# Dumore Series 37 Drill Rebuild



## echesak (May 4, 2014)

Howdy Folks,

Sorry for the length of this post…  I wanted to share the rebuild of my little Dumore Series 37 sensitive drill press.  I bought it from a fellow HM’er in Kansas.  It arrived in good mechanical condition, though needed new bearings and a lot of rust removal. 

I did some research on rust removal and decided to try Evapo-Rust, especially since it was available locally (which is a miracle).  I’ve not done much de-rusting, as I live in the desert, where it’s dry.  Things just don’t rust much here.  I can say that I was very impressed with the Evapo-Rust.  It’s reusable until exhausted, water soluble and cleans up easily.  I tested it first on an old rusted wrench that was left outside for many years.  It stripped the rust very quickly and thoroughly.





I proceeded to disassemble the drill.  I ordered and installed replacement bearings.  I cleaned the rust from all the small parts with Evapo-Rust.  But due to the size, I removed the rust from the base, by electrolysis.  Although it was my first time with this process, it also worked very well, though was a lot messier.





I had contacted Dumore to see if they had parts or manuals for the drill.  They do not support this drill any longer, but emailed me a manual for it.  While going through the manual, it recommends turning the motor commutator, if it’s worn, which mine was.  I chucked it in a 3-jaw and center in the tail stock of my lathe.  I checked the concentricity of the commutator, and other motor parts, with respect to the shaft.  Everything was within 0.005” so I machined thin cuts off the cummutator, until fresh copper was exposed, and the ruts were gone.  I also polished it with fine carbide paper (400, 600 and 1500 grit).  I also cut the insulator from between the copper.  This also helped clean the edges of the copper.  I was nervous about doing this, but it turned out to be pretty straightforward.

Before




After




I cleaned up the inside of the unit from old carbon brush material.

Before:




After:




I then proceeded to wet-sand the parts in preparation for new paint. Prior to painting I hit everything with a rag, damp with Acetone.  It’s difficult to tell from the photos, but the drill’s original paint has a metal flake paint finish.  We drive Toyotas, and I noticed that it was very similar in color to my wife’s 4-Runner.  So I checked at Pepboys for a Dupli-color paint for this Toyota.  To my surprise, it was a near perfect match. 





Overall, this was a very cool project and a great little drill.  I love the adjustable tension knob (opposite the handle), that allows the retraction pressure of the quill to be adjusted.  Very nice!     

Before:




After:

















I have lots of photos posted here, for those that are interested in seeing more:
http://www.ericchesak.com/Galleries/DIY/Dumore-Drill-Rebuild/

I'm still missing a couple screws.  I wanted to replace a few of the slotted screws with button head socket head screws.  So next order from McMaster will include these.  The unit runs really well, had adjustable speed from low, to about 16k RPM.  I already mentioned the adjustable tension.  It also had adjustable depth stop and a cool little drawer on the front for the chuck key and other goodies.    It is also missing a spring that fits on the column, which helps prevent the chuck from crashing into the base when the head is moved.  It's on its way from the seller and I'll clean it up and get it installed after arrival.  

The depth stop is housed underneath the small acrylic tube on the top of the drill head.  It looks like it was installed wrong one time and the depth stops rubbed against the inside.  So I may try machining a new one from lexan or acrylic rod.  But it would be only for appearance.  

The machine runs true and is smooth.  Should work well for what I need it for.

Thanks for looking.  Hopefully this is helpful for others.  If there are any questions, please let me know.

Eric


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## valleyboy101 (May 4, 2014)

Nice job Eric,
The commutator came out really nicely,  I understand your hesitation in machining an irreplaceable part, but it had to be done.Am I correct that it has a flat belt drive?  What is its speed range and capacity?
Michael


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## echesak (May 4, 2014)

Thanks for the comments.  You're correct, it has an XL toothed belt.  I bought the wrong width and had to trim my belt to the right width (until I get another Mcmaster order in).  The belt has 2 cogs, for high and low speeds.  The low speed cog set operates from 1-5000 RPM, and the high speed, from 3000-16000RPM.  By capacity, I assume you mean drill capacity.  It's a tiny Jacob's #0 chuck, so it has a capacity of 0-5/32".  This works out perfectly for me.  I was a little concerned about the chuck, as it didn't work too well when I first got it.  But clearing the thin layer of rust, and a little ISO 32 way oil and it is really smooth.   The manual indicates that it has a constant speed control (adjusts the current as the load changes.  

I chose bearings to allow the spindle to about 23k.  I was aiming for a 2x factor, but that's as good as I got, in the ABEC-1 class industrial bearings.  But bearing-wise it should be fine.  The belt resonates a little at certain speeds, so a little speed adjustment up or down out of the resonance keeps it running smooth.

Eric


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## tertiaryjim (May 5, 2014)

That's some really nice work. Both cosmetic and mechanical.
Good to see such a nice and unusual drill press put back into service.

I'm planing to use the electrolisis method to clean some parts soon.
What did you use for a resistor and what amperage did you see?


