Myford Super 7 Gearbox Taper Pin

I have had a "Mishap" with my gearbox on my Myford Super 7. On the main shaft of the gearbox, the smallest gear (part 141 - 16T) is pinned to the shaft with part no 142 Taper pin which is #0x3/4".

I have had to drill out the old taper pin which has not damaged the shoft or the gear. However I cannot find a supplier of the correct taper pin. Myford do nothave any and all suppliers now seem to work on Metric pins.

Does any reader know where I can obtain a no 0 taper pin x 3/4" long.

David,

I have a selection of taper pins but no idea of the sizes a pin in # 0 comes in. If you can tell me those dimensions I'll happily post you one, assuming I have one. If not I'll make one for you.

I was wondering how you had got on since your holiday

Best wishes Brian

Hi David, Just FYI McMaster Carr in the US carry a large range of taper pins and they are generally not very expensive. Link below. May help ID your pin by comparing diameter and length specs. Hope the info helps. If McMaster Carr still carry these, I'd be surprised if a major UK industrial supplier or drive components supplier could not get them, if need be.

https://www.mcmaster.com/taper-pins/taper-pins-5/

Hello again David,

I don't think you have tried very hard, lots to find via Google and eBay

Try EKP supplies.

Imperial pins are identified by the diameter of the larger end, the number system seems to be defunct. The taper is 1 in 48 and I suspect your pin will be 3/32 inch diameter

Best wishes Brian

Hi Brian if you want a replacement taper dowel I have some and if you like you could collect if near or I could post if not. I have sent a message with info.

David

Hi Brian,

Removing the pin from the main shaft was quite an anxious time but drilling out worked ok using the jig that I mentioned to you before. I managed to replace the tumbler gear that had a broken tooth.

The taper pin that would fit the 16T gear would be something like 3.9 mm on the big end and 3.5mm on the small end with a length of 20mm. I bought some 4mm taper pins from RS-online, but of course metric taper pins are specified by the small end diameter and the pins were too big.

The only ones that I have seen are at:

**LINK**

I got quite excited until I saw the minimum order price of $50 !! That is a lot to pay for a requirement of one taper pin!

I suppose if all else fails I could carefully grind one using 4mm silver steel and a tool post grinder but it would be a hit and miss affair as regards the taper angle. No-one seems to sell imperial taper pins in reasonable quantities.

Incidentally, when the crash happened, I was running the gearbox via the Graham Meek metric screwcutting adapter. It was the MYFORD box that was damaged and the Tufnol gears took the strain ok. That speaks well for the new home made adapter.

If you do have a suitable taper pin I would be much obliged.

Kind Regards

David

Hi Brian look at the top of web page and there should be an envelope symbol top ledt hand side click that you access you messages. Make sure you are logged in to see symbol.

David

Edited By David George 1 on 01/10/2020 13:36:06

Hello David George,

I think you are confused!

It is David Haythorthwaite who needs the pin, not me, I have some that I am going to measure now that he, David H has quoted dims. for the replacement and in any case I have also pointed him at EKP suppliers , a UK organisation who have pins in both imperial and metric sizes who may have what he needs off the shelf.

Thank you though for your input

Brian

Hello again David H,

My stock of taper pins I'm afraid doesn't include the size you need.

I suggested EKP supplies, you will find them via Google. If they are unable to help you I'll make one for you from 4 mm silver steel. Send me a PM if you need that, along with your address so that I can post it.

Best wishes

Brian

It is just possible to fit the large 72 tooth gear of the quick change gearbox on a clutch, it prevents damage if a crash happens. Niko.

I have some 11/64" x  2" long here, that can be fitted and cut to length if that would help.

PM me if they are of any use to you and I'll post a couple out to you.

Edit:- Just checked and I also have some 5/32" (#0) x 1" in my stash

Nick

Edited By Nick Hughes on 01/10/2020 17:41:18

Hi Brian

The pin that I would need is a 5/32" uk pin and EKP do not supply one. Thank you VERY MUCH for your kind offer to make one for me, but I have just made one from silver steel and it sits nice and snug in the taper hole. I shall only finally drive it home when the main shaft is in place with all the gears on it.

Thanks for your input Woody.

Thank you Nick, I have sent you a PM.

Speelwerk it was the 39 tooth tumbler gear on the end of the selector arm that broke a tooth - not the large 72 tooth wheel. However I shall investigate your statement that others have put a clutch in the train to protect the box.

Thanks for your input.

David

David,

Good for you, and also good to know you will be running on the home straight again.

Purely out of interest, was the idler gear made in steel and was it hardened? I ask because I had a screwcutting gearbox on a 1902 Hendey lathe to rebuild as a commission, the input gear was 28 T in soft steel that had bent teeth, bits of other gear teeth made in cast iron imbedded between the teeth and other such distortions, but none were actually broken.

It was of course unusable and the soft steel idler gear linking this badly abused input gear with the cone of gearing was worn down to mere stumps of teeth. Once again, they were all present and you described your failure initially as being a broken tooth.

Actually, the idler gear that links input to the rest of the gearing does work hard for it's living.

Best wishes for the future

Woody

I turn up my own taper pins. It's not hard. To set top slide, use a dial indicator on a parallel bar in the chuck to set the exact number of thou taper per inch of carriage travel and away you go.

Edit: Ooops. Didn't see your last post. Well done.

Edited By Hopper on 01/10/2020 23:14:37

Hi Woody,

Yes the tumbler gear on the Myford S7 was hardened - and all the gears in the box look as new with perfectly formed teeth and no signs of wear. On the transfer gear, just one tooth had broken off at the root. The tooth jumped over the next tooth and was occupying the valley of the next tooth.

I am very unsure of the reason that it happened, I admit with great shame the the gearbox oil was low and the lower shaft of the gearbox was very tight. It was possible to turn it, but the shaft had to be punched out once the pin had been drilled out of the 16T gear. I hadn't realized that the gearbox was tightening up and when using the powered cross slide to face a 5" diameter lump of EN8, the bang happened and the belt slipped.

The problem with powered feeds is that you get no "feel" with them. I am lucky that it did not do even more damage and I shall watch the gearbox oil level with great interest in future. As a person who once wrote an article for MEW on how to lubricate the Myford, I am ashamed to have let it get low on oil. It would appear that the "captive" screw holding the gearbox to the lathe had been leaking oil.

Kind Regards

David

Sorry to dig up an old thread, but I'm about to remove the shaft too. Is there a way to drive the pin out and save it? I really dont want to drill it out especially if they are not really available.

Hi you should be able to punch it out with a 3mm pin punch. Make sure you hit the small end square with a solid punch and small hammer. Measure the both ends with a caliper to check size. If it dosn't move make a split jig with a tapped hole in a piece of steel clamped to bush, line up hole and use a screw with a hardened pin to push out taper pin.

David

Taper pins are not made of carbon steel, use a soft steel or the hard steel pin will do more damage and be much harder to drill out. Silver steel is 1.5/1.6% carbon so not good. Even a soft wood nail would be better.