line boring bar material question

Aaronwelder · Apr 12, 2017

Hi everyone working on a line boring setup. Similar to Climax or York. Have power feed and large drill for the job . Hopefully won't looked frankenstined once it's finished. But I am wondering for those who have been there and done that. What is the best material for line boring bars. I have the mill and square broaches . 3/8 and 1/2. Bars are going to be 1 1/4 and 2 inch. One website uses hard chrome plated induction hardened high tensile strength alloy steel. Claiming that without a thick layer of chrome plating, your boring bar will need to be sanded and/or oiled regularly to prevent rust. The chrome is so hard it prevents scratches or scars on your shaft. So no 1045 precision ground then or the like ? How difficult is it to run a square broach through this stuff and thread? Ideas or thoughts?

Dan from Oakland · Apr 12, 2017

TG&P 4140 HT would be my budget choice to get started. If you want to go 1st cabin from the start, look into hydraulic cylinder ram material- its chromed and ground and is not super expensive. Chromed bars run smooth but oil is cheap, so you have to be realistic in your choice. Good luck.

ManualEd · Apr 13, 2017

Aaronwelder said:
Hi everyone working on a line boring setup. Similar to Climax or York. Have power feed and large drill for the job . Hopefully won't looked frankenstined once it's finished. But I am wondering for those who have been there and done that. What is the best material for line boring bars. I have the mill and square broaches . 3/8 and 1/2. Bars are going to be 1 1/4 and 2 inch. One website uses hard chrome plated induction hardened high tensile strength alloy steel. Claiming that without a thick layer of chrome plating, your boring bar will need to be sanded and/or oiled regularly to prevent rust. The chrome is so hard it prevents scratches or scars on your shaft. So no 1045 precision ground then or the like ? How difficult is it to run a square broach through this stuff and thread? Ideas or thoughts?

Induction hardened chrome plated can't be worked with HSS tools.

You either have to spot anneal where you want to drill/tap/broach or used carbide drills and special taps.

1045/4140 precision ground works fine. You just have to take a bit more care of it. Buff the marks and rust off of it once in a while.

Nitro is my choice for line boring bars. Its about as accurately sized as 1045 PG, but is mid 60's rockwell a few thou deep, and won't rust. You can work it easily enough with HSS tools. Just need something stubby like a center drill to make a nice surface for the drill to start on, then drill right through and tap.

It's not as ding resistant as IHCP, but it takes a decent smack with a hammer to dent it.

RC99 · Apr 13, 2017

Just remember that mild steel and high tensile steel all bend the same amount with the same amount of pressure up to the yield point.

Ray Behner · Apr 13, 2017

I think hyd. piston rod material would be my choice. It's a 1045/1050 grade and can be purchased without ind. hardening. Generally pretty true.

ewlsey · Apr 13, 2017

I used 1045 TGP. IT worked fine. I also just reamed round holes. I can't see the benefit of square holes. You can buy round HSS blanks as easy as square. Mill or grind a flat on it and away you go.

eKretz · Apr 13, 2017

Use whatever you can get cheapest. If you're doing extended boring work, like 12 foot long bores (sounds like you're not) make sure you run a gravity oiler on the bushings to reduce bar wear and improve damping. If you're using the bar for occasional short work just use a hand oiler every now and then to keep the bushing wet. The bars don't wear out very fast - in a couple decades they'll still be going.

For the tool holes, we always used round holes in the bar then put a square holed sleeve in (round O.D. - available at McMaster or MSC) - using the set screws in the bar and holes drilled through the sleeve to keep the sleeve in proper alignment. Works great and is easily replaced in case of damage.

nofxz · Apr 13, 2017

I have cut a lot of keyways in the stuff you speak of. You will never touch it with a HSS broach.

cpifer3 · Apr 14, 2017

I'm not sure how your driving your bar ( rotation wise) but when I cut a key way in the length of my 1 1/2 bar it warped like a rainbow. I used chrome cylinder rod and was able to straighten it within reason , it's Held up well . What do you plan to drive your bar with? Key way?? Shank on end of bar??

CarbideBob · Apr 14, 2017

The best?
Carbide works very nice for line bars for the big guys.
Not cheap, seen $40,000 per bar but excellent results poking holes through many engine blocks.

How many holes do you need? Many surface treatments available for a steel bar.
Bob

Aaronwelder · Apr 15, 2017

I have a bosch gbm 32 drill with a 4 speed transmission and a Align power feed unit that hopefully put together will be a robust unit. I was thinking of designing the unit like a york but been taking a look around at other ideas on the Internet. Pros and cons of many of them but will have to narrow down.

Aaronwelder · Apr 15, 2017

Thanks everyone for chipping in on this thread. I prefer getting different angles of opinions of a subject before I go ahead and regret it later. Size of bores I am planning are going to be around 2- 5 inch in diameter. I will not be using this every day but like every other tool "when you need it you need it" or you will be paying for it and 2 weeks before some other shop can get the job done.

plastikdreams · Apr 15, 2017

There are a good amount of line boring vijayos on you tube...I'd check them out and message the author, most are willing to chat about stuff.

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