MechMate CNC Router Forum

Go Back   MechMate CNC Router Forum > Common Assemblies & Parts > Driving Mechanisms: Rack/pinion, gears, screws, belts & chains
Register Options Profile Last 1 | 3 | 7 Days Search Today's Posts Mark Forums Read

Reply
 
Thread Tools
  #1  
Old Thu 22 May 2008, 20:25
J.R. Hatcher
Just call me: J.R. #4
 
Wilmington, North Carolina
United States of America
Send a message via Skype™ to J.R. Hatcher
"Grub"/set screws for pinion gears - fitting and locking them.

Copied from JR's thread:

Ed may I suggest backing the grub screw (Gerald's term) out 1 at the time and putting loctite on them. Make sure it's the type that can be removed.
Reply With Quote
  #2  
Old Thu 22 May 2008, 21:59
Greg J
Just call me: Greg #13
 
Hagerman, New Mexico
United States of America
Self-locking "set screws" (grub screws) are also available.

Removal is quite easy.
Reply With Quote
  #3  
Old Fri 23 May 2008, 06:07
DMS
Just call me: Sharma #9 India
 
Rajasthan
India
Quote:
Self-locking "set screws" (grub screws) are also available.
Greg,
Could you plz elaborate what are these ?
Reply With Quote
  #4  
Old Fri 23 May 2008, 07:29
Greg J
Just call me: Greg #13
 
Hagerman, New Mexico
United States of America
Sharma,

McMaster Carr (www.mcmaster.com)
Part Number: 98796A132

That part number is for an assortment of different sizes.
Reply With Quote
  #5  
Old Mon 02 June 2008, 15:42
dmoore
Just call me:
 
Recommendation: LocTite on "grub"/set scews for pinions

Myself another person with a MechMate have both experienced slipping of the pinion gears due to the backout of the grub screws. Based on this I would recommend the following:
  • Go to the largest size grub screw possible. I used #10 but I'd consider going to 1/4" if you can make it fit
  • Use LocTite on the grub screw to keep it from backing out
  • Alternative: Locking the entire shaft to the pinion with Loctite 680: https://tds.us.henkel.com//NA/UT/HNA...ile/680-EN.pdf
Posted to the motors section for more visibility. Based on the following post by JR:
http://www.mechmate.com/forums/showt...&postcount=139
Reply With Quote
  #6  
Old Mon 02 June 2008, 19:23
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
...or
When the hub length permits, I use (2) very short set screws. One to lock onto the shaft and one behind it to make sure the 1st one doesn't back out.
Sorta like a double lock nut. Of course, locktite is always used.
Reply With Quote
  #7  
Old Mon 02 June 2008, 20:23
sailfl
Just call me: Nils #12
 
Winter Park, FL
United States of America
That would be blue locktite, right?
Reply With Quote
  #8  
Old Mon 02 June 2008, 21:30
dmoore
Just call me:
 
Quote:
Originally Posted by sailfl View Post
That would be blue locktite, right?
I used red, just to be "sure".
Reply With Quote
  #9  
Old Fri 06 June 2008, 09:13
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Before we get into LocTite, let's look at the number/location/size of the screws in the pinions . . . . .

The direct-drive stepper motors have two flat surfaces, 90 degrees apart, so that 2 screw can be tightened onto the shaft. However, the geared motors, for some unknown reason, have only one flat surface for a single screw, even though these motors produce higher torque?? Do not be tempted to tighten a second screw down directly on the round surface of a shaft - the shaft is soft, gets a ding in it, and the pinion doesn't slide off again! When I get around to fitting the geared motors, I will grind a second short flat surface into the shaft.

When using the small 20T pinions, there is very little thread length available for the screws. Soft (unhardened) pinions could get the threads stripped by overtightening the screws.

With a hardened pinion, or a bigger diameter one with more thread, you can tighten the screws until you bend/twist the allen key/wrench. That is, if you have a decent quality screw which is relatively hard. (cheap screws let the key/wrench strip out the mating hole - nasty)

If attention is paid to the above factors, Loctite is not necessary. Loctite is a "patch" for deficiencies in the above, or, extra insurance on top of the above factors.

