_0049.jpg
Here is a facing tool I use for aluminum. It is very aggressive but will easily take .100 doc and makes beautiful coils...not strings
http://img.photobucket.com/albums/v210/torker/IMG_0050.jpg

Davek0974
12-22-2008, 03:45 AM
Hi all, great thread.

I was taught that the things to check first when getting chatter were tool projection and workpiece rigidity. It sounds like the work is a 1" bar 12" long supported (i hope) with a live centre, but no one has asked how much tool is sticking out? if its a lot then surely it will chatter?

I wouldnt have thought that a heavy cut along a 1"x12" bar was a good idea on any setup without either getting chatter or risking a wrap-up, unless a travelling steady was used.

I'm using carbide but i'm getting to the point where i want to sharpen HSS for fine cuts as carbide hates them, so i'm getting some good tips from this thread. I've picked up some HSS blanks and will have a go now. I can also vouch for the crappy steel effect, i had some at the beginning and nearly gave up! Then i got some good stuff and boosted my confidence no end.

oldtiffie
12-22-2008, 04:40 AM
A "traveling" steady rest works wonders as it resists any upward or back-ward forces caused by the tool at the cutting edge that normally cause the work to both "lift" and get forced "back".

Your Old Dog
12-22-2008, 07:48 AM
Don't know that I can lend much except to tell you what my problems were at one time.

Too much bit hanging out of the tool holder. I learned to think in terms of rigidity.

Too much stock hanging out of the chuck. I learned to think in terms of rigidity.

I now lock the gib screws on the compound vice when it's not being used. I learned to think in terms of rigidity.

If I am facing, I lock down the apron. I learned to think in terms of rigidity.

Recently discovered two screws on the back of my apron that allowed movement so I snugged them up, big improvement. Yes, I've learned to think in terms of rigidity.

Good luck.

DICKEYBIRD
12-22-2008, 07:52 AM
I have a middle 80's era Taiwanese 8x16 which is very close to the 9x20 other than the size. I had a lot of chatter problems until I took off the compound and mounted my QCTP directly to the cross slide. I only put the compound back on when I need to cut a short taper (rarely) or do some threading (even more rarely.)

The difference in rigidity is amazing. .050" d.o.c. in decent steel is easy if the rpm is lowered. Contrary to popular advice, I use the cheap Chinese 3/8" "Indexable Turning Tool" sets with TCMT carbide inserts. The TCMT inserts have positive rake and work a treat for everything I cut. Plus, they are cheap enough that if I crash & screw one up, I can afford to buy another one without losing sleep over it. The insert retainer screws that come with the sets are soft and have to be replaced but that's no biggie.

Yes, I know how to grind HSS but only do so when a form tool or otherwise special tool is needed. I have a decent grinder with a good wheel on it and enjoyed learning the HSS grinding ritual but have since drifted back to using inserts. My shop time is limited and when I'm into a project, I like to spend my time making chips instead of covering up my machines to keep off the *&@$#@*% grinding dust and maintaining a crisp HSS tool. That's my story anyhoo.:)

airsmith282
12-22-2008, 10:14 AM
aare you using a follower rest if not then id be putting on on there other wise your going to be making a really badley tapered bar in the end.
also given that a follower rest is a great tool for better accuracy i would take smaller buts besudes whats the hurrry, if your dry cutting any steel its goingto heat up alot and as it gets hot it expands and then when it cools its not going to be the right OD in the end it will either stll be to big or to small also the structure of metal is also as such that when they make it its not all the same tensile strenght 100% the lenght anyhow so turn really slow and ligter cuts or turn slow or a bit faster but keep it cold as you can .

as for HD steel the sutff is total crap i have a few rods here i bought and its a Bas****ard to try and turn. i never had alot of luck with it.its no better then a weight set bar steel in fact i thinks its the same grade of junk good for making stuff you dont want any one else to see becuase of how embarssing the cutting and finishing results are ..

