The Home Machinist!

I have an odd airgun project that needs an annular cutter with an OD of approx. 3/8" and an ID of approx. 1/4". Although I've found some 3/8" cutters, none of them spec the ID. Although I've come up with an alternate method to do what I need to do, it occurred to me that maybe I can make a cutter from a 1/2" lathe tool blank. I've already got a 1/2" square 5C collet on the way, and I know I can turn/drill/bore the annulus, but I don't how I should profile the cutting teeth. Any suggestions? Also, can you machine HSS with HSS, or should I be planning on using carbide? Any related comments are also welcome. Later.

Dave

I expect you won't enjoy success trying to drill a HSS blank. Not even with carbide, but I could be wrong.

Have you given any thought to starting with annealed tool steel, then heat treating? In either case, if you hope to enjoy a tool that cuts well, you really need to cylindrically grind the OD and ID, so there's some relief (a slight taper towards the shank will serve well).

In regards to tooth configuration, emulate the teeth of a slitting saw, with large teeth for greater depth. You must consider that the gullet must store generated chips until they can be cleared by backing out the cutter, so small teeth do not function well.

Harold

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Wise people talk because they have something to say. Fools talk because they have to say something.

Would trepanning with a single point tool be an option?

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Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

Good luck annealing an HSS bit enough to work it other than grinding...... which means doing a single tooth cutter. Might be best.

Think of it as grooving, not annular cutting.

What you seem to be trying to make (annular cutter) is a "hollow mill", screw machine stuff. For a non-production cutter, use some W1 or O1 tool steel, and harden after milling the teeth. Material should be fine if you don't try to cut fast with it.

Screw machine folks usually use them for cutting down bosses to correct diameter, sometimes putting a pilot pin in the middle if it is to follow a hole kinda like a counterbore, only reversed. Dunno about them doing much trepanning that way, there are other tools to do that.

As for teeth, allow a good amount of chip space.... there isn't anyplace for the chips to go other than packing into the "gullet", so you may need to back out fairly often if "trepanning".

Likely be much better to do a single tooth tool for it. Less work, better chip flow.

Harold, you were right, even with a cobalt drill bit, I could just barely scratch the surface. That pretty much rules out using the lathe tool bit. Annealed tool steel sounds like the right plan, of course, what I have on hand stops at 5/16", and I need 3/8". This project has just been one road block after another, I just want to get it done and out of my hair.

Glenn and JTiers, trepanning really isn't an option, the hole needs to be offset in the face of a cylindrical piece, which would mean setting it up in the 4 jaw chuck. Neither my abilities nor my POS 4 jaw are up to that level of precision (YET!).

Thanks for the responses, guys. Later.

Dave

I made my own holder and use these inserts for face grooving/trepanning. They come in a multitude of different widths, configurations, and lengths of cut. Razor sharp and cut pre-hard steel like it was butter.

http://www.ebay.com/itm/PICCO-R-010-300 ... 500wt_1413

Follow the link on the ebay page to the specs.

An example of the different widths available.

http://www.ebay.com/itm/5PCS-ISCAR-PICC ... 064wt_1163

You might also use these as an example for grinding your own from a HSS blank.

Not too sure I understand the part about holding the tool in a 5C collet.

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Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

Dave I am not sure what you are trying to do, but here goes my thoughts.

If you are after a face groove that isn't to deep for something like an O ring groove. Then maybe your mill and a boring head will work for you. I have ground round 1/2" HSS blanks in short lengths to make a face grooving tool of the proper width of the groove and then using a boring head and a piece of scrap. Made a few test cut to adjust the groove diameter to size. Then got to the actual part and with the quill locked touched off and feed up with the knee to the proper depth. Works fine for hydraulic manifold blocks and such things and faster than a 4 jaw if you already have the tools ground up for several O ring sizes from previous jobs. Even used them in the lathe a few times with the Aloris style drop in holder that have the groove for boring bars.

Hope this is what you are looking for.

Richard W.

A picture or drawing would likely help figure out a good solution....

Words are fine, but pictures can usually be interpreted basically one way only.

Perhaps a list what you have to work with as well.

Finding out that you don't have a usable four jaw chuck makes a significant difference.

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Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

I did not see what size the HHS blank was, so I'll assume it's 1/2" square.
If you want to use that HSS blank, you could mount a Dremel with a rotary stone on your toolpost.
Start out with the spindle stopped and grind a flat to the centerline of the bit, diagonally across 2 corners.
Then, using a small diameter stone, hollow out the flat side enough to start the next stp
Start the spindle at slow speed, then radius to 1/8" for a 1/4 ID.
Then radius the exterior for the 3/8" OD.
Lastly, hand-grind the cutter edge with some relief

Better to use 3/8" drill rod. Bore the center to 1/4", then cut (mill, grind, file) off half the end and grind your cutter tooth.
Then harden per SOP for drill rod.