Small Boring tools

[RandaB]

Hello,

I am making the valve chest and slide bar for my 3/4" miniature traction engine, both out of CZ121 brass. I need to bore out holes in them, both 8mm dia., one through hole (25mm) and one blind hole (30mm).

Can anyone direct me to a suitable boring bar? I'm having trouble identifying any, I do not have any small enough. I've considered reaming but surely boring is easier for blind hole.

RandaB     

[TomG]

You know, end mills make very nice boring bars in a pinch. 1/4"x1" long four flute end mills are readily available over here, so I imagine something suitable is available over there as well. Just set them up on center and slightly angled to get some clearance. Obviously, use the largest one practical.

Tom

[wawoodman]

Tom,
Would a 4-flute be center cutting? I was under the impression that (generally) 2-flute are, and 4-flute aren't. Or, can you find it if you look for it?

[f350ca]

You drill the entry hole as you would for a boring bar first Mike, then go in with the end mill using only one flute. I've done this several times on tough material like stainless using carbide end mills. They seam to be less prone to chatter as well.
Along the same line, you can grind away three of the four flutes of a tap, then grind away all but the first couple of teeth then use it for single point threading and get full form threads.

[EdK]

(01-21-2017, 05:10 PM)wawoodman Wrote: Tom,
Would a 4-flute be center cutting? I was under the impression that (generally) 2-flute are, and 4-flute aren't. Or, can you find it if you look for it?

Yes, you can get both 4-flute and 2-flute end mills that are center cutting. That's the only type I buy.

Ed

[wawoodman]

(01-21-2017, 06:14 PM)f350ca Wrote: You drill the entry hole as you would for a boring bar first Mike, then go in with the end mill using only one flute. I've done this several times on tough material like stainless using carbide end mills. They seam to be less prone to chatter as well.
Along the same line, you can grind away three of the four flutes of a tap, then grind away all but the first couple of teeth then use it for single point threading and get full form threads.

Maybe I'm thinking about this backwards. 

So you put the workpiece on a lathe faceplate, and hold the end mill in the toolholder. Move the end mill into the work, pull it back, retract the compound a few thousandths, move the end mill in, rinse and repeat. Correct?

[ieezitin]

Mike,

Yes your thought is correct. 

Anthony/

[wawoodman]

Thanks!