All Loctites can be "released" after quick application of a heating torch - they don't like heat.
Reply With Quote
  #10  
Old Mon 10 August 2009, 15:02
lumberjack_jeff
Just call me: Jeff #31
 
Montesano, WA
United States of America
Slipping set screws

I have fulling steppers with a 12mm shaft and a 4mm key.


My pinion gears are McMaster 20 tooth 20pitch 20pa. They are bored 1/2" dia. I drilled them for (2) ea #10 setscrews, 90 apart.

Is it feasible to put a matching keyway in my pinion gears?

If not, is it advisable to orient the grub screw such that it presses on the bottom of the keyway?

If not... should I just grind a flat for the setscrew?
Reply With Quote
  #11  
Old Mon 10 August 2009, 15:18
jeffa
Just call me: Jeff
 
Iowa
United States of America
Jeff,

Does the 1/2" diameter bore seem a little bit sloppy on the 12 mm diameter motor shafts? The fit between the two should be very close...softly tapping the pinion gear onto the motor shaft would be about right.

Putting a keyway in your pinion gears is pretty straightforward. On the McMaster-Carr website search on 'keyway broaches'.

The broaches to cut a keyway into your pinion gears might be a little pricey, so you might want to find a local shop that would do for you on the cheap.

I'm sure you would be really happy with the rigidity of a keyway. You can then drill and tap a set screw directly on top of the keyway.

Best regards,

Jeff A

Last edited by jeffa; Mon 10 August 2009 at 15:25..
Reply With Quote
  #12  
Old Tue 11 August 2009, 00:05
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
That is a small pinion and there isn't much "meat" in the collar. Certainly not enough for a grub-screw over a key. A key by itself won't handle the rapid reversals we experience. A grubscrew into the shaft keyway might be okay (no key)

The proven practice is to have a pair of grub-screws 90 degrees apart. The flats on the shaft need not be precision - the major purpose for the flat is easy removal of the pinion after the screws have gouged the soft shaft.

Use good quality screws that can survive a massive tightening - bending a quality allen key/wrench is the norm.

Minimum screw diameter 5mm. (pitch 0.8mm)

A pair of 10-32 screws could work, but I don't think a pair of 10-24 screws will do it.
Reply With Quote
  #13  
Old Thu 21 January 2010, 12:38
Oleks
Just call me: Oleks
 
Poltava
Ukraine
Other than grab screws ways to hold pulleys on shafts?

There are reasons not to have on pulleys excess ring for grab screw. Many types of locking devices available but all are rather expensive. Could somebody suggest design not too complex to make with manual lathe. For shaft 14mm, width of pulley 19mm. What kind of metal (treatment) to use?
Attached Images
File Type: jpg Self-centeringLock.jpg (94.2 KB, 1162 views)
Reply With Quote
  #14  
Old Thu 21 January 2010, 13:26
Oleks
Just call me: Oleks
 
Poltava
Ukraine
OR just make two holes for grab screws through teeth and give it LockTite as well?
Reply With Quote
  #15  
Old Thu 21 January 2010, 23:33
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Oleks, we have too little space, and the pinion gear is too small, to use those tapered locks as you first showed. The grubscrew (or setscrew - same thing) solution works okay if:

- at least 2 screws are used
- they are 5mm diam. or bigger
- the thread of the screw is not too coarse
- the screws are tightened until the key (wrench or spanner), of good quality, twists permanently.
- the screw is of a good quality and is not damaged before the key is damaged
- you use a new key for each screw
- there is a small flat spot on the shaft where the screw makes contact

and finally;

- a bit of LocTite is added. But this is not as important as any of the other factors above. LocTite will not solve a problem caused by any of the factors above. If the above factors are correct, the LocTite is not needed.

Adding more screws under the gear teeth will also help, but 2 good screws outside the teeth should be enough.
Reply With Quote
  #16  
Old Fri 22 January 2010, 04:22
KenC
Just call me: Ken
 
Klang
Malaysia
Many years ago, in my 1st job, my boss drill a hole through the gear & motor shaft then drive a transition fit dove pin through to lock everything up. Its not as easy as it sound though.
Reply With Quote
  #17  
Old Fri 22 January 2010, 13:29
Oleks
Just call me: Oleks
 
Poltava
Ukraine
I'm going to make as Gerald tells on pinions and 24 teeth timing pulleys (aluminum, but I can afford metal ones too).
And I have 72 teeth aluminum timing bar and could save some 30-40% of it not making that extra (well, I do not know how to call it in English) ring, bushing - where holes for set screws usually made. Is it sound idea to make holes for screws through all body starting on teeth?
Also in mind was - if some locking devices could be made then cheap plastic pulleys possible to use. Once three devices are made - pulleys can be changed with less effort.

