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280mark
03-16-2011, 10:00 AM
Hi all, after wanting a lathe for many years a friend gave me this Smithy 3 in 1. It's about 10 years old but only has about an hours use on it and it looks in very good shape with plenty of tooling. He said he could never make it work right but I didn't ask him to explain as I was more concerned with getting it before he changed his mind. I've got it home and set up and now know what he meant, say if you had a piece of stock in the lathe chuck with about 2 inches sticking out to be turned down. The first 1/2" cuts fine then it starts taking a deeper cut as it progresses until it starts to cut too deep and bogs the machine down. This happens with and with out the power feed. It's as if it was cutting a taper. Excuse me if I don't know all the proper machining terms as I am a novice at this but I'm willing to learn and although this is an "offshore machine" it should be able to be made to cut straight. So I'm asking for your help please. Just as in many hobbies I've had what equipment you start off with may not be what you always stay with, it gets bigger and better(and expensive). Thanks, Mark.

steve.murphy
03-16-2011, 10:03 AM
Welcome. Most lathes have an adjustment on the tailstock for just this.
Good Luck Steve

http://www.smithy.com/training_teaser.php?id=8

anders nørgaard
03-16-2011, 12:43 PM
Hmm... sounds to me like the chuck/bore doesn't run parallel to the beds :rolleyes:

From what you explain, my understanding is that the machine is cutting a taper that has got a deceasing diameter, the closer you get to the chuck.

You can find out if that is a fact. Cuck up a piece of round stock and make sure it runs true. Mount a dial gauge on the cutting bit sleigh. Preload the gauge to a certain/random reading. Manually move the sleigh towards the chuck MACHINE NOT RUNNING!! Watch reading on gauge. If the lathe is set up right, the reading shouldn't change! :cool: ;)

That was the Danish version of checking your lathe. If this wasn't clear, maybe one of the local guys could chime in :D ;)

Rick (madera)
03-16-2011, 01:29 PM
Hmm... sounds to me like the chuck/bore doesn't run parallel to the beds :rolleyes:

From what you explain, my understanding is that the machine is cutting a taper that has got a deceasing diameter, the closer you get to the chuck.

You can find out if that is a fact. Cuck up a piece of round stock and make sure it runs true. Mount a dial gauge on the cutting bit sleigh. Preload the gauge to a certain/random reading. Manually move the sleigh towards the chuck MACHINE NOT RUNNING!! Watch reading on gauge. If the lathe is set up right, the reading shouldn't change! :cool: ;)

That was the Danish version of checking your lathe. If this wasn't clear, maybe one of the local guys could chime in :D ;)

That's how us American Machinist do it also:D;)

another thing to do is, turn your lathe on, set the lathe bit at .010 from the material and run the machine with the power feed on. and see if it moves in or away from the material without cutting.

TheRodDoc
03-16-2011, 03:36 PM
You need to make sure you are using a proper tool holder and angles. The tool could be slipping and turning into the work.

Here is an inproper holder for the task and direction of cut in drawing. You can see that if the cutting preasure is more then the holder clamp can hold, then it turns the cutter and it digs into the work. the more it does the harder it pushes the cutter into the work till something breaks or stops. There are many types of holders but the principle is the same. If possable always use a holder that swings the cutter out of the cut instead of into it. ( second drawing )

7952

7953

bob haverstock
03-16-2011, 05:39 PM
Well said, I think that the tool block is rotating, forcing the bit deeper into the material.
Bob Haverstock

You need to make sure you are using a proper tool holder and angles. The tool could be slipping and turning into the work.

Here is an inproper holder for the task and direction of cut in drawing. You can see that if the cutting preasure is more then the holder clamp can hold, then it turns the cutter and it digs into the work. the more it does the harder it pushes the cutter into the work till something breaks or stops. There are many types of holders but the principle is the same. If possable always use a holder that swings the cutter out of the cut instead of into it. ( second drawing )

7952

7953

280mark
03-17-2011, 11:42 AM
Thanks for the quick response guy's! I'll check it out this week end. I'm using the adjustible tool post where you can put in 4 bits and rotate it around for different cuts. I have tried several angles on the bits to no avail and have centered the tip of the bit with the point on the dead center. I'll need to find a suitible piece of round stock to check the bed alignment with the Brown and Sharp D.I. and magnetic stand that came along with it. Mark.

cwilliamrose
03-17-2011, 12:20 PM
I've been using this tool (http://www.validusgroup.com/Lathe-bit-centering-tool--P98.aspx) to get the bit centered. It works well and it's inexpensive. They have several styles. I used to use the method that calls for a piece of flat stock placed between the work and the tool bit. The tool bit is centered when the flat stock is vertical. Either method is more accurate than eyeballing the end of the dead center and it doesn't require spinning the tool post around to "see" the dead center or even having the center mounted.............Bill
http://www.validusgroup.com/Assets/ProductImages/redtool.jpg

kit
03-17-2011, 01:07 PM
That's a good little tool Bill, thanks for posting it.

NewOCork
03-17-2011, 03:30 PM
I have had this happen when the tool bit isn't properly secured in the 4 post tool bit holder by the allen screws.

