18 replies to this topic

[nicklouse]

thoughts and considerations on the best way to do this?

 

some thoughts I have had.

 

use a countersink tool to center over the hole (not drilling).

 

have a (find) rod made up the correct diameter to go inside the threads and fit to drill head.

 

screw in a head stud and use that to center the block before clamping it in place.

[Icey]

All of the above are OK. Ideally you'd use an indicator of some sort (typically a coaxial) and either sweep the OD of the hole or that of a dowel that fits tightly in the hole.

[bikewiz]

How about a drill and tap combo bit? Or chuck up the tap in the drill and align it. I think you'll only get it perfect if you have a cross slide vise.

https://www.regalcut...tap-combo-tools

[DeadSquare]

This is where a broken drill bit comes in handy.

Sharpen it with only about 3/8" of flute, so that the shank is running in the thread.

It helps if you can find a thick wall bit of 5/16" tube to line the thread, to sink a pilot in the bottom of the hole.

[Spider]

If you need it absolutely spot on, use the Magnet Stand and a DTI.  I routinely do this in the Mill.

[nicklouse]

It helps if you can find a thick wall bit of 5/16" tube to line the thread, to sink a pilot in the bottom of the hole.

like that.

[nicklouse]

If you need it absolutely spot on, use the Magnet Stand and a DTI.  I routinely do this in the Mill.

mmmm trying to imagine what i a´would be doing with the DTI

 

spent a few hours trying to work it out while driving round this.

 Capture.JPG   78.89K   0 downloads

[weef]

Hi  what is it that you want to machine ?

[nicklouse]

Hi  what is it that you want to machine ?

Just extending the head stud holes.  
 

as it was not done originally and I want to counter drill the top thread off as they again were not originally done.

[weef]

I would consider the cylinder block to be a bit big for a pillar drill.  Have you thought about a magnetic base machine directly on the block face as this will ensure the drilling operation is at right angles to the block. The correct size drill, ie the tapping size, in the magnetic machine chuck will locate the drill directly over the hole then substitute the tapping drill with a broach of your desired size. This should ensure positioning and accuracy for the machining operation.

[nicklouse]

I would consider the cylinder block to be a bit big for a pillar drill.  Have you thought about a magnetic base machine directly on the block face as this will ensure the drilling operation is at right angles to the block. The correct size drill, ie the tapping size, in the magnetic machine chuck will locate the drill directly over the hole then substitute the tapping drill with a broach of your desired size. This should ensure positioning and accuracy for the machining operation.

yep that was another thing that was nagging me. will have to see how it sits on the base.

[Tupers]

Have you thought of renting a mag drill to do the job?

You’ll probably end up spending a bit on the drills you’ll need but it would be easier to setup than a pillar drill with fewer variables.

[nicklouse]

or i have a chat with some other none engine engineering companies out here.

 

i am currently just looking at if i do do it myself how.

 

if i were back home it would be easy.

[Spider]

 

Hi  what is it that you want to machine ?

Just extending the head stud holes.  
 

as it was not done originally and I want to counter drill the top thread off as they again were not originally done.

 

 

Ah,,,, OK,,,, now I know what your doing,,,,

 

I just do them in the Pedestal Drill. I might have photos somewhere.

I use an M10.5 Drill bit. To 'Centre' it, I slip the gearbox in neutral and turn the chuck backwards with the tip of the drill bit initially about 1- 2 mm off the block and then start pushing the block until it gets closer to centring, working my way to the point where it's in contact with the edges of the hole in the block.

 

I highly recommend setting a depth stop. Depending on how your drill bit is sharpened, it can bite and take all the threads out quicker than you can blink.

 

Then drill away. You'll find that the drill will want to self centre itself regardless as to how well you have actually centred it. I usually only take the top 2 threads out, that's enough.

[nicklouse]

cheers Chris.

 

gearbox case is off for washing now so will be on that this weekend.

 

still not found a workshop that will do this so may have to sort it.