the Carpentry Way: New Plane of Reality (IV)                                                          

New Plane of Reality (IV)

The adventure continues with my newly-received SCM S-630 planer. I've been doing a fair bit of research on Tersa heads, past and present, including looking over the original patents, been in touch with people in Italy, in Switzerland, the US and Canada. Both MBM in Italy and the fellow at in Canada agreed that the head has to come out and be sent to the factory to be re-assembled and rebalanced. I had a talk with a tech rep at SCM in Georgia, and he suggested, however, a way where I could try to replace the bolts and carefully fit the knives back in. His explanation didn't make total sense, as he talked about tightening the gib plate down to where it wouldn't let the knives insert, then unscrew the bolts gradually, counting the turns, until the knife would just insert.

But, all things considered, it made sense to at least try and re-set the bolts holding the plates and see if the head will lock up the knives properly and plane wood cleanly. If it won't then I'll be looking at either sending the head back to the factory, or buying a new head. Prices for new insert knife heads did not excite me. Here's the breakdown of what I found:
Uh, ouch! Still researching costs on other options too, but for the time being, I decided to try a re-fit of the plates, as that was by far the least costly solution. These gib plates were not removable after I took all the bolts out, so I wasn't able to get in there and clean every nook and cranny as I might have liked. So, I gave the head another once over with rust cleaning chemical, then sprayed a product called PB Blaster in to the gibs, which is a penetrating solvent intended for loosening sticky mechanisms. After letting that soak in a while, I used compressed air to blow the grooves as clean as I could. Then I chased all the threads and put the bolts back in.

Contrary to the advice of the SCM tech, it was not possible to even fit the knives at all until the gib plates were well tightened down. I think he must have been thinking about some later or earlier style of head which had some sort of spring loading underneath the gib plate, who knows?  Anyway, I was pleased to find that the gib plate needed to be fully tightened before the knives could even be slid into place. I had a small piece of tersa knife blade about 3/4" long which I used as a gauge and to slid along and clean the inside space some. It seemed to work well. After a few hours of work i had all the knives back in, and all the bolts in, save one.

One bolt had snapped during dis-assembly, so I was left with the grim prospect of removing a frozen, red loctite-fixed bolt which was buried under the gib plate. I've done enough wrenching on rusty vehicles, both cars and bicycles, to have had a few run ins with the dreaded rusty snapped off bolt. I've come to a few strategies for getting them out, techniques which generally work well for me, 9 times out of 10. Your mileage may vary of course, but I thought it might be of interest to at least some readers to run through how I tackled this problem.

The bolt in question is 6mmx16mm, and had sheared off just underneath the bolt head, leaving a fairly flat topped stub in the bore. I started with a small drill, about 3/32", and carefully drilled a hole as close to the middle of the bolt as I could. The result:

It's a little off center, but not too bad.

Next, in the hope of softening that red Loctite (the 'permanent' thread-locking chemical), I used a heat gun for a while:

Not sure how much that would help, but it was worth a shot.

Next, I grabbed a LH-spiral cobalt drill bit, 1/8" size, put the drill in reverse, and drilled out the hole:

I've learned not to bother with the 'Easy-out' type of screw extractor, as they can all-too-easily snap off in the hole and give you an even bigger headache than you started out with. They are made of a very hard and brittle steel, so if one breaks off, there's no ready way to drill through the remnant.

Continuing on, I vacuumed out the hole as best I could:

Next, on to a slightly larger LH cobalt drill:

I repeated the same steps again, until I was drilling out the hole with a 7/32" LH drill bit. This bit is a little shy of the ideal size bit for drilling the hole if you wanted to later tap it - a 13/64" bit is the right size for that - however the 7/32" bit removes most of the waste while accommodating some slight off-centeredness with the drill hole.

The nice outcome with these LH spiral bits is that once you have punched out most of the bolt, the resistance of the bolt falls away and then the drill bit will catch the bolt and unscrew it right out, like this:

I find this sort of work a bit stressful, so I was quite elated when I felt the bolt give up its fight and came back out of the hole. As it does, it tends to clean up the threads too!

Then on to cleaning up the threads with a fresh tap (this was necessary as my other tap snapped unexpectedly when starting to clean out the hole and I had to spend 15 minutes teasing the tap remnant back out):

Then the bolt could be reinstalled, at least temporarily:

Whew! Made it through without excessive trauma. What a relief.

Now, the bolts I removed from the head originally are of uncertain condition, given that one snapped and others were removed with an impact driver and did put up a fight. Those bolts might be stressed and could fail prematurely when re-tightened, so a wise course is to toss them I think. I picked up some 6x16mm bolts from the local hardware store, however I cannot expect these to be decent quality (just like most of the stuff in the hardware store these days, sad to say). Metric bolts come in several strength grades, the toughest of which is 12.9, So, I found an online supplier, based in Massachusetts, called Bolt Depot, that stocked grade 12.9 bolts in a 6x16mm size, and to boot their price was about 1/3 of what the local hardware store was charging for cheap quality bolts. So I ordered up a full set of 36 bolts to replace all the cap screws - these I will put on with blue Loctite and sequentially torque down to a setting something like 10% lower than the bolt is rated for, to be on the safe side.

Meanwhile, I have hooked the air compressor up to the planer and completed the dust collection piping for the machine as well. The planer is now on the floor in final position. I have close to 12 feet of room on the infeed end, which should be plenty.

I peeked in at the side of the planer motor and could make out its data plate. Turns out that I have a 9Kw, or 12 h.p. machine, not a 10 h.p. machine. The more the better - yeah baby! This planer was pretty lavishly optioned, and I appreciate that.

I did some calculations given the motor's horse power, 208v., 3-phase power supply from 100' away, motor efficiency which I estimated at the standard 85.5%, and motor power factor of 0.85, means that the machine will consume about 34 amps peak, and require an electrical feed with 8 gauge wire.  I have hooked up a new power cable to the machine, using 8 gauge, 4-strand jacketed wire. Since I am crossing over the 30 amp threshold for the first time, equipment-wise, I can't use the same plugs and receptacles that my other 3-phase machines happily operate on. Ideally, I would go to a 40 amp plug and socket, but they don't seem to make those. After 30 amp, the next size up is 50 amp, and a 50-amp rated plug and socket cost me $110.00. I have the receptacle mounted on the post next to the planer and need to put in some EMT conduit. I did some conduit wire fill calculations, and 4 strands of 8 gauge wire need a 1" conduit size.You can only fill 40% or the conduit's interior area with wire, by provisions of NEC (electrical code).

I think I should be able to put power to the planer in the next couple of days, and I am excited to see it come alive and have fingers crossed that the Tersa head will work as it should. All for now, over and out - thanks for your visit!  On to post 5