Gerald, are your instructions valid for aluminum pulleys?

Thank you.
Reply With Quote
  #18  
Old Fri 22 January 2010, 14:19
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Only valid for alu. pulleys if you have enough screw length so that the alu does not strip out. For the steel pinion gears, we only have about 5mm screw length - if that was alu, it would strip. I think for alu you will need at least a 8mm long screw, 5 or 6 mm in diameter.

If you have a belt drive, the fixing of the motor pulley to the motor shaft is less critical because the belts absorb some shock.
Reply With Quote
  #19  
Old Mon 25 January 2010, 05:42
Oleks
Just call me: Oleks
 
Poltava
Ukraine
Quote:
Originally Posted by Gerald D View Post
2 good screws outside the teeth should be enough.
If I make it like this. will 19mm width give enough contact area with shaft?
Attached Images
File Type: jpg Pulley_72.jpg (41.6 KB, 1090 views)

Last edited by Oleks; Mon 25 January 2010 at 05:48..
Reply With Quote
  #20  
Old Mon 25 January 2010, 05:52
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Oleks, that should work okay. Use 4 screws, each 10mm long. Tighten the first 2 screws onto the shaft, then put the next set of screws directly behind the first screws (finally you have 2 screws in each hole). I would do this without LocTite.
Reply With Quote
  #21  
Old Mon 25 January 2010, 22:11
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
Oleks,
If you have conical point grub screws....you could drill from the 'side' of the plate at the same angle *say 30 or 45 degree* that matches the point of the grub screw and not violate the belt teeth area. just a thought.

...or lighten the entire pulley and use a right angle driver in the now removed area to tighten shortened screws and still leave the teeth area untouched.

Good luck.
Sean
Reply With Quote
  #22  
Old Tue 26 January 2010, 00:17
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Quote:
Originally Posted by smreish View Post
...or lighten the entire pulley and use a right angle driver in the now removed area to tighten shortened screws and still leave the teeth area untouched.
Right angle thread taps are just a bit hard to find outside your country Sean.

The big pulley has such a large amount of teeth covered by the belt that the holes will have no effect.
Reply With Quote
  #23  
Old Wed 27 January 2010, 06:13
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
...good point Gerald
Reply With Quote
  #24  
Old Wed 23 June 2010, 09:53
digitallightning
Just call me: Dan
 
alberta
Canada
I know this is an old thread, but I wanted to share an "old guy" trick i picked up from a co-worker: The proper way to tighten a setscrew is to tighten it up, back it out a quarter turn, then tighten it up again, and repeat until you are happy. Using this trick i have NEVER had a setscrew come loose since i started using the trick. What happens is the setscrew bites firmly into the shaft, making a recess that fits the screw perfectly, increasing contact area and friction. this trick works best with the setscrews with an inverted cone machined into them, and even better with the type that have teeth on their gripping end.

Another trick to prevent stripping out a Allen key socket is to FIRMLY tap the wrench into the socket with a hammer, to ensure that it is completely seated in the socket, this really cuts down on stripped sockets, and is necessary for removing a properly seated setscrew. (i've had to torch off a few bearing lock collars before....)
Reply With Quote
Reply

Register Options Profile Last 1 | 3 | 7 Days Search Today's Posts Mark Forums Read

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
2D Set Cutouts bfauska The Show Room 0 Thu 17 September 2009 22:53
Circles are not cut round - loose pinion gears sailfl Troubleshooting 21 Sun 15 February 2009 18:19
Drilling & tapping the pinion gears for locking screws lunaj76 Driving Mechanisms: Rack/pinion, gears, screws, belts & chains 11 Sat 29 November 2008 06:49
Fitting encoders to stepper motors Thomas M. Rybczyk Motors & their mountings 11 Thu 01 March 2007 11:55
Zero backlash gears vadeem Motors & their mountings 6 Fri 24 November 2006 09:55


All times are GMT -6. The time now is 09:31.


Powered by vBulletin® Version 3.8.3
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.