Page 1 of 2 12 LastLast
Results 1 to 15 of 28

Thread: A little help from the machinists among us, please

  1. #1

    A little help from the machinists among us, please

    I recently acquired this neat little hand crank grinder. You can see it's specs, etc. from the ad page. What I'd like to know is the following: despite the width of the wheel in the advert, it looks like the non-threaded part of this arbor shaft is only about 1/2" wide. Isn't this the limit of the width of any wheel that I might use?
    Secondly, I have no way of knowing what thread pitch this shaft is. It seems to be 7/16", but I can't thread a 7/16-20 nut onto it. Do you simply count the threads per inch?
    Thirdly, anyone know a good source for reducer bushings and arbor flange washers?
    Please excuse my ignorance and thanks in advance for any answers you might provide.
    Attached Images Attached Images

  2. #2
    I'm not a machinist but will take a stab at this. I don't see why you can't put a larger width stone, up to about 1" on that. To get the width of the stud there without benefit of calipers, you may be able to use a wrench of appropriate size to gauge the diameter. A thread tool helps to determine tpi, but yes you can count threads per inch--I count 14 on a half inch from the photo there, so I'd guess a 1/2" right hand 28 threads per inch. Some grinders and lathes have left-hand nuts. McMaster-Carr has every imaginable piece of hardware you might need, including flange washers, bushings, nuts, etc.

  3. #3
    Join Date
    Jan 2009
    Location
    Williamsburg,Va.
    Posts
    12,402
    You can use any width wheel that leaves room for the flange and nut. The unthreaded part of the shaft will make the wheel run true. Look how wide the wheel is in the old illustration.

    Count the threads per inch. However many whole threads there are in an inch is the threads per inch. I hope it isn't some special thread so you would have to use their parts. It could possibly be that a wheel that wide had a partially threaded hole so it screwed on.

    That is a right hand thread.
    Last edited by george wilson; 07-01-2011 at 11:58 PM.

  4. #4
    Join Date
    Nov 2010
    Location
    Upstate South Carolina
    Posts
    114
    Joe
    It is hard to tell from the photo with the ruler but it appears to be about 24 threads per inch. Looking at the last thread under the ruler there is a possibility it may be a left handed thread. Standard thread sizes for fine thread are 3/8 dia. at 24 threads per inch and 7/16 dia. at 20 threads per inch. If the diameter of the shaft is 7/16 and the thread count is 24 you will have to find a non standard nut. Double up on that if it is left handed thread. You are also correct about grinding wheel width. If you do not use spacing washers a 5/8 wide wheel will be the thinest you will be able to use and still tighten it on the arbor.

    PS Another picture showing the start of the first thread on the end of the shaft will show for sure if it is a right or left handed thread.

    Ed
    Last edited by Ed Looney; 07-02-2011 at 12:11 AM. Reason: clarification

  5. #5
    Join Date
    Jul 2009
    Location
    Mission, Texas
    Posts
    976
    Another way to determine the direction of thread is to observe the direction of normal operation. Like a circular saw blade, the tightenning direction should run counter to the operating direction. Thread gauges are pretty in expensive.
    Mick

  6. #6
    Quote Originally Posted by Joe Bailey View Post
    Thirdly, anyone know a good source for reducer bushings and arbor flange washers?
    McMaster Carr would be a good place to look. You could also find your grinding wheel there too. If the thread is 28tpi as suggested, they have 7/16-28 nuts too. If it's 24tpi, then not so much.
    That's an interesting grinder. Most of the hand cranks I've seen have the crank and the wheel in the same plane.
    If it ain't broke, fix it til it is!

  7. #7
    Thank you gentlemen, for your answers - they are greatly appreciated.

  8. #8
    Join Date
    Nov 2010
    Location
    Upstate South Carolina
    Posts
    114
    Quote Originally Posted by Mark Baldwin III View Post
    McMaster Carr would be a good place to look. You could also find your grinding wheel there too. If the thread is 28tpi as suggested, they have 7/16-28 nuts too. If it's 24tpi, then not so much.
    Mark
    Thanks for posting the information on the 7/16 by 28 tpi. That was a thread size I was unaware of for bolts and nuts. I have seen taps for that thread but had until your post thought it was only used for plumbing / tubing applications (typically banjo bolts). One of the things I appreciate about this forum is no matter how long you have been doing something you can still learn.

