Larger tool post or cut off blade holder Grizzly lathe

I have a G4016 Grizzly lathe which is a 13 1/2 x 40 " lathe. I am trying to cut off or part 3" aluminum bar stock. While I am able to do so succefully with a 1/2 x 1/8" blade it is not very fast. Ive cut reliefs in the blade and whittled away a larger path for the blade but I break blades and spend quite a bit of time getting what I want for a finish on the back side. I also have a need to make a number of this one particular item that makes its a pain to remove this and cut it on a band saw let alone finishing the back side of the material as well.

Do any of you have any simple ideas for a larger tool post. I was thinking about buying a larger tool post and making a bottom tensioner plate threading it to fit the new tool post and then buying a parting tool holder for this. I only need it for parting as I am happy with all other functions of my lathe so far any way.

Another Idea I had was to make a tool holder that will support a cut off blade that is 3/4" tall and attempt that but this is fairly complex for my new skill levels I do have a really nice mill and would probably learn a lot making one but I also want to make sure I have the correct fit of my blade. Exploding a larger blade because Ive made something that does not support the blade correctly is a concern as well. I do believe my lathe is large enough that I have the room to still get a larger parting tool in the correct position for proper cutting but that is just what my thought is.

Or am I looking for something that cannot be done on this size of a lathe. Thanks in advance

I think that a larger blade (taller) would be an obvious improvement, and I recommend T type blades. So far as size, a 3/4 or 7/8 tall blade would be a target So far as holders go to the tool catalogs and see what is available, then figure out what sort of tool block would be necessary to hold it. One thing that will help is to keep the parting tool over the cross slide, not overhanging it. Note that parting is not a method of finishing a part, only of separating it from the rest of the bar and refacing the parted off face will be necessary in any case; parting tools will nearly always draw to one side or the other and result in a concave / convex face.

I had parting problems with my 13-36 jet lathe.
Had to scrape the compound and cross-slides and make new gibs before it had the rigidity for that operation.
Even if your machine is tight and well fitted it's imperative that the parting tool is on center and aligned properly.
The top and sides of the parting tool should also be honed. All edges have to be really sharp and smooth.
You didn't say what alloy aluminum your working but if its not a soft gummy type you can part at fairly high speeds.
120 RPM or so but keep it well oiled and if it gets hot let it cool down.

I gave up on the parting blades and went with this Positive-Stop Blade Cut-off tool from Shars. No problems now.

If I understand correctly you are doing the front work then parting off, are you parting to center or to a bore?

If parting to center use an inserted blade as wide as the machine will push say 3/16-1/4" or so as you are going 1 1/2" deep, an angled insert will reduce the nub but not remove it completely so back work will still be required. When using a wide blade much material is turned into chips, if you part 500 parts with a 1/4" blade that is over 10' of material gone.

If parting to a bore an angled tool will part off clean, with ideal conditions back work may not be required aside from deburring by hand, use flood coolant.

I parted 6 pieces of 1" ball screw with a 1/4" insert blade today, the stock was cased to 60 RC, I had no problems with it.

Good Luck

I have a Grizzly G4003G 12 x 36. It always parted fairly well but replacing the compound with a solid block made a huge difference in parting. It cuts steel and aluminum very well with no chatter and a good feed rate.

turn the cross f

I made another post about this Its titled " parting tool holder adapting larger blades to smaller tool parts" its had some views but no responses yet. maybe you can find it via the forum. I bought some Empire t style parting blades that were almost an inch in height and just under 1/4" in width. I ground the height down about 1/8" on my surface grinder which was simple. Built a jig that sandwiches the T blade with just the slightest clearance then machined my spinning tool post on one side allowing the blade to drop enough to hit close to the centerline of my lathe . I can flat part work pieces fast and with a flat virtually no dish or convex, cuts with the smoothest finish. Theres pictures in that post. I paid $70 for 25 of these blades on ebay and they are fantastic parting blades. I made my first cut on a 3" piece of solid aluminum stock with the blade almost 3" out of the jig in attempts to make it chatter. It still cut fast and flawless. This is the cut in the photo. Recently I have made a couple more cuts with the tool extended no more than needed and its literally amazing. Id venture to say I can part a solid 3" piece of aluminum in less than 2 minutes.

Be careful in oversizing cutoff blades. Make sure your compound mount can take the added forces. A few years ago I made a tool holder to hold oversized (for my lathe) cutoff blades and the cast iron under the compound broke right out of the cross slide. It's weaker there because of the groove that allows the compound to swivel. Fortunately a new cross slide was only $115. As shown in my previous post I now use a tool block in place of the compound. It makes all lathe operations work better with better finishes due to added rigidity
.

I really like T style cutoff blades especially the coated black ones. A few things you can do to help the cut is rather than grind it in normal fashion being horizontal is grind it vertical so you end up with a hollow grind and have a leading edge. Make the leading edge so that it parts the peace off and then it would have to clean up the nub on the stock in the chuck. You can definetly make a finished part with a nice finish. If you have to stick your blade out too far you can use a machinist jack to help support the blade. Stickout as short as possible though!

Splat said:

I gave up on the parting blades and went with this Positive-Stop Blade Cut-off tool from Shars. No problems now.

Click to expand...

Another vote for the Shars tool. I had difficulty parting with the "T" blades. A few successful partings, but mostly a catch at some point. I have used the Shars tools for a few months with good results. I like the relief on the side of the cutter. I now get the long curly chips I was trying to get with the "T" blades.

Getting the tool set 90 deg to the axis of the lathe is very important. I had been doing this with a straight edge between the face of the work and the blade. After my first catch with the Shars tool I decided to check with a dial indicator. I was off a couple of thou. As depth of the work increased, the slight lack of 90 deg caused some binding. I then used the dial indicator to get this exactly 90 deg and now parting is straight forward.