Corky

280mark
03-20-2011, 07:06 PM
Well I'm making progress, indeed it was the bit turning into the work from a loose compound angle tool post. It seems that there are 2 adjusting screws on the slide and one had a stripped lock nut and both were loose. I made one new screw and snugged them down and tried it. It's much better and no longer gouges in but it's not perfect. I still have a .003 deviation in 3" and in places the cut is not exactly smooth. I have no manual for this machine but I can only imagine it was never set up properly, for example there is almost 1/2 turn of nothing on the c/a tool post screw before it moves, that can't be right! So I appreciate all our help to get this machine up and running properly. Thank's, Mark

shortbus
03-21-2011, 07:30 AM
Mark, did you see this web link? All the manuals are on line for the machines. http://www.smithy.com/index_inside.php?id=244

kit
03-21-2011, 11:30 AM
I still have a .003 deviation in 3" and in places the cut is not exactly smooth.

In what cicumstances?
If you have for instance a bar held in the chuck and you machine it with a blunt tool / to high a feed rate / tool set at the wrong height you are going to easily get that on any lathe, the work piece is bending.
The clue being, is the work getting thinner the closer you get to the chuck where it can't bend away from the tool?.

TheRodDoc
03-21-2011, 01:34 PM
Mark,

If you have not done it yet, The first thing you have to do is use a machine setup level to level the bed. level on each end to check for twist and also level length wise. These levels are very precise.

The lathe needs to be shimmed and bolted to the stand or table with 0 twist in the bed. Then you can cut a test cut. Use a new insert. Use a larger dia. piece of stock for testing.

280mark
03-21-2011, 08:33 PM
Wow,lots of great info guy's, thank's! I've seen the Smithy site and looked at the downloadable manuals but they were for the current models, although some of the info should be the same. I Googled Smithy CB 1220, the model I have and found the manual and printed it. I suppose I have made the rookie mistake of hurrying into making the chips fly when I should of set it up by the book. So no more half-assing it I'll first set it up properly, starting with the Rod Doctor's suggestion, moving it to a stronger bench and leveling it out. Then doing the set-up with the back lash and gib adjustments and much more reading on the subject before the chuck spins again. Bear with me, with your help we'll make it right. Mark.

shortbus
03-22-2011, 07:26 AM
Mark,
Use a new insert. Use a larger dia. piece of stock for testing.


RodDoc I totally agree with every thing you said but the part about 'insert tooling'.

A die maker for 45 years I helped a friend start to learn to machine . He is a millwright but never did machine work. He set up the new Smithy correctly and started to make things. But was getting a slight taper that no amount of adjusting would remove. Went to his shop and he was using insert tooling that someone told him he had to have.

I ground up a HSS bit and the taper in the cut went away. The insert tooling is just not made for this style of lathe. Even new inserts aren't as sharp as a HSS bit. The spindles of home shop lathes aren't built for the amount of force it takes to use inserts. That where the taper comes from.

Richard K
03-22-2011, 06:47 PM
RodDoc I totally agree with every thing you said but the part about 'insert tooling'.

A die maker for 45 years I helped a friend start to learn to machine . He is a millwright but never did machine work. He set up the new Smithy correctly and started to make things. But was getting a slight taper that no amount of adjusting would remove. Went to his shop and he was using insert tooling that someone told him he had to have.

I ground up a HSS bit and the taper in the cut went away. The insert tooling is just not made for this style of lathe. Even new inserts aren't as sharp as a HSS bit. The spindles of home shop lathes aren't built for the amount of force it takes to use inserts. That where the taper comes from.

Listen to what you are saying. It makes absolutely no sense at all. The HSS cutter did not solve the problem. A light cut solved the problem. The problem is a flimsy lathe or a flimsy setup.

In a way you may be right. The Smithy lathe is not very solid and you can not take a light cut with carbide. So you can grind up a HSS cutter and it works, but you still will have the same taper problem when you try to take a heavier cut.

The problem is NOT the insert. The problem is a weak machine.

shortbus
03-23-2011, 07:37 AM
<SNIP>

The problem is NOT the insert. The problem is a weak machine.


In a lot fewer words than I said, You got my point across. Sorry I'm not as good as you in describing things.

Unless you have a machine strong enough you should not use insert tooling.

jlrussell4
03-23-2011, 08:39 AM
Mark,

For years I had 2 Atlas lathes. They are not a very sturdy lathe. You need to level as Roddoc said. You also need to bolt them tightly to as solid a surface as you can get. After getting them squared and bolted, check and adjust the head stock and tail stock as necessary. There is lots of information on the internet to tell you how to check. Google is your friend there. Use HSS tooling as stated and take fairly light cuts and you will be .O.K..

280mark
04-05-2011, 08:14 PM
Hi All! It's working like a champ now, I'd say 95% of the problem was excessive clearance in it. By adjusting the gibs it cuts very good now. I still plan on a strip down for a good clean and lube and the move to a solid bench. Looking for some tooling such as a parting and boring tools. Then it's time to try my luck using the mill head, you'll probably be hearing from me for some more advice. Thanks again, Mark.