Boucher
12-22-2008, 11:15 AM
Yup...sharpen that bit just like in the diagram shown. Back rake and side rake.
I grind/sharpen mine a little different but the idea is the same. I seldom grind the bit after that...a good hone...nice and shiny. The tool is very sharp...it actually CUTS the metal... unlike an insert that has to displace the metal first.

How do you grind the back rake, side rake and chip breaker? What order do you grind the surfaces. I inherited a box of old HSS tools from an old shop going out of business. Lots of good examples and working stock. Some chip breakers appear to be groove cut with perhaps a dremmel tool.

Fasttrack
12-22-2008, 12:47 PM
Fasttrack, you'll like this lathe. The monarch I got for TechShop, Sorry for the size of the pic! 15HP, 24" Swing:

http://i398.photobucket.com/albums/pp69/TechShop/Machine%20Shop/DSC04015.jpg

Phil, go to someplace like OnlineMetals and pick up one of their assortments of either 12L14 or 1144 "Stressprooof" rod. You get a good assortment to play with and the stuff machines great.

Even on my 10EE I have a hard time getting a good finish on crappy CRS.


Ahh you know me well! If its big and its old, I'll probably love it :) I forgot about Monarch's 60 and 6xx series lathes. Whenever I hear Monarch, the first lathe that comes to mind is, of course, the 10EE. Those big ones were awsome machines, too though! There is one of about that size and vintage in the machine shop at Fermilab. Always get a kick out of seeing that machine shop.

(BTW Macona, your pm box was full. I tried to pm you a thank you for the vacuum feedthrough. It works great, so thank you very much! I'll be working on the same project next semester but we were succesfull in generating an electron beam)

Carld
12-22-2008, 01:39 PM
Boucher, there is no special order for grinding except the chip breaker goes on last. You can grind the side clearance, the tip clearance and then the back rake if needed, then put the chip breaker on if needed.

I don't always use a chip breaker or a back rake. I mostly use backrake for non ferrous metals. For steels I use a flat top and level with the centerline of the work. It helps to have a lathe tool grinder as shown in the photo that is blueish gray. With that grinder you can adjust the table for the angle you want and there is a guide to set the side angle if you want to use it. I mostly go free hand on the side angles.

http://i82.photobucket.com/albums/j276/yeathatshim/P1010003copy.jpg

Phil McCrackin
12-22-2008, 03:31 PM
Thanks guys, for all the advice and here are the pictures I promised.

Torker, my bit looks nothing like yours, maybe that's my problem

http://i205.photobucket.com/albums/bb164/troll123_photo/IMG_1230.jpg

http://i205.photobucket.com/albums/bb164/troll123_photo/IMG_1232.jpg

http://i205.photobucket.com/albums/bb164/troll123_photo/IMG_1233.jpg

http://i205.photobucket.com/albums/bb164/troll123_photo/IMG_1237.jpg

Phil McCrackin
12-22-2008, 03:38 PM
More pictures

http://i205.photobucket.com/albums/bb164/troll123_photo/IMG_1238.jpg

http://i205.photobucket.com/albums/bb164/troll123_photo/IMG_1242.jpg

http://i205.photobucket.com/albums/bb164/troll123_photo/IMG_1246.jpg

http://i205.photobucket.com/albums/bb164/troll123_photo/IMG_1251.jpg

Phil McCrackin
12-22-2008, 03:42 PM
Last set of pics

http://i205.photobucket.com/albums/bb164/troll123_photo/IMG_1253.jpg

http://i205.photobucket.com/albums/bb164/troll123_photo/IMG_1254.jpg

http://i205.photobucket.com/albums/bb164/troll123_photo/IMG_1231.jpg

One off topic

http://i205.photobucket.com/albums/bb164/troll123_photo/BigAirAug29551.jpg

dan s
12-22-2008, 04:03 PM
I think the tip radius is a big part of your problem... it looks to be 3/32" it needs to be more like 1/64" or 1/32". A large tip radius like that is pushing the work away from the cutter.



