# Home Made HSS Boring Bar



## Al Slitter (Oct 19, 2014)

Greetings All;
I want to make a boring bar for my 7" x 12" lathe, my thinking is to make up some small HSS cutters that will be inserted 
into the bar and locked in place with a grub screw.
I anticipate the boring bar to protrude 5" or 6 " from my OXA tool holder and have a diameter of 1/2" or 5/8"

First question: The material for the boring bar should it be tool steel or would cold rolled steel be fine.

Second question: The mounting of the HSS cutter should it be 90 degrees to the boring bar or 45 degrees or some other angle.

My intent is to have a general purpose boring bar which will do light cuts only, my lathe is a mini lathe so for the most part I stay with HSS
as I  like the fine finish that HSS gives.

Thoughts please


----------



## Rbeckett (Oct 19, 2014)

Sounds like a great idea and I would go with tool steel and use 1/4 inch pieces of HSS for the tooling.  I would cut the slot at 90 degrees and install a set screw or two to hold the bit tight and no chattering hopefully.  The 7X lathes do lack a lot of rigidity so light cuts will be the order of the day when you get it cut and all put together.  Have fun and don't forget the pics as you go!!!

Bob


----------



## Surprman (Oct 19, 2014)

I just built a home made boring bar yesterday.  I recently made a nice boring bar holder for my lathe that will hold a 3/8, 1/2 and 5/8 diameter ba (there are pictures of it on this forum).  I used cold rolled steel for my bar and turned it to 5/8.  I have a bunch of 1/8 inch HSS blanks so I drilled two holes in my bar, one at 90 degrees at one end and another at 45 degrees at the other.  I then spent a some quality time with a small square needle file to make the holes square to accept the blanks.   All  I need to complete the bar are the two set screws.  I drilled and tapped the holes in the rod to hold the blanks in the center of the bar.  In retrospect, I probably should have milled off a flat parallel to the 45 degree slot and drilled and tapped perpendicular to the axis of the blank.  I think it will still work the way I have it though.  I'll post pictures of it when I am done.


----------



## Terrywerm (Oct 19, 2014)

I made a boring bar some time back for a specific project, but this one was 3/4" in diameter and uses a 1/4" bit. It is made from a piece of CRS that I had laying around and is 9 1/2" long. I did not square out the tool bit holes however, and it seems to work just fine the way it is. I want to make one or two that are similar, but smaller in diameter, 3/8" and 1/2" diameters. Here are the pics of the way I made my 3/4".


----------



## rgray (Oct 19, 2014)

I'd suggest starting with drill rod. I have built quite a few bars and started with 1144 stressproof, but have better results with 0-1 drill rod hardened and tempered. If you don't have the equipment to do the hardening they will still work fine and you may have the ability to harden in the future.
I got the square broaches from 1/8"-3/8" but a round hole works to. I also have needle filed round to square (alot of work)
90 deg and 45 deg are probably best I have made a few 30deg for special things.

Pic is of a 3/4" and 1" they are 12" long. 45 deg at one end and 90 at the other.


----------



## Al Slitter (Oct 21, 2014)

Thank you everyone for all of the information and advise.
I will go with two boring bars a short one out of some medium carbon steel that I have and the longer one out of tool steel.
I have decided to go with a boring bar that will be at 90 degrees to the work and will use a couple of broken end mills as the cutters.
After completion I will harden the tools then anneal the tool to release some of the strain.
My thoughts on going with the 90 degrees is based on using the boring bar as an internal threading bar as well.
I hope that that makes sense, I will take a few images of the process and finished items once complete. I hesitate on showing the work as
compared to others on this site I am just a rank amateur!


----------



## John Hasler (Oct 21, 2014)

Interesting that you got good results with square cutters in round holes in your boring bar.  I've been considering doing just that with one I'm making.  How tightly do the cutters fit the holes?


----------



## Terrywerm (Oct 21, 2014)

They just slide in with just a hair bit of clearance, John.  The setscrew seems to hold them in place just fine.


----------



## Bishop (Oct 22, 2014)

Other than general durability will hardened drill rod make for a more ridged boring bar than normalized rod? If the Young's modulus doesn't change with hardening wouldn't that mean the stiffness would remain the same? Sorry but everything I learn is from reading so I might have that all messed up. 

Cheers
Shawn


----------



## Al Slitter (Oct 22, 2014)

I am happy to see that this thread is continuing on.
First off I want to correct an error I made previously, I had said that after Hardening the boring bars I would Anneal them,
what I meant to say was that I would Temper them. Sorry about the error!

