Turning Tools for 9x20 Lathe

[Big Shed]

Having just become the proud owner of a Steelmaster 9x20 (http://www.assetplant.com/index.php?page=shop.product_details&flypage=shop.flypage&product_id=54&category_id=104&manufacturer_id=&option=com_virtuemart&Itemid=62) Lathe with electronic variable speed I have a question (one of many to come I'm sure).

Asset Plant & Equipment supplied a 9 piece indexable 1/2" carbide turning tools.

Reading one of the publications downloaded from the 9x20 user group, it says that 1/2" tools are too big for the 9x20 and one should use 5/16" or 3/8" at most.

Also reading about the QCTP from Harbor Freight on Steve Bedair (http://bedair.org/Toolpost/HFtoolpost.html)'s site, it says that this QCTP will not give enough adjustment for 1/2" tools and one should use 5/16" or 3/8" tools.


So, should I change my 1/2" set for a 3/8" or 5/16" set?

And which Quick Change Tool Post should I get? Have looked at the CDCO (http://www.cdcotools.com/index.php) one and the Harbor Freight (http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=39083) one as well as the tools4cheap (http://www.tools4cheap.net/proddetail.php?prod=piston) one.

What do other 9x20 owners use?

[.RC.]

I think carbide tools on a small lathe will not work very well...The lathes simply do not have the rigidity and power to make full use of carbide given the cost of the inserts.. I would have thought HSS would be much more suited being cheaper and more versatile..However I do not own a lathe of this size so might be all wrong..

[rodm]

Carbide is fine on these lathes but you have to get negative rake inserts. I use 12mm tools on both my 9X20 and 10X36 lathes. I am using the standard tool holder on both lathes.
I buy carbide inserts from US ebay suppliers and 100 tips is about $250 AUS landed so you don't shed any tears at $2.50 when you break a few. Share around with mates to lower the outlay.
Make sure you get a couple of extra boats for the QCTP.
Oh yeah nothing wrong with RC suggestion to use HSS and you should at least try it so you get some skills at sharpening. You might need a special shape bit one day so it will be a good investment in your time.

[pipeclay]

Before you jump at buying any tipped tools,do some more research into the rake angle of tools,I think you will find that your type of machine has horse power suited to Positive rake rather than Negative.
Negative rake tools are really more suited to 3plus HP machines.
Check the specs on your lathe in regards to centre height,then check the dimensions of the Quick change holders your looking at.

I would probably look for a holder that could give you +/- 1/4"-6mm travel and with the largest tool opening slot.

[rodm]

Happy to be corrected on the positive/negative rake as I am not 100% sure which is which.
The tips I use have are like these
http://cgi.ebay.com.au/3PCE-REPLACEMENT-INDEXABLE-CARBIDE-TIP-12MM-or-16MM_W0QQitemZ260274932537QQihZ016QQcategoryZ12578QQcmdZViewItemQQ_trksidZp1742.m153.l1262
They have a hollow around the perimeter

[Retromilling]

Yes Pipeclay is dead right about positive rake for small lathes.
You are looking at a Triangular Positive rake insert .
Once you get the correct height tool holders then find the insert size that fits.
Then choose the insert design with positive rake with the sharper edge design.
Then choose .02 point radius for finnishing and .04 for roughing.
Dont buy any inserts until you have your correct tool holders.
There is insert edge designs that are more suitable for soft gummy materials also.
Using an insert that is designed for hard short chipping material on a soft gummy material will smear up the point and ruin it.
So HSS tool bits may be a cheaper and more flexable option for some non ferros applications once the extra tool holders are paid for.
HSS tool bits also give you the ability to custom grind a particular profile cutter that inserts don't allow without extra tool holders and special inserts.
I believe the hobbyist is well served by having both systems to choose from.

[Retromilling]

Happy to be corrected on the positive/negative rake as I am not 100% sure which is which.
The tips I use have are like these
http://cgi.ebay.com.au/3PCE-REPLACEMENT-INDEXABLE-CARBIDE-TIP-12MM-or-16MM_W0QQitemZ260274932537QQihZ016QQcategoryZ12578QQcmdZViewItemQQ_trksidZp1742.m153.l1262
They have a hollow around the perimeter

Positive rake is an insert with the clearance front rake built into the insert.
It can not be turned over and the other side used.
Negative rake has a 90 degree front face on the insert and it requires a tool holder with the correct front rake built into the tool.
It can in most cases be turned over to use both sides.
However a negative rake insert requires a lot more rigidity and horse power so it is not any good for small lathes unfortunately.
The insert that you link too has a deep chip breaker that makes the cutting edge behave more like a HSS cutter with a steep top rake .
This presents a sharper pointing up edge to the job making it more suitable to long chiping soft materials and low HP.
You can not buy this insert with confidence because it does not state the size of the insert it'self . Only the shank size of the tooling. So missmatch mistakes may happen.

[brittleheart]

Just a few thoughts,
I notice that the power rating of your lathe is 0.75kw or 1hp.
I have used both negative and positive rake inserts for years without a problem on my machines and they have less power than this.
The newer inserts available are extremely advanced with many cutting/wiper geometry choices that make turning a different experience.
I do not understand why they advise a smaller tool size, the deeper the more rigid (within the limits of holder/centre ht).
For example, I purchase a s/hand tool to suit the very common TNMG insert (negative rake), milled it down from 20mm to suit the 12mm holder, and fitted quality (also more expensive) inserts to get good results.

I think the correct selection of the insert is of more importance than many realise.
Example, this insert used on 4140, 1045 or Stainless, for machining shafts is effortless, even for the hercus.
http://www.taegutec.com/ProductLines/ProductLineSubDetail.asp?CountryID=1&ProductLineDetailID=1&ProductLineSubDetailID=83&MenuItemID1=4
Note that these inserts are primarily designed for high speed CNC machines, as the broad variation of feed rates can show. Which is great for us types, who like to make small precise cuts with little power.
(May I state that I have no commercial interest in these products, but is a typical example of the modern inserts available.)

I would encourage a bit of experimentation and trial/error to asess what you prefer, besides, I still find that learning from mistakes provides the odd discovery worthwile.

Peter

[Retromilling]

It is true that you can use certain negative rake inserts on smaller lathes but it will place more load on the spindle bearings. In some cases it will not finnish as well as positive rake inserts. Also in the small insert sizes that he will be buying , negative rake is hard to find. In my catalogues negative rake starts at 11 mm inserts and gets bigger.
I would think that if you turned a soft gummy al on a small lathe with a negative insert you would be hard pressed to get a good finnish and place a lot of unecessary strain on the machine.
Free machining steel would work better.
For the beginner positive rake inserts is a good place to start for low HP low speed lathes as they cover a wider useage.
Edge geometry of different styles of postive rake inserts is varied to allow machining of soft and hard metals at slower speeds and low HP.
There is a lot of things you can get away with when you are experienced but new lathe owners need a reliable place to start to gain that experience .
Most people are not going to be able to mill down inserts to fit tooling.