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The Shop => Electronics & IC Programing => Topic started by: christraxon on June 15, 2011, 10:30:15 PM

Title: Help please Lathe running slow in reverse
Post by: christraxon on June 15, 2011, 10:30:15 PM

Hi all

hope someone can help? i have a clarke cl300m mini lathe and have just replaced the bearings which went fine but as i was testing out the lathe i notice that when i put the lathe into reverse using the switch on top the reverse speed is only about a third of the forward speed. is this normal or has somthing blown.

thanks

chris

Title: Re: Help please Lathe running slow in reverse
Post by: John Swift on June 16, 2011, 04:27:10 AM

Hi Chris ,

I don't know why they do it , but they do run the motor at about half speed in reverse

depending on how old your lathe is it can have one of two speed control boards


old machines use a FC250J speed control board (with two F.E.T transistors on one heatsink),
 part of the   forward /reverse switch links terminals  P1 and P4 in forward  for the faster motor speed range

later lathes use the XMT2325 speed control  (3 diodes and  2 thyristors on 5 heatsinks)
part of the forward / revese switch connects terminals P4 and P5 for fast (forward)
and P4 and P6 for slow (reverse)

one thing to watch out for is the push on connectors don't grip very well once you disturbe them

when I replaced the spindle bearing on my CL300m ,with taper bearings I had a bit of fun
making new spacers using the lathe was fixing !!

that was after working on the speed control  see hear :-
http://www.model-engineer.co.uk/forums/postings.asp?th=38809


 John

Title: Re: Help please Lathe running slow in reverse
Post by: christraxon on June 16, 2011, 05:28:59 AM

thanks for the reply john

so it it normal for it to run slow in reverse then my board is the XMT-2325.

thanks

chris

Title: Re: Help please Lathe running slow in reverse
Post by: raynerd on June 16, 2011, 08:39:20 AM

Chris, yes I believe this came up on another post in the last few weeks but from experience, my CL300 went slower in reverse.

Title: Re: Help please Lathe running slow in reverse
Post by: trevoratxtal on February 16, 2013, 02:51:25 AM

Many lathes are set to run slower in reverse, the reason is.
To lessen the chance of the chuck unscrewing.
Trev

Title: Re: Help please Lathe running slow in reverse
Post by: andyf on February 16, 2013, 04:52:24 AM

It's a well-known feature of mini-lathes. Switching the motor to reverse brings an extra resistor into the speed control pot circuit, to (roughly) halve the speed. Some say that this is because the motor brushes are slightly angled for best performance in when running forwards, I don't know about that, but whatever the reason, it's meant to go slow.

It isn't to stop chucks unscrewing,  because mini-lathe chucks are bolted on to a spindle flange.

Andy