[Mike]

Here is a quick reference to different types of guide bushings.
Photo 1:
Top left: Old style Bosch. Installed by removing the bottom plate of the router.
Bottom left: New Quick change style Bosch. Installed by dropping into place and sliding a lever. Note the quick change adapter with a PC style bushing installed.
Bottom center: Typical Porter Cable base plate with bushing installed.
Bottom near right: PC style bushing.
Bottom far right: Rousseau mounting plate installation bushing. Note the removable top ring locked in place with an Allen screw. Guided by the template with a straight cutting bit installed; removes the main cut out for the router. Removing the top ring reveals a smaller guide used for cutting the lip that supports the plate.
Top right: Typical Craftsman router with guide bushing. Bushing is plastic and held in place with 3 screws.

Photo 2: Craftsman bushing; sits on top of the sub base plate, 3 screws.
Photo 3: The larger Oak Park/Lee Valley style on the left; PC style on the right.
Photo 4: Reducers in both styles.
Photo 5: Milescraft kit with base plate, bushings and an adapter to use PC style.
Photo 6: Trend metric or Imperial guide bushings in HD plastic, steel and the T3 adapter for PC.
Photo 7: Trend UniBase/bushing which will fit most routers.
Photo 8: Makita bushing; attaches with two screws on older models, new models have a quick release lever and require no screws. Bushings work with either style.

 

[Mike]

At this time 40mm guide bushings are still not available in North America.

 

[Mike]

The only way to get the 40 MM guide bushing in North America is to order it and the matching base plate from Trend in the U.K. I have asked Trend N.A. to start carrying this product but so far no response.

 

[Mike]

Outside of easier math, it strikes me the 1-1/2" (37.5 MM?) should be capable of most of the jobs using template guides that the 40 MM guide will do. Granted not all bits will fit but there is ample clearance for the collet and swarf removal. Since the 40 MM guide is not available isn't this a viable alternative for North American members?

 

[Mike]

Tom, in thinking over the goals of using the larger guide bushings wouldn't pattern following bits with bearings accomplish the same results? By way of example Whiteside makes bearings in 11? different OD's which fit a multitude of their bits, and that is just the 3/16" ID bearings. These are tip mounted and perfect for table use but they also manufacture larger ID bearings which can be mounted on the shank. Is there a safety consideration using bearings as opposed to guide bushings? I can't see any. Am I missing something?

 

[Mike]

Ok, the guide bushings will allow you to set the router in place before plunging the bit. I can see the safety difference between this and using a bearing guided bit. With a bearing you do not have proper alignment until the bit is fully plunged into the work. There is also the depth of cut to consider, it is not variable using a bearing. The bit would need to be fully extended for the bearing to contact the template. This makes sense to me. Thanks for helping me sort this out.

 

[Mike]

Dewy, I dont normally work with metric sizes and took a guess which was close enough to make my point. The bushing IS large enough for Tom's method.

 

[Mike]

Ken, if you get a 40 MM it will be special order. As Dewy pointed out the largest Oak Park bushing is 38.1 MM so short of the math being slightly different from Tom's it will do the job. I will check with our local parts source and see if Makita has the 40 MM available in the US. I need to visit with them anyways.

 

[Mike]

Wanda, Makita offers larger sizes of template guides which are very useful. Most places in the US and Canada do not stock the larger sizes but they can be ordered. I think if I owned a 3612C I would stick with the factory bushings. There are advantages to using the two piece brass bushings but the adapter you have limits the size to the PC style; it will not accept the larger Lee Valley/Oak Park style bushings. Tough call on this one; either way will work.

 

[Mike]

I updated the first post in this thread with more photos and information.

 

[Mike]

A Chinese company contacted me about increasing their business. I gave them specifications to build metric guide bushings in both PC and the larger Oak Park/Lee Valley styles using a CNC. They sent me these sample bushings which were out of tolerance, hand produced with the wrong threads because the tooling was cheaper. I will find a different company who wants to produce these items.

 

[Mike]

I have the "Imperial" plastic set Phil, as well as the two plastic metric sets from Trend. They are a sturdy design and way better than the Craftsman plastic guide bushings. About on par with the Milescraft set.

 

[Mike]

Chuck, the Milescraft set is popular and I think most come with the adapter which accepts PC style guide bushings. I prefer the Woodcraft brass bushing set because all the collars are 1/4" height so you can make all your templates from 1/4" material. Other set are a mix of 1/4 & 1/2".