Clearance Fit in Cast Iron Pulley Bore

[Oldneweng]

I was boring out a cast iron double pulley today for an aquaintance! It is a job I promised to do some time ago. I wanted the stationary motor at home so I could check fits etc. He couldn't be bothered. I finally measured it up at his place. Had a problem with the key because it seemed to be mushroomed at the rear of the existing pulley. The front was covered. Blind end with bolt into end of motor shaft. The new(?) pulley is about half the size. This all drives a circular wood saw which was running much too fast. The blade was getting into a wave motion.

Anyway I have bored it from 0.625" to 1.0005" to the best of my inexperienced ability with the new bore gauges. It was a long slow process with many and multiple measurements in order to get experience with bore gauges. I was taking 5 measurements and getting 5 identical answers within 1 - 2 tenths. That is my mic measurement. I cannot claim this is the absolute measurement as I would require a precise bore to practice on and get my hand in so to speak.

My real question is how much clearance should I allow. There is as I have said, a key and keyway (0.250") and a grub screw on top of the key.

I am also open to any suggestions about the best ways to use bore gauges.

Dean

[pipeclay]

Your clearance on the bore is ok,you could even get away with .001".

In regards to the bore gauge is it a bore gauge (with dial indicator ) or telescopic gauges.

The bore gauge you can really only use it one way.

If its a telescopic gauge it can be used in a couple of ways,it would be easier if you describe your method of use first.

[Oldneweng]

Your clearance on the bore is ok,you could even get away with .001".

In regards to the bore gauge is it a bore gauge (with dial indicator ) or telescopic gauges.

The bore gauge you can really only use it one way.

If its a telescopic gauge it can be used in a couple of ways,it would be easier if you describe your method of use first.

Oops. stuffed again.

Telescopic gauges.

Method. Close and lightly clamp arms. Place inside bore with arms placed up/down and release. I found variations when using it crossways.
Hold handle as close to parallel to bore as possible, moving around to ensure close fit.
Tighten clamp gently.
Pivot to release pressure on anvils. (Are these called anvils?)
Remove from bore and tighten clamp some more.
Measure with mic.

I was wondering how to get a precise bore of known size to practice measurements on. I just had one of those moment while having a shower. I had been using a 22mm bearing to check my mic with. Duh! Tommorrow I will find a bearing with a bigger bore and look up the specs for it!:~

I have an adjustable reamer that covers the 1" range so I can touch up the bore easily.

Next will be cutting the keyway. That is why I was following the thread about this recently, very closely.

Dean

[Bryan]

I was taking 5 measurements and getting 5 identical answers within 1 - 2 tenths.

You're a better man than I am. Or you have better telescoping gauges. My cheap ones drove me mad so I bought 2 of the dial indicator type. Still cheapies but way better than the telescoping horrors.

[pipeclay]

Try closing the gauge to smaller than your bore,place the gauge inside your bore,tilt the gauge on about a 10 degree angle or there abouts,and then release the lock until it expands against the side of the bore,then nip it up,then lift the handle end through the bore until it is free,then remove and check with your mic , depth is not overly critical as long as the bore is parallel, if the bore is deep you may need to check on the outer edge as well as internally to check parallel.

The shallower the bore the more awkward it can be.

The other method to use is the same as you would use when using an inside mic.

[Oldneweng]

Try closing the gauge to smaller than your bore,place the gauge inside your bore,tilt the gauge on about a 10 degree angle or there abouts,and then release the lock until it expands against the side of the bore,then nip it up,then lift the handle end through the bore until it is free,then remove and check with your mic , depth is not overly critical as long as the bore is parallel, if the bore is deep you may need to check on the outer edge as well as internally to check parallel.

The shallower the bore the more awkward it can be.

The other method to use is the same as you would use when using an inside mic.

Thanks Pipeclay. I will have another try tomorrrow with a bearing bore as a check and see how I go.

Actually I lied about boring the pulley from 0.625. My big boring bar needs an 18mm hole and it was in the tool post so I drilled out to 19mm first. Besides the 14mm diam min hole boring bar is wasted on a cast pulley like that with a keyway to remove! The first check with the gauge after boring showed a taper of 0.002" so I was pleased when this disappeared after a few cuts. In the end I could not pick any taper.

