Hand Drill Repair

[RussellT]

Hi All

I have been repairing a Goodell Pratt 5 1/2 B hand drill that belonged to my father and to his father.  I’m posting this project log now the project is finished, I didn’t do it earlier mainly because I wasn’t sure I would finish.  It is however a true Madmodder project because the effort was completely out of proportion to the end result.
 

Russell

[RussellT]

The main handle on the drill had clearly been repaired before and the ferrule had been redrilled and had a "pin" retaining the handle. The pin was six strands of copper wire with nasty sharp ends.

I took the pin out and removed the handle. I discovered a piece of wood had been let into the handle and the extra hole through the ferrule had been drilled through the threaded iron of the drill. Unfortunately it had missed.

The metal between the original and the new hole had also cracked.

After some thought I decided that this had to be fixed. My objective was to make this a usable tool and this would eventually have broken. I cut the old thread off and drilled the frame with an 8mm hole. I found a bolt with the same thread as the original and turned that down to 8mm and loctited the two together.

[RussellT]

The next problem I tackled was that the crank knob wouldn't rotate. I thought this was probably due to rust on the shaft. I drilled off the riveted over end and removed the knob. I hit a big snag here. I thought the shaft was tight in the knob because it was rusty. It turned out that the shaft was too short because of previous attempts to tighten up the riveting. That had also swollen the end of the shaft inside the knob, so the knob split as I tapped out the shaft. I glued it back together. I used superglue because the low viscosity meant I could get it in without having to remove the small brass ferrule from the knob. I turned a new shaft and re-riveted the knob in place.

[RussellT]

The main handle had already been repaired once but the new bit of wood disintegrated as I took it to pieces. The first task was to clean up the hole in the handle and make it round which was easy once I'd worked out how to hold it in the lathe.

The next step was to make a wooden threaded insert for the handle. I tried making a tap from a bolt with the right thread but couldn't cut a thread in the end grain. I decided to use a dremel type tool to cut the thread. I made a special cutter for the tool, and a special tool holder for the lathe.

The pictures show the bits and how they go together.

[RussellT]

I repaired the ferrule by silver soldering a brass wood screw in the hole and cutting and filing off the extra bits and refitted the handle. I made a missing part from the chuck and a new side handle, using dimensions for both from some helpful people at UKWorkshop.co.uk.

[RussellT]

All the bits were together and it drilled holes.  However there was still a missing part.  This is a 2 speed drill and the slow speed pinion was missing.  This was an excuse for a long delay in progress.

I tried asking on a US forum for the missing pinion with no success and I set up a search on eBay which only found me drills that were in better condition than mine. I read up on gear cutting and mitred bevel gears in particular. All that revealed were that these were not theoretically correct gears.

So having exhausted all avenues of procrastination I decided to try making a pinion. I decided to try making one in plastic first as it would be much quicker to machine and it would be an experiment.

I measured two angles from the drills handwheel. One was the angle the top of the teeth made with the axis of the drill and the other was the angle the bottom of the gaps between the teeth made with the axis. Because of limited space around it I had to make a sort of mini bevel gauge but I ended up with angles of 39 degrees and 28 degrees.

[RussellT]

I made a gear blank out of acetal on the lathe with an angle of 39 degrees and setup the milling machine to cut 20 gaps between the teeth at an angle of 28 degrees using a home made dividing head (another product of procrastination) which used a lathe changewheel to index 20 positions.

At this point I had to confront the main problem that had been putting me off this job. What shape should I make the gaps between the teeth. Best approximation methods for home cutting of bevel gears suggest three cuts for each gap would be needed so I decided to make a cutter the shape of the smallest part of the gap using the other pinion as a model. At this point I realised that the gaps between the teeth are parallel sided and the wider gaps are created by deeper cuts at the larger end of the pinion so only one cut should be needed.

