Boring bar holder

[Denver]

I've made several sizing dies for my Star and Lyman sizers with my lathe using drill bits and chucking reamers, but haven't tried it with a boring bar. I only have the rocker post tool holder, so what type of holder will I need to use a boring bar? Thought about taking one of my bit holders and drilling it out so the shank of the boring bar will fit. The one I'm looking at is solid carbide with a 5/16 shank and min bore diameter of .29 inch. I figured that would work for anything down to 30 cal.

Helpful hints appreciated

Denver :drinks:

[jhrosier]

I took a piece of scrap aluminum that fit the tool post and about a couple of inches long, drilled it a bit larger than 1/2" for the boring bar shank, and them slit it down one side with the saw so it can grip the bar.
A smaller bar might need the slit extended nearly through the far side.

Jack

[Pavogrande]

With a lantern holder there are a couple of methods -- an armstrong/williams type holder - My #8 armstrong holds about a 1/2" bar and the willams will hold to about 5/8" Which means the cutter is either ground down from 1/2" as needed or a 1/2" bar with an adjustable tooth is used -- The other type is a round washer affair notched for several sizes of bars, fits over the lantern and the bar sort of becomes the rocker - --
Mine are for a 12" atlas but probably are nearly the same on others -- I seldom use them as they require a lot of fiddling --
Reading this over, my description is not the best -- I would be glad to email photos, send me a pm if you like -- gb

[garandsrus]

Denver,

This (http://www.gizmology.net/boringbar.htm) is pretty similar to what I made. It works very well.

John

[JIMinPHX]

There are boring bar holders that you can buy for a rocker tool post. If you get one, get it oversize for what you are doing now (like 1/2" or 3/4") & then make a bushing to step down to 5/16. That way you will also be able to use it with larger bars & it will be more versatile. You don't want to end up buying a holder for each size of bar that you will eventually need.

Personally, I hate rocker posts. I would just bite the bullet & make a big cube of steel with a few slots & set screw holes to hold my tools. That's what I've always done in the past when I was working with older machines.

[JIMinPHX]

These are some different types of boring bar holders that I have made over the years. maybe they will give you some ideas.

[JIMinPHX]

Hey, by the way, you might want to double check the min bore on that 5/16 bar. Usually min bore is a little bigger than the shank size. When the min bore is smaller than the shank, that usually only counts for a short depth where only the head of the bar is inside the hole. That only works for bars with offset and/or reduced heads. I think that you need to go with a 1/4" bar like the one on the right in my picture. That's my .30 cal die making bar.

[Denver]

Hey, by the way, you might want to double check the min bore on that 5/16 bar. Usually min bore is a little bigger than the shank size. When the min bore is smaller than the shank, that usually only counts for a short depth where only the head of the bar is inside the hole. That only works for bars with offset and/or reduced heads. I think that you need to go with a 1/4" bar like the one on the right in my picture. That's my .30 cal die making bar.

The bar I'm looking at is Enco #317-5653. It has a max cutting depth of 1.25 inch. I figured that would be adequate for the depth I need to bore the sizing dies I want. It's a solid bar with a reduced head as in your description.

[Denver]

Denver,

This (http://www.gizmology.net/boringbar.htm) is pretty similar to what I made. It works very well.

John

Thanks John. That looks like it will work nicely.

Ron

[JIMinPHX]

I haven't bought anything from Enco in years, but I just took a look at their website & that type of bar does look usable. I think that you need to go with the next longer one though (#317-5654). The drawing that I have for a sizing die shows 1.557" as the overall length, A 1-1/4" deep bar would come up a little short of that.

Make sure that you take gentle cuts with that dinky little bar. Carbide snaps off pretty easily.

[Denver]

I haven't bought anything from Enco in years, but I just took a look at their website & that type of bar does look usable. I think that you need to go with the next longer one though (#317-5654). The drawing that I have for a sizing die shows 1.557" as the overall length, A 1-1/4" deep bar would come up a little short of that.

Make sure that you take gentle cuts with that dinky little bar. Carbide snaps off pretty easily.

The dies I have that were made by Star measure closer to 1.475 and have the bottom counter bored about a quarter inch or so. I plan on drilling the hole to within a few thou of finished size and using the bar to clean up the hole and leave a minimum to hone to final dimension.
Your warning about gentle cuts is duly noted.

Thanks,

[JIMinPHX]

I didn't realize that you were making dies for a Star. I was going by Lyman dimensions. The shorter bar should be more friendly to work with. Once you are out more than 4 or 5 shank diameters in length, things can get a little tricky.

