Drilling and Tapping behind a threaded hole (aligning/clocking a tap?)

[Ttrees]

To illustrate the point I am making get a bolt and run two nuts down it. Bring the two nuts together you will see that you can either have them locked together, in which case the bolt won't turn, or if they are sufficiently loose to allow the bolt to turn between both at the same time, then they aren't locked together. You can't have it both ways.

Thanks for your input, I don't mind trying though.
I doubt I would have the ability to make up another solution like on the lathe.

Seems as your saying the original hole would need to be drilled out and no threading involved,
but I still think there's a chance of achieving this, as there maybe wear of those threads or whatever
to allow some clearance.
This in my eyes is not the same as two nuts in which the flats wouldn't match as I'm hoping to get the fit for the quill with no play, and tap, then fettle afterwards.
This is evident on the return spring split thread, where this is achievable, agreed it's not the same thing either, but is a good illustration of the tolerance/slop required

Agreed might need to clean the bottom of the slot to some extent, and the sides will require some time to achieve no slop nor catches.
I've got the files and plenty of markers to scrape some witness marks down a bit.

Not decided on what material the gib will be yet, might try a ply from some hinges yet.
Cheers

Tom

 

[Fergie 307]

If the ridges are an issue then provided they are regular in height, which they probably are, then there is a very simple solution. Just ensure your gib, block or shoe is at least three times as long as the gap between ridges. Then it will ride on the ridges quite happily. I have now read the model engineering post and see that the guy on there did exactly what I originally suggested, and have done with my own machine. Make a shoe to snugly fit the slot. Now either attach a pin to the shoe which fits into a hole in the adjusting screw, or vice versa. If the pin is on the end of the screw then just ensure that it is slightly shorter than the shoe is thick. You want to be pressing the shoe into the bottom of the slot, not the pin. Assemble it, with the adjustment backed off, then just adjust the screw so it pushes the shoe into the slot enough to eliminate play but still allows the quill to slide smoothly up and down. You can make the pin from a drill, just drill the end of the screw, then cut the shank off the same drill and glue it into the hole and grind to the length required. You need the end of the screw round the pin to be nice and flat so it bears evenly on the shoe. Really very simple and the only mod to your machine is the pin in the adjusting screw, everything else is exactly as it is, no need to do anything to the main casting or the quill. Bit of filing to make the shoe and a couple of holes to drill. I really would encourage you to adopt this very simple solution first. If it doesn't work to your satisfaction then you have lost nothing in the attempt, but it works a treat on mine, and apparently also for the guy on the forum you linked to. I could have done it in the time taken to write these posts !

 

[Fergie 307]

Thanks for your input, I don't mind trying though.
I doubt I would have the ability to make up another solution like on the lathe.

Seems as your saying the original hole would need to be drilled out and no threading involved,
but I still think there's a chance of achieving this, as there maybe wear of those threads or whatever
to allow some clearance.
This in my eyes is not the same as two nuts in which the flats wouldn't match as I'm hoping to get the fit for the quill with no play, and tap, then fettle afterwards.
This is evident on the return spring split thread, where this is achievable, agreed it's not the same thing either, but is a good illustration of the tolerance/slop required

Agreed might need to clean the bottom of the slot to some extent, and the sides will require some time to achieve no slop nor catches.
I've got the files and plenty of markers to scrape some witness marks down a bit.

Not decided on what material the gib will be yet, might try a ply from some hinges yet.
Cheers

Tom

tom
No. I merely suggested that the only way to securely mount your block would be using a threaded rod and nut, but as I say I think the whole block idea is essentially flawed. If you are he'll bent on your idea of trying to thread through both components than can I suggest you try doing it experimentally first on two random bits of metal. You will see then that it won't work, because you can either have a thread that passes through both in alignment, or you can have the two parts held securely together, you can't have both as you will find if you try it. I would hate to think of you coming to this realisation after potentially damaging the thread on your machine in the attempt. I am not sure you understand the solution from both the forum you linked to, and my suggestion which is really exactly the same. Or if you do understand it then I am at a complete loss to understand why you don't follow it, at least initially.

