Shaft Keys- Purpose?

Forum for Maintenance and Repair topics. Feel free to ask questions or contribute.

Moderators: HopefulSSer, admin

Post Reply
Duckman
Gold Member
Posts: 36
Joined: Tue Aug 01, 2017 7:53 pm

Shaft Keys- Purpose?

Post by Duckman »

I am rebuilding a 1954 headstock. I have the keys for the idler shaft and motor shaft, but they are not in great shape. Dings and burrs. I am not sure if I need to replace them or maybe smooth them down with emery cloth or some light filing. My analysis would really be helped if I understood what purpose they served. Can anyone explain? thanks
DLB
Platinum Member
Posts: 1984
Joined: Fri Nov 08, 2019 11:24 am
Location: Joshua Texas

Re: Shaft Keys- Purpose?

Post by DLB »

The keys maintain rotational alignment between the moving sheaves and fixed sheaves and prevent the sheaves from slipping on the shafts. Without that alignment, the sheaves would not close properly to a large diameter. Dings and burrs could interfere with the smooth operation of the moving sheave, which essentially slides on the shaft and key. Because of the 'bend,' the Idler version is a non-standard key.

- David
edma194
Platinum Member
Posts: 1874
Joined: Fri Jun 19, 2020 4:08 pm

Re: Shaft Keys- Purpose?

Post by edma194 »

Changes to the shape of an old key can cause problems with the sheaves opening and closing. These are inexpensive parts so I'd recommend changing them, but as long as the sheaves will slide on them the old ones will be okay. I'd be concerned with eventual wear on the sheaves from anything but smooth contact between the sheaves and the keys.
Ed from Rhode Island

510 PowerPro Double Tilt:Greenie PowerPro Drill Press:500 Sanding Shorty w/Belt&Strip Sanders
Super Sawsmith 2000:Scroll Saw w/Stand:Joint-Matic:Power Station:Power Stand:Bandsaw:Joiner:Jigsaw
1961 Goldie:1960 Sawsmith RAS:10ER
Duckman
Gold Member
Posts: 36
Joined: Tue Aug 01, 2017 7:53 pm

Re: Shaft Keys- Purpose?

Post by Duckman »

I will just buy new keys. I have to replace the idler shaft, eccentric bushing, belts, and some parts for the speed controller. Might as well get the keys, they are relatively inexpensive.
User avatar
chapmanruss
Platinum Member
Posts: 3448
Joined: Tue Aug 26, 2014 8:16 pm
Location: near Portland, Oregon

Re: Shaft Keys- Purpose?

Post by chapmanruss »

Duckman,

Something to remember when buying "new" parts for the older Shopsmith Tools is a lot of changes have occurred since the introduction of the Mark 5 in 1954 until now. Many of those changes occurred in the Headstock. Although certain specifications have remained the same many parts have to be changed as an assembly not individually. I mention this since you are replacing parts of the Idler Shaft Assembly. Over time the bearing has changed, the eccentric has changed and even the Headstock casting itself has changed where the Idler Shaft Assembly is held. Originally the Eccentric was held in place by the clamping action of the cap screw and nut. This proved to be a problem not being able to apply enough pressure to keep the eccentric in place and a pair of Bearing Retainers (P/N A3274) were added to correct that problem. These Bearing Retainers can be seen in the second edition of the manual. WARNING: Do not overtighten the cap screw and nut or you may break the Headstock Casting. If your 1954 Mark 5 has these Bearing Retainers I would recommend you continue to use them. If not, then you may want to consider modifying your Headstock casting to include the retaining screw & washer used to keep the eccentric in place. That can be seen in the picture below of a 1956 Greenie "B" Headstock.

_
Idler 1956 Greenie.jpg
Idler 1956 Greenie.jpg (79.39 KiB) Viewed 385 times
.
I haven't owned an "A" Headstock Mark 5 Greenie to know if it has the space to add the screw & washer shown above. Later an additional screw was added to the eccentric itself to help retain it in position.
Russ

Mark V completely upgraded to Mark 7
Mark V 520
All SPT's & 2 Power Stations
Model 10ER S/N R64000 first one I restored on bench w/ metal ends & retractable casters.
Has Speed Changer, 4E Jointer, Jig Saw with lamp, a complete set of original accessories & much more.
Model 10E's S/N's 1076 & 1077 oldest ones I have restored. Mark 2 S/N 85959 restored. Others to be restored.
Duckman
Gold Member
Posts: 36
Joined: Tue Aug 01, 2017 7:53 pm

Re: Shaft Keys- Purpose?

Post by Duckman »

Russ, I think I understand. I think I have the Greenie "A". I am pretty sure that replacing the idler shaft and the eccentric bushing will work. Everything I have read indicates the critical specs on the headstock castings has not changed, and I compared measurements between a 1984 headstock and the '54. Same. (It is really interesting to compare the old sand casting to the new castings. The older casting is much thicker). My 1954 headstock does not have that bolt that threads directly into casting to retain the eccentric bushing at 12 o'clock. It has those two claw looking things down at 6 o'clock. I cannot recall what the proper nomenclature is. I think I saw a Jacob Anderson video where he showed them. I think SS switched to the retaining screw pretty quick. The original system was really pretty stupid IMHO, but I plan to retain them as I think you are suggesting. I have no interest in trying to drill and thread a hole in the casting for a retention screw at 12. I have a couple of owners manuals but not one for 54 so it is a bit tough working this this sometimes. Big Thanks
Post Reply