Dilemma – neither lathe nor mill working

[John CoatesParticipant @johncoates48577]

Thanks for all the help to date. This weekend the lathe was moved to its final position and the milling machine was assembled on the bench

 

Now I have hit a real snag.

 

The lathe came with a Nu T-link belt and a cone pulley (2″, 3″, 4″ and 5″ pulleys). The grub screw in the cone pulley turned to cheese and I do not know what grub screw to buy to replace it. I only have metric bolts and I am sure this is imperial. I bought a new drive pulley with an adaptor for the motor spindle and a new V belt but I need to make a tensioner to take up the slack before I can use it. So the quickest way to get up and running is to get the old cone and belt working.

 

1. How do I find out the diameter and pitch of the missing grub screw? Where would I buy a replacement from once this was established?

 

Mill.  A secondhand Chester Champion. I had already bought a collet chuck and end mill & slot mill set for the lathe and the 3MT fitting fits the Champion. But the draw bar is different (I would have had to make one to use in the lathe anyway). The one in the mill is 11mm dia and fits the chuck that came with the mill. The collet chuck needs M8 x 1.25 pitch. As stated above I have no lathe (yet) to turn a new draw bar (and I would need to turn a metric thread on an imperial lathe with no 127t change wheel, which for a newbie like me is a daunting prospect!). Basically I need a draw bar that is M11 dia at the top to fit the mill but then M8 x 1.25 at the bottom (for 42mm worth of thread).

 

2. Quickest fix (bodge) for this could be to buy a length of threaded M8 x 1.25 bar and cut to the same length as the original draw bar. Two nuts at the top to lock a washer to mirror the original. I could weld the nuts together for extra strength. Does this sound a dumb idea?

 

Ahh, the journey of the newbie on the road to engineeringdom is strewn with stumbles so please bear with me. I though I was close to getting started but I am once again so far away

[John CoatesParticipant @johncoates48577]

Need help to get up and running

[David Clark 13Participant @davidclark13]

Hi There

Measure the inside diameter of the screw hole.

This will enable you to get an idea of the screw thread size.

You might find a similar screw on the machine that you could borrow to check the thread with.

Maybe a stop screw or something.

 

For the drawbar, studding would probably be fine.

Turn a top hat adaptor to ensure the studding runs true.

The top hat bush would need to fit the 11 mm diameter and be larger in the lip.

 

regards David

 

[TerrydParticipant @terryd72465]

Hi John,

 

David is quite right. Most manufacturers use a limited range of diameters and type of threaded components as this keeps down overheads (amongst other reasons).  You should be able to locate an example of the screw elsewhere on the machine that you can test the threaded hole with.  But don’t forget to replace it immediately after use otherwise you’ll need two items instead of one!!  Don’t ask me how I know

 

Best of luck on your journey to engineering heaven, some of us were lucky enough to have served apprenticeships and were able to learn from truly skilled craftsmen, but at least you have the internet to help find advice.

 

Best regards

 

Terry

[John CoatesParticipant @johncoates48577]

“You might find a similar screw on the machine that you could borrow to check the thread with. Maybe a stop screw or something.”

 

David and Terry. As we say in Yorkshire “Thar’s reet clever buggers!” Well done

 

The cross slide locking screw fits. This is 1/4″ dia by 20 tpi.

 

So where can I get one?

 

Thanks, John

[John CoatesParticipant @johncoates48577]

Which if I’m reading my Zeus book correctly is a BSW thread?

[macmarchParticipant @macmarch]

1/4″ 20tpi is 1/4″ Whit.  It will be difficult to get a socket grub in this thread so you can use a 1/4″ UNC instead.

 

[John CoatesParticipant @johncoates48577]

I could always get a bolt of this thread and pitch then cut to length and cut a slot in the top for a screwdriver. It’s only to lock the drive pulley into the groove in the motor spindle so the force on it should not cause it to seize into the hole

 

A possibility if such grub screws can’t be easily found?

[Sub MandrelParticipant @submandrel]

> A possibility if such grub screws can’t be easily found?