More pictures

http://i205.photobucket.com/albums/bb164/troll123_photo/IMG_1251.jpg

Phil McCrackin
12-22-2008, 04:12 PM
Yea, I noticed that in Torkers bit picture, he had what looks like a pointed tip.

Like I said earlier, I was going by a book I bought but they may have been talking about larger machines.

Liger Zero
12-22-2008, 04:16 PM
Wow thanks for the pics, I'm learning a few things just looking at your setups.

Oldbrock
12-22-2008, 04:23 PM
I notice you have 0 top rake and much too big a radius on your bit. Positive top rake should slope down from the cutting edge toward the tailstock. about 10 degrees, more for aluminum and 0 or flat for brass and bronze. some back rake is also good for steel and aluminum. That is the top surface slopes down back from the tip toward the toolpost, pulls the chip away from the machined surface to avoid galling it. Grind the tool with a sharp point and then just hone a little flat in line with the material maintaining clearance. Use about 80 feet per minute. R.P.M = speed (80) x 4 divided by the cutting diameter. For 1" it would be 320 rpm. I use soluble oil and water at about 50 to 1 and have always had good results. Hope this helps and have a Great Christmas and great finishes in the New Year. Peter

Ryobiguy
12-22-2008, 04:32 PM
That looks a lot like the first toolbit I made to cut some home depot crap steel, almost the same situation.

From the top view, I'd grind the trailing edge back a bit to get rid of the radius at the leading side. For roughing, you want a tiny radius, just enough to prevent the corner from being a point. Probably best to leave a nice straight edge from the grinder, and radius it by hand with abrasive file.

It also is a flimsy setup with that diameter for that length, so it may chatter or at least leave a horrible finish (overall because it's bad steel,) particular towards the middle. To maintain diameter accuracy, I guess the best bet would be super fine feed with super small tool radius so there's less force making it spring away from the cutter in the middle of the bar.

Torker -- I've recently been playing with a similar chip "breaking" groove setup for aluminum. I ground it what I thought it should be, but it worked better cutting in the other direction! Interesting how the chip peeling off follows the contours of the first bit of the edge, you have to direct the forming of it to shape the curl of the chip, to try and make it peel off in front of the cut so it doesn't rub the finish of what's been cut already.

-Matt

S_J_H
12-22-2008, 04:38 PM
looking at your pic, It looks like you are plunging into the part and then turning? The tool radius is a bit large to be plunging into the part like that.
You will not be able to take a max DOC turning between centers and no follow rest on that part either.

I owned a 9x20 for a few years and turned it into a hobby to improve it. Geez I sure did a lot of work to that machine!
Get some 12l14 and you'll be able to maybe take a .1" DOC (.2 off the diameter) under power feed. Be warned though that the worm drive on the 9x20 is not very robust. In 6061 about .125" DOC (.250 off the diameter) is possible under power feed. Again it's really pushing the 9x20 hard though.
My old 9x20 taking a .125" DOC in some 6061 with a ccmt insert-.
http://i109.photobucket.com/albums/n48/S_J_H/7xcompoundconversion014.jpg

Steve

Fasttrack
12-22-2008, 05:54 PM
Phil - I think someone has already mentioned this (maybe more than once) but I think you'll find that adding a follow rest or a steady rest will greatly improve your situation. The tip radius is definitely too large for this application. You might be able to get away with it on a shorter piece, but even if you were on a big ol' Pacemaker, you'd want a follow rest to use such a big radius bit on such a tiny diameter piece. I think if you get a "sharper" (i.e. more pointed) bit and rig up some sort of follower, you'll get much much better results. The follow rest doesn't need to be anything special. Below is a simple one I rigged up to machine the output shaft for a go-kart transmission. Just a simple piece of square tubing, some threaded rod, a t-nut and an old bearing. (Actually the bearing is from the T/A on my Pacemaker. They were all rusted and seized up so I replaced them but saved a few that I thought I could loosen up by soaking in WD40)

http://i108.photobucket.com/albums/n22/fasttrack237/go-kart/100_0663.jpg

http://i108.photobucket.com/albums/n22/fasttrack237/go-kart/100_0660.jpg

dan s
12-22-2008, 06:18 PM
Phil,

This is the type of Bit J is talking about. It's a 1/2" square bit to scale.

