Need Help!- 9X20 Chinese Lathe

[zeoncomp]

Hello,

I got one of the 9X20 chinese lathes from HF ... I did some mods to it - (according to a lot of owners) - but it seems that I cannot overpass the fact that I cannot cut (or part) ...
What happened is - I have for example an inch diameter bar A-36 steel and try to cut let's say - an inch out of it. I am using a cutting tool - (yes it is sharp) - it starts cutting - I can see the curl coming out but quickly will stop - I believe that the correct terminology is "dig in" If I feed very very very slow is better - but it will take me 5 min to cut that 1 inch.
So the cutting tool does not go "under" the material is just stuck - looks like it got in just too much. I do position exactly next to the chuck to eliminate whateverallignment issue.
I did try fast speeds, slow speeds - it works better on 160 rpm
What am I doing wrong ?

Thank you

[MrWild]

A36 is air hardening tool steel. It isn't mild steel and requires slower speeds, smaller depth of cuts and slower feeds. It is a tough tool steel to machine and isn't free cutting like a mild steel like CRS or HRS. Are you just learning the ropes and got this steel for practice, or are you making something. You are just going to have to deal with pokey slow doing die work on a 9 x 20. It isn't rigid or powerful enough to hog away at harder-to-cut steels, and they are a far cry from aluminum feeds and speeds.

Also, you don't say if you are using carbide or HSS bits. If using carbide, how are you using inserts which are ready to go, or cemented carbide lathe bits? Cemented carbide bits need to be sharpened to proper shape and really should not be used in their raw state. when using HSS bits, you need to slow the work even more. On the order of 50 RPM with cut off bits, and a s-l-o-w feed. Sharp High Speed Steel bits need oil to help them cut. Get some cutting oil and an small brush to put some on at the start of each cut. Yes, five minutes is about right for a cut in tool steels if you are using HSS and a small lathe.

There are some tricks to a nicer cut if using HSS steel bits like stoning the edge for a smoother edge than straight off the grinder. Cutting geometries also can help. You want the nose (leading edge) of the tool radiused a bit, and not a sharp point. This also makes for a stronger tool that has an edge that lasts longer and can handle faster (not much) speeds and feeds.

[Fegenbush]

MrWild,

I hate to contradict you, but ASTM A-36 (ASME SA-36) is standard hot rolled steel with a minimum tensile strength of 36,000 psi similar to AISI 1018 in most characteristics (AISI 1018 actually has a ASME number, but I can't think of it now).

Per Machinery's Handbook, using HSS cutoff tool, turn at 420 RPM, 8 IPM

Check the center alignment of your cutoff blade. To me, it sounds like you might be a bit above center.

[bearwen]

I have a HF 9X20 and would have to agree with Fegenbush. I would check the alignment of the tool to center.