Trend MFT jig

[pgrbff]

A while back, having a fairly large piece of black moisture-resistant MDF to hand, I bought the above jig to make a MFT bench.
The grid did not come out square, and it was put aside.
Usually, I'm quite accurate and have been called worse, so I'm not sure where I went wrong. What I didn't do first was check that the factory edges were square before starting.
Anyone else have any issues?

 

[Spectric]

Providing you referenced from the previous set of holes and not any edges of the board then it would have no effect, the hole pattern would be correct but maybe not in relation to the board edges. Did you centralise the cutter in the guide bush using a cone ? If the cutter is not concentric in the bush then you could make the hole slightly off centre and these errors would accumulate. Also is the bush a snug fit inthe guide ?

 

[sammy.se]

I used a different brand jig and the jig was fine. I didn’t centre my router bush so it’s not accurate :-(

 

[Distinterior]

I work with a lot of sheet material of various types & thickness and the rule of thumb that I always adhere to is,.... When working with ANY sheet material, ALWAYS assume any factory edge is rough and not to be trusted as straight or square.

 

[Spectric]

A good starting point is to give yourself a known straight edge from which you can work from, just like we used to get monday / friday built cars I think we get the same with some sheet goods where a batch is just off.

 

[porker]

I had a similar issue with my first attempt when I used an RS Pro jig which looks like it uses a similar method to the Trend one.

As stated above this was due to the cutter not being concentric with the guide bush. I have a metal lathe so turned an accurate 30mm tool to centre the bush. The second attempt went fine and I couldn't measure any error using straight edge and squares

Another tip which used thin aluminium tape wrapped around the guide bush to make the dogs fit perfectly. This needs a scrap piece to test by trial and error but worth doing before you bore all your holes

 

[pgrbff]

To be honest it was a while ago. it is possible I referenced from an edge more than once. Will try again but the smallest sheet of 19mm here ie 200 euro, 366X185.

 

[Spectric]

To be honest it was a while ago. it is possible I referenced from an edge more than once.

Initially align with an edge if you want to but then always reference from the last set of holes so keep the holes in line.