Line Boring Bar Material

charalson · Feb 10, 2018

Good morning all,

I’m going to be building a one off line boring operation in the near future and I’d like the community’s input on boring bar material. I was looking at 4140, 8620, or O-1. The bore is approximately 2” diameter spanning 4 aluminum lugs each about an inch thick and overall 12” long. Any suggestions for bar material are welcome and any heat treat as well. If I heat treat I’ll probably send it out for grinding afterwards. Thanks,

Chris.

JRIowa · Feb 10, 2018

NAECOMET Tungsten Based Heavy Metal Boring Bars & Tooling

If you're going to make a bar, make from heavy metal.
If you don't want to mess with it, go to Cline or CTS
ClineTool
Indexable Tool Repair | Indexable Cutting Tools
JR

MattiJ · Feb 10, 2018

JRIowa is thinking of ordinary boring bars?

I don't want to think about the price of 1.5" diameter and 28" long heavy metal bar for one-offsie line boring project :nutter:

4140, 8620, or O-1 should work the same, get the one that is easiest to find in precision grind in your size. (assuming you need a slip fit trough the support bearings)

Ken hosford · Feb 10, 2018

all steels have about the same youngs modulas [ how flexable ] so you want to look for surface finish and straightness hardness may help galling so maybe thompsen shafting

DDoug · Feb 10, 2018

Are you going to broach square holes for the tools bits ?

charalson · Feb 10, 2018

I plan on drilling and reaming several holes before hardening and then silver solder or braze in toolbit sleeves, the kind that have the set screw behind the toolbit to feed out.

Miguels244 · Feb 10, 2018

Dura bar might be a good choice.

Monarchist · Feb 10, 2018

charalson said:
I plan on drilling and reaming several holes before hardening and then silver solder or braze in toolbit sleeves, the kind that have the set screw behind the toolbit to feed out.

Small diameter bar as such things go if the bore itself is but 2" ID.
12" plus-plus for grasping length is not atrocious, either.

I'd look for factory-made, used if cash was that tight. Gots to be other "DIY" needed that has a better payback on yer time?

DDoug · Feb 10, 2018

I would suggest 4140 ht TPG, and just broach the square holes, tap
the holding screw hole as well.
At 28-32 Rc, you'll be able to drill, broach & tap it, yet it will
be tough for in service usage.

Easy Peasy, Lemon Squeasy.

ewlsey · Feb 10, 2018

The ones I have seen are either plain jane 1045TGP, or chrome plated clyinder rod material, often listed as 1050.

LKeithR · Feb 11, 2018

digger doug said:
I would suggest 4140 ht TPG, and just broach the square holes, tap
the holding screw hole as well.
At 28-32 Rc, you'll be able to drill, broach & tap it, yet it will
be tough for in service usage...

My thoughts exactly; this doesn't strike me as being a super heavy-duty application. Worst case scenario is that you've gotta
make lighter cuts to avoid chatter and/or deflection...

...Easy Peasy, Lemon Squeasy.

Seriously?

dian · Feb 11, 2018

NAECOMET Tungsten Based Heavy Metal Boring Bars & Tooling

how much is that stuff? couldnt find any prices.

crazygoat · Feb 11, 2018

Something must be off somewhere in the original OP description. He said 12" OAL and Mattij said a 28" long bar. 12" is not that long for store bought bar. 28" bar is a whole nuther ball of wax. He did say line bore, tho. I am confused.

ApexMachining · Feb 11, 2018

Chrome plated cylinder rod material works particuarly well for line boring bars as it makes galling almost a non-issue.
It is also centreless ground, so is usually quite round/straight.
4140 would be best, but given that it is a one-off in aluminium, I'm sure you could make do with 1045.

With regards to toolbits, using a small CCMT style boring bar works quite well, this saves having to worry about using the square sleeves or broaching. (the set screw will align the tool as it is tightened onto the flat of the boring bar).
Using the small boring bar also means the hole in the line boring bar can be drilled on centre, where as square tools would typically require the holes to be drilled off-centre.

crazygoat · Feb 11, 2018

Lets see if I got this right. 4 lugs, 1" thick and 12" between the two outside lugs. Must be on a piece of earth moving equipment. My original thinking was that this was a piece that was going to bored in a lathe and the "line boring" was just a misnomer.

DDoug · Feb 11, 2018

crazygoat said:
Lets see if I got this right. 4 lugs, 1" thick and 12" between the lugs. Not 12" oal. Correcto? That would make the oal in the 48" range, right?

Plus whatever length needed for the feed motion, is the way I read it.

MattiJ · Feb 11, 2018

ApexMachining said:
Chrome plated cylinder rod material works particuarly well for line boring bars as it makes galling almost a non-issue.
It is also centreless ground, so is usually quite round/straight.
4140 would be best, but given that it is a one-off in aluminium, I'm sure you could make do with 1045.

With regards to toolbits, using a small CCMT style boring bar works quite well, this saves having to worry about using the square sleeves or broaching. (the set screw will align the tool as it is tightened onto the flat of the boring bar).
Using the small boring bar also means the hole in the line boring bar can be drilled on centre, where as square tools would typically require the holes to be drilled off-centre.

CCMT style boring bar sounds good, now if someone just comes up with neat idea how to adjust the cutting depth easily.
(micro boring catridge is too obvious choice)

DDoug · Feb 11, 2018

MattiJ said:
CCMT style boring bar sounds good, now if someone just comes up with neat idea how to adjust the cutting depth easily.
(micro boring catridge is too obvious choice)

Unless your boring a welded up repair bore, then the ability
to swap in a piece of ground HSS will help immensely.

charalson · Feb 11, 2018

Everyone,

Thank you for the suggestions and opinions. I’m going to go with 4140 material for the bar and then send out for heat treat and finish grind. As Monarchist eluded to, I’m prohibited from giving more details in order to protect the confidentiality of my customer, but just know that the bore has to be done in-situ. Thanks again,

Chris.

David Merrill · Feb 11, 2018

Ideas: line boring - YouTube

David Merrill

Line Boring Bar Material

Aluminum

Diamond

Titanium

Cast Iron

Diamond

Aluminum

Diamond

Diamond

Diamond

Diamond

Stainless

Titanium

Stainless

Plastic

Stainless

Diamond

Titanium

Diamond

Aluminum

Aluminum

Similar threads