How to Cut a Precise 2.75" hole in 1/2" Mild Steel Plate

[Travelover]

Can you not just redrill the existing hub for the new stud pattern.....

Unfortunately, no. The long of it is that it is a UHaul trailer. They used a flange on the axle (1st picture) which adapts to a Camaro front bearing hub (2nd picture). It is very robust, but has no brakes. I looked at every possibility to add brakes and decided that I needed to get to a standard trailer spindle setup (3rd picture) so I could just use off the shelf electric brake hardware. The hub in the sketchup drawing is my adapter from the UHaul axle flange to the standard trailer spindle. I will mount the brake backing plate to the hub when I bolt it all up.

 

[KWentling]

Thanks.

How about the clearance between the 1.75" spindle itself and the 1.75" hole in the center of the adapter. I have 2" overlap there. Looser OK?

I'd try for .002 -.004 or so. The more the support it has the better.

Kim

 

[Travelover]

I'd try for .002 -.004 or so. The more the support it has the better.

Kim

Thanks for sharing your expertise.

 

[Artisan]

Drawing your part in a CAD program and giving the completed file to a water jet or plasma or whatever cutting company will create a very exacting part. I think you wanted the hole within 2/10000's, THAT is VERY tight and you wll pay big time for that close of tolerance. A water jetter would have to turn on the horsepower big time because a water jet will tend to cut sort of a funnel shape hole and maybe be off .003 . It depends on the operator or the machine.

I suggest to EVERYONE to obtain SolidWorks or AutoCAD or whatever and get some training in at least 2D design. It will change your life. I think it, I draw it, I send the file via email to a waterjet company and a week or so later I get my parts delivered. It is amazing, I LOVE IT. :thumbsup:

Below is what I think you need. If you want the 1:1 file shoot me a PM and I will send it to you in .dwg format.

 

[otis whitehead]

just a note oil does little for a hole saw. If you have shop air blow out the chips as you cut .USE EYE PROTECTION!!! THis does two things cools the bit and clears the chips. As a welder i would make it a bit loose tack and check and then weld out with a full pen weld..Good luck.

 

[like2wheel]

just a note oil does little for a hole saw. If you have shop air blow out the chips as you cut .USE EYE PROTECTION!!! THis does two things cools the bit and clears the chips. As a welder i would make it a bit loose tack and check and then weld out with a full pen weld..Good luck.

I would agree with that, but if you prefer a tight fit, wouldn't it be easier to cut the hole the next undersize with any conventional method, then turn the spindle on the lathe to fit that hole?
You could cut from the back end & leave a shoulder for it to register against.

 

[Travelover]

Drawing your part in a CAD program and giving the completed file to a water jet or plasma or whatever cutting company will create a very exacting part. I think you wanted the hole within 2/10000's, THAT is VERY tight and you will pay big time for that close of tolerance. ...........

Thanks for the offer. I really only need a couple of thousandths, not ten thousandths accuracy.

 

[Travelover]

just a note oil does little for a hole saw. If you have shop air blow out the chips as you cut .USE EYE PROTECTION!!! THis does two things cools the bit and clears the chips. As a welder i would make it a bit loose tack and check and then weld out with a full pen weld..Good luck.

Thanks, sounds like good advice.

 

[Travelover]

I would agree with that, but if you prefer a tight fit, wouldn't it be easier to cut the hole the next undersize with any conventional method, then turn the spindle on the lathe to fit that hole?
You could cut from the back end & leave a shoulder for it to register against.

I could do that - it seemed logical to make the hole the right size for the OD of the tubing rather than modify both. I'd have to clean up the hole made by the hole saw on the lathe to make it true.

 

[Mechanos]

Seems to me like you're overthinking it a bit. I doubt that trailer axle manufacturers hold such tight tolerances when building axles. They also usually use 1/4" plate for the brake mounting flange. Even if you were to achieve your tolerance goals, as soon as you put the welder to it, the plate will more than likely distort out of your tolerances. If you absolutely must have mounting flange perfectly true, cut your hole, weld your plate on and then chuck the spindle assembly in the lathe and face the plate to true it up.