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8520 "Down Stop?" adjustment dial.

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bwthor

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#1
Would anyone be able to provide the dimensions of this down stop dial, along with the thread pitch. I recently picked up an 8520 from an old high school shop, and it is missing these parts.
8520Dial.PNG

The fine adjustment gears are missing as well, but I found some info on those on this site already. Someday, I may try and tackle those gears, but I'm not too concerned about them yet.
 

jcp

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#2
The dial is 1" dia. with a 7/16" bore, 1/2" tall with 50 divisions. Screw is 20 pitch. Not to difficult figure out the screw length. There is also a piece that attaches to the spindle that works with the nut to make the adjustment. I can try and take a picture of these.
Hopefully, someone has theirs disassembled and can get some measurements for screw length, nut and spindle stop. The nut is the half shaft piece and the spindle stop is the half circle piece above it.
I too had to repair the fine feed gears. I used a gear from McMaster Carr and instructions from either this site or Practical Machinist to repair them.
 

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bwthor

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Hey jcp, thanks for the info and the pic. I think I should be able to piece something together from your explanation and picture. I do have another question though. On the left side of the quill, there are two flathead screws, and mine are missing. What is the purpose of these? I assumed that they were to "preload" the quill, but I see that the outer part, closest to the screw head is threaded, so putting a bolt in there wouldn't do much. Is the inner part a pinned section, and the bolts are just there to help keep things alined when the tension screw is loosened when moving the quill up and down?

Also, I see you have a scale on the main bar that would be used as a guide when angling the head. I don't have that, is that just another part missing on mine, or would you have a later model?
 

jcp

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bwthor, here are some more pics that may help. The nut, the lower part you see on the screw, is just a piece of bar stock that is cross drilled and tapped 7/16-20, then the top is milled away. The upper piece is also a piece of the same dia. bar stock. It is drilled length wise for a socket head cap screw ( whatever the hole in the spindle is tapped) then counter bored for the SHCS head leaving a short sleeve for the screw to attach it to the spindle.. The outer end is cross drilled for the adjusting screw to slip through and the bottom is milled away to match the half bar nut. Hope with the pics this makes sense.
The screws on the left of the spindle housing tighten the bore to the spindle for a slight drag and the bolt can be tightened to lock the spindle at what ever height is necessary.
By the way my mill is a 8530, but I think the down feed and spindle lock setup is the same as yours.

IMG_0612.JPG
IMG_0614.JPG IMG_0615.JPG
Oh yeah, I priced a dial from Clausing......they did have stock on hand.......at just over $350.00 each. I made my own.
 
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PMartin

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At $350 a piece, I'll bet that when they get an order for one they hand a print to a guy in the shop and tell him "make one of these, pronto!" "In stock" really means "it will be in stock just as soon as Charlie can make one".
 

bwthor

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Many thanks for the additional pictures, they will help out a lot. Gotta wonder how much it would cost to build one of these only from parts from Clausing...
 

wa5cab

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#7
Paul,

My experience with ordering parts from Clausing has only been for Atlas machines but if their inventory computer said that it was in stock, it was. If a part wasn't in stock, their computer tells them whether it is on backorder, available on special order only, or discontinued.

bwthor,

You really wouldn't want to know what an 8520 would cost if you bought all of the parts and assembled it (assuming that they had the parts). It would be about like what your current automobile or truck would have cost you had you bought all of the parts and assembled it yourself. Conservative estimate is about 10X. Not counting the cost of tools and specialty items to do it with.
 

PMartin

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Robert, I was speaking slightly tongue-in-cheek. Sorry you didn't catch that.
 

wa5cab

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#9
OK. :oops:
 
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