Starting to think like a true engineer

Neil

[TerrydParticipant @terryd72465]

Hi John,

 

Always try to use the correct threads if possible, substitutes are never quite good enough, It’s worth digging around, either on the internet or in local engineers suppliers and hardware stores. You never know what you can find, there’s loads of stuff still out there.  Try here, they have a limited stock, buy a few while you can:

 

http://www.modelfixings.co.uk/steel_grub_screws.htm#Whit%20grubs 

 

They are very good for all sorts of things, I’ve used them in the past and have been well impressed with their service.  They are a husband and wife team and deserve support.  It’s worth having a look around their site for all sorts of unusual things and they have acquired stuff for me at very good prices when I needed it.

 

By the way it is good practice to use 2 grub screws in this kind of application. Use the first one to lock the pulley on to the shaft and the second one on top of the first  to act as a locking screw, rather like a locknut on a screw.   (But don’t forget that you have used two if you need to disassemble as I know someone who has in the past and bent a shaft and pulley when trying to hammer them apart. OUCH.).

 

Best regards

 

Terry

 

PS don’t be tempted to over tighten, it’s never necessary.  Take a tip from one who’s tried (Bob Dylan – Nashville Skyline)

 

Terry

Edited By Terryd on 19/04/2010 22:32:12

[TerrydParticipant @terryd72465]

P.

 

Regarding the grub screws on ModelFixings, don’t worry about their short length if you use two as I suggest the amount of material in contact is incredibly strong.  Don’t think that you have to over engineer, It’s not necessary.

 

Terry

[Frank DolmanParticipant @frankdolman72357]

     http://www.emkaysupplies.co.uk stock nine lengths of hex socket grub

   screws in 1/4 BSW. They have always supplied me quickly and

   accurately. No other connection. Prices good for very small numbers

   a bit fierce if you want a lot!

[John CoatesParticipant @johncoates48577]

Thanks Terry and Frank

 

Two grub screws now on way to me from that nice bloke at Model Fixings. Also picked up a length of M8 x 1.25 from a local supplier

 

As an aside would this be a good boring head to buy:

 

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=370190534559

 

It takes a 1/2″ BSW thread (so that’s another draw bar!) but could be used in the 3MT taper in both the mill and the lathe tailstock

 

Thanks again

 

John

[John CoatesParticipant @johncoates48577]

Quick update.

 

The good news is the Lathe is now working. Had bought a 2.5″ pulley from RDG and by taking a link out of the Nu T-link I got this to work. Currently giving me a range from low speed at 74rpm and a top speed of 650rpm

 

Bad news is the M8 x 1.25mm threaded rod doesn’t fit. Seems the bolt I tried was ever so slightly on the larger side of 8mm and the threaded rod is on the anorexic side of 8mm and just pulls straight out. Testing the bolt again reveals it can be coerced out so looks like M9x1.25 is the one. Back to the shop!

 

[Sub MandrelParticipant @submandrel]

Check it isn’t 3/8″ whitworth first!

 

Neil

[John CoatesParticipant @johncoates48577]

Stub

Thanks mate. Will do

John

[Gone AwayParticipant @goneaway]

One point for the future:

 

If you are going to be messing around with machines of various sources and vintages you will ultimately need to amass an appropriate  collection of taps and dies. For example I have a working range of UNC & UNF (naturally, since I live in Canada), Metric, BSW, BSF, BA.

 

Used carefully by hand they make useful thread gauges in this situation as well as cleaning/repairing threads. You can also (for example) thread a length of drill rod  (silver steel) to make a replacement grub screw if you’re stuck.

 

Most of my oddball (around here) sizes were picked up over a period of time either from UK sources and/or via  eBay.

[KWILParticipant @kwil]

http://www.Toolfastdirect.co.uk  stock BSW socket grub screws

[TerrydParticipant @terryd72465]

Posted by KWIL on 21/04/2010 08:57:10:
http://www.Toolfastdirect.co.uk  stock BSW socket grub screws

 

Hi KWIL,

 

Unfortunately though. they only have one length in stock (of 1/4 BSW)) and those are in packs of 100 at £18 plus vat plus carriage.  A bit steep when you only need a couple,

 

Regards

 

Terry

[John CParticipant @johnc47954]

Try: Live Steam Models

http://www.livesteammodels.co.uk/pdf/MES2010b.pdf

 for small quantities of imperial grub screws. Very reasonable and sensible postage too!

John

[Author]

Posts