Dean

[Oldneweng]

You're a better man than I am. Or you have better telescoping gauges. My cheap ones drove me mad so I bought 2 of the dial indicator type. Still cheapies but way better than the telescoping horrors.

Mine are cheap. I think they cost $17 including postage. They seem to work. When I first got them a couple of months ago I had a quick try and was way off. Today they just seemed to work. I have been reading up on the subject tonight and have seen mention of having to work on cheap sets such as stoning the anvils to make them smooth and burr free. Mine seem ok but I am just a beginner.

When it comes to measuring them with a mic however I would have to say that I am far from a beginner but my experience is from around 30 years ago. I worked in a production setting with centreless grinders and was taking measurements with my mic all day long. Same mity I use now. I broke the adjustment tool many years ago because the adjustment ring was very tight for some reason. I have never been game to use any other type of tool. I should make a tiny strap tool and dismantle it to loosen it up. It still seems to be accurate tho. It has not seen much use in the last 30 years.

Dean

[Ueee]

Hi Dean,
I have a set of the cheapo's too. Some seem to be ok but others aren't. They move when they are tightened up. You have to get the balance between tightening up enough so they don't move when measured, but not so tight that they move....
I recently got a Mity .2-1.2 internal pin type mic, but am yet to use it.

Ew

[Retromilling]

If the shaft is 1" exactly then a bore of 1.0005 should be a push fit . If it's a bit on the loose side then put it on with plenty of medium Loctite .

[Oldneweng]

Hi Dean,
I have a set of the cheapo's too. Some seem to be ok but others aren't. They move when they are tightened up. You have to get the balance between tightening up enough so they don't move when measured, but not so tight that they move....
I recently got a Mity .2-1.2 internal pin type mic, but am yet to use it.

Ew

Had a better look at them today Ewan. Just like you said. Some are good, some are not. The one I had been using was one of the good ones. The largest end of the largest gauge was the worst. It still had machining marks in it.

292163292161292162

The second and third picture are the same view but different lighting. In sunlight it looks almost mirror smooth. I used the dremel to lightly sand some and then polish them all while rotating in a drill. I also deburred inside and out all the ends of the whole gauge set and polished these ends. Except for the smallest gauge. I was not going to pull that apart. I had had enough by then. I just gave it a polish in situ. Run your nails over any edge and an obvious burr could be felt.

Regarding whether they move when tightened and/or move as required when setting them in the bore, I also wondered about the surfaces in the slot and on the end of the locking pin but decided that I would worry about that question later. I imagine that a smooth surface on the bottom of the slot would help. This was not apparent at all on my gauges.

I had a go at using them afterwards inside bearing bores using the method mentioned by Pipeclay and got a mixed result. Sometimes the gauge would be undersize. I am still working on gaining proficiency. I checked the bore of the pulley and got a reading 0.005" oversize. Another check gave me the same result as previously reported.

One thing I would be interested in is to compare these gauges with those from a quality brand.

Dean

[Oldneweng]

If the shaft is 1" exactly then a bore of 1.0005 should be a push fit . If it's a bit on the loose side then put it on with plenty of medium Loctite .

The pulley is to fit the output shaft of a B & S stationary motor. 16.5 hp I think. I have a vertical shaft B & S motor (11.5 hp) here which I polished up the somewhat rusty shaft and tried the pulley on for size. All I can say is that I don't believe I could arrange a better fit. Slid on by hand but slowly. I like that. (Keith Fenner)

Now I am working on the keyway. I have started milling a slot with a 1/4 inch cutter but it is only long enough to go about half way thru. After I have finished that slot I have to decide whether I can line up from the other side after turning the pulley over. Maybe use a 6mm cutter and clean up the remainder with a 1/4 inch square HSS cutter in the lathe. The olde wind the carriage in and out trick.

