DREMEL drill press Gear making

I keep a lot of junk because of missing parts and sometimes I just don't feel like disposing it. One of these items happened to be a DREMEL Multiprocessor DELUXE DRILL MODEL 212. It's not so deluxe after the pinion and rack system broke.

When I inspected the problem, the culprit was a plastic gear. No parts were available for replacement ( obvious reason being $ minded Dremel wanted to make more money from newer models). It was bubbled wrapped and kept in the storeroom for nearly 2 decades and was slowly forgotten until recently.

I decided to repair it, not that I needed it badly, and to challenge myself to do something that I have never done it. It was no easy task. There was little information about gear making and I am not in this industry or a metal fabricator. As far as I know, production gears are made from cold forging techniques.  They have dies with the opposite shapes and a whopping 200 tons of pressure  is applied to a billet of softer material into the die . A bit like making jelly in a mould but instead if pourIng  molten metal into a mould, excessive pressure is used.  Examples are Shimano  crown gears in fishing reels using this type of cold forging process.  But who am I kidding, DIY project  using 200 tons  of force!

So the only way to make a replacement gear is the use of a gear cutter. I need just one gear and it's a one off thing.

From the broken gear, measurements were made, number of teeth were interpolated into the imaginary calculations. These were not difficult being a science student in my teenage days, I can still remember geometry and properties of circles very well. It worked out that the gear had 16 tooth and  it's pitch was determined from the straight rack by way of vernier measuring. Believe me it took me many weeks to accurately determine the pitch of the gear. If the wrong diametrial pitch was taken, the resulting gear will never mesh properly.  There are also many types of gears and the one I was working on is an involute gear. So call involute because the curves on the gears are part of an involute circle. Very confusing when I first started understanding this, but the more I read, the more interesting it got.

The easiest way to make this gear replacement is using an involute gear cutter. Gear hobbIng is also possible but ........

So making a gear is actually removing material from  a complete round rod to form the tooth of the gears,  so technically it's not gear cutting but that's what they call it anyway. Like why they call a skyscraper building when it's already completed ? Anyway I know to cut 16 tooth means I need to rotate the blank rod 22.5 degrees precisely for each pass, otherwise the finished product looks odd and of course it won't mesh with the straight rack. 

7075 aluminium was chosen . If I were to do this again, I would select 60xx aluminium.  7075 being a harder Alu alloy  it's was so damn hard to cut it. Next time stick with something that's not an overkill. 

16 passes were made and the resulting gear was amazing. 

There was a problem, I made the cut too deep so the mesh was sloppy. So second one was made ( I too have my fair share of failures ) and I cut it shallower. And there's a formula to follow when cutting the depth of gears . Lesson learnt.

The second gear made was much better and I move on to solve the rotating stem that must be attached to the gear. Dremel used a positive type of engaging mechanism.  It's too complicated to replicate on the aluminium  it has a shape much like a Mercedes Benz logo. 

I went for an easier approach . Just epoxy the gear and the rotating stem assembly.  I made a tight fit  recess to receive the stem so that it would not be sloppy and I was wrong.  Later I learnt that a bit of slop would assist in the epoxy  stage.

Because the stem and the gear are two seperate pieces,  to find a common center is difficult.  So the recess part of the gear was made slightly bigger for adjustment just before the epoxy sets.

Before epoxy, I cut a 0.5,mm slot so that the return coil spring can be attached. This slot must be made exactly across the diameter otherwise  the rotating gear will be off center and it will bind

With that done, the gear is mounted on the lathe and dial in to get the best possible runout of 0.10mm,  zero is ideal. The stem was well made by Dremel and had a 0mm runout. 

The stem was mounted onto the tail stock and epoxy (JB weld) applied and the 2 pieces are bonded together.  Best possible bond is to have no air gap.

The next 6 hrs was checking for runout just before the epoxy sets after which no adjustments can be made.

After 24 hrs, the epoxy sets and the part is ready for assembly. Aluminium bushing was turned out to better support the stem during use so that the stress distributed on the bush. Later I made Delrin bush to replace the aluminium one. 

And with the parts made, just assemble it together and use the press.

 There was still some binding between the gear and the rack so I used engjneer's dye to locate the binding and removed some more material from the gear. And that little bit of material removed made a huge difference.

The final and finished product.

