Problem drilling the pinion concentric
 

I've just trashed 5 pinions trying to drill them concentric using a good drill press a vice, a vice and clamps, a vice clamps and accurately centered pinion.

the existing pinion hole is 10mm, the motor shaft is 14mm and I've tried going up in 1mm steps, 2mm steps and straight at it with a 14mm drill bit.

I'll have to reorder pinions on Monday and I'll ask the supplier if they can machine the pinions to 14mm and include the two grub screw holes but I'm curious


How do you do this without using a lathe?


John

John,
If you have the patience, I have done the following before:
(needed are a drill press and the handheld drill motor with a removable chuck)

1) take the jacobs chuck off the power drill motor and then find a bolt that fits the chuck. In the US it's usually something standard, but on occasion it has left hand threads
2) set on the drill press table surface a very solid, sacrificial plate.
3) chuck up the drill bit closest matching the drill jacobs chuck.
4) BOLT the jacobs chuck to the plate and bolt the plate to the table.
5) chuck up the pinion in the DRILL PRESS jacobs chuck.
... you now have a vertical lathe with a stationary tailstock.
6) set the RPM on the drill press to following machining rules....remembering 1" of bore =- 360 RPM, thus 12mm (1/2" ~) would be 720 RPM....
7) add cutting fluid

This should get the job done....all is kept vertical and in line.

I have done this for years until I actually got a lathe!

Good luck.

SEan

let me see if I've got this right....

You are rotating the pinion in the drill press chuck.

The HSS drill bit is held stationary in the jacob chuck which is bolted to the drill press table

hmmm, wouldn't have thought of that in a million years.



So I presume I'm not the first to discover this issue and I'm not a complete all thumbs numpty for trashing the pinions?


John

I used lathe chuck bolted to mill table. Put a centering holder (blank milling bit) and grab it with lathe chuck then bolt the chuck to the table, rise the mill and change the blank with drill. Now when you put the pinion in chuck it is centered with drill.

John
You got it right....
Now, instead of ordering new pinions, is there enough of the hub left where you can OVER bore the existing ones you have then add a sleeve bushing?

Supplier wants 62 pounds sterling, roughly 75 euro extra to bore 5 pinions to 14mm.

Bit saucy I think.

I'll ring around and see if I can find a local engineering shop that could do it for me


@Sean, because its off centre the thinnest spot is about 1.2mm, so bushing and then tapping for grub screws would be messy, I think.

John

..I guess what really surprises me that the most common, and probably the most simple of all 7 machines invented over since the time of DaVinci, that pinions are so hard to find.

I can walk down to a number of local motor suppliers and get a pinion mostly the right size.

I guess those of us in the states have it easy, but only able to get the wrong pinions (but close) abroad truly amazes me.

Good luck all.

Sean

Sean,
If you have a supplier who can do metric 24 pin module 1 pinions 20 degree with 14mm hole, then please pass it on. Shippng can't be worse than local machining charges.

Good point Red. Me too Sean. :)