back rake: 0
side rake: 30
lead angle: 0 (aka side cutting edge angle)
side relief: 7
front relief: 7
front angle: 5
tip radius: 1/64"

Perspective View
http://img175.imageshack.us/img175/5274/perspectivequ9.png (http://imageshack.us)

Top View
http://img261.imageshack.us/img261/5352/topfs3.png (http://imageshack.us)

End View
http://img392.imageshack.us/img392/166/endjo9.png (http://imageshack.us)

Side View
http://img72.imageshack.us/img72/8486/sidenz1.png (http://imageshack.us)

torker
12-22-2008, 06:47 PM
Good pics Dan!
BTW..I grind my chip breakers with a cup wheel on my homebrewed cutter grinder gadget(It's ok Russ...no pic). Phil..if you tried my bit you'da thunk you bought a new lathe...
Get the side rake on there... it'll suprise you.
You may notice...my bit has been regound in different configures too many times...needs a proper regind to replicate the angle J is talking about. And believe it or not...there is a very small radius on it. I hone the radius on it with an oil stone.
Russ

BadDog
12-22-2008, 07:17 PM
Good pics Dan!
BTW..I grind my chip breakers with a cup wheel on my homebrewed cutter grinder gadget(It's ok Russ...no pic).
Russ
Wheeew! I don't think I could take that today... ;) :o

Phil McCrackin
12-22-2008, 07:51 PM
"It looks like you are plunging into the part and then turning?"

That is exactly what I was doing. Is this incorrect?

Well thanks to all of you, I have some new things to try.

1. regrind by bit

2. retro-fit my steady rest with a bearings; it only has brass pads and before when I tried to use it on aluminum, it carved out a ring and I did use oil.

3. Slow my speeds down.

Any comments about my bit height? Its basically even with the dead center.

About how long should I expect to get out of a bit before it needs re-sharpening? (minutes, hours, days.....),AL @ steel


Hey Dan, That picture is awesome, thanks a million, it will really help me out.

It should be a 'sticky'.

dan s
12-22-2008, 08:33 PM
"It looks like you are plunging into the part and then turning?"

That is exactly what I was doing. Is this incorrect?

Yep, that's incorrect.




About how long should I expect to get out of a bit before it needs re-sharpening? (minutes, hours, days.....),AL @ steel
It depends,

tool life is a complex relationship between speed, feed, & doc. The higher they go, the shorter your tool life gets. check out my thread on wall charts, I'm going to post a turning one after dinner.

BillH
12-22-2008, 08:50 PM
"It looks like you are plunging into the part and then turning?"

That is exactly what I was doing. Is this incorrect?

Well thanks to all of you, I have some new things to try.

1. regrind by bit

2. retro-fit my steady rest with a bearings; it only has brass pads and before when I tried to use it on aluminum, it carved out a ring and I did use oil.

3. Slow my speeds down.

Any comments about my bit height? Its basically even with the dead center.

About how long should I expect to get out of a bit before it needs re-sharpening? (minutes, hours, days.....),AL @ steel


Hey Dan, That picture is awesome, thanks a million, it will really help me out.

It should be a 'sticky'.

It's hard for me to write this right now. My mother just died of a massive heart attack.
Phil, you will develop a feel for things. If the bit gets dull, just an oil stone to freshen up the bit. If you drag your tool over your finger nail and it snags, its sharp enough. You created a finishing bit, to be used only for light finishing passes.
You don't want to plunge that type of bit into the work. I am not surprised it is chattering. Use a follow rest. Better yet, use a 3 jaw chuck or 4 jaw chuck and turn the part near the chuck, if the overhang is 3 or 4" use a live center.
Turning between centers, try cutting the workpiece near the support ends, the middle will require a follow rest.

bollie7
12-22-2008, 09:14 PM
Bill
My condolences on your loss. Not much can be said that will make it easier for you. Just try and remember the good times with your Mum. I lost my Mum about 7 years ago and my Dad about 5 years ago. I still miss them and think about them a lot.

regards

bollie7

uute
12-22-2008, 09:36 PM
Hi Phil,

Great thread. On your follower rest, the brass pads should be fine on steel for most things.

uute

J Tiers
12-23-2008, 12:06 AM
Pics of what I was describing. I think the picture angle makes the side rake seem less.
Sorry for the chips, it was working recently.....

http://img.photobucket.com/albums/0803/jstanley/slicer1.jpg
http://img.photobucket.com/albums/0803/jstanley/slicer2.jpg
http://img.photobucket.com/albums/0803/jstanley/slicer3.jpg

tattoomike68
12-23-2008, 01:19 AM
If you are cutting making a roughing pass let it houl, crank the feed as long as you dont stop the machine.

Yankee1
12-23-2008, 02:32 AM
Positive Rake cutting tool holders

--------------------------------------------------------------------------------

Hi Phil
I would advise anyone buying a small 7x12 to purchase a insert type tool holder such as "www.plastools.com" makes. Most carbide type tools are negative rake and require more power to use. The tool holder sold by Plastools is built specifically for small lathes and works very well. I have one and I really like it. It uses the least expensive insert and has six cutting edges. It uses the TNMG-222 and cut far better than the other carbide tools available which are negative rake. Take a look at their website. There is a lot of great information on it.
Chuck

Phil McCrackin
12-23-2008, 09:08 AM
BillH, I am very sorry for your loss and my prayers are with you.

Phil McCrackin
12-23-2008, 09:18 AM
If you are cutting making a roughing pass let it houl, crank the feed as long as you dont stop the machine.


Sorry Mike, I can not do that. It bugs me waaaay to much to listen to that. I would rather stuff my rectum full of M-80's and sit over a flaming hibachi. :)

JT, the top rake on the pic you just posted looks very small, was that pic just to show the side rake?

uute, I''l try it today on my steel practice bar.

Bob Ford
12-23-2008, 10:03 AM
This link will give you good info. http://sherline.com/latheins.htm

They are a good machines for small work.

Bob

torker
12-23-2008, 10:10 AM
Sorry Mike, I can not do that. It bugs me waaaay to much to listen to that. I would rather stuff my rectum full of M-80's and sit over a flaming hibachi. :)

ROFLMAO!!! Damn that was funny... my chuckle for the day :D

J Tiers
12-23-2008, 09:31 PM
Sorry Mike, I can not do that. It bugs me waaaay to much to listen to that. I would rather stuff my rectum full of M-80's and sit over a flaming hibachi. :)

JT, the top rake on the pic you just posted looks very small, was that pic just to show the side rake?

uute, I''l try it today on my steel practice bar.

There AIN'T NO STINKIN TOP RAKE. None.... zero, nil.

I don't believe in it..... or at least in it making a significant difference, for me, on my machine, doing what I do.

It DOES make grinding more difficult, but it doesn't seem to help..... Try NOT putting any on.

J. Randall
12-23-2008, 10:53 PM
J Tiers, now you have me confused. In your first post you stated rake, and the pictures although not to good looked to me like some side rake ground on the top of the tool. Are you maybe calling the front lead angle on the tool "rake" when talking about the 30 degrees? Please help us understand.
James

BadDog
12-23-2008, 11:03 PM
JT, those pictures clearly show positive rake with respect to the direction of feed.