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## echesak (May 5, 2014)

tertiaryjim said:


> That's some really nice work. Both cosmetic and mechanical.
> Good to see such a nice and unusual drill press put back into service.
> 
> I'm planing to use the electrolisis method to clean some parts soon.
> What did you use for a resistor and what amperage did you see?





Thanks for the comments on my rebuild.  I used an old piece of rebar for  my anode.  I could have optimized the set-up a lot better with a larger  tank.  But I used what I had.  I placed the rebar horizontally in the  tank, and the drill base, on the other side.  I also used baking soda,  instead of washing soda (none to be found around here). It seemed to  work just fine.  Some sites use baking soda, others use washing soda.   Again, I used what I had, and it turned out perfectly.

One thing I  expected was that the cleaning action would be more vigorous on the  area of the base closer to the anode.  This is definitely the case.  Although the entire part was cleaned, the area near the anode even had  the paint removed (and probably was not rusted beneath).  

It's  very dry here (10% humidity currently).  But once I removed the base,  and the water began to dry, a thin rust-colored film began to appear.   So I immediately cleaned the surface with alcohol and then applied a  coating of car wax.  This protected the surface in its raw metallic  form, but prevented any further rust.  I was careful not to get wax on  the sides, as I was planning to paint.  Even so, I cleaned everything  that I painted with rag dampened in Acetone.  

There are a  million sources of info on the web.  Just search for "electrolytic rust  removal" or similar.  With my vast experience using this technique (one  time), I think a tank shown in this instructable would probably work the  best, for even removal.  

I used a 10A battery charger, but I think any current  would work.  I believe that the more anode area that you have, with  larger parts, the current will probably rise.  But with my single 12"  rebar piece, my current was around 1A.  It was slow, but that was fine  with me.  I left it overnight.  I checked it about mid-way and rubbed  the surface with a plastic scotch-brite pad (didn't want to mar the  surface with the metallic pad).  This helped to remove some of the black  material that is on the surface, once the rust is removed.  After a 5  minute cleanse, it went back into the tank.  In the morning, I removed it, did a little more rubbing with the pad and hosed it off.  It looked really good.

I left mine outside,  since any electrolysis technique will break down the water into hydrogen  and oxygen.  It's carried away quickly, but at higher currents, I could  envision it generating a lot of gas.  It was a really simple technique and makes me look at estate sale finds in a different light.  It worked wonders on this little drill press, with it's very light coating of rust.  The area where there is rust will have pits.  So the lighter the rust the better the part will look when it's done.

Thanks again for taking a look, 
Eric


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## Andre (May 5, 2014)

Wow, nice clean up! What speeds does it run?


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## echesak (May 5, 2014)

Andre said:


> Wow, nice clean up! What speeds does it run?



Thanks...  The belt has 2 cogs, for high and low speeds.  The low speed cog set  operates from 1-5,000 RPM, and the high speed, from 3,000-16,000RPM.  

Eric


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## tertiaryjim (May 5, 2014)

Hadn't thought to limit current by reducing the anode size.
Since I need to do a fairly large part I'll use light bulbs as resistors and cover a large area with the anode so it will clean up evenly.


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## echesak (May 5, 2014)

tertiaryjim said:


> Hadn't thought to limit current by reducing the anode size.
> Since I need to do a fairly large part I'll use light bulbs as resistors and cover a large area with the anode so it will clean up evenly.




Are you trying to limit your current because you're worried that your set-up will over-tax your power supply? or some other reason?  You might give it a try without the resistors, as it may work fine.  I was surprised how little current mine drew. 

Eric


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## hermetic (May 5, 2014)

Cracking good job on the commutator (and the rest of course). You are right, you couldnt leave it as it was, and you did the undercutting of the insulation as well. We used to use a piece of hacksaw blade with the "set" ground off a bit for that job. Looks real Good!
Phil
UK.


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## Rapscallion (May 5, 2014)

Good job Eric.
Some pretty high speeds it has. Good for diamond bits, tiny drills and dremel tools.
It also has what looks like a proportionally small chuck and column. Like it was built for high-speed applications.
Nice little asset.


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## echesak (May 5, 2014)

Thanks Folks.

@ Phil - To undercut the insulation, I used a V-ground tool bit from my lathe, mounted sideways in the bit holder.  It was a little tough to line-up the bit with the insulation, but then it was just a matter moving the carrage to grind out the insulation and chamfer the copper.  Not perfect, but it worked OK and it seems to run great.


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## tertiaryjim (May 5, 2014)

echesak said:


> Are you trying to limit your current because you're worried that your set-up will over-tax your power supply? or some other reason?  You might give it a try without the resistors, as it may work fine.  I was surprised how little current mine drew.
> 
> Eric



I was concerned that the electrolyte would be too conductive and tax the power supply.
Also as a safety as with lights I couldn't get full current if I messed up and ground the setup.
The mix of one table spoon of washing powder to one gallon water doesn't sound very conductive so I'll give it a try.
That would save me some time and effort.


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