Hardened steel drilling help

[Mr Fixit]

Hi Group,

I've got a boring head that I need to size the 1/2" hole in the tool for a boring bar that is 5/8" and I have found out it is hardened steel, because it took my 5/8" drill bit and turned it into a dull counterbore bit.

So, I have a 5/8" masonry bit, a 1/4" carbide round deburring tool, and I have Dremel stones to grind out a hole. The question is what will work that I have to cut the new hole? If I need to get something I will, but I'm hoping what I have will work.

TX
Mr fixit for the family
Chris

[oxford]

Since there is a few different style boring heads, how deep is the hole and blind or through?

[old mart]

I would use a carbide end mill and keep my fingers crossed, or a carbide drill for hard steel. You have to think of not only making the hole bigger, but it will have to be a good match for the tools that fit in it. Nothing you have mentioned stands more than a snowballs chance in hell, unless you intend to weld the tool in place.

[reggie_obe]

I wouldn't modify my boring head even if it was a CCC one.
Can you turn down the boring bar shank to fit?
Is this an emergency repair? Is buying a 1/2" bar out of the question?

[Mike279]

Turn the bar and leave the head alone gets my vote too.

[RB211]

The cutting tool is expendable. Just buy the appropriate boring bar for the head.

[Mr Fixit]

OK I'll take your advice and not modify the boring head. The boring bar is carbide, how do I reduce the size of it. I will assume a bench grinder with a green wheel is not the first choice.
Any suggestions on reducing the boring bar?

TX
Mr fixit for the family
Chris

[RB211]

OK I'll take your advice and not modify the boring head. The boring bar is carbide, how do I reduce the size of it. I will assume a bench grinder with a green wheel is not the first choice.
Any suggestions on reducing the boring bar?

TX
Mr fixit for the family
Chris

Solid carbide? I take it there's no center hole at the cutting end, so between centers won't work, with a tool post grinder or grinding fixture on a surface grinder using a diamond wheel.
I guess you could chuck it in a lathe only deep enough to be safe and concentric, tool post grind the stick out, then grind off what was in the chuck, if you can live with a shorter shank. I would just buy a new boring bar.

[oxford]

I would just buy a new boring bar.

This.

[Randy]

In a home workshop I'm all for making modifications to make what you have work, but not in this case. Practically impossible to do either mod accurately enough in a home shop. Buy a new boring head or a new boring bar. Heck, even hand grind a boring bar out of drill rod from the hardware store and harden it with a torch.

[Rich Carlstedt]

Yes, Changing either one will result in Heartaches .
The only way left is using a 5/8 carbide endmill, and not the 5/8 Masonary drill bit as it will make a large oversize hole
that 5/8 endmill will cost what a used boring head cost IMHO
And you better be ready for having a very solid spindle to do it

Rich

[Mr Fixit]

Hi Fellas,

OK buying a new boring bar it is. I like the 5/8" bar because it cuts so nice and still with multiple passes not a lot of flex between cuts so very rigid. 1/2" should be ok, but maybe a bit more flex?

Either way it's what I need to keep the project moving forward so $$ out the door for a new boring bar.

TX
Mr fixit for the family.
Chris

[Jon Heron]

Yesterday I went to drill out my cheap chinese bar to mount to an old Alaskan mill. The scratch test on the tip told me it wasnt hardened but there was a damn bearing under the side plates for the sprocket, doh!
The 1/8 pilot bit went through like nothing then I rounded off a 5/16 and 3/8 HSS bit instantly...😑 So I hogged it out with a carbide burr in my dremel which gave me a million tiny slivers in the sides of my fingers where the skin is soft...
In any event its on there now. The rest of the bar was just steel and drilled no problem.
I may get a bigger bar depending on how this works out, for future reference will a carbide end mill drill the bearing out?
Cheers,
Jon

[RB211]

Hi Fellas,

OK buying a new boring bar it is. I like the 5/8" bar because it cuts so nice and still with multiple passes not a lot of flex between cuts so very rigid. 1/2" should be ok, but maybe a bit more flex?

Either way it's what I need to keep the project moving forward so $$ out the door for a new boring bar.

TX
Mr fixit for the family.
Chris

Modulus of elasticity is why solid carbide flexes less than HSS