Milling cutters I saw in Moltrecht

That looks like a Valenite Center-Dex end mill to me. See:

Don't think of it as a fly cutter. Think of it as a short boring bar. Many many boring bars have square holes, one at 90° and one at 45°.

Don't have one of these but I did get a set of import boring bars from Enco. They are made in India and were real cheap and work just dandy. One of my favorite lathe tools to use.

GWE

ENCO is basically a supplier of DIY tools for people not asking much from their tooling. Try a real tool and cutter supplier like their parent MSC. In reality MSC doesn't neccessarily have the good stuff but they have a lot of the stuff. Leigh at MarMachine

Snip

These are used to fly cut gear teeth among other things. You grind the involute tooth form on a piece of high speed steel and cut the teeth one at a time. see:

Grant Erwin:

None of the boring bars I have seen have holes in them for holding cutters.

Many of the boring heads I have seen have holes in them for holding cutters.

I have no need for a tool holder with the adjustment capability of a boring head for holding single point cutters at right angles to a spindle. I have need of a holder which can simply hold the cutter at a right angle to the spindle for simple one-off form cutting.

Boring heads cost five to ten times what fly cutters cost, and I have no need for the extra features paid for by that difference.

Apparently gear cutter holders [right angle] were about as common as fly cutter holders at one time. this is no longer the case. As a project in our machining class we cut some change gears and had to make our own tool holder. You can use a boring bar but the tool is held above center so you will need to grind 1/2 of it away to get the tool on center to generate the correct profile. If you want positive rake or hook the remaining material gets very thin. Law's book has detailed plans for a holder. One tip is to use a shoulder bolt for the shank by turning the head down. You can drill, tap and counter bore for the shoulder bolt and then loctite it in place. Then locate the tool slot etc. from the shank. We also had good luck using a #2MT drill chuck shank with a 1/2 fine thread as a shank. Only the tang was hard and we were able to cut the shank to the correct length for use with a drawbar. Modified shank was then drilled and tapped to fit our drawbar. This gained us about 1 inch of headroom.

GmcD

Bottom of page 75, Enco:

see:

Hmm. I never noticed those before.

It looks like it would be easy to cut off one end and turn a smaller shank on one of those to get exactly what I've been after.

Pretty cheaply, too..

Thank you.

Depends somewhat on what you want to run it in. On how you want to hold it.

I've got a fly cutter just like that. 40 taper, think it takes a 5/8" or 3/4" square bit. Made by Brown & Sharpe, if I recall correctly, so it's not new by any means.

Pretty easy to make one. Or, if you want a straight shank, a 90 degree boring bar should be fine.

John Martin

I think that you are confusing two things with the same name.

There are boring bars made to mount in boring/facing heads, and I have never seen one of those with sockets for HSS tool bit. (Square holes.)

However, boring bars made for *lathes* often are made of plain steel, with square holes and setscrews as described for holding HSS lathe bits to do the actual work. Sometimes, the bore is hollow and filled with lead shot to reduce chatter.

These lathe boring bars typically have different angles at the two ends. The end with the bit held at 90 degrees is for plain through boring. The end with the bit held at 45 degrees is intended to be used for boring to the bottom of a blind hole and then to face off the bottom of the bore. Those cannot be used in a boring head, and are not intended for such usage.

Granted, these days, there are nice carbide insert boring bars, sometimes made with solid carbide shanks, and these don't use HSS lathe toolbits.

My most recent use of such a boring bar was for some inside Acme threading in a size a bit too large for my insert tooling. Even with nice insert tooling, the old tools are quite useful at times.

Enjoy, DoN.

You're somewhat right, Don, but "boring bars is boring bars".

I've got two boring heads for my mill, and both take 1" shank tooling. That's a bit larger than most of the brazed tip carbide or HSS solid boring bars you see. So I use the types of boring bars normally used in lathes - both indexable carbide and HSS insert. And there's no reason you can't use the 30 or 45 degree bars. I have cut some of them off so I don't have a full foot of boring bar hanging out of the boring head when I don't need that much, but that's about the only modification.

OK, I do have some of those solid brazed carbide and HSS bars intended for boring heads. Most of them are 3/8" shank. I can use them in the boring heads, with a reducing bushing. But I tend to use them more often in the lathe for short, small diameter boring jobs.

Backwards? Maybe, but it works. So does using an endmill as a single-point boring tool, although that's not what it was made for.

John Martin

Bridgeport boring heads came with this sort of bar, for example...

O.K. Nicely offset so the cutting edge is on the centerline.

But still -- a square *slot*, not a square *hole* in this case.

Enjoy, DoN.

Not the one that looks like a fly cutter, the one closest to the boring head in the lower row, and at least one of the two in the upper row have square broached thru holes. Here's slightly better photo.

O.K. I see it now.

Thanks, DoN.