J Tiers
12-23-2008, 11:27 PM
There is "side rake" per the definitions pics posted before......

http://littlemachineshop.com/Reference/RakeRelief.php

There is no back rake, which is what I assume was questioned as "top rake"...... I used the same term as the question. Probably should have said "no back rake" instead of assuming that was the feature meant just because I know there isn't any and the questioner said there didn't look to be much.

There is "side rake", and "side relief", and "front cutting edge angle" (small). There is NO back rake, NO side cutting edge angle, and minimal nose radius.

BadDog
12-24-2008, 12:58 AM
Just as you imply (indirectly), to simply say "top rake" is more than a bit vague (requiring we make the assumption), much less to simply say "rake" by itself. I particularly dislike the terms "back rake" or "top rake" because they are not really descriptive or accurate, but rather more an accepted slang with assumed relations (or so it seems to me).

Rake is always there, no exceptions. It may be either positive, neutral/normal, or negative. It is simply the relationship of the surface across which the chip flows relative to the cutting edge in the direction of travel. If feeding in for a parting/grooving/form tool, then (primary) rake (Pos/N/Neg) is oriented back from the end of the plunging cutter. Similarly for the typical low angle fly-cutter, but primary rake is parallel to the surface, not the bit. But if the bit is somewhat perpendicular and fed along the axis making an OD "turning" cut, then primary rake is oriented as such; what you call side rake. But this is just an artifact of how the length of the bit is oriented to the cut. There may also be a secondary rake, but that goes beyond my point...

But in all cases, "rake" exists, even if neutral (or rather normal to the shear). I think these terms seem to be used far too loosely, and that seems to be a big part of the confusion that surrounds grinding lathe bits, particularly when discussed verbally/textually. I know that lack of consistent terminology caused me a LOT of confusion when I first tried to sort it out. I think I now have a decent functional handle on it now, though what I have come to believe is correct/accurate/consistent terminology certainly isn't the norm, at least it is consistent within my own mental model...

J. Randall
12-24-2008, 03:19 AM
Good post BadDog, and that was the way I was taught, that the grind of the top of the tool is your rake, all other angles are relief, profile etc.
Thanks J Tiers, I will have to try the 30 degrees of side rake, I don't think I have ever put on more than 15 when cutting steel, and that seemed to work pretty good.
James

J Tiers
12-24-2008, 08:43 AM
yep... rake is relative.

This discussion used a particular set of terms per the link, so I am using those. But. as you note, the rake ground in is modified by the orientation of the bit to the work.

Just look at lantern post tool holders.... There are one holding the bit flat, and there are ones tilting it "up". Obviously the very same GRIND would have very different basic rake angles relative to the work when held in the two holder types.

And, then, when either one is actually set up for a cut, the basic rake angles for the holder and grind are modified by the way the holder/bit combination is set in the toolpost relative to the work.

because the work is round, a positive rake can end up negative simply by where it contacts the work. Obviously much trickier on small diameter work, since a smaller absolute position change makes a larger angle difference.

It is probably better to describe the application to the work in terms of the angles AS IF the edge were applied on-center in the intended type holder.

For instance, my pictured grind is used in a "4-way" toolpost, which holds the top edge of the cutter bit on-center. Mine actually accepts 4 standard sizes of cutter from 1/4" to 1/2 inch square. It is arranged so that the top of each size will be on-center. Naturally if the tool edge is ground below the top, it will have to be shimmed up. An Aloris can be set on-center regardless, with no shimming.

torker
12-24-2008, 08:57 AM
Geez...seems like this is all getting very complicated.
It's so simple...grind your cutter with the 30* side rake and be done with it...
Yup...you will learn what ever else will work for you but the bottom line is...the cutter will cut steel like a knife...very free cutting.
When i first took J's advice I didn't think the edge would hold up.
I find that the edge actually lasts far longer...the tool cuts cooler and with far less stress.
I seldom grind mine after I've got what I want.
A quick honing on the oil stone is all it needs.
Russ