It was a good learning experience making this part. A lot of thinking was involved.

Timing belt, water pump and crank seal replacement

I had some free time and decided it was time to replace some vital parts of a vehicle that I bought second hand.  These parts clocked the 100,000km mark so it's due for replacement. I have replaced these items before on some other vehicle make but I must say that Japanese cars are much easier as compared to  continental cars.

Before you start, it's a good ideal to have zip loc bags ready to keep and label all the bolts removed.  It will save you lots of time when putting back everything.  Ask me how I know.

Your car may be different from the description below but it will not be significant. Refer to your service manual. You need one weekend to do this job, long weekend is prefered.  I did this almost 1 year ago so some steps described may not be in the order done.

Prepare all the tools required.

Abbreviation used TB -timing belt, WP -water pump

First park the car on level ground and support the vehicle on car jacks. Choke the rear wheels and apply the hand brakes. Disconnect the battery terminals.

Remove the alternator and aircon belts. Loosen all the spark plugs

Dismantle the valve cover, protect  the overhead cams with a clean towel.

Undo the 3 bolts that attachs the pulley to the water pump. Remove the  TB plastic covers that protects the TB from contamination. The picture below shows the first half is removed and the lower half needs to be removed as well. There are usually 9 bolts that hold the 2 pieces of TB covers to the engine housing.

With the lower half of the TB plastic cover removed, the  full glory of the TB can be seen.

Next remove the crank shaft pulley center bolt. This one is super tight. Service manual recommends the use of a special tool to tackle this . There is another method. The electric starter itself is a powerful enough to undo the bolt. Arrange the breaker bar to bear against the drive shaft .When the engine is cranked, the bolt does not rotate and is loosen. This step requires the gear box to be in the neutral position otherwise something bad will happen. Reconnect battery terminals to use the starter  and undo the terminals when done.

Remove the crank shaft pulley to expose the crankshaft sprocket. The sprocket is a small toothed wheel that connects the TB. A woodruff key can be seen in the picture. Removing this key will loosen the crankshaft sprocket and expose a seal that needs to be changed.

Support the weight of the engine with a car jack and remove the right hand engine mount and bracket. The bracket gets in the way to remove the water pump . The bolts to the bracket are tight so use a cheater bar for leverage again.

I normally mark the position of the belt and pulleys with colored marker so that assembly will be a breeze. This method has proven to be the  best as compared to aligning the embossed arrows on the 3 pulley wheels at TDC ( top dead center) . Get to the  crank shaft pulley (temporary assemble back the pulley with the same bolt) and turn this pulley clockwise until the engine is at TDC. When the engine is rotated clockwise to the TDC, mark with colored marker the position of the timing belt relative to the 3  pulleys. the pulleys and TC are clearly marked with different color to prevent mistakes. The factiry has marking on the exhaust and intake sprocket to show when the engine is at TDC. usually the two arrows will pointing towards one another.

On the bottom left is the tensioner bearing, it keeps the belt tension in place and this needs to be replaced. The right hand side is also another bearing that needs to be replaced.  Usually the timing belt kit comes with all these parts. The belt goes around the intake and exhaust sprocket and also around at the bottom of the crank shaft sprocket.

 

Unhook the spring that is attached to the tensioner bearing and undo the center bolt to loosen the bearing. Now move the bearing away from the belt. The belt can now be removed with ease.

The bottom picture shows both bearings and belt removed. 

Get to the bottom of the car and remove the wooduff key and remove the crankshaft sprocket. You will be able to see a rubber seal . This is the crankshaft seal that seals the engine oil and needs to be replaced. I made a special tool to extract this piece of seal . Its very tight but care must be exercised not to marr or scratch the journal of the crankshaft. If its damaged, the crankshaft will have to be replaced.

Special tool in use. The triangle shape  is part of the timing belt marking.

 The seal is removed and journal inspected for deep scratches.

Replace with a new seal. Use the grease provided in the kit to ease the seal into its place. Tap it in squarely with a socket of a correct size diameter  PVC pipe

Remove the intake and exhaust sprocket and replace the seals as well. Two open enders are used to lock the cams in place to remove these two sprocket. the cams have a key way to accept the tools for lock down. Care must be taken not to damage the journal of the camshaft otherwise these have to be replaced. A note about the camshaft seals, they tight and removal might need a bit of struggle and swearing. Fitting in the new seals is exactly the same as the crankshaft seals

Right side replaced. Left side has no seal and awaiting for replacement.