If anyone has concerns about Hardening and Tempering there are two great video's that cover this on U-Tube, the links are listed below:

http://www.youtube.com/watch?v=hw4Rl0uG7ok

http://www.youtube.com/watch?v=1wqbiU5sC30


----------



## rgray (Oct 22, 2014)

Bishop said:


> Other than general durability will hardened drill rod make for a more ridged boring bar than normalized rod? If the Young's modulus doesn't change with hardening wouldn't that mean the stiffness would remain the same? Sorry but everything I learn is from reading so I might have that all messed up.
> 
> Cheers
> Shawn




I'm at a loss to find understandable answers to that. I was told that in the past and didn't bother with tool steel because of it. 
I was making my boring bars from 1144 stressproof. When I did make one out of 0-1 drill rod that I hardened and tempered , It seemed to work much better and seemed stiffer. Maybe its all psychological. I put more work into it it's gotta be better "right"
I copied this from wikapedia. I also searched for young's modulus numbers for 1144 and 0-1 but couldn't find any.



rigidity and strength: the strength of material is characterized by its yield strength and / or its tensile strength;
rigidity and stiffness: the beam stiffness (for example) depends on its Young's modulus but also on the ratio of its section to its length. The rigidity characterises the materials, the stiffness regards products and constructions: a massive mechanical plastic part can be much stiffer than a steel spring;
rigidity and hardness: the hardness of a material defines its relative resistance that its surface opposes to the penetration of a harder body.


Another thing I ment to add earlier....HSS is available in round also. My van norman boring bars use a round HSS insert in the cutter carier.


----------



## chips&more (Oct 22, 2014)

There are many options to this subject. You could have the pride to make one yourself. You could buy a double end one on say eBay for around 14 bucks and it will have square holes. Or, you could get the best of the best and find a solid carbide shanked boring bar that accepts carbide inserts. And unless you are a bargain hunter, this carbide boring bar will give you sticker shock big time! But, if you do a lot of boring, it’s worth it, chatter…what chatter? Good Luck, Dave.


----------



## Bishop (Oct 22, 2014)

My head wants to think that a hardened steel bar will be stiffer than a non hardened bar of the same material. I would be interested in knowing for sure though. I have hardened a few parts but it's more for durability and because I like heating things up red hot and dunking them in oil. : )


----------



## Dranreb (Oct 22, 2014)

I made this bar from unknownium to take round HSS because I had some lying in a draw, the 45 deg end is good for when I want to face an internal shoulder as it can project beyond the end of the bar.










Bernard


----------



## Al Slitter (Oct 22, 2014)

As I am looking for a better way of doing up a boring bar I ran into this process, discussed in The Home Shop Machinist.
http://bbs.homeshopmachinist.net/threads/43179-What-material-are-boring-bars-made-of

(Quote) In a tool room I worked in hundreds of years ago, we used to make chatter free tools from cold roiled mild steel. 
The tool was drilled about 7/8 of its length & tapped @ the end, eg:  1" bar drilled 1/2" & tapped 5/8" fine thread, 
molten lead was  poured in leaving 1" of thread, they were left in the canteen freezer  over night, a hi-tensile bolt was torqued up cut off flush & welded. 
The difference in surface finish between std & the lead damped tools on the same machine was astonishing. 
Cheaper than carbide in the bigger sizes.


----------



## Bishop (Oct 23, 2014)

Filling a bar with lead sounds like a cool trick, will store that one away in the grey matter for the future. It's not a boring bar but to add to the thread. Here's an internal threading tool I made from O1 tool steel on the lathe. Makes getting the correct angle on the cutting tip quite simple, a small boring bar/ internal grooving tool could be made the same way I suppose.


----------



## John Hasler (Oct 23, 2014)

I wonder how a lead-filled piece of schedule 160 pipe would work out as a boring bar.  Or a piece of a scrapped rifle barrel fiilled with lead.


----------



## lotechman (Oct 24, 2014)

Bishop said:


> Other than general durability will hardened drill rod make for a more ridged boring bar than normalized rod? If the Young's modulus doesn't change with hardening wouldn't that mean the stiffness would remain the same? Sorry but everything I learn is from reading so I might have that all messed up.
> 
> Cheers
> Shawn



Yes almost no difference in Young's modulus.  Stiffness and vibration damping is what is wanted.  Strength really doesn't matter... well almost doesn't matter.  The frame of a machine tool works on the same principle.... stiffness is primary.


----------

