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Rebuilding a benchtop drillpress.
websterz:
I was given a little 5 speed Chinese drillpress today. The motor is smooth as silk, the bearings and pulleys are all in great shape, it just needs a spindle shaft. Hey...I know a machinist...maybe I, er, HE can make a shaft! :dremel:
Step ahead an hour. The drillpress is broken down to component parts. Lots of hardened grease everywhere. The spindle bearings are soaking, I have a piece of 1/2" drill rod in the lathe, turned down to fit the aforementioned bearings. The other end of the aforementioned shaft is the root of my quandry. In cross section the shaft has to look like this:
I presume the shaft is (was) solid, broached out of a larger diameter so that the keys are cut rather than applied later. Remember, Chinese 5 speed, not high precision. The keys are only .112 wide, rather on the small side to try and cut and then attach to the shaft. I only need 3 inches of total length keyed. Here's my idea.
Now that I have a working h/v rotary table I thought about drilling and tapping a series of holes down the side on the shaft, rotating 90* and doing the same but staggering the holes on 1/2" centers, then repeating for the other 2 rows. After LocTite'ing in screws I would come back and mill them to width and depth. This has to be a slip fit.
Think it will work? I have nothing invested but time, and if it can't be fixed I still have a nice little motor and a lovely base and pillar for a tapping fixture. I'd rather have a small drillpress though... :thumbup:
bogstandard:
Webby,
What you have just described is the basic method of replacing a missing gear tooth, drill a row of holes fairly close together, loctite threaded rod studs into holes and then file them down to the rough shape of a tooth. Done it many dozens of times with 100% success.
Your method should work perfectly well, but get as many screws along each line as you can, as unlike a gear tooth which is only in contact a little of the time, your drive pins will be in contact and in use all of the time. In your case I would use 5/52" thread (4mm) or at least 1/8" (3.3mm). This would allow you to remove all traces of the threads on the driven faces, so allowing them to slide up and down nicely in their slots.
BTW, to machine the whole end up is in fact rather easy if you use a larger bar.
John
websterz:
--- Quote from: bogstandard on May 26, 2009, 05:49:04 PM ---
BTW, to machine the whole end up is in fact rather easy if you use a larger bar.
John
--- End quote ---
Is it now? Care to share some tips? :bow: :smart:
Bernd:
Here's what I would do. I would mill four slots with a 3/32" (.0938") end mill to the .112" or a bit larger. I would then mill down some .125" flat stock to .112". Then cut into 4 pieces 3" long and silver solder them into the slots. Mount in lathe chuck and turn the outside to proper diameter to fit into the other part.
Lots of work, but then I was one for never taking the easy way out.
Regards,
Bernd
bogstandard:
Webby,
Look at the attached C-o-C and supply the dimensions.
I would also need to know whether the four splines have a curved top to suggest whether they were machined out of round bar or not. Plus whether the continuation of B is the size of the bar that is what the other end plain bar is sized at.
A 1/8" plus a 3/16 or 1/4" slot drills, rotary table and tailstock will be required.
If you have these measurements and items, plus the courage and time, I can knock you up a machining sequence to get to something very close, or even perfect to what you are after.
If not, then please use my original text recommendation, as I don't want to waste considerable time and effort if you are not going to carry it out.
But no cheating, piccies of during machining and the finished article will be required.
:worthless:
John
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