[How-To] Lead screw key

DavidR8

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On my new to me Clausing 100 Mk3 the power cross feed doesn’t work.
I suspected a missed key and my suspicions were confirmed when I pulled the carriage and apron.
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First question is how is the key retained?
There is what looks like a hole for a pin at one end but I don’t see a similar pin on the bevel gear end.
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Second question: does anyone know the dimensions of the key?
 
The key likely had a hollow milled projection the engage the hole, as far as the dimensions, do you not have a steel rule?
 
The key likely had a hollow milled projection the engage the hole, as far as the dimensions, do you not have a steel rule?
I do, just wondering how precise it has to be.
I'm thinking snug in the gear but a sliding fit on the keyway on the lead screw?
 
I do, just wondering how precise it has to be.
I'm thinking snug in the gear but a sliding fit on the keyway on the lead screw?
Yes, how do you plan to do the projection to fit the drilled hole?
 
Yes, how do you plan to do the projection to fit the drilled hole?

I thought I’d determine the hole size by finding a drill shank that’s a good fit and then using a roll pin of the same diameter pressed into a matching hole in the key stock.
Does that sound like a feasible idea?

My concern is that there will be very little material left around the edge after the hole is drilled. Maybe the pin doesn’t need to be a snug fit?
 
I thought I’d determine the hole size by finding a drill shank that’s a good fit and then using a roll pin of the same diameter pressed into a matching hole in the key stock.
Does that sound like a feasible idea?

My concern is that there will be very little material left around the edge after the hole is drilled. Maybe the pin doesn’t need to be a snug fit?
All the pin has to do is keeping the key in place, if it were mine, I would use rectangular key stock and machine it to be one piece with the pin portion.
 
All the pin has to do is keeping the key in place, if it were mine, I would use rectangular key stock and machine it to be one piece with the pin portion.
That's a good idea. I thought about doing that as well but was not sure I could manage the small part. I'll give it a whirl!
 
It is not clear from the photo as to whether the pin hole is square or round. But the first thing that I would do is to determine the key's Clausing part number. The second would be to call Clausing and determine whether or not they still have any keys in stock. If they do, order one. If they don't, ask them for a copy of the part drawing. I have never tried to buy any Clausing parts from them but would assume that they did as they did with the Atlas parts and had all of the original parts drawings scanned as .TIF's. If you cannot read a .TIF they will convert it to a .PDF before they email it to you.

If you end up having to make the key, you will need some rectangular key stock or flat bar of the proper dimensions . If the key is round, you will need a hollow end mill with the proper hole diameter. If square, most any end mill. And a working vertical or horizontal mill.
 
It is not clear from the photo as to whether the pin hole is square or round. But the first thing that I would do is to determine the key's Clausing part number. The second would be to call Clausing and determine whether or not they still have any keys in stock. If they do, order one. If they don't, ask them for a copy of the part drawing. I have never tried to buy any Clausing parts from them but would assume that they did as they did with the Atlas parts and had all of the original parts drawings scanned as .TIF's. If you cannot read a .TIF they will convert it to a .PDF before they email it to you.

If you end up having to make the key, you will need some rectangular key stock or flat bar of the proper dimensions. If the key is round, you will need a hollow end mill with the proper hole diameter. If square, most any end mill. And a working vertical or horizontal mill.
Thanks, I tried calling Clausing three times last week during their business hours and kept getting a message that they were closed. I'll try again today and see.
 
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