What is this thread size? Trying to repairing a bench grinder spindle

[ianmurphy]

I got this crappy little bench grinder for $20. Only problem with it is the spindle threads are all damaged on the left side (the side that has the left hand threading unfortunately). I want to buy a left hand die and try to clean them up, only problem is I don't know what the thread size is. I took the right side nut off and took some measurements (see photos) and now I'm trying to determine the thread size. I dont have a thread gauge, but maybe I need to get one. Looks close to either 9/16"-12 or 1/2"-13? The actual measure diameter is 0.453 and I count about 12 TPI. I took the nut of with a 3/4" wrench if that helps.

I don't know the make or model of the grinder because the name plate sticker is all worn off. I guess there isn't a standard size for these nuts? This grinder has a 3/4" arbour diameter if that matters. Also, there is like a 1.25" (30.84mm) bushing on the right side, whats that all about?

Thank you guys in advance!

 

[Gordon Heaton]

Well, as for the bushing, grinding wheels come with various center hole sizes, and most come with plastic bushings to adapt to a number of shaft sizes.

The wrench used on the nut means nothing.

The left-hand thread should be the same size and pitch as the right. If you don't have a thread gauge, find or buy a few known size inch and metric nuts and see which one fits the right-hand thread.

 

[michiganbuck]

QT [1.25" (30.84mm) bushing on the right side, whats that all about?]
1.250 That is for use of common surface grinder wheels.

 

[john.k]

Thread is likely 12mmx2mm (12x2) from the dimensions given....,the grinder is likely Chinese ,as most have been for 40 years odd.

 

[johnoder]

1.25" is 31.75 mm

 

[ianmurphy]

Man I hope not, that sounds like a very odd size. Especially if I'm looking for a left hand die. Thanks for the input

 

[ianmurphy]

1.25" is 31.75 mm

lol yes I am aware. I rounded up to 1.25" because its the closest standard arbour size, assuming thats what the bushing is for

 

[deltap]

It doesn't look that bad. Take a 3 corner file to it and clean it up as best you can. A metric thread file would also work.

 

[ianmurphy]

It doesn't look that bad. Take a 3 corner file to it and clean it up as best you can. A metric thread file would also work.

Actually the threads in the picture are from the right hand side, and it's the left side that's chewed up. I didn't post a picture but they are pretty bad

 

[Bill D]

Older dodge cars used left hand lug nuts on one side. I do not remember the thread maybe 1/2-13? It worked on my old USA grinder.
Bil lD

 

[ianmurphy]

Just to update this topic, the threading is indeed 1/2"-13. I got some bolts and that one seems to fit (although a tiny bit loosely) I am guessing the spindle is just worn down so I measured less than 1/2" diameter. Or maybe my measurements were just off. Thanks everyone for their input.

 

[michiganbuck]

Might get a high thread quality new nut for both ends.

 

[michiganbuck]

Older dodge cars used left hand lug nuts on one side. I do not remember the thread maybe 1/2-13? It worked on my old USA grinder.
Bil lD

I remember that , how dumb likely some dumb engineer read that race cars with spindle nut have lefts on one side..a lot of broken lugs broke off with that.

 

[SVE Performance]

The wheel bolts on that vintage dodge would be 1/2-20 both RH and LH . Bill

 

[john.k]

Left hand thread was standard with truck wheels for maybe 50 years or more ,until the fancy aluminium wheels came in and some production engineer said ...hay we can save heaps with all right hand threads.......wheels on big trucks coming off all over ,so now we have to use all the stupid plastic retainers on the nuts ,and on an older truck with the LH nuts ,the cops will tell you it should have stupid plastic retainers....Millenials.

 

[WizardOfBoz]

Thread is likely 12mmx2mm (12x2) from the dimensions given....,the grinder is likely Chinese ,as most have been for 40 years odd.

I'm really having a problem thinking that an ID of 0.453" is a 1/2 thread. And you have 17.1mm over 7 crests, or about 2.44 mm, which is a long ways away from 1.95mm.

Please, before you risk life and limb, buy metric and inch thread gauges. I suspect you have 12mm (0.472) by 2mm threads, and the the "looseness" you mention isn't looseness at all, but improper fit.

 

[john.k]

Like the Westinghouse truck brake compressors I used to sell...ex army ,like new ,but used ,and less the nut and pulley ...compressor $50 ..gee thats cheap.....can you get the nut and pulley....Yep ,Westinghouse have got them ........two days later its ...."Westinghouse want $100 for the nut and $1000 for the pulley."......When I would say .."no refunds on used brake parts ..its the law-a"

 

[EPAIII]

17.1mm = 0.673" but your movable caliper jaw is on an incomplete thread. So perhaps seven threads = 0.7" for 10 TPI. And your diameter could be a well worn 1/2" or it was just undersized from scratch. I have seen worse. So perhaps 1/2-10, English thread, not metric.

For heaven's sake, do get an English and metric thread gauge. And some thread wires would remove the doubt about the diameter by getting the pitch diameter instead of the OD.

 

[dian]

Thread is likely 12mmx2mm (12x2) from the dimensions given....,the grinder is likely Chinese ,as most have been for 40 years odd.

have you ever seen a m12 x 2 thread?

 

[DDoug]

I'll wager:
1. the die will cost more than the $20 you spent on said grinder.
2. The repair will not hold, as a die don't put metal back on.