Re: Mill parts

On 11/19/2024 4:27 PM, Snag wrote:

   I'm in need of help finding a part for my bench top mill , RF45 clone . It's the same as the Grizzly G0484 and they show the part as discontinued . I'm looking for a replacement X axis lead screw nut . The Grizzly part number is P0484032 , maybe someone is making a replacement since there must be 10's of thousands of these machines around . The thread is Acme 15/16 (24 mm) diameter with an eight TPI thread . I've seen articles about people making replacements using plastic - maybe ABS? - and heat/pressure forming the threads but I'd lots rather find a direct drop-in replacement .

Would have responded sooner, but I do not have a proper Usenet client installed on the house computer.
My first response would also be to sleeve the existing nut.  This addresses your request.  I would suggest very tight sliding fit and use sleeve and bearing locker.
The search for a new one is what it is.  A search.  I have no special insights other than as you clearly already know that these machines may be sold under different labels.  I suggest may be ask Matt at Precision Mathews.  Admittedly he may be more responsive on parts to a customer than somebody who just wants parts, but he is very good at supporting customers.
Now for the tangents.
Backlash should not be a huge issue if your gibbs are adjusted, you use your gibb locks, and you mostly conventional mill.  Accuracy probably is not a huge issue, but if it is take all measured moves using the hand wheel dials in only one direction.  If you really need to be able find a postion accurately in two directions there are two solutions.  The nice one is a DRO with glass scales.  The alternative is some dial indicators mounted to the table.  I have a dial indicator mounted semi permanently on one of my lathes.
As was already mentioned ABS is a terrible idea for all the reasons stated.  Acetal (Delrin is a trade name) is used for bearings, axis nuts, and a variety of other things.  Its pretty tough and there are commercial products made form the stuff.  HOWEVER.  Acetal does not accept any common adhesive well at all.  It would not be a good option for boring and sleeving the old nut.  Bronze or even brass would be better.  I do not know if adhesives would stick to oilite bronze.  Maybe another rabbit hole to research there.
I looked.  I do not have an acme tap that big.  You will have to cut it on your lathe (or buy a very expensive tap) after grinding a suitable inside cutting tool.  It will probably chatter pretty bad, so it might be time to consider making a solid tool post that bolts directly to the cross slide.
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Bob La Londe
CNC Molds N Stuff
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