Question about HF 7 X 10 Minilathe

Bill the Cat

Bill the Cat

Proud maker of CAT cues
Silver Member
I just purchased a Harbor Freight 7 X 10 Minilathe (Model 93212). I haven't purchased tooling yet and I'm confused. Nowhere in the manual does it state what size tooling to use, so I took a quick measurement from the base of the tool post to the centerline of the spindle. It looks to be 3/8" to me, but every place I look on the net points me to 5/16" tooling for 7 X 10 lathes.

Does anybody have this model that can tell me what size tooling you use?
 
If you are exactly at center-line, the tool-bit won't cut.
Whether you use HSS bits or carbide, the cutting edge should be just a smidge BELOW center-line.
The 5/16" bits will work fine and if you like, you can shim underneath the bit in the tool-block to bring them up to whatever height you like.
 
I used to modify the Harbor Freight lathes about 20 years ago and they used 3/8 tooling then. The quality has dropped alot on the machines and the price has also dropped, but I think the tooling size would still be the same.
 
Tool height

Thanks for the input guys!

I will be going with the 3/8" tooling.

KJ, please don't take offense, but I do have to take exception with your statement about tool height. Ideally, the tool should be "exactly" on the centerline of the work. If your not on center, you are effectively changing the geometry of the cutting edge. Going below center can change a positive rake tool to neutral or even negative rake. It's not as critical when cutting softer materials like wood, but, harder materials will tend to "pull" the tool into the work if you're below center.

If you're on center and the tool doesn't cut well, you have the wrong tool geometry (rake & relief) for the material you are cutting. In addition, if your not on center, you leave that nasty little nub when face cutting :(
 
> My main repair machine is an Enco which is pretty much the same thing,with the standard toolpost.

The 5/16 tools I have that haven't been reground across the tops are right on center.

I tend to use the 3/8 tools more though and have to shim them up in the back with a popsicle stick to drop the nose.

On a small machine like this,I don't think it's as critical to have the tool exactly on center because of the lack of real torque.

I agree with KJ to a certain extent,a hair low (.005 or so) is better than high. Tommy D.
 
I mostly use indexable tooling on both of my mini lathes but I have a couple of tool steel tools that I use and they are 5/16. I can't get the holders to drop low enough to use 3/8 cutters. I agree with KJ though as it is a whole lot easier shimming a tool a little than it is trying to grind the base to the correct height even when using the standard 4 way holder. I use a quick change T/P on both of my small lathes, a 7X10 and a 7x12.

On another point, my 7X10 is a Central Machinery that was made in 1983. My 7X10 was bought used in 1993 and my 7X12 lathe is also a Central Machinery that was made in 2006 and I bought new. The newer one has thread cutting abilities where as the older one does not. I paid 320.00 for the new one, on sale, plus a 20% off coupon. The only trouble I have had with either is to blow a two amp fuse caused by throwing the forward/reverse switch into reverse before coming to a stop. That, I don't think can be blamed on the machine. I will say that I have four Atlas lathes that I would dump before ever considering parting with either of the mini's.

Dick
 
Bill the Cat said:
Thanks for the input guys!

I will be going with the 3/8" tooling.

KJ, please don't take offense, but I do have to take exception with your statement about tool height. Ideally, the tool should be "exactly" on the centerline of the work. If your not on center, you are effectively changing the geometry of the cutting edge. Going below center can change a positive rake tool to neutral or even negative rake. It's not as critical when cutting softer materials like wood, but, harder materials will tend to "pull" the tool into the work if you're below center.

If you're on center and the tool doesn't cut well, you have the wrong tool geometry (rake & relief) for the material you are cutting. In addition, if your not on center, you leave that nasty little nub when face cutting :(
Click to expand...

Bill,

No offense taken. It's simply an example of how some people do things differently. I've previously stated in another thread that questioning leads to discussion which leads to a better understanding. So let's talk.

I'll admit that the 'book' calls for the top surface of the tool bit to be at axial center-line but I'll also admit that I don't always go by the book. I've been spinning a chuck for a lot of years and in that time I've been blessed with the opportunity to look at things a little differently. At times, you look at trying things just to see; then you know.

Now, you mentioned changing the geometry of the cutting edge. BINGO!!!
I find that carbide bits cut better with a neg. rake, particularly on steel. On my particular style tool post the only way to 'in effect" achieve neg. rake, is to lower the tool bit height just a smidge. The bit is now at a neg. rake to the work.

I mentioned that I use both carbide and HSS bits, each for a different purpose. I use the carbide for just about everything but I use the HSS for cutting rings to size. I grind these bits the way I want and they have a 10 to 20 degree chip relief. I can set these at near center-line (or an eyeballed thou or two below) because the geometry is ground into them.

Tommy mentioned shimming the rear of his bit with a popsicle stick to get his geometry. Quite a novel idea but hey, that's how it's done. Creativity.

It's my understanding that the minis that were built in the early `80s used the 3/8" bits. The newer models use 5/16" bits but you may have to shim them.

Have a GREAT 4th everyone.
 
If the new ones use the 5/16 bits needing shimmed a little then they are probably set up for 8mm now.
 
> Funny you mention the popsicle stick shim KJ. The reason for this is that is the way the machine came to me,having bought it from a room owner that happened to have a cuemaker move his shop into the poolroom.

It came with a 3/8 cutter in the post,and had an old wood shim under the very back. I never understood why until I started into machine shop school,and got to establishing tool height on a real lathe.

My best guess is the wood was handy. Later on,I measured it to see how thick it was,and got .040. Once I decided to replace it,I took a plain popsicle stick/toungue depressor I bought in a package at Wal Mart,and sanded it a little,then put it under the cutter and clamped down real tight and pressed a "pocket" of sorts into it,and forgot it.

On MOST of my 3/8 cutters,I only regrind on the very end,and leave the factory angles on the top and sides as-is.

This trick is a hanger for shimming a 5/16 cutter up close to correct height,most of them come up about .065,and you'd need about a 1/16 shim,so you would be VERY close.

There have been times,however,when I've bought cutters that weren't flat on the bottom, I like to grind them clean in those cases,or milled them flat at school.

The tool that requires the most "exacting" setup on most lathes is parting off,and have never used anything but HSS for this on my machine.

My primary parting tool was surface-ground from a 3/8 wide but 7/16 tall blank at school. It has a flush left-hand offset for getting as close to the chuck as possible for rigidity,and the bottom is ground to .312,leaving a shoulder I can butt right up against the square edge of the toolpost.

It has about an inch of ground length,because I needed this tool at first to part off some 1 7/8 hot-rolled rod at school when our usual parting blades were on order. It's slightly thinner in the back by design,and is now ground to about .050 wide at the tip.

I eventually ground off the chipbreaker I had on there for cutting steel. If the tool is truly sharp,I don't think it's needed for parting ferrule rods,wood tenons,etc. I touch it up every so often on a diamond-grit stone,but since I stopped cutting steel with it,I haven't had to use a grinder.

Maybe this trick will help Dickie. At school,the new Sharp lathes were fitted with an Aloris CXA post. We had the same problem as well,and the instructor was out of EVERYTHING but 1/2 shank. What I did was replace the long set screw that holds the locking nuts with a 1/2 longer screw,and created enough travel I was able to use a 3/16 HSS on a particular project. I eventually took the whole toolpost out of the equation and made a thinner "riser' plate to mount the post on for those 2 lathes. Tommy D.
 
Last edited:
You must log in or register to reply here.
Back
Top