I made a cutter out of silver steel and mounted it to an arbour and cut the teeth so that the gaps between teeth were about the same size as the teeth.

The only remaining difficulty was the diameter which was difficult to measure. It turned out to be too small - but since it's tapered I could make it seem larger by removing material from the small end and much to my delight it actually meshed quite well with the existing gear although it was now too thin.

I made a second one using the same technique but using measurements from the first attempt. This time the teeth seemed to mesh a bit too deeply so I skimmed the top of the teeth in the lathe. It fitted reasonably well and the drill worked.

[RussellT]

I have assumed the missing gear was originally made from cast iron as if it were steel it wouldn't have broken so I bought a piece of cast iron and made another gear blank.

I hardened and tempered the home made cutter and tried again on the milling machine.

Then I cut the slots on the back to engage with the dogs on the drill. Can you spot the mistake here?

[RussellT]

Then I assembled the drill.

It worked. I drilled a few holes using both speeds.

Success. I'm really pleased with that.     

Russell

[awemawson]

Nicely executed and a well worth save in my opinion 

[pycoed]

Bravo!

[WeldingRod]

Impressive, and I love the family history aspect!  Bravo!

Sent from my SAMSUNG-SM-G891A using Tapatalk

[JerryNotts]

Well Done!

Jerry

[PekkaNF]

Very good.

That bevel gear making is great. The fly cutter looks really nice. Did you use button method? Relief? Offset when making cutter vs. using it or stoning?

Pekka

[RussellT]

Thanks everyone.

Pekka, the design of the cutter was one of the problems that made me keep putting this off.  In the end it was much easier than I expected.  I used the other pinion from the drill to set the shape of the gaps between the teeth.  The crucial thing I found is that the gaps between the teeth get wider because the depth of cut is deeper.  This is not theoretically correct and even Ivan Law's book recommends using three separate cuts for each gap as a simplification for the home workshop.  That means that traditional methods for shaping the gear cutter won't work - it also means that the top of the teeth are flat rather than shaped.  This appears to be consistent with the other gears on the drill although there is some wear which has shaped the tops of the teeth.

To make the cutter I tried to measure the included angle of the gaps between teeth on the other pinion and used the top slide to turn the cutter to the right angle.  I needed a couple of adjustments to get it right but I started with the cutter quite thick.  Once I had the V profile right I used a combination of freehand turning and files to match the point of the cutter to the existing pinion.

I made the profile on the end of a silver steel bar (the largest I had on hand) and to turn it into a cutter I put a shim under one jaw of the three jaw chuck and then drilled a hole to mount it to an arbour and parted it off.  That gave me a hole slightly off centre.  I used a hacksaw and file to remove nearly half the cutter leaving the cutting edge on the part furthest from the mounting hole.  That gave me the clearance on the cutter.  I ground the top face with a little top rake before making the plastic versions and again after hardening it to cut the cast iron.

I have been debating whether I should have done more to shape the tops of the teeth but I think I have done it the way it was done originally.

Making this pinion was definitely the most challenging part of the repair, mostly because I didn't have one to copy.  It turned out to be easier than I expected but I was still very pleased with the outcome.

Russell

[ddmckee54]

COOL!!!

Thread milling, on a lathe, in wood - I love it.  Not many people have done that, you are part of a vary exclusive club.

One other thing that helps when tapping wood is to saturate the wood with thin CA glue.  This effectively plasticizes the wood fibers and the wood will tap better.

Don

[krv3000]

hi brill I love this type of drill never needs charging battery never goes flat and all ways on hand

[Meldonmech]

 
  Hi Russell
                      An interesting project, I have a number of hand drills, various in size and manufacture. Some have needed   handles which were broken, which I have  turned from hardwood, stained and varnished.
I regularly use these and find they give much more control when drilling holes in softer materials. I have various drill bits      permanently fitted, for drilling pilot holes in timber, and countersink bits to follow on.
 
                                                         Well Done, Cheers David