Boring Bar question

[deadin]

I need to bore a 3.25" deep hole a bit under 5/8ths dia. in a piece of 12L14.
Unfortunately my longest boring bar will only go to 2.25" (I can only handle 3/8ths bars.)
I'm looking at a couple of bars from LMS and have a couple of questions.
One is a 6 inch (#1779) that uses carbide inserts. It calls for CCMT21.51 inserts and doesn't come with any.
Can I use TCMT21.51 in it?
The other is a 5 inch (#1720) that uses HSS indexable inserts and comes with 3 inserts, but is twice as expensive as the carbide one.

I would just drill the hole but I can't find a bit of the right diameter and the hole needs a square bottom.

Opinions??????

Dean

 

[gbritnell]

You say you could drill the hole but don't have a bit that size? Does the hole need to have the precision of being bored or will drilling suffice? There are several options, one is to make your own bar out of drill rod and silver solder a piece of carbide onto the end. The other is to buy a 5/8 drill, drill the hole to depth, grind the flutes flat like an end mill and then go in and square up the bottom of the hole.
gbritnell

 

[Maryak]

As you need a flat bottom in the hole and the diameter does not appear to be critical for size, I would forget the boring bar and buy the size drill you need.

After drilling to depth with the normal, (1180), angle, regrind the drill to a flat bottom drill and finish off.

Hope this helps

Best Regards
Bob

 

[deadin]

I guess that I should have admitted that I'm trying to recover from a "whoops". The hole needs to be pretty close to 19/32nds. (.593 max). The part that goes into it should have been 5/8ths but I got a little "eager" in turning it. :-[
I need to have it close enough to locktite or epoxy the part into it, or even pin it if I can get a slip fit.
Either that or I need to make the shaft a little bigger......

 

[Twmaster]

The suggestions from Bob and George sound like the way to go.

However, I'll answer a part of your question that did not get an answer. Those boring bars.

No, you cannot use TCMT inserts in place of the CCMT inserts. C style inserts have 80 degree tips. The T type has 120 degree tips.

Also, before you buy a bar from LMS look around on FeeBay. I see the same or similar bars for less than $20 plus shipping new. Some are as low as $16. Not knocking LMS. They are an overall good outfit. Just some of their stuff is pretty spendy.

 

[Ned Ludd]

Hi Dean,
I am surprised that no one has mentioned making a "D" bit of the right size. With one of these very easily made tools you can achieve both an accurate diameter and straight hole and have a flat bottom too.
Ned

 

[kvom]

This thread points out the fact that it's easier to fit a shaft to a hole than vise-versa. You might find it easier to drill to 5/8 and remake the other part.

Loctite such as 620 can work with fairly large gaps up to .015 or so.

 

[Tin Falcon]

The other is a 5 inch (#1720) that uses HSS indexable inserts and comes with 3 inserts, but is twice as expensive as the carbide one.

Dean HSS is arguably the best cutting tool for our small hobby needs. The Warner boring bars are top notch quality and Made in USA Latobe PA by a family of craftsmen. They attend the ME shows and support the Hobby, as does LMS. I have several sets of there tools they are top notch and they stand behind there product. As far as putting out good money for good tools vs Chinese imports that is a choice we all have to make. Yes I have sieg brand stuff and cdco tools in my box as well.
That being said a D bit could be your most economical solution.
Tin

 

[maverick]

The Warner boring bars are worth the money. The HSS inserts can easily be touched up to a fine edge and slightly
altered to suit different materials or applications. Our hobby finds the need for a wide range of operations and these
are a good card to have in your hand. That said, the flat bottom needed on the 5/8 hole poses a problem as this much cutter contact tends to chatter. The flat bottom drill or D bit looks good.

 

[Lew Hartswick]

If youre just going to "locktite" a pin in the hole WHY does it need a flat bottom?
Drill a 1/32 under size and ream. Another way to do it.
...lew...

 

[deadin]

WHY does it need a flat bottom?

Sometimes a pictue is worth a thousand words..... ;D

Also, I've run out of barrel material, so remaking the inner tube is not a great option.....

Dean

 

[mklotz]

That looks suspiciously like the deck gun I built.
Am I right?

 

[deadin]

Could be the same gun. The plans were originally posted in a 1944 edition of MODEL CRAFTSMAN.
I found these in an issue (date unknown) of a model railroad magazine and were posted under the name of S.A. Walter.
If it turns out to be the same, I will probably have many questions for you as I get to them. The first being that I see no sign of any kind of shell extractor mechanism. How does the empty get removed? A ramrod down the barrel?

 

[Jasonb]

Looks to me like the treaded part is an insert so you don't need a flat bottomed hole. The cross hatching does not match that of teh 1" dia part altough its a little blured on teh drawing you have psosted

Jason

 

[deadin]

I read the plans as having the threading as one with the outer shell. It is an interrupted thread that the breechblock (also an interrupted thread) slides into and then rotates 60 deg. to lock. I can't see any way to make it other than as a part of the breech bolster.

 

[Jasonb]

Whats the 11/16 dia refer to if the thread is cut into the end of the 1" bar?

 

[deadin]

I think the 11/16ths refers to the depth of the cut-away in the interrupted thread.