 

[Ttrees]

Hello again
Just about got most of this done

That slot was needing to be continued for the gib

I wonder if engraving might be more apt for the job instead of filing, as I had a few slips along the way.

Maybe duct tape might have been the ticket here, as the masking tape did nothing.
Sweaty and a bit tedious business is a recipe for slips

This file turned out to be a great tool along with the single or second cut "farmers own" for the job

Some lapping and hinging

These parts needed to be fairly good, so got a scraping to eliminate the convexity from filing and gang lapping.
I found a chainsaw file pretty good for something narrow like this, just a bevel ground on the bench grinder, nothing else.

Kept in the vice to be blued again and checked with a single rub on the plate

Bevels ground on the components, didn't find I was getting best from the low setting with 2.5mm rods, so swiched to higher mode and made sure to let cool down after a quick tack on each side was done.

The perfect finger trap!, made sure not to use my index finger for the job.

Ground down that 8mm plate to 3.9mm took a while,
sometimes its just lucky to be stupid, as if I had some 4 or 5mm plate, it might have deformed.

The holster/block needed to be heavily chamfered on both sides to sit tight against the inside..
After which I had a long fight getting the gib fitted, and needed to chamfer/bevel the gib.
It was very difficult to get, and only after having another go at it today, I managed it with the help
of some much needed oil.
Was so covered in grease I didn't want more lubrication, it was essential, as was perfect spot lighting for sighting into the machine from RHS.
Its so stiff now that the quill needs help moving it, couldn't be better.
Have to clean up yet and maybe think about putting a screw in the plate.
Probably doesn't need it but some insurance would be nice.

Tom

 

[Ttrees]

Finished up this, turns out it wasn't a regular thread afterall, even though anM6 nut could thread onto the old grub screw, not so the case the other way round,so went ahead and drilled it for
an M8 tap, which made that decision up for me, and having the three good taps and drill was nice.

Not knowing if the gib actually was still in the block, I took a chance as it felt good and full adjustment was available.
Probably should have taken the pinion and handle assembly off again to check,
but still had the other half of the gib material after cutting it.

Crossed me fingers and hoped for the best.
Missing few photos of the more "interesting stuff", sorry about that,
best the camera isn't too close if the going gets tough.

Pretty sure the hole wasn't actually on centre, so things look as they should.
Can just about make out the fit of the gib, with the more feint line on the right side.
Close enough to keep that gib centred...wherever it is....
Thankfully there was the casting there which would keep the gib from sliding

I reckoned it was worth having a go, and thankfully things went smoothly and successfully,
no hint of any discrepancies whatsoever.

Found a nice wee hex bolt, but maybe better off finding something a bit longer for grinding a point later on, as its hard to know how well it is holding the gib, I reckon it's likely plenty deep into it.

Cleaned up and done some plunge testing, the fit is exactly as I want now as it loosened up the tiniest bit
Still way too stiff, but somewhat tolerable for the jobs I use this drill for.

After which the tramming test with an L shaped rod was done, and thankfully the quill still plum, a also checked again with the quill lowered...
another substantial phew, as its now bolted to stay at 90 degrees!

Had another test with the long bit, and still seem to have some movement, thankfully much less,
and quite a lot more force required compared, but it still ain't no Bridgeport.

Now I've got the quill more stable with the gib,
New v belt, some decent hold downs made,
An indexing jig for centering the work
(possible table support)
Hopefully it will be the last of my cattywompus holes.

Still could likely start putting some money into this for a dial indicator and base,
to at least try and make those MT's a bit nicer, or spring for a new chuck...
Hopefully I can get away without that stuff.
Besides there maybe more lessons or experiments to be learned, possibly for drilling an
oversized'ole which needs be done.
That will be interesting, keen to get testing my jig again and rig up for drilling again.

Likely confusing photo underneath as the jig's getting table height set before changing bits and after which centering up on the smaller bit with what could potentially be a lathe vice
I'll likely cross that bridge only if I need to.

Eager to see how things go.
Tom