How to use boring bar?

[ricracer16]

So I just starting using my minimill again and I am trying to bore a hole and I can't get a smooth finish. It's rippled. I tried different speeds of the spindle speeds with no luck.

What am I doing wrong?

Also does anyone know where I can find drill bits bigger than 1"? I just bought some silver & demming drill bits from HF but I wondered if there are any bigger sets out there.

thanks in advance.

[KEJR]

I'm not great at boring on a mill, but I can say to go to Enco and look at their Deming drills, I've seen them to 1.5"

I know from boring on a lathe that if the tool is not set to center with the proper rake that it will squeak and chatter causing crappy finish. Sometimes you can vary the speed.

Of course, always, always use the shortest fattest boring bar you can use for the job. Its about rigidity.

KEJR

[Boucher]

I have drills up to about 2 1/2". The ones that I have are all Morse Taper. I bought them used from a machine shop closing. They are of limited use. I use them more in the lathe than the mill. With a minimill the silver and demming drills will get you large enough to use the boring bar or boring head. You don’t say what material you are working with or how thick and what size you need to do. Hole saws work for softer materials. The boring head works well but there is some learning curve. For hard materials you really need a sharp cutting tool. I have had to make a several passes without advancing the tool to get the spring out.

[Carld]

Have you tried different feeds also? Sometimes a slight radius on the tip of the cutter will give a better finish. Are you sure the cutter is parallel with the center line of the bore? You can't have the tip leading or positive rake when boring.

[ricracer16]

Thanks for all your tips and help. I didn't know there was a definate way of placing the tools in the machine. I will start over and make sure everything is in correctly before starting.

And I will check out the demming bits at enco.

Sorry for not giving all the information. I was working on a scrap piece of 6061 T6 aluminum which is 1/2" thick.

My goal is to make a headlight brackets that will fit on my SV 650. Then once I have mastered that one I want to move up and make steering dampners and other parts with my new tools.

Thanks again for all your help.

I will try to get some photos on here as soon as I can.

[MuellerNick]

What diameter has the boring bar and what's the stickout? Too long, and you will have certainly chatter.


Nick

[Oldbrock]

I assume you are using HSS cutting tools with lots of top rake. Should work fine on aluminium. Peter

[adamd]

Make sure that the cutters point is aligned with the center of the boring head. If using high speed steel tool make sure you grind enuff relief so it does not rub. Use the largest dia boring bar that you can and minimize your sick out no more 4 time bar dia if posable.
Adam

[ricracer16]

So I did some work today and aligned the boring bore and changed the angle. It helped a great deal. Also I think I was trying to take to large of a pass. This time I was take light passes and finally got it down to 41.237mm. A little bigger than 41mm but close enough for my first practice boring hole. Here are one of the designs but I changed it once I got the part started and brought over to the bike for checking dimensions and size and some before and after photos.







I started with a small drill bit then progressed through bigger drill bits until I got to my biggest S&D drill which is a 1".

After that I used the boring bar to get it to 41.237. That was a lot of work and a long time. I'm not sure how much time it took but this was a lot of time just to get it to this stage.

I know i'm learning and teaching myself but that has to be an easier faster way. I found some bigger S&D drill bits that will bring me closer to my optimal diameter but still that was still alot of time. I was also thinking of using a 3" rotary table that I got from HF but its really small and couldn't find anything small enough to bolt it to my mill. I'll have to figure something out tomorrow.

Anyway, if you guys can provide some feedback that would be great.

thanks in advance.

[Boucher]

For that size hole and that thickness of Aluminum a good quality hole saw will get you closer. I use WD40 for cutting fluid and air to clean chips. I also sometimes drill some like 3/8 holes just inside the tangent line to help get rid of the chips. With a hole saw it doesn't need to turn very fast but it does need to be held securely. If you get close to size with the holesaw you can finish with a fly cutter if you tweek the tool bit to the correct size. For one or two parts the boring tool is better but if you are going to do several the flycutter is faster.