# small hole boring bar



## cuslog (Jul 27, 2021)

Need to bore ~.246" hole x 1.000" deep into 4130 tube, concentric to the OD so lathe job.
Thinking I need a carbide boring bar. Looks like ~$50 and 1~2 weeks from USA maybe $15 from China but I don't think they'll do the depth.
Anyone else been down this rabbit hole ?


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## YYCHM (Jul 27, 2021)

Could you drill and ream it?  Not quite following when you say a hole in a tube?


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## DPittman (Jul 27, 2021)

You could grind your own out of hss if you think hss will do the job?
I got a real nice tiny  carbide boring bar from Aliexpress a while back.  I don't recall the dimensions of it right now but if you would find that helpful I could dig up the specifics. (I'm just out camping with my kid today so no access to my shop for a day)


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## Chip Maker (Jul 27, 2021)

https://www.kbctools.ca/itemdetail/1-428-BB2001300

Or... what about on a mill with a v-block, indicator and reground endmill or boring head and homemade boring bar?


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## cuslog (Jul 27, 2021)

YYCHM said:


> Could you drill and ream it?  Not quite following when you say a hole in a tube?


Hole goes in the end of the tube (.313 OD x .243 ID x 36" long) need to increase ID to .246" and its important that the hole be parallel to the long axis of the tube too.
Tried grinding down a .250" carbide endmill, nasty job, turned into a mess - I hate grinding / breathing that carbide dust - I can still taste it.



Chip Maker said:


> https://www.kbctools.ca/itemdetail/1-428-BB2001300


Yes, thanks, that looks like it would do the job. I've bought Micro 100 endmills before, they were really nice. BTW - searched KBC for "carbide boring bar" - that never came up for me.


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## YYCHM (Jul 27, 2021)

I have a HSS boring bar that will get in there if you want to give it a try.  NE Calgary.


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## PeterT (Jul 27, 2021)

The Micro 100 come in many variations, they are nice tooling but rather spendy (carbide). They have flat+circular shanks so you can use in your toolpost or boring bar depending on the size. T
https://www.kbctools.ca/itemdetail/1-428-BB2001300

Craig might be mentioning the same thing I was going to suggest - a 3/8 or 1/2" shank standard cutter for boring head. They come in good carbide, crappy offshore carbide and decent grade HSS. They look generically like this but all I see are the small sizes. Some of my toolholders have a bottom Vee seat (vs just a flat) which will accept round shanked tools like this. But the set screw on top isn't the best arrangement. If tehshank is too hard it can be difficult to he stock, set screws on one. Otherwise you would have to grind a flat or use a sleeve.
https://www.kbctools.ca/itemdetail/1-453H-040
https://www.kbctools.ca/itemdetail/1-4326-B9M

They do make insert boring bars down that small but maybe a bit specialized and expensive for a single job


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## cuslog (Jul 28, 2021)

Thanks for the replies - reaching in 1" is the challenge. Already tried HSS and its quite "chattery".


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## Johnwa (Jul 28, 2021)

A piloted D reamer should work. They’re pretty easy to make out of a piece of tool steel.this link shows the general idea





The grinding part doesn’t have to be that accurate, just take a bit more that 50% off the diameter.  Years ago I made one out of an allen wrench using a drill and file.  

The hardness of the 4130 might be an issue.


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## DPittman (Jul 28, 2021)

cuslog said:


> Thanks for the replies - reaching in 1" is the challenge. Already tried HSS and its quite "chattery".


I don't know if this would work for you but it's carbide.  I got it off Aliexpress awhile back for $18 shipped. I haven't actually had an opportunity to try it out.


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## cuslog (Jul 28, 2021)

DPittman said:


> I don't know if this would work for you but it's carbide.  I got it off Aliexpress awhile back for $18 shipped. I haven't actually had an opportunity to try it out.


Thanks for the offer but I ordered the Micro 100 bar this morning, should be here Friday.


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## PeterT (Jul 28, 2021)

DPittman said:


> I don't know if this would work for you but it's carbide.  I got it off Aliexpress awhile back for $18 shipped. I haven't actually had an opportunity to try it out.


If its what I'm familiar with they are more for making internal grooves, feeding radially, not traversing. I could be wrong. They sometimes have strange names for cutters.


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## Susquatch (Jul 29, 2021)

cuslog said:


> Thanks for the offer but I ordered the Micro 100 bar this morning, should be here Friday.



After you try it, let us know how well it worked. I do a fair bit of boring small holes with hss and I'd like to find a better tool too.


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## DPittman (Jul 29, 2021)

PeterT said:


> If its what I'm familiar with they are more for making internal grooves, feeding radially, not traversing. I could be wrong. They sometimes have strange names for cutters.


Oh interesting, I can see that they might be better suited to that.  Would it be asking for a wreck to try boring with such a tool?


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## PeterT (Jul 29, 2021)

Probably yes because you would be pushing on the side of the tooth in a mode it wasn't intended. Boring tools would have a lead in angle & relief incorporated in the grind.


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