[JIMinPHX]

If you fee like taking a stab at a Lyman type sizing die some time, then the drawing on post #97 of this thread may be useful to you -

http://castboolits.gunloads.com/showthread.php?t=48453&page=5

[KCSO]

Denver I have a rocker post boring bar holder for a 9" South bend and I never used it. I'll try and post a picture.

[Bret4207]

Make sure your lathe cross slide is solid enough to make use of a boring bar, especially carbide. My little Atlas 6" isn't.

[JIMinPHX]

Bret,
Have you tried snugging up your gibbs & holding the tool up short?

[Denver]

After a little more searching, I was able to find cobalt HSS boring bars in the Production Tool Supply catalog. I can get one that has a min bore diam of 1/4 inch and still have a 1 1/4 inch depth of cut. They also have carbide tipped bars, but only down to 5/16 min bore diameter. I might get one of those for use on the larger size dies I need. The two together are little more than the one carbide from Enco.

:Fire:

[JIMinPHX]

MSC has just about everything that any machinist could possibly want. The prices are fair & the quality is as advertised. They sell name brand, made in USA & import grades of tooling. If you watch their monthly sales circulars, you can sometimes find small carbide insert bars for a fraction of the normal price.

[garandsrus]

I use a carbide boring bar on a 6" Atlas/Craftsman lathe with a rocker style tool post. I sized the aluminum holder (see above post) without the rocker piece in the tool holder. The aluminum needs to be longer than the cupped washer on the tool post so that both ends are supported.

To center the hole for the bar, I just put the aluminum stock in the tool holder and then drilled the aluminum while it was in the holder. You can even use the power feed while drilling the hole :)

I have used the boring bar around 20 times and it seemed to work great each time.

John

[Bret4207]

Bret,
Have you tried snugging up your gibbs & holding the tool up short?

Yup, and I still get chatter. I need a HSS tool ground nice and sharp and I need to stop abusing the poor little guy, but you do with what you have.

[Cap'n Morgan]

Yup, and I still get chatter. I need a HSS tool ground nice and sharp and I need to stop abusing the poor little guy, but you do with what you have.

A commercial dampened boring bar can work wonders, but often it's enough to wrap a rubber band around the bar and - if there's enough room - a few rounds of solder wire wound tightly atop the rubber band. The idea is to kill the "bad vibrations." The trick will also work when boring out thin-walled bushings.

[JIMinPHX]

Yup, and I still get chatter. I need a HSS tool ground nice and sharp and I need to stop abusing the poor little guy, but you do with what you have.

What was the tool tip radius on the carbide bar you tried?

[Bret4207]

What was the tool tip radius on the carbide bar you tried?

Got me. It was one of those sets from Grizzly. It works but not as well as the old HSS tooling I have that's worn out. Same for the insert tooling I got from Grizzly. The only carbide tooling had that worked well was old stuff from the 70's with zero top rake.

[JIMinPHX]

The last digit in the number that describes a carbide insert is the tool tip radius. TPG322, TPG321, & TPG3205 are all triangles with positive ground clearance angles of the same size (inscribed circle). The one that ends in 2, has a big fat tool tip radius & is usually used as a roughing tool (although CNMGs are usually better for heavy roughing than TPGs are). The 1 is a general purpose finishing tip radius that is half the size of the 2. The 05 is pretty darn near sharp & probably what you need on a little lathe like you have. I'm not saying that you need to get a TPG3 series bar. I'm just saying that you probably need an insert with an 05 tip radius. I forget the actual numbers involved in calculating the actual radius of the tip are. I think that it was something like .015" x the last digit, but I don't really remember for sure. It's been a long time since I looked all that stuff up. It was back when I was cutting my own insert pockets because I was making my own CNC tooling for special jobs.

[Buckshot]

http://www.fototime.com/76745E9F64C31AA/standard.jpghttp://www.fototime.com/F927426EF9100A0/standard.jpg

...........I bought these from MSC. They're from Circle C and are solid carbide bars with coolant hole, and a steel head to accept carbide inserts. They're good for 10x stickout using the recommended DOC and feed. I have the 4 sizes they put on sale (3/16, 1/4, 3/8, and 1/2"). MSC will put them on sale a couple times a year (usually 2 sizes at once) and IIRC were $107 to $147. The 2 smaller sizes come with 10 inserts and the other two larger sizes have 5.

In leaded steel they'll produce a reflective finish. In regular medium and high carbon tool steels you'll still get a finish better then a reamer can provide. For large holes I use larger steel shaft carbide insert bars and finish with these, depending on the finish required or if I don't have he correct reamer. The minimum hole size for the 3/16" x4" is .200" (shown, right photo), 1/4"x4" is .300", 3/8"x6" is .437", and the 1/2"x8" bar is .525".

...............Buckshot