Another take on the Sensitive drill

[Roger B]

Following Steamers post I decided to have a go at making a sensitive drilling attachment. This will be needed as I move towards more carburettor work. The basic parts are from RC Machines, an MT2 mandrel with a 16 mm hole, a 10mm diameter B6 chuck mandrel and a chuck.

The adaptor was a simple turn and ream 10mm. The handle was another simple turn and thread. The forked piece was more interesting. I can mill on the vertical slide, but the motion in the X and Y directions is limited and clamping things on is a pain as all the bits try to fall off due to gravity.

In general I was happy with the fork but the radius at the top is not symmetrical, possibly a result of the lack of rigidity.

I will see how much more I can complete before the next trip to China.

[steamer]

Cool!   Looks nicer than mine!

Dave

[Don1966]

That looks good Roger, I am interested to see how it looks complete.

Don

[Roger B]

A little bit more done.

Thank you for the comments. I hope that the finished article lives up to your expectations.

[steamer]

A little bit more done.

Thank you for the comments. I hope that the finished article lives up to your expectations.

More importantly...I hope it lives up to yours!
 

Dave

[Roger B]

If it works it meets my expectations 

A little bit more.

[Ginger Nut]

Looks great

[Roger B]

Some progress and some learning experiences.

While putting the adaptor and chuck assembly in the headstock to check for run out I let it slip. The chuck arbour snapped off just behind the chuck! It was a brittle break from an existing crack about 1/4 of the way across. I was able to get the bit out of the chuck by holding it in the vise. The other bit was more of a problem, it was too snug to shake out and too hard to drill and tap the end to pull it out. Finally I drilled through the grub screw hole in the MT2 mandrel and was able to push it out with a bit of bent wire.

Some problems:

1) The chuck arbour would have been too hard to cross drill for the operating pin.

Solution: make a new arbour from silver steel

2) I need to learn how to cut a accurate taper.

Solution: read what other people on the forum have done and try it.

3) When I tried it the MT2 mandrel was also too hard to drill and file. I need to mill two flats and drill and tap some holes

[Roger B]

Having thought about it I decided to try and anneal the MT2 mandrel. This meant that the Loctite holding the adaptor in place would be destroyed so I hoped I could get the adaptor out.

I held the mandrel by the tang in the vise and heated it to dull red with my blowlamp (camping gaz/ plumbers type of thing). It was kept it hot for about 5 mins and then let to cool naturally. I was unable to pull the adaptor out and in my effort it did sufficient damage to mean a new one would be needed.

The annealing was a success, I could now drill and file it! The old adaptor was parted off and drilled out at 15.5 mm. The remaining shell came out easily. Making the new adaptor was quick except for the usual fun with the short stroke on the tailstock and tangs on the end of my larger chucks. I decided to drill to 9.8 mm and ream to 10mm later when it was assembled into the MT2 mandrel.

Finally the new adaptor was pressed in with some green Loctite and checked. The outside was true to 0.04 mm 

[Roger B]

Some more steps. The joys of milling in the lathe 

As the only template for a B6 taper I had was broken I decided to draw up the taper in Draftsight and print it out oversize to set the compound slide angle. The fit of the taper was not too bad, certainly good enough for the loads this is going to see.

A bit more work on this and then back to the engine.

[AussieJimG]

Prompted by all this activity and by the requirement to drill a number of  0.5mm holes, I finally made a sensitive drilling device.

There are designs for these in several places but I just made the one shown to fit the chuck from my Dremel tool and to be fed into the work by hand.

It's a bit rough and could do with a few modifications but it only took a couple of hours and it worked for al the holes I had to drill.

Jim

[steamer]

Hey Jim

I have a sensitive drill attachment that looks just like that for my BIG lathe...it's a chuck with a straight shank arbor mounted in a 3MT arbor on hardened steel bushings ( commercial drill bushings) and it looks just like that.   Works very well.

Thought I'd try something different for latest one.

Dave

[Roger B]

Finally finished and tested 

The setup for milling the slot took a little thought due to the limited travel and clearances but did ok.

As a trial I centre drilled the end of some 3mm brass rod with a 0.5mm tip drill and then drilled a 0.3mm hole about 3mm deep. The drill is straight, there is a little bit of swarf in the picture that makes the tip look bent.

[steamer]

I like mine Roger!  I hope you like yours!

Dave

[Roger B]

I do, it looks ok and more importantly it works!

I want to do some experimenting with carburettors and although I have the little Proxxon drill for flat bits making small holes in the lathe was a little fraught.

[Don1966]

Ok! Between you and Dave you convinced me I have to make one. Really nice job Roger.

Don