My new bearings arrived today from engineersmateltd on ebay, nice fast turn around. I ordered 1 x 6206-2RS (30x62x16mm), 1 x 6007-2RS (35x62x14mm) deep groove bearings and 2 x 30206 (30x62x17.25mm) Taper Roller bearings for a combined cost of £11.57 with free P&P.
I decided to dismantle the spindle head and then compare the spindles before going ahead with the replacement.
First I knocked out the 3MT spindle with a hide faced hammer, which came out leaving both bearings still in the spindle housing, this meant I now had to push it past the bottom bearing, so I used a 13mm socket and an extension to locate inside the spindle thread and knocked it out with the copper face of the hammer.
Here is the 3MT spindle placed side by side with the new R8 spindle.
I apologise for the rather hazy photos, the battery my in usual camera decided to die just as I was about to take the first shot, so I carried on anyway using my work phone for the pictures.
The bearing locations look like they should work, the R8 spindle bottom bearing is 2mm thinner than the one for the 3MT spindle, so that accounts for the difference in start point for the top bearing and the length difference from mounting face to the end of the threaded part – in all good to go.
I then set about removing one of the bearings with a slide hammer bearing puller. The top pulley did not want to budge, so I pulled the bottom one instead.
Then I knocked out the top bearing with a bearing installation tool, a copper faced hammer and the number 3 sized die, this time it came out fairly easily.
Next I installed the R8 bottom bearing (6007-2RS) using the number 4 sized die.
And repeated the process for the new top bearing (6206-2RS).
Then I installed the new R8 spindle with a number 2 sized die, ensuring that the top bearing was not being pushed out in the process.
Then reassembled the rest of the spindle head.
I put some copper ease on the threads of the bearing cover screws to prevent them rusting/seizing in place, I will probably do the same with the spindle nut and any other screws/bolts that are used to reassemble the mill.
I then checked the runout of the spindle with a dial indicator and could not detect any noticeable runout from the inside or outside of the spindle.
In all it took me about 30-45 minutes to perform the swap and that included stopping to take pictures.
I am very pleased with the result and now have the spindle I wanted and the basis of a 4th axis relatively cheaply.
