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I've noticed that my bench grinder is getting a little weak with light pressure. It's a cheapo that lasted a lot longer than I would have expected. Anyone have a recommendation for a 6" or 8" bench grinder? Pedestal or bench top?

Thanks,

deWalt, I bought an 8 in a few years ago. It was expensive but well worth the money. I have an el cheapo that I abuse for hard coarse grinding. But any precision grinds or tool dressing I use the deWalt.

You might look for an older one at a garage sale. I have an old 6" craftsman and an 8" craftsman, both are running strong. The 6" is probably from the 60s

I built a very versatile grinder/buffer from a set of 3/4" pillow blocks, a length of drill rod and a 3/4 HP electric motor. One end of the shaft is turned down to 1/2" diameter and threaded for 1/2-20 screw-on arbors for a wire wheel, and muslin or felt buffing wheels, while the other end has a 1/2" left-hand thread for attaching a grinding wheel. The motor has a 3-step pulley and a drive belt for spinning the shaft at different speeds. Turning the LH thread on my lathe was quite a learning experience! The whole works is mounted to a steel plate with a tripod leg arrangement for stability.
Jerry

Jerry, here’s where I can attempt to teach the teacher. There’s two ways that I have turned left handed threads on a lathe. The first is to cut a relief where the thread ends, to the depth of thread. In other words, if the length of thread that you want is 2”, thats where the relief will be cut. I usually use a cutoff tool that has been radius’s or a tool bit thats ground similar. Then thread as usual starting at the relief with the carriage feed going away from the the head stock.

The second method is to turn the tool bit upside down, reverse the direction that the lathe is normally running, then thread as usual. This method is not the preferred way, because the force is trying to pull the tool up away from the holder and cross slide which goes against the way the lathe is designed. As long as you are only using it for small threads, it works really well.

If your expertise is beyond these methods, I humbly apologize for trying to teach the master and take my seat.

I use the "thread from left to right method, with a square plunge cut a few thousandths deeper than the minor diameter of the desired thread to give the tool bit a starting point. I have used the inverted tool bit/reversed spindle method, but the lathe I'm currently using has a threaded-on chuck that's not too friendly about cutting threads with the spindle running backwards- - - -it tries to unscrew the chuck! With a pin-drive or key-drive chuck and a spanner nut on the spindle, that's not a problem. One really fun thread that I don't like to try to turn is for a 1903 Springfield rifle barrel- - - -it's a 10 TPI SQUARE thread, (Not ACME) with a thread depth of .050"! That leaves NO room for error whatsoever as it's machined- - - -the thread spacing and depth must be absolutely perfect if the barrel is going to fit the receiver properly! A Springfield also has a coned breech with a counterbore for the boltface to fit into, but very few gunsmiths, me included, try to duplicate that feature on a replacement barrel!

When I was teaching auto mechanics at a Tennessee state trade school, one of the projects the students across the hall in the machine shop were required to complete was a stainless steel shaft for a plumbing gate valve with a 1 1/4" diameter 8 TPI left hand ACME thread. They used the upside down tool bit, reversed spindle method to do that project. Quite a skill test, there!
Jerry

My toughest job was turning double lead internal ACME threads for MOV’s (Motor Operated Valves), when the stem to try it on, was out in the field. The fit on MOV’s is critical to their operation, so you would err on the side of too tight, then put it back in the lathe and take another cut if required. We didn’t have collets that big, or 3-jaws chucks that ran that true, so all the work was done in 4-jaw’s. Indicating and and picking up your thread again was always fun. We had so many different valve’s, it wasn’t cost effective to buy ACME taps to finish them off.

Sticking on course with the OP’s, with grinders you get what you pay for. The cheaper it is the less power it will have and the more vibration you will get. Vibration is the Achilles heel for grinders as it shortens the bearings life. If you google for bench grinders, and check the ratings you will see that the biggest complaint is vibration. In some cases you can decrease the vibration by removing any imperfections on the shaft or on the supporting collars and finally, dressing the wheel. The better grinders have cast machined collars and the cheaper ones will be pressed steel.

If you can locate a used Baldor, buy it.

I have two recommendations for new both with 4 star ratings.

Shopfox
https://www.amazon.com/Shop-Fox-W18...er-hand-tools&sr=1-8#customerReviews

Jet
https://www.amazon.com/Jet-577128-G...880157&s=power-hand-tools&sr=1-3

Speaking of grinders- -- - -I just bought a Storm-Vulcan Model 15 crankshaft grinder. I'll be setting it up with a 20" diameter 7/8" wide grinding wheel for changing the stroke on 235 and 261 stovebolt crankshafts, grinding an offset in the center of the connecting rod journals for a NASCAR tool steel connecting rod made by Carrillo. I'll be changing the stroke from 3 15/16" to 4 3/8", a total stroke increase of 7/16". That turns a 235 into a 266 cubic inch engine, and a 261 goes to almost 300. The engines will look totally original from the outside. I'm also working on an idea to turn a 216 into a 266, using full-pressure 235 components. It will also be a "sleeper"- - - -no outward modifications visible!

