plunge cutting pushes the router up in the clamp

[pshupe]

Has anyone else had this problem? I was plunge cutting a piece and had a 1/2" dia router bit in it with a very slow plunge value and it was pushing the router up in the clamp. The clamp was tight to the point that I thought I would break something. I think the clamp is a poor design as it cannot tighten adequately. I had put my router up about 2 inches so that a long bit would still have chips cleared by the vacuum. I did a few cuts like this with a very tight bolt and then the router started to slide down until it hit the taper of the router, and also pushes up when I plunge a large diameter bit.

Any advice is greatly appreciated. Is there a fix for this? I have a Bosch 1617 evs and it works pretty well but the clamp is kinda lame.

Regards Peter.

[jeb2cav]

Hi Peter -

Give this thread a look - a couple of solutions presented that should help you resolve this.

http://cncsharktalk.com/viewtopic.php?f ... 37&p=10431

[2Big]

The clamp force on the router is not great. I have a mako HD shark with the larger porter cable router and I notice some slippage when I tighten or loosen the router bit. I put a washer around the bolt and nut on the clamp and have not had further issues. Just one question on the router bit you are plunge cutting with, is it a center cutting bit? Most are not and require some 'ramping' on the Z plunge.

[Wolffie1]

I have had that problem as well.

The clamp is just too slippery and flexible.

1)The circular opening in the clamp may not fit your router, run a length of masking tape around your router before you tighten the bolt, that gives the clamp something to grip on.
2) do not tighten the 2 front bolts until you have tightened the clamp, there is just not enough movement for the clamp to tighten, if the bolts are already tightened, it will only have the small part between the bolts and the clamping bolt for adjusting the grip.
3) I changed the 2 front holes to slots, so the bolts could move a bit when I tightened the clamp, then tightened the bolts after.

Cheers
Wolffie

[rungemach]

you can make a new clamp using a less flexible material.

I prefer aluminum for my clamps and made a quick HD clamp in aluminum for testing, using a stock clamp that was sent to me by another forum member.

I notice two things about the original plastic clamp that was sent to me. The first was that the bolt tab was starting to bend from the clamping force, and secondly, the recesses in the clamp were barely deep enough to accommodate the body pins on a PC 690 router. If the recesses are too shallow, the router pins can hold the clamp off of the router body a little if they are in the clamp area.

The clamp I ended up with has deeper and wider pin recesses and a slightly larger tab for the tightening bolt and nut.
I used 5/8 thick plate stock as that is what I have around. It could be made a full 3/4 if desired.
This clamp was cut on my modified shark pro. I spot the mounting holes with the cnc and drill them later.
The router hole and outside profile are cnc cut. 20 ipm and .020 per pass, upspiral 2 flute carbide bit.

Bob

[Wolffie1]

Good job as always Bob,
I changed my mind about making the new router holder.
I have ordered an R20 water cooled spindle and will wait for it to arrive before I cut the inside hole.
No more problems with bit shank sizes

Cheers
Wolffie

[pshupe]

That looks very nice Bob. I think the design is very poor to start with. At the very least there should be slots for the 2 front vertical bolts, so that you can tighten the clamp as much as you need, and then tighten the bolts in the right spot. The larger gap you designed also makes more sense. I would be interested to find out how yours works. I doubt if you tighten your clamp quite a bit that your bolt holes would line up, unless you over sized them. It would be nice if it used the groove in the side of the router, as the plunge base does. I will try just taking out the bolts and opening the clamp as much as I can and put in a thin rubber gasket then tightening the clamp as far as I can and hopefully the bolts will line up so I can tighten. If they don't I will just drill them. Unfortunately the design doesn't allow much space to get in there because the router tapers. It just does not work very well at all. If it doesn't work I may look at designing a whole new holder to mount onto the axis. Thanks.

Cheers Peter.

[rungemach]

Hello Peter

Since aluminum is many times stronger than hdpe, the clamp does not deform when tightened, and can clamp very tightly.
If the router hole is sized exactly, the hole locations do not shift off center very much.
If the router hole size is right on, you need to spread the clamp slightly with a flat bladed screwdriver to slip the router in.

Then you have several options for the front two holes.

1) Drill the front holes slightly oversize in the clamp.

2) Use a slightly smaller fastener for the front bolts. 6mm (.23) or 10-32 (.19) with washers are quite strong.

3) Put the clamp on the router and tighten. Bolt to the shark using the two rear holes. Then open up the front holes to match by passing a .25 drill through if needed.

4) Wait to drill the front holes until you can mark their location with the clamp on the router and in the shark. Mark the two front holes and drill them in the exact location.

bob

[jcatcmc]

My fix for this particular problem was to drill and tap a 3/16" locking screw through the clamp and drill small dimple into the router body. Nip up the screw after tightening the clamp , end of problem .

Regards to all.

[pshupe]

Thanks guys - I will be looking into this soon. I have solved the problem for now by ramping all my machining. That works really smooth and as one would expect much less upward force on the bit / router, which is no doubt easier on the bearings as well. Thanks again and I will let you know when I get to the "strengthening of my clamp"

Cheers Peter.