Tom Senior Light (S) type Head

[mike robinson 2Participant @mikerobinson2]

I am changing the single phase motor on a newly acquired Tom Senior E type, example photos are here (**LINK**) for a Newton Tesla VFD package. The original motor cable is routed up through the main tubular column and exists through a closing plate with a plastic grommet. The top plate as attached to the top swivel casting by what look like 2 dome head screws but without slots. I need to remove the cover plate when I install the new motor. I had assumed there they were rivets holding some form of spring clip keeping the cover in place, but having tried to lift / move it it simply wont move and before I take other measures I would appreciate advice from anyone who has done this before…… Thanks !

[mike robinson 2Participant @mikerobinson2]

how to remove the column top cap (cable entry cover plate)

[Clive FosterParticipant @clivefoster55965]

Pending definitive advice from someone who has actually at one apart its very likely that your un-slotted dome head "screws" are hammer drive screws. Very common for light duty, expected to be permanent, fixings in cast iron such as void covers, name and information platers. Rather than a screw thread the shaft has a very fast, multi-start, shallow helix enabling them to be simply driven in with hammer and push to give a firm hold.

Google "hammer drive screws" for pictures.

Generally accepted removal technique is to get under the edge with a star edged lever and carefully wrinkle them out a bit at a time working round the head rather than trying to lever from one side. Worked for me on a SouthbBend threading gearbox data plate but considerable verbal encouragement was needed along with great care to avoid significant damage to the plate.

Normally quite hard so knocking the head off and drilling out to tap for proper screws isn't usually practical. But if the plate can be simply turned to put the fixings in another place knocking the head off and grinding off the protruding shaft is probably the quickest and easiest way.

Clive.

[mike robinson 2Participant @mikerobinson2]

Thanks Clive, Yes, I was worried they might be a hammer drive screws. I will try verbal encouragement first

[mike robinson 2Participant @mikerobinson2]

Can anyone advise a current supplier and part number for a replacement drive belt on a Tom Senior S type head (as fitted to the E Type light milling machine. The drive belt markings say Fenner Z495. It very old and measuring it I get 3/8" wide .230" deep with an included angle of 35% – but that's measuring the old one. I have taken a look on the Fenner site which is more then overwhelming…. appreciate any guidance, thanks !

[Clive FosterParticipant @clivefoster55965]

Mike

Z is a classic V belt section officially measured in inches inside length. But many manufacturers specify in mm. Far as I can recall Fenner have done so since at least 1980 (ish).

Z495 corresponds to Z 19.5 in inches. Bearing Station :- **LINK** is one firm that carries them. Bit over a fiver by the time it arrives.

They also quote datum length which is pretty much the outside diameter, but not always exactly so these days see :- **LINK**. It's what you use to convert the measurement round the outside of the pulleys to the official length.

Clive

[mike robinson 2Participant @mikerobinson2]

That's very helpful Clive and saved me a ton of googling – many thanks. One is on order….

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