How would you enlarge this hole

[Shaun @ Tru6]

I had some tooling made and screwed up on the dimensions of 2 holes. it's a sandwich construction, 2 pieces of steel plate with a 1/4" thick curve in the middle. Outer holes line up. Inner holes are off on the inner plate. I need grind away a few mm's to move the hole up to match the outside ones.

Get a small burr and grind away?

[rwest]

Shaun,

Could you drill from the correct size to the wrong side using the good holes to keep the drill lined up?

Rutager

[dad911]

Clamp or tack weld together, and use the good hole to line up the bad.

[JJ 911SC]

Side Cutting Drill Bit

Look like: https://www.amazon.com/Sideways-Cutting-Drill-90mm-TE629/dp/B01M2CMOUU

[Shaun @ Tru6]

I like JJ's drill bits but yes, I can bolt one outside and the inner curved piece together and drill from the outside which is 1/2" thick steel to use as a guide. Even with that much steel as a guide, my gut is telling me the bit would want to glance away.

[Red88Carrera]

Clamp everything together, then use a small round jeweler's file to correct.

[LEAKYSEALS951]

In my peabrained experience with trying to clamp things together to redrill, even with the 1/2 thickness, I always end up walking the good holes in the direction of the bad hole to some extent. Always happens. It all depends on how precise it needs to be, If it really needs to be right, I would have a machinist move the holes with those bits and a damn good drill press/milling mount which would give him full control over the hole overbore direction. The harbor freight stuff can do it 1/2 arse, but with my crap it still walks a little off. A round metal file might not be such a bad idea.

edit- this is assuming you in your application you couldn't just clamp them all together and bore out everything to a larger hole size in a drill press.

[john walker's workshop]

Round file. A die grinder bit will catch and chew up the hole.

[1990C4S]

Air tool and a burr. Or end mill on proper milling machine.

[Tobra]

I like JJ's idea too.

How thick is that and what is it, door for your hot box?

[rwest]

You could also try a drill bushing to keep the bit from wandering.

[Buckterrier]

Originally Posted by john walker's workshop

Round file. A die grinder bit will catch and chew up the hole.

You forgot the elbow grease
But this would be the best unless you want to spend big bucks taking the thing to a machine shop.

[Scott Douglas]

If you have a drill press:
1. Screw/pin the two good holes together.
2. Clamp the pieces together on the other end, nearest to where you're going to drill.
3. Do the clamping in such a way that you can then clamp the pieces to the drill press table.
4. Use the correct size drill in the drill press and use it to align the pieces on the table and clamp so they can't move.
5. Match drill, taking your time and letting the drill do the work, ie don't push too hard, it's going to be an interrupted cut so take small bites, you won't get a continuous chip.

[masraum]

Round file.

[Shaun @ Tru6]

All great ideas, thanks. I will try Scott's drill press idea tomorrow. Holes are 6mm in diameter. I may use a 2mm drill bit first to remove some of the arc which may also help with the bit wanting to walk off the edge.

Tolerances aren't really critically, just need to be able to secure the sandwich together with M6 bolts. I tapped one of the outer plates so it's easy to loosen/tighten them repeatedly.

[Shaun @ Tru6]

Originally Posted by Tobra

I like JJ's idea too.

How thick is that and what is it, door for your hot box?

outer wall is 1/2 thick HRPO steel. That's my guide. Inner that I need to open up is 3/16th.

It's a tool I thought up to straighten and recurve early decklid grille ribs.

[A930Rocket]

Try a flat bottom drill bit in a drill press.

https://www.amazon.com/Fisch-FSF-320791-Point-Chrome-Vanadium/dp/B005GC6WRC/ref=sr_1_1?ie=UTF8&qid=1487554487&sr=8-1&keywords=flat+bottom+drill+bit

[Scott Douglas]

Shaun, I would not recommend going in with a 2mm drill. It won't have any support from the guide piece and will bend, catch an edge and probably break.
If everything is clamped securely, nothing should move when drilling.
Don't forget to secure the drill press table itself as well.
Be sure to wear eye protection too.

[MBAtarga]

You guys are wasting Shaun's time. Shaun - you just need to order a few bolts for offset holes - top row - second picture - in the chart below:

[Shaun @ Tru6]

that is frickin hilarious!!!!!!!