Balancing a grinding wheel that size is very critical to safety, and also for getting a good finish on the crankshaft journals.
Jerry

Gentlemen,

Thanks for your recommendations and input on the bench grinders. Hopefully, I can make an informed decision in the near future. I may even look to Craig's List, you just never know what you might find!

HRL and Phak1, I'm taking a basic machining course at the local community college. I'll have to ask my instructor about his technique on cutting left-handed threads.........LOL!

Thanks again,

Andy
Left handed threads are easy. You just start at the left and go right.

Phil, I have machined many double lead stem nuts.
You really have to keep your mind on your work and don't let the boss tell you how to do it.
Ever do a buttress thread?

I also agree on the Balder grinder. They are the best made.

Don

Mauser rifles have a buttress thread where the gas shield fits into the back end of the bolt. I've got a special tool bit stashed away ground to turn that thread when I need to fabricate a copper heat sink to protect the threads when I'm welding on a custom bolt handle. The thrust bearing face of the thread is angled at 5 degrees, and the other side is 45 degrees. The thrust of lifting the bolt handle and compressing the firing pin spring is carried by the flatter angle. There's no really good reason for it, as other, less sophisticated rifles use a conventional 60 degree V thread on the bolt parts, but Paul Mauser over-engineered everything about his designs- - - - -way back in the late 1800's!
Jerry

I have had great luck with my old craftsman “block grinder”. I bought it used and cleanedxit up and replaced the cord. Its from the 60’s and runs great all the time.

And it looks cool...

It’s all metal too, not like today. Nice find!

I've been trolling Craig's List..........

If this was complete, I'd go get it!

CRAFTSMAN

still using my reconditioned bench grinder i bought in 1976.............3/4 hp craftsman.......now watch it die since i bragged on it!

That's my LUCK...

Weird, my 3/4hp 8 inch Craftsman grinder I bought used 30 years ago died yesterday. It uses an obsolete starting relay that I tried to repair by cleaning the contacts, but it still won't go unless I give the wheels a good spin to get it moving. I hate to give up on it, but maybe it's time for a newer one after I get tired of spin starting it.

The capacitor has crapped out on it. That relay runs power thru the capacitor for starting, then takes it out of the circuit. Is there a cylinder on the side of the motor or maybe under the base? That's the start capacitor.

My grinder does not have, or use a capacitor. It uses a Klixon 4CR starting relay in series with the start/run windings. It also needs to be an exact match for the motor size too. I don't know if I want to go to the trouble to find a pricy replacement and have it still not work.

4100 Fire Truck - The Klixon start relays are sealed units...correct? You mentioned cleaning contacts? There should be relays available out there to get you up and running. They don't make bench grinders like that anymore.

My bad. So it's a split winding motor, rather than capacitor start.
The Klixon relay is a bit pricey, but you should be able to find a direct replacement. Here's one source: Klixon 4CR series relays

Pulled it back apart today to troubleshoot with my meter. Good thing I didn't buy a relay. The start winding was open. Guess I'll spin start it and start shopping for another good used one, instead of a cheap new one. I really like the 3/4hp 8 inch size. Not too big, not too small.
I just came up with an easy way to spin start it. Took a 3 in wire wheel in my cordless drill and held it up to the wire wheel on the grinder to bring it up to starting speed, and flip the switch and away it goes.

We are lucky here in Southern Maryland, we have an electric motor shop that handles these small jobs. I took my locked up swimming pool pump motor in and they checked it out and added new seals and a bearing and the bill was $33.00.

Check your area to see if you have a motor shop that can help.

Mike B

Hope your using a face shield...but then again that jump start method sounds risky. A wire spinning wheel engaging into another non spinning wire wheel.....hello? Hate wire wheels....had a piece of wire removed from the cornea of my right eye awhile back. Got lucky....healed w/o any significant vision loss.

I don't have any experience with a variable speed bench grinder like the Shopfox and I can see pros and cons. Would that speed controller be hard on the motor windings? I can purchase the 8" Jet thru NAPA for $250.00. I'm still searching Craig's List..........

I found an exact new looking match with a cast stand for my dead 3/4hp Craftsman for $150, but it's like 500 miles away.

As more and more vocational shops in high schools get closed down, it's possible to find very high quality, lightly used professional-grade tools and equipment at fire sale prices from the local school system surplus property departments. I've seen grinders, welders, wood and metal working equipment and even lathes and milling machines go for virtually scrap iron prices. Once us old geezer mechanics, machinists, welders, plumbers and woodworkers pass on, there won't be many young folks coming along to take our places. They're not being trained in any significant numbers.
Jerry

Not many, but some will find a way. Some youngsters are born with a curiosity of how things were done before they showed up! And hopefully, they are smart enough to go find a library that hasn't closed down to study up on the subject!!