20mm diamater transfer punch? Where to buy?

[Prizen]

Hi all

I wish to accurately replicate a workbench top (mdf) which has a series of 20mm holes drilled. I have figured that the most accurate way would be to clamp the new blank top underneath and a 20mm diameter transfer punch to locate the centre of the hole on the new top. Once complete I would route out the holes using a suitable 20mm cutter.

However, I cannot find where I can purchase a 20mm punch.

Any ideas?

 

[MikeG.]

If you have a 20mm Forstner bit, just place that in the hole and either turn it by hand, or give it a little tap with a hammer, and it will leave a mark at the centre point.

 

[porker]

Hi,
Chronos do a 5-20mm transfer punch but looking at it I don't know how accurate it would be as it looks like a cone that I would think would have a degree of error in how perpendicular it was held. If you are using a 20mm cutter you would need to use one with a centre point (which most router cutters don't have). If you do have a cutter could you use the cutter itself as the transfer punch?
I'm dubious how accurate this method will be though. I used a template from cncdesign which uses a standard 1/2" router cutter and standard guide bush. It is made so an MFT top can be replicated including the fixing holes.
Matt

 

[AES]

Arc Eurotrade (link in the sticky at the top of this section) do a set of transfer punches, IF I remember correctly, actually 2 sets, one metric one imperial. usual disclaimers.

HTH

 

[Eric The Viking]

I have a set, one conical and one stepped. Neither goes out to 20mm, and the pointed pins are a sloppy fit in the middle, anyway, so you cannot rely on them for accuracy.

The Forstner bit thing would be by far the easiest, but if this is some sort of MFT, it probably won't be accurate enough if there is any wear in the holes of the original piece..

 

[AES]

The other thing you could do is make your own.

Find a bit of steel or ali bar which is a snug fit in the existing hole and "turn" a centre point on one end. A lathe is of course ideal for that, but if you don't have one available you can easily make your own which should be OK unless you want absolute accuracy (in which case a transfer punch is probably not the way to go - though I must say, my own set is accurate to about +/- 1 mm or a bit less, which IMO is fine for a lot of stuff).

To make your own just attack one end of the bar with a file to get it more or less conical by eye. Then chuck it in a drill and hold the point against a belt or disc sander, if necessary first marking a 45 degree line on the sander table with a soft pencil. Run the pointed rod in the drill SLOWLY, holding the point against the spinning disc/belt, adjusting your hold of the drill until the angle is just right. You don't need a really sharp point, just enough to make a clear mark on the job to be drilled.

As said, NOT the most accurate, but "good enough" for a lot of purposes. What's the job BTW?

 

[marcros]

a word of warning- if you buy a cheap set (mine are Silverline!), they may be listed as metric but they are not, they are imperial. I have never measured the accuracy, because I use them for squaring off pen blanks on a jig, so just get the closest fit.

 

[toolsntat]

You have the existing and the holes are good.
Can you not use a top guided plunge cut router cutter and your existing top?
Cheers Andy

 

[Prizen]

I couldn't plunge at 20mm which would risk damaging the good top, which hasn't been used, holes in it are perfect

 

[chaoticbob]

Arc Euro Trade do universal transfer punches . They are based on the 'punch in a cone' idea, but have a sliding collar on the outside of the cone which ensures that the punch is held perpendicular to the work. The larger size goes up to 26mm
Robin

 

[toolsntat]

I couldn't plunge at 20mm which would risk damaging the good top, which hasn't been used, holes in it are perfect

I was thinking along the lines of a 1/2" cutter.
Cheers Andy

 

[Prizen]

Tks Andy. How about the second cut to bring the hole to final size; how could I be sure I am on centre?

 

[MikeG.]

You're not following. Andy is suggesting using a following cutter........a cutter with a ball-bearing guide, and running that around the inside of the existing hole to create a replica in the sheet below. It wouldn't matter what size the cutter was (so long as it was smaller than 20mm).

 

[toolsntat]

Sorry, just realised I am repeating, in a way, what was already suggested.
post1275492.html#p1275492

I'd fit a 20mm guide Bush to my router, and choose a suitable half inch cutter which can be plunged without clogging.

Plunge a half inch hole in each location, then swap the cutter for something larger - maybe a 16mm and repeat.

Fit a bearing guided cutter and set the depth so you cut 3mm of so into your new sheet, and slowly, carefully duplicate the full-size whole into the new sheet, being extra careful not to damage the CNC master.

Once you've got a full sized matrix 3mm deep, remove the master and repeat until your hopes are full depth.

PS: In my experience forstners clog hopelessly in MDF, but mine are pretty cheap and nasty.

 

[Phil Pascoe]

^^^^ https://www.wealdentool.com/acatalog/On ... m_279.html

This type of cutter - just make sure it has a bottom cut. So long as you plunge carefully past the depth of the bearing it won't damage whatever you're using as a templet.

 

[OscarG]

Arc Eurotrade (link in the sticky at the top of this section) do a set of transfer punches, IF I remember correctly, actually 2 sets, one metric one imperial. usual disclaimers.

HTH

I have the metric set, been pretty happy with them, but only goes up to 13mm though.

 

[Levitric]

Hi all

I wish to accurately replicate a workbench top (mdf) which has a series of 20mm holes drilled. I have figured that the most accurate way would be to clamp the new blank top underneath and a 20mm diameter transfer punch to locate the centre of the hole on the new top. Once complete I would route out the holes using a suitable 20mm cutter.

However, I cannot find where I can purchase a 20mm punch.

Any ideas?

Did you ever get this resolved, I too have come to the same conclusion as ylurself so am interested in how you got on.

 

[profchris]

A 20mm auger bit is under £10 from Screwfix and Toolstation. Accurate enough to use as a centre punch? Or even go mad, put it in a brace and drill the first few mm of the holes to use as a guide for later routing. Or even madder, go all the way with the hand brace! (NOTE: I have no idea what precision is needed, an auger might be too sloppy for this work I suppose).