I am not sure whether I will be involved with fitting the pulley or not. I will take it around with a puller to remove the other pulley and see what happens. Funny things happen around this guys place. I will call him D. As I mentioned the key was mushroomed at the back of the existing pulley. I don't know who fitted it or bashed it. D told me he intended cutting part of the motor shaft off as the previous owner had ground it to a smaller diameter for some reason. The existing pulley is only contacting the shaft for about half its length. The machine used for this grinding job was the highly accurate "angle grinder". I will do what I can to fit the pulley in a proper fashion but if things start going off at a tangent, which is very likely with D in charge then I will duck out and leave him to it. He has some very funny ideas. SWMBO was talking to him about buying a Victa ride on mower from him. He wants $150 for a mower he paid $100 for a couple of months ago. She had a look today and decided straight away that the best recourse was to walk quickly away from it. He had done some repairs to it. I have seen some of his repairs. Best not go there! He really is a bit of a laugh.

Dean

[Oldneweng]

Thanks for all the assistance guys. Finished the keyway tonight and dropped it off. I am more than happy with it. First ever internal keyway.

Dean

[Retromilling]

The pulley is to fit the output shaft of a B & S stationary motor. 16.5 hp I think. I have a vertical shaft B & S motor (11.5 hp) here which I polished up the somewhat rusty shaft and tried the pulley on for size. All I can say is that I don't believe I could arrange a better fit. Slid on by hand but slowly. I like that. (Keith Fenner)

Now I am working on the keyway. I have started milling a slot with a 1/4 inch cutter but it is only long enough to go about half way thru. After I have finished that slot I have to decide whether I can line up from the other side after turning the pulley over. Maybe use a 6mm cutter and clean up the remainder with a 1/4 inch square HSS cutter in the lathe. The olde wind the carriage in and out trick.

I am not sure whether I will be involved with fitting the pulley or not. I will take it around with a puller to remove the other pulley and see what happens. Funny things happen around this guys place. I will call him D. As I mentioned the key was mushroomed at the back of the existing pulley. I don't know who fitted it or bashed it. D told me he intended cutting part of the motor shaft off as the previous owner had ground it to a smaller diameter for some reason. The existing pulley is only contacting the shaft for about half its length. The machine used for this grinding job was the highly accurate "angle grinder". I will do what I can to fit the pulley in a proper fashion but if things start going off at a tangent, which is very likely with D in charge then I will duck out and leave him to it. He has some very funny ideas. SWMBO was talking to him about buying a Victa ride on mower from him. He wants $150 for a mower he paid $100 for a couple of months ago. She had a look today and decided straight away that the best recourse was to walk quickly away from it. He had done some repairs to it. I have seen some of his repairs. Best not go there! He really is a bit of a laugh.

Dean

I hope that was one of those precision angle grinders :doh: We all know someone a bit like that . A 16 Hp motor is worth a lot of money fancy butchering the shaft with an angle grinder . Some people have no engineering skill and others are just born naturals. I know a farmer who is illiterate but a brilliant mechanic and engineer he can't read or write very well but he can fix and make anything , even build some of his own farm machinery for special jobs . When you first meet him you think he is a moron then after you know him you feel rather inferior . It is either in you or not , in D's case NOT .
Glad to see you worked it out.

[Stustoys]

Hi Dean,
Not the greatest photo, but Mit v Cheapies.

Not easy things to get pictures of but the mit looks worse than it is, the cheapy looks better than it is.

Stuart

[Oldneweng]

Hi Dean,
Not the greatest photo, but Mit v Cheapies.

Not easy things to get pictures of but the mit looks worse than it is, the cheapy looks better than it is.

Stuart

Thanks Stuart. The most telling thing about those pictures is the finish on the head of the gauges. I will have to see how much use these gauges get and how much trouble they give. Just did a quick check on EBay for Mity gauges and came up with zilch.

I know what you mean about getting pictures. I used my Kodak 16 meg compact and my Nikon 5200 DSLR to take quite a few pictures. Of about 8 pics with the Kodak 7 got deleted immediately. The Nikon did better. I want to get a macro lens for it but may have to settle for closeup filters for now. I have always liked macro photograpy. I have 2 Minolta film SLR's and a 2 x converter with macro function. Can take a nice picture. It is also possible to fit one lens to the front of another lens which is on the camera. The second lens is fitted via a filter thread adaptor ring so the lenses are mounted filter thread to filter thread. I have taken a full frame photo of a 2mm high object this way. Not ideal tho.

Dean

[Oldneweng]

I thought I would finish this thread off by saying that I was told the pulley was working just great and D is happy with it. Praise indeed from that type of person. :D

Dean