Page 1 of 3

Dempster 6ft No 12 rebuild

Posted: Wed Jun 29, 2022 4:35 pm
by fiegland
I started the tear down of my Dempster 6ft No 12 mill today, and I have three initial questions.

1. How do I remove the Wheel Spider from the Main shaft? I see a Key but am not sure how to remove it.
2. The bumper arm (not sure what it called, see attached pics) seems to be worn thin. It is supposed to look like this or is this worn and needs replacing? If it need replacing, anyone know of a good source for Dempster parts?
3. How do I begin with removing the main gears. I want to pull everything out and sand blast the gears but can't seem to figure out where to start on the removal. Any suggestions.

Thanks,
Larry.

Re: Dempster 6ft No 12 rebuild

Posted: Wed Jun 29, 2022 5:28 pm
by windybob
I don't see the key in the slot of the shaft. If the key is indeed in the slot it is tapered, and you need to take things apart and out of the case first. If there is indeed no key in the slot then the rear hub (brake hub) (rear spider) should turn on the shaft. If you have a 1- piece key, it will be about 3 1/2 inches long. If it came out with the outer hub, that's good. You can drive a wedge in the slot between where the ears are that the bolt goes through to get it loose. It will NOT spread much, it is cast, and will break. You have a late model oil seal on the main shaft (more on that later).

Take off the cast tie on the top of the 2 guide rods. Loosen the 2 square head bolts and soak in oil, and tap under it. It comes off the top of the guide rods. Where the one (longer) guiderod goes through the large diameter bullgear shaft, take a chisel and loosen the locknut then unscrew the guiderod. That guiderod goes through a steel bracket that also holds the bullgears in. The gears will be able to be removed , after you disconnect and pull the shaft out that hold the top of the pitman arms on the crosshead and yoke. If you loosen the locknut and unscrew the other (shorter) guidrod, then the gears, crosshead, yoke, pitmans and and shafts will come out as a unit, then you can take things apart from there. The crosshead that goes over the guiderods needs be free so you can move it. If it is stuck, the rods might not unscrew.

Re: Dempster 6ft No 12 rebuild

Posted: Wed Jun 29, 2022 5:30 pm
by windybob
Your tail buffer is fine. just take it apart, clean it up straighten the shaft and reuse it. That thin spot is cast like that.

Re: Dempster 6ft No 12 rebuild

Posted: Wed Jun 29, 2022 5:39 pm
by windybob
Larry, those guide rods really need to be clean and slick otherwise, the crosshead will me next to impossible to get up and off the top of them. Might wire brush them, and sand them with emery paper. You really don't want to be beating on that crosshead, it has thin spots in the casting that crack easy. Also, it looks as though you have the older model inside, that has a pin through the top of each pitman-to-shaft assembly. If there is a pin holding each pitman on the shaft, grind one side of the pin down, and knock the pins out. Don't worry about saving the pins. Once you get the 2 pins out, then the shaft should be free-floating, and you should be able to drive it out. then your pitmans will be free of the crosshead. This shaft has a habit of being stuck to the pitmans, crosshead, or yoke. If the shaft is bound up tight, there are other ways to coerce it.

Re: Dempster 6ft No 12 rebuild

Posted: Wed Jun 29, 2022 6:13 pm
by mtblah
Larry , when Windy uses big words like "coerce " he is really serious . usually it's heat , time , penatrating oil , more time , bigger hammer , etc .

Re: Dempster 6ft No 12 rebuild

Posted: Wed Jun 29, 2022 6:28 pm
by windybob
:lol:

Re: Dempster 6ft No 12 rebuild

Posted: Wed Jun 29, 2022 7:06 pm
by fiegland
Windybob, there is definitely a key in there. Looks to be broke off if it’s supposed to be three inches. You can sort of see it in this pic. I was able to get the cross tie off of the two guide rods. At my son’s afternoon activities now but will try removing the rod this evening. Soaking the nut in oil for now. So I should focus on remove the guts first since the key is in there?

Re: Dempster 6ft No 12 rebuild

Posted: Wed Jun 29, 2022 9:18 pm
by windybob
ok I see it now. You have a home made spacer on the shaft there between the front and rear hubs. That threaded spacer should just slide off. Someone has worked on the mill before, argo the late model oil seal, vs the square head nuts and bolts. Here's a trick...

Every 6 and 8 ft Dempster comes with it's own hub removal tool. It's the bolt and nut that tightens the rear hub to the shaft. The key is tapered, so Ideally the shaft should sl;ide out the front side of the hubs. Your front hub obviously is the old type, (short) instead of the newer type(long) that actually touches the front of the brake hub. So, your kind has a 2 key assembly instead of the 1 long key assembly. the later, (longer) front hub actually is a s long as yours, plus the pipe spacer that you have. One long key goes through both all the way from the front to the back of the brake hub. So yours is the older type. Here's the trick... Take the nut and bolt (should be fine or SAE thread) and the nut lay flat, and grind either the front or the back down a little at an angle. The slot in your hub is angled, so the nut needs to be. Insert the bolt, and where the bolt starts to go into the slot, put the nut in there. You should have enough room left for a small piece of 1/8 inch steel. You are making a spreader, so as the bolt gets tight, it passes thru the nut and pushes on the steel. This will spread your hub enough to get it to slide off. Hopefully the key comes with it, because it's tapered If the key stays in the shaft, the hub may not slide over it. If it catches on the hub, and slides on the shaft you are homefree. CAUTION... If you crack the hub by spreading too far, than you can post in the "Mistakes I made" section of the site. You dont have to spread it far, in fact you may not even see it move. But spread it you will. You can tap on a thicker part of the brake hub, or drive it off with a rod from the back with the rod down close to the center. Your brake drum hopefully still has some thickness to it, I can't see from the pictures, but if it's less than 1/8 ince, you will have another chore to re-line it later. Hopefully it 1/4 or 3/8 thick. If this doesn't make sense, let me know, I will try to explain further tomorrow.

Re: Dempster 6ft No 12 rebuild

Posted: Thu Jun 30, 2022 9:23 am
by Ron Stauffer
I have encountered a fair number of Dempsters in the NE sandhills that had a pipe spacer between the hub and the spider. Dealers in that area put them on when they were originally put up to help keep the hubs tight. I have taken down a lot of Dempsters to put in solar on the CO Front Range and have never seen a pipe spacer in any. Maybe it was a transplant.

You will want to make sure the mast pipe still has the retainer nub on it as the bottom mast clamps of the motor arent enough to hold it in by themselves

Greetings from the other side of the mountains

Ron Stauffer
Montrose CO

Re: Dempster 6ft No 12 rebuild

Posted: Thu Jun 30, 2022 2:05 pm
by fiegland
Well, I had some success today, but still have one problem. I got the gears and pitman arms out, but I can't seem to get the main shaft out. The key is really stuck. WIndybob, I haven't tried the wedge yet because I am afraid of breaking the hub. I can use a crowbar and get the main shaft to slide forward around an inch, but there is some sort of spring pushing back. Anyone know where to 'release" that spring? I don't see it in the exploded view so am not sure what's holding the shaft in. The rear bearings slide forward when I slide the shaft with the crowbar. Any other suggestions before I try spreading the hub?

Thanks,
Larry.