hole saw problem

Sean Farrell

I dont have access to a pillar drill.....so trying to keep a hole saw bit straight and true is proving diffcult when using the power drill. In fact the drill motor overheats when I'm drilling into the veneered mdf....18mm is proving a tough task. I try to keep the speed of the drill at a constant and try not to force to much pressure downwards....however when it gets deeper burning occurs and the teeth of the bit get stuck in the stock. As a result the hole ends up uneven and slightly too big meaning i have to use tape around the insert to fit it in properly. Ant ideas of what method is best to drill an insert hole straight and true that wont burn ur power drills motor. The insert hole is supposed to be 57mm btw. Would be grateful for some help...thanks.

kadman

You would be better off using a forstner bit for holes in mdf. Hole saws were never a sucessful tool
for precision boring. Unless off course you take the time to tweek the bit with sharpeniing the teeth
comparable to a good handsaw sharpening, it will work.

Old school adjustable expanding brace bit, with the threads ground off the point, and used in an electric drill,
was also excellent at boring large holes, but a sacrificial backing piece should be used to keep the drill stable
and online for the final finish.

I personally dont see hole saws as the right tool for this, but if its your only option, sharpen it if you can,
and keep your speed down to say 250rpm for large holes. If you need pressure to drill, then its not sharp
enough. And any out of the box hole saws I,ve seen always needed sharpening. Moderate hand pressure should
be all thats needed, not brute force.

Forstner type bits , in case you are unsure about them.

http://www.ebay.co.uk/itm/Forstner-Bit-Set-for-Boring-Coreing-Precise-Holes-into-Wood-16-metric-sizes-/111649181906

A sharp tool is the most important thing for precision cutting.

recipio

Sean,
as Kadman says, hole saws are not precise tools and are very power hungry.
Even a drill press with 550 watt motor ( about average ) will struggle with any bit or hole saw over 40mm.
You seem to want to put another disk back in the hole with a snug fit ? I think you are getting into the area of template routing - using a template with a bush and detachable collar to make the 'male and female' parts ?
Otherwise you could buy an acrylic template with a range of holes. Cut out the circle roughly with a jigsaw and finish with a flush bearing mounted router bit.
Lastly, for cutting large holes - say for a speaker - the best method is a router mounted on a circle cutting jig.

Sean Farrell

Nice idea recipio, .....i thought maybe use the hole saw with the power drill to initially cut thru the veneer, then put on the forstner bit for a clean job. I'm finding it hard to find a forstner bit above 55mm......and would a bit that big work on a power drill?

recipio

Sean Farrell wrote: »

Nice idea recipio, .....i thought maybe use the hole saw with the power drill to initially cut thru the veneer, then put on the forstner bit for a clean job. I'm finding it hard to find a forstner bit above 55mm......and would a bit that big work on a power drill?

'fraid not. You might get away with big bits if you had a floor mounted drill press and a 2 HP motor - my drill press is 750 watt ( 1 HP ) and struggles with anything over 40 mm.
I see you already have a few holes drilled. Why not use one to make a template in 6mm MDF using the jigsaw and flush trimming router bit. It will do a few dozen holes before needing replacement. Incidentally acrylic hole templates are hard to get - I got one online from www.rockler.com
MDF is seriously hard on the standard Chinese Forstner bits now available.
If you ever do get a drill press consider buying a tungsten tipped adjustable bit from www.wealdentool.com. Unfortunately they only to up to 50 mm.

Sean Farrell

On reflection.....and having had my dinner.....your template routing suggestion is a more obvious option recipio(i was getting too cocky there). i'm trying to make a photo weather station that involves 3 inserts ie for barometer themometer and hygrometer. Each insert has to aligned exactly below each other at an equal distance from each other. so one template properly done with the router would do the job perfectly.Its the several attempts at making the template that daunts me.....but once done its there for good if i look after it.

Sean Farrell

On further reflection,...and after having my desert....recipios suggestion of just a one hole template would be more obvious as it would be less difficult to replace than a 3 holed template. I could never multi task...eating and thinking never mix!!!!

recipio

Just stick a bit of 6mm MDF on to your already drilled holes using double sided tape, cut out roughly with a jigsaw and use a top guided router bit to finish to an exact size.It helps to cut the MDF to the same size as your workpiece to be able to align up the position of the holes.You can get top and bottom guided router bits in 1/4 inch shank to a depth of about 30 mm.

Sean Farrell

At long last i have returned to my fountain of knowledge and have come to pay my respects. Yep..the hole saw method burnt out the motor on my drill(very cheap one i must stress, easy to replace)...the templates i made from 6mm MDF, like Recipio suggested worked well and lasted longer than i thought...the holes started to get bigger as i used them more....it was easy to make another template. So theres the end product..A nice photo weather station made from routed 19mm pine veneered MDF. Thanks all for your help...its appreciated...even thou it takes me a long time to acknowledge it i'm sorry to say. respect to u all.

recipio

Well done that man !
Did you do the pyrography as well ? Very nice.

Sean Farrell

Thanks Recipio...god i'd love to have done it with pyrography but i'd need a bit of practice there. Ended up using adobe photoshop to reverse text and then printing with a laser printer. I then used a very hot iron to transfer onto the veneered mdf, finished it off with a black sharpie fine tip marker (phew) .I did the same with the acorn images....mostly sourced online, with the intention of finding pen and ink images that transfer more easily. I suppose black and white images also. The images worked out well for a gift i made for a friend of mine who likes cycling ..see above..also i managed to iron on a couple of images of my nephew on another weather station i'm giving to someone as a gift....some day I'll be that good with a soldering pen....someday