Enlarging boring tool shank

[Sshire]

I was just given a set of 8 boring tools for a boring head. They are 3/8" shank tooling. My Criterion head (DBL-202) takes 1/2" shank tooling. Can I make some sort of sleeve that would enlarge the 3/8 shank?
Main questions are
1. Is this a good idea?
2. Would this be safe?
3. If 1 and 2 are "yes" answers then can I get some ideas?
Thanks
Stan

 

[dalem9]

Just make a bushing and then split it down one side ,then put the splite 90 degrees to the clamping bolt.Dale

 

[user 284]

Yes it will work, It's safe enough. I'd drill/machine ports so that the boring heads set screws lock onto the boring bars original flat surfaces. That will lock your boring bar and the adapter in place.

Pete

 

[dalem9]

That will work to Pete ,maybe even better then my idea.Dale

 

[user 284]

Dale,
Your idea should work just as well. LOL, The OP should make both and let us know.

Pete

 

[dalem9]

To help with removing the bit I always grind a flat were the set screw tightenes on the tool bit. Dale

 

[maverick]

Used dale's idea many times. Made the bushing from brass or 303 stainless.
Never a problem.

 

[Sshire]

Thanks everyone!! None of those ideas occurred to me.
I'll grind flats, make the bushing, split it, drill holes in it and report back.
Keep the suggestions coming.
Thanks again
Stan

 

[rhankey]

I would encourage you to go with sleeves with holes rather than slits. Either ought to be just as easy to make, or cost about the same to buy.

My second hand Criterion boring head came with a couple commercially made sleeves. These sleeves have holes so the boring head grub screws can tighten down directly to the boring bar. This appears to hold the boring bar much more securely and doesn't distort or damage the sleeve at all. I have used slotted sleeves in other lives, and though they work, they don't seem to hold the inner bar quite as securely, and they get damaged quickly and can become difficult to remove after a few uses.

Just my 2 cents.

 

[Sshire]

My new lathe arrived on Tuesday. Spent Wed and Thurs removing parts and cleaning high tech Asian secret formula goopy stuff from everywhere. (pictures are coming if anyone cares to see the 5,421st lathe arrival on HMEM.)

This is my first ever metal lathe and after spending most of yesterday turning a bunch of 12L14, 6061, mystery metal and brass into chips while I sorted out how this machine works I decided to make the sleeve for the boring bits. (This was my total lathe experience if you don't count The Complete Video Works of Rudy Kouhoupt and Tubalcain on Youtube)

Found a piece of brass close to .500 and turned it down to a sliding fit in the Criterion head.
Stepped up in size through 3 or 4 drill bits chucked in the tailstock and then finished with a .375 reamer. The test fit of the .375 bit was so good that i couldn't push it all the way in because of the pressure! Be nice if I can get pistons to fit like that.

Drilling for the pass-thru hole for the locking SHCS in the Criterion.

Finished sleeve on a .375 shank bit

Sleeved bit in the boring head

Another angle.

Thanks so much for all the ideas about making this.

Best
Stan

 

[user 284]

Criterion did/does make hardened and ground sleeves just like that, But AFAIK not to go from 3/8"-1/2" or at least any that I could find that Criterion makes. Going by memory, You can even get 1"-3/8" reduction sleeves for those with large boring heads. Criterion do make really nice boring heads. You may not have any problems at all, But a hardened steel boring head tool bore/brass adapter/hardened steel boreing bar isn't the best coeficient of friction combination for your parts usage design, Steel on steel would have been better. But it just might be problem free. You did a really nice job anyway.

Pete

 

[Sshire]

Pete
I consider this a test to see if I could hit the fit with my total lathe experience being about 3 hours. I'm going to try to redo it in 12L14 tomorrow. I'm also going to try some test bores with the brass but I'll feel more comfortable with steel.
Thanks for the comment.
Best
Stan

 

[user 284]

If you did that with 3 hrs experience you did a awesome job. I'm far past the impressed level.

Pete

 

[Sshire]

Thanks Pete. Makes me feel like I might be getting somewhere.

I used the brass sleeve this morning. My new lathe (are all Chinese lathes a kit?) had binding on the compound. 3/4 turn of the handle was smooth, the remaining 1/4 was tight. This, I assume would not lead to smooth finishes.
After dissassembly (tearing it apart), I eliminated everything but the plate with the hole for the shaft. Oooooh, boring bar brass sleeve test!
Put it on the mill, centered with the Blake (sounds like I know what I'm talking about) and bored the hole a few thou bigger (OK, you can't bore a few thou smaller.)
Reassembled the compound; turns smooth as silk. Problem solved, boring bar sleeve works. Still going to do a steel sleeve.
Best
Stan

 

[user 284]

Stan,
You may already know this, But others may not. Criterions web site has a large amount of very good information about boring, boring heads etc. The information is really useful no matter what make of boring head your using. For larger bores Criterion offer a 1/2" shank cross hole boring bar that is designed to fit that head you own. You can't buy directly thru Criterion, But I did buy mine thru MSC.

Pete

 

[Sshire]

Absolutely right. Criterion has a great deal of info on boring that applies to any head. I had seen the cross head bar but doubt that I'll need to bore anything that large (until a friend sees the shop and says "hey I've got this big hole that needs to be bigger")
I got a great deal on eBay. Probably because it was listed as a boring head for a Bridgeport. I called Criterion and they said that, (for whatever reason,) the DBL202 with an R8 shank is listed as "for Bridgeport." Very few bids.
I did well on that one.
Stan