    Thanks again

    Ed

  9. #9
    Join Date
    Jan 2009
    Location
    Williamsburg,Va.
    Posts
    12,402
    Late last night I thought those were 1/16 grads!!! Will look to see what odd old taps I have,but correct t.p.i. must be established first. you need a flange too with that odd 7/16" hole. All now come with 1/2" hole as far as I know,unless a washer would do.

  10. #10
    Thanks George - I appreciate your efforts on my behalf.
    (I've been soaking up your advice in this forum for a long time.)

  11. #11
    Join Date
    Jan 2009
    Location
    Williamsburg,Va.
    Posts
    12,402
    I have 7/16-14 and 7/16-20 ,28,32,and 48 thread taps. I have hundreds of taps,some odd sizes. I can make anything,but if it isn't one of these threads,you'd have to send the grinder,so I can make sure the nut I'd thread in the lathe would fit. I just made a cap screw for a member's Record plane in an oddball 27 thd. per inch size,without the plane for checking. The screw went in a bit snugly,but did work. You need the nut,a flange,and a 7/16" to 1/2" sleeve to get that grinder going. I don't know if you can get wheels with a 7/16" hole without looking it up.

    I'd recommend cutting the 7/16" to 1/2" sleeve into sections that you can stack on the arbor to use narrow or wide wheels. What's the narrowest wheel you can mount on the non threaded part of the arbor? With a wide flange,very narrow wheels could be mounted,but we're talking about more and more time in making them.

    YOU COULD JUST SEND THE SHAFT to save postage. Go ahead,give me the shaft!!!

    Having the crank at right angles to the wheel seems very unhandy to me. Only one I ever saw like that.

    P.S.: 24 thd. is the only one I couldn't find. I'll have another look again today. I seem to have everything else BUT 24 thd..
    Last edited by george wilson; 07-03-2011 at 12:10 PM.

  12. #12
    Get yourself a thread pitch gauge and all of this guess work is irrelevant. They are cheap and required in your toolkit if you are planning to fiddle with your machinery much at all. Use a dial caliper or micrometer to determine the spindle diameter. With these two pieces of information you KNOW what nut you require to make this grinder work. Your abrasive supplier will have bushings for your wheel. They will be plastic and they will suck. This is where it is nice to go to a machinist and have them turn up a 0" clearance bushing for you. I use delrin or aluminum.

    Nice looking grinder. I wouldn't want to have to use it as my go to grinder but I would love to have a restored version in my shop to look at and spool up on occasion. Good luck.

  13. #13
    Join Date
    Jan 2009
    Location
    Williamsburg,Va.
    Posts
    12,402
    I have looked again. Very disappointed that I don't have a 7/16-24 tap. I have a huge number of regular and oddball taps. I even have 7/16"-7(yes,seven) thread taps. Says "cast aluminum" on it. Have multi start taps,all kinds of left hand taps,metric taps.

    I can single point bore out a nut,but I do want to have the shaft to check it. In metal,.001" too small,and it won't go on. A thou or so too big,and it's a very sloppy fit.

  14. #14
    I'd vote for 28 TPI, I counted 14 between 4 & 20.

    I'd try this: http://www.mcmaster.com/#cadinlnord/95621a400/=d0pay7

  15. #15
    Just another reason to love woodworking -- it's practitioners are quick to share their knowledge. Thank you George, Chris and Brian.

    George: I agree the setup is odd and counter-intuitive. It is configured like a sickle grinder. I think you're supposed to get the apprentice to crank while you sharpen?? Let me see if I can get the shaft apart. Better yet, let me see if I can determine what thread pitch I have. The action on this thing is extremely smooth (it uses a worm gear rotating in ball bearings, in an oil bath)

    Chris: I thought about getting a gauge, but none of the ones I saw online described what pitches were included, and so I assume these oddball sizes were unlikely to be among them. Do you know of a specific model?

    Brian: Thanks for the link - I ordered it - I figured "what the heck!" - maybe I can nail down one piece of this puzzle.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •