R8 extension? Do they exist?

Got a boring job to do in the mill. Big ugly casting, and I need to reach about 7" down through a 3.25" hole. Problem is that my ram is

3.5". I would like to use my boring head rather than a fly cutter. Does anybody make a R8 male by R8 female extension? Around 5" would do it.

Thanks,

Bill

Reply to
BillM
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Think again.

And you will realize that a "collet" needs to be compressed which your extension would not be.

Your best bet would be to get a shaft like 3/4", and bore a hole to fit your cutter, and use a weld-on style setscrew to hold it. And mae the cuts light.

i

Reply to
Ignoramus13673

Uh, wha? Boring heads are not typically held in collets. They have their own arbors - the arbor threads into the boring head.

However, you're right in that R8 is not self locking. The extension would have to have a small draw bolt to hold the boring arbor inside.

Or just get a long boring bar (roughly the same idea). However, this is not ideal, and it sounds like Bill doesn't want to do this.

A spindle extension would likely have the most rigidity as it would be larger in diameter than a boring bar extension. May have to lower the knee to adjust the boring diameter, but sometimes life sucks.

An extension could be turned on a lathe. PITA though. In fact, I'd probably just turn a male R8 taper on to one end (not trivial, but not murder either), and the boring head thread in the other. Turning a female R8 taper would be *way* more involved, and it likely wouldn't be concentric enough to do perform useful work beyond holding a single- point tool anyway. The boring head thread could be completed in 30min or less.

Regards.

Robin

Reply to
robinstoddart

Feed the table/saddle up. Sheesh, you youngsters

Reply to
John R. Carroll

Reply to
Ignoramus13673

Of course you do! Who Else? LOL

Reply to
John R. Carroll

Bill's quill (I assume he means quill) is too big to fit through the hole which leads to the hole he's trying to bore, so feeding the table/ saddle up will still cause a collision.

Sheesh indeed!

Regards,

Robin

Reply to
robinstoddart

LOL

Ronin, You get the proper bar and feed down with the table and up with the quill. That's why the make the feed thingy run in both directions. Well, that and back gear. Us old geezers know a thing or two you know sprout

And to you as well. Now. Get a Molsen's in Ye' hoser!

Reply to
John R. Carroll

Bill's quill (I assume he means quill) is too big to fit through the hole which leads to the hole he's trying to bore, so feeding the table/ saddle up will still cause a collision.

Jeez---yes I meant QUILL. Sometimes my brain/fingers interface gets a little out of whack.

I can do it with a 7" or so long bar. chunk of

1 1/4 CR, turn one end to 7/8" to fit my largest R8, slot the other for a single point tool. No biggy. What I would LIKE is to have the ease of adjustment the boring head provides. I may try turning a 1" dia. piece of 4140 to 1/2" to fit the boring head, and brazing a tip on the other end. Boring head diameter is 2", cutter would be around 5" long. Going to take a while either way---it's a wallowed out front pivot hole on a John Deere 4WD tractor front axle mount.

The idea of turning a long male R8 by male boring head thread adapter crossed my mind, but I'm pretty sure the boring head thread is metric. Possible, but kind of a pain in the butt on a 1948 South Bend lathe.

Bill

Reply to
BillM

On Jun 10, 11:45=A0pm, "BillM" wrote: =2E..

You could put a set screw behind the bit in the slot to adjust it outward. Put some paper tape around the setscrew head and graduate at least 1/6th of a circle with a protractor, using the Allen wrench handle for a pointer. A 1/4-20 setscrew feeds 0.050 per turn. 5 degree marks would indicate 0.0014" increase in diameter.

If the end of a 7" bar is hard to hold steady enough to slot, drill a hole for the bit and use setscrews crosswise to guide it. Then you wouldn't lose your lathe center hole if the taper needed adjustment.

Reply to
Jim Wilkins

By the way, the OP could probably get by if he used a "toolholder" as opposed to a collet, and a long end mill. That could give you extra 8" or so, but will be expensive.

i
Reply to
Ignoramus3909

Well...Ive got a couple as well.....the 1.5" x 18" is on loan to one of the local machine shops....hummm..its been a couple years....about time he paid for it.....

Gunner

Reply to
Gunner

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