Install the two sprocket back and torqued down to service manual specification.

Now drain the radiator of all its fluid and store it in a container. Dispose the fluid responsibly. Place a note on the steering saying" Top Up radiator fluid before starting engine.

Locate a black  O ring ( shown below) that needs to be replaced in the metal radiator hose that is part of the radiator hose. I had to to loosen the air con bracket that holds the air con compressor in place to access this O ring. 

Replace all radiator rubber hoses if there are signs of worn out. Undo the bolts that secure the water pump and pull out the mechanical pump. More radiator fluid will flow out and get ready to catch them under the car.

The old radiator gasket is probably  stuck and  needs to be removed by using a sharp razor  blade. Use fine grit sand paper to remove any remaining stubborn gasket.

Before installing the new pump,  compare the new pump with the old one and see any significant difference. Once satisfied, use Permatex Aviation Form A gasket sealant liquid to adhere the gasket to the the pump. I do not like to use sillicon gasket , these sillicon will give lots of issues later including clogging the cooling system. 

Apply the permatex sealant on both sides of the gasket and install the water pump. Torque down the bolts to specification.

Transfer the color marking done on the old TB to the new one. Install the new TB and align the colors marking of the TB to the color markings  on the 3 sprockets made earlier.

Install the TB  and it's two bearings. Hook the idle bearing spring in place and push the bearing against the TB slightly and tighten the bearing bolt to specification.  Tighten the other TB bearing bolt to specification.

Temporary install back the crankshaft pulley and turn the engine clockwise 2 times and check that the timing marks line up according to the service manual.  Once satified, install back the TB covers 

Install back the WP pulley and troque down. The crank shaft pulley bolt needs to be torqued down to 180 Nm ( needs to be very tight, it's the only thing that secures the pulley to the crankshaft ). Install back the 2 belts and all the other components  in reverse. Make sure there are no extra bolts left and all bolts are torqued down to specification. 

It's a good ideal to replace the valve cover gasket as well.  

Top up the radiator fluid and connect back  the spark plugs  and batteries terminals are the last to be connected.  

Before you start the engine, make sure all your tools are accounted for. 

Classic Mitutoyo 505-626 vernier caliper crystal replacement

I inherited my Dad's  analogue calipers which was still in good condition except that it had a broken crystal.

The first challenge was to dismantle this caliper and clean it thoroughly but it's not a bed of roses. Built n the 70's, little was known how it was assembled and I had a boggling 3 days of thinking. Finally I placed the bezel against  2 blocks of wood and gave it a hard push. 

Inside was so filthy , filled with dust, accumulated dirt and dry grease. So I took out all the parts and cleaned it thoroughly. The bottom picture shows a magnified view of the dial pinion

The main pinion placed against an Australia 5 cents.

Below shows the process of derusting parts in a degreaser solvent. 

Below shows a cleaned part

Cleaned up item vs a dirty part. Quite a contrast.

Now everything clean, dry and ready for assembly.

After the cleaning process, I assembled the caliper and check for significant signs of wear and tear. The caliper was still accurate. 

Then comes the next wave of challenge . Replace the broken crystal that has no spare parts.  The crystal takes a dome shaped so that it clears the movement of the  hand dial during operation but a brand new crystal replacement is just  a flat  piece of polycarbonate that has to be pressed into the bezel. That means the crystal is slightly bigger that the bezel but it cannot be too big otherwise it will crack during installation.  Just a tat bigger.

The second challenge is to cut a perfectly round polycarbonate. Conventional scissors and penknife is not going to make it. 

The third challenge is to introduce a 5 degree bevel angle to the edge of the crystal's circumference so that when it is pressed in, the crystal's circumference sits squarely to the bezel ( hard to describe) 

The crystal must have a thickness of 0.65mm for it to flex to a dome shape, not any thicker and thinner is not ideal for  protection against impact. 

The only way to cut the crystal with all the above properties is the use of a lathe. I used a dremel parting wheel to achieve this . With a special attachment that I have made so that the Dremel tool can be mounted onto the tool post and angled to the required 5 degrees. 

It took 3 attempts to get the right diameter before it was pressed into the bezel.

Below you can see the bevel angle of the crystal. Without this angle the crystal will be seated poorly on the bezel .

The final product that's cut out perfectly round .

The last challenge is pressing the crystal to the bezel. 

Professional workshop uses a hand press and  a dome shaped cup that uniformly presses the crystal into the bezel ( one minute job).  I had to use sone household items like a plastic bottle to work the crystal slowly into the bezel. It's one hell of a struggle. When it finally went in, it was such a relief.

Took me slightly more than  one month to crack this puzzle of crystal replacement .

Super Pacer (Owen Kampten)

Built this in April 2012, classic pattern ship. Designed by Owen Kampten.
I converted the Nitro engine into an electric motor. First the wings ribs were cut out and stick the pieces together. Symmetrical wing foils are nasty so all the tools came in to help.

 After slotting, stick on the nylon hinge piece to the wing rib

 Making the ailerons using stock triangle but not the right gradient so more work

 

Cutting slots in the ailerons to receive the nylon hinges and make the bevel angle for smooth movement

According to the plans the wings have a dihedral angle so cut a  dihedral brace and test fit the brace. Everything I do must fit in tight and not too much slop, a habit from too much of helicopter building.

 Next make the aileron torque tube from 3mm carbon steel and brass bearing for again smooth movement. and solder on the threaded couplers

 Now cut the slot in the Aileron to receive the torque tube

 Don't forget to insert the brass bearing before you close the other end of the torque tube. Its a night mare to bend these 3mm carbon steel. But wait there is worse coming. Some pictures

Stick in the nylon hinges with extra reinforcement.

 Cut the 5mm hard wood which goes to the center rib. Epoxy it to have strong bond since the wing attaches to the fuse with this hard wood, no CA for this one.

 Checking for alignment and sticking the lower spar

 Planking the wing's top sheet. 

 After planking, glue in the servo bracket and get ready to cut out the servo pocket

 Cut the landing gear support square pegs, X marks the spot for precise drilling

 Sheeting the lower wing leadimg edge

The remaining servo bracket glue in place

 Glue in the square pegs to support the 5mm landing gear carbon steel wire.

 And yes the nightmare of bending a 5mm landing gear (below picture)  to the perfect right angle, pure madness and brute strength

 

More pics of the lower spar and the angle joint at the center of the wing

 Next the elevator connect rod and its assembly

 Cut out fuselarge and make the push rod from hard wood round peg and 3mm carbon steel

 Also the former for the wing attachment. A bit too short so CA comes in handy and make up for the length

 Next : Glue the former in place and the triangular stock piece.

 Then comes the motor mount made from 10mm ply with ventilation holes and glue it in place together with the triangular stock pieces.

 The battery tray is next

 With that done, I cut the rudder and the slots to receive the nylon hinges. Marking the rudder for taper sanding

 Planking the bottom of the fuse, cross grain.

 Next comes the wing tip. Made from balsa block. Did not want to buy as it was expensive so stick all the balance wood I have and made two blocks

 Now remove the excess material and sand to shape

 Wingtip done and servo mounted with aileron in place

 Next do the wing mounting for the fuse using ply. holes are drilled at an angle so that the plastic screw sits flush and nice. The two ply are join at an angle but right angled to the fuse, tricky part, and still needs to be aligned to the wing's mounting holes.

Next is to bend the 3mm carbon steel for the tail landing gear. Very hard to bend 90 degree bend and not in xy plane but xyz plane. Don't forget the brass bearing before the last bent, if not its damn........

Now a little mod to the tail wheels. To make the plane as light, I chose the plastic wheels. But it is not smooth so I added brass bearing in the wheel so that it rotates on the steel landing gear, get the idea? Ok a pic is worth a thousand words. Look carefully, you can see the brass tube. Add a drop of oil and its ultra smooth. The wheel has almost no weight and with this mod it will last a long time and more importantly it rolls perfectly straight so that take off is true.

 The horizontal stab with holes shed off 2 grams of weight.

Mould the aircraft's canopy. a picture is worth a thousand words. 

  Complete the build of the Super Pacer

Flies like a dream!!

With 9x 8 prop drawing 32A, plenty room for improvement. Could fit a 10 x 7 prop with 42A draw. The flight was good, rolls were axial in both directions. Model flew straight and true. Very happy! 6 minutes of flight time, landed at 3.8 V per cell (3s 2700mah).