Precision boring help!

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Krich

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Hi guys,

Just curious is the resident experts on the board here could point me in the right direction concerning a project I'm working on...

I'm needing to use a routing with a Rabbet Router Bit to enlarge an existing hole by 22.2 mm in overall width and 1/2 inch in depth.

I would use a bearing at the bottom of the router bit to roll around the bore to keep the circle true.

I thought I had found a nice Rabbet Router Bit and Bearing Set that came with metric bearing sizes which would have enabled me to go in 9 mm (the hole needs to be 22.2 mm over all diameter so 9 mm in would be getting me cloe to my goal) at Mega-Rabbet Router Bit and Bearing Set but they are out of stock.

So, does anyone have any ideas on tools I can obtain to help me achieve the mark I'm trying to hit when enlarging the bore by 22.2 mm in overall width and 1/2 inch in depth?

Any ideas or suggestions would be appreciated, thanks!
 
The only thing that comes to mind if you need an exact offset and a bearing/bit combo isn’t available is to find a smaller bearing where you could make a metal sleeve on a lathe and press it lightly over the bearing to get the exact size you need.

I own a router but haven’t done any really close work with it like that. others may have some ideas.
 
Interestingly, there are several variations of the tool, on amazon, and at a substantially reduced cost.
 
Somehow I can't picture the desired end result. The wording implies a 22.2 mm dia increase in one sentence and a 22.2mm overall dia in another sentence.
 
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Sanding is not going to work... the material need to be cut.

22.2 mm over all diameter so the cut itself needs to be 11.1 mm wide all the way around (it's a boore so it's a circle) and 1/2 inch in depth
 
Dimensions like this are common in machine shop work, e.g. designing / manufacturing custom parts. A standard CNC (computer controlled) milling machine can also hold very tight tolerances. Their high speed bits are designed for aluminum / steel, so wood will be no problem. CNC is used in 'production' manufacturing of wood pieces, where higher speed / feed rates are possible compared to metal - but I assume your project is a one-off vs hundreds, so this won't be important. For the details see:
So, find a small CNC machine shop near you that is willing to do a custom job like this. I found one near me that made a small set of stainless steel pipe fittings, for example. If you are interested in this approach to woodwork, you could also buy a small CNC router; the first URL has some examples.

I hope this is helpful.
 
If I had the money to go to a machine shop, I'd just buy stuff and not do my own work.

I was hoping to find a rabbit rouiter set with bearings to provide a lot of options for width of cut. I see some stuff available on Amazon so I'll just have to go with that if there are no suggestions for this
 
What is the diameter of the hole before enlarging?
 
78.1 mm and I need to enlarge it to 100.3 mm and in the space that is enlarged I need a 1/2 deep cut or 12.7 mm

It doesn't literally have to be perfect with these specs, but my goal is to get as close as possible.
 
A 7/16th rabbet might be slightly too large but maybe by using tape in the original hole the rabbet cut could be reduced. I don't know how thick cardstock is but something similar glued into hole might work. Practice on wood scraps until you get 11.1 mm. It might work just to tape the bearing but if bearing heats up the tape might come off during use and mar the rabbet.

MLCS has free shipping; MLCS rabbeting router bits and kits
 
OK, thanks. I had read something about adding something around a bearing to get a larger roll to help get closer to the desired cut size

I guess sometimes a little jerry rigging is in order :cool:
 
Eddie_T said:
Somehow I can't picture the desired end result. The wording implies a 22.2 mm dia increase in one sentence and a 22.2mm overall dia in another sentence.
Click to expand...
Same problem here... and then he made it vastly worse...
Plus, come in here with metric dimensions and most of us have no clue just how big it is... and then mix metric and inches...
And we're still assuming the material is wood, not plastic... or some kind of metal...
Also, what are the two holes to be used for? A dowel rod getting glued into the smaller hole? A smaller pilot round on the bottom of a larger round object?
Is the base 'material' object small enough to be placed in/under a drill press, milling machine, lathe?
Looks like about a 3" hole being enlarged to about 4" and then about a 7/8" hole being drilled into the bottom of the bigger hole... or I'm totally confused... and don't know why any of this is being done...
Where he is located would also help, maybe he's close by one of us that has appropriate tools... But I suspect he's in Mexico, UK, Europe, NZ, Australia... maybe Asia...
 
Here's the end result I'd be looking for....

Pic2__JPEG.jpg

Pic1__JPEG.jpg
 
Krich said:
Here's the end result I'd be looking for....
Click to expand...
OK... I think that made things 5% clearer...
Also, how big is the existing smaller hole (if any)?
Is this in aluminum?
An automotive application?
 
Trust me you do not want to try cutting that with a router and router bit.



You need a lathe, milling machine with turntable, milling machine with boring head or CNC milling machine.

If you don’t have that equipment then you need to source it out and have someone with the proper metal cutting equipment do it for you.
 
Trust me you do not want to try cutting that with a router and router bit.
Click to expand...

Hot rodders have been doing this for years and years, ever since they have had alloy wheels.

It's doing the same thing as a machine shop would do for a fraction of the cost.

Besides, I've already had one set of wheels screwed up by a machine shop that took too much material off cause they were ignorant ramuses that I should be taking to small claims court to make them pay for the wheels they messed up.

So, you can relax... these wheels have WAY more material than needed to be safe so taking a little off isn't going to hurt anything and yes there has been engineers look at this and agree it's not effecting the integrity of the wheel.
 
Krich said:
Hot rodders have been doing this for years and years, ever since they have had alloy wheels.

It's doing the same thing as a machine shop would do for a fraction of the cost.

Besides, I've already had one set of wheels screwed up by a machine shop that took too much material off cause they were ignorant ramuses that I should be taking to small claims court to make them pay for the wheels they messed up.

So, you can relax... these wheels have WAY more material than needed to be safe so taking a little off isn't going to hurt anything and yes there has been engineers look at this and agree it's not effecting the integrity of the wheel.
Click to expand...
I’m not worrying about the integrity of the wheel design that is a whole different conversation to be had.



I worked in and around the metal machining industry for 43 years and there are proper ways to safely machine such a part and ways I wouldn’t think of trying. If you had a shop that messed your job up that is no indication that all machine shops don’t know what they are doing only that you found a bad one.

Go ahead and have at it with a router and bearing bit and let us know your results.
 
Lots of guys have done this with no bad results with safety or otherwise. This is why I'm taking my time to see how I can do this with as much precision as possible so it can be done just as good as what a machine shop can do.

The wheels I'm working with are about $800 a set... I've already lost $800 on one set and I don't really want to gamble with $800 each time I go to a different machine shop to see if they know what they are doing or not.

I'm finding out in these modern times a lot of folks couldn't care less about doing good work... they just want the money.

Back in the day I used to be a painter in aa machine shop which is no longer around. Those guys were all about precision and did nothing until they had the right specs as they were trained engineers. Finding people like this anymore is a big challenge!
 
Krich said:
So, you can relax... these wheels have WAY more material than needed to be safe so taking a little off isn't going to hurt anything and yes there has been engineers look at this and agree it's not effecting the integrity of the wheel.
Click to expand...
It's not the safety of the wheels we are worried about but YOUR safety trying to deal with the extremely high forces to be encountered while trying to hand rout aluminum!
The machinery Bud mentions above is very powerful and can take those forces in stride. Also, like he says, you may want to find a smarter shop. Or rent the proper equipment.
In 1966, I went from high school into the General Motors Engineering program via GMI... the same program Mary Barra went into 13 years later... (